Roller LA Deck Height

[cal30_sniper]

During my junkyard diving this weekend, I came home with a 360LA Roller Cam engine out of a '92 Ramcharger (530096921 casting). I've had an '89 Roller Cam 318 sitting in the corner of the garage for a while that's intended for a Volare swap, but I couldn't pass up the 360 roller motor for $200. It's high mileage (184k), but turning it over by hand didn't reveal any issues, and borescope inspection appears to be the original factory setup (not a rebuild).

Now to my question, did these late LA roller motors use the old 9.599" LA motor deck height, or had they already transitioned to the Magnum deck height (9.585" from what I've been able to gather)? Some threads I found spoke as if the LA roller motors had already gone to the shorter deck height (I found reference to 9.577-9.578" as the blueprint spec for these years). Has anyone else measured deck height on a stock 360 LA roller motor? What am I dealing with here? How about factory piston relief size?

I know, Chrysler blocks are all over the place, and the only accurate way to tell is to pop off the heads and measure how far the factory slugs are down in the bore, and compare that to their compression height upon disassembly. I'm just trying to do a little planning ahead, and determine whether this block is worth fooling with right now.

Discussion on why I'd like to know deck height:

I'd like to use commonly available +10 or +11cc dished pistons for a Magnum engine to work well with the EQ Magnum heads I have, but if this block is at the LA deck height, that will likely take significant milling to maintain any sort of decent quench. Alternatively, I could look at something like the Icon 742 (10.1 CR with zero deck and .039 headgasket), but that's an expensive set of pistons for what I'm trying to do. I'm not having any luck finding other pistons in the +9 to +11 cc range at the LA deck height. I think KB107s (+5cc) will result in excessive compression with the 64cc iron heads (10.6CR with zero deck and .039 headgasket), while something like the KB362 (+19.4cc) would be a little low (9.1CR with zero deck and .039 headgasket). I'd really like to shoot for 9.5-10:1 static compression and .040" quench, for use of regular pump gas at 5500+ elevation.

I think of the three listed above, the KB362 is likely the right answer, but it would be better to be able to use a Magnum type replacement piston, both for the ideal piston relief size and for cost. However, if the LA roller block is at or near the old 9.599" deck height, that's going to take a lot of milling to get down to zero deck. For example, the Speed Pro H655 is a +11.23cc piston with a compression height of 1.612". For a 9.599" deck height, that would require .074" of milling to get down to zero deck. A 1.675" compression height piston like the Icon or KB would only take .011" of milling to get down to zero deck, and would actually be almost at zero deck in a 9.585" deck height (.003" out of the hole in a perfect world). I don't know what "deck height" the commonly available LA intakes are set up for. Is there a rough number of how short the deck height can be before milling the intake also becomes necessary?

I'm probably focusing too much on quench, but I really would like to run on regular pump gas while still having enough static compression to work with a decent sized cam. Proper quench is about the only way I know of to do both without going to EFI. Maybe I'm overthinking all of this.

 

[rustycowll69]

am I missing something here? are you concerned about 0.014" difference in deck height? It seems like a lot of hand-wringing over such a small amount of material. I'm not an automotive machinist, but just a minimal clean up cut will probably take 0.004", another 0.010" doesn't seem like a big deal to me. It's not like cutting a sl/6 an 1/8".

 

[Bobzilla]

During my junkyard diving this weekend, I came home with a 360LA Roller Cam engine out of a '92 Ramcharger (530096921 casting). I've had an '89 Roller Cam 318 sitting in the corner of the garage for a while that's intended for a Volare swap, but I couldn't pass up the 360 roller motor for $200. It's high mileage (184k), but turning it over by hand didn't reveal any issues, and borescope inspection appears to be the original factory setup (not a rebuild).

Now to my question, did these late LA roller motors use the old 9.599" LA motor deck height, or had they already transitioned to the Magnum deck height (9.585" from what I've been able to gather)? Some threads I found spoke as if the LA roller motors had already gone to the shorter deck height (I found reference to 9.577-9.578" as the blueprint spec for these years). Has anyone else measured deck height on a stock 360 LA roller motor? What am I dealing with here? How about factory piston relief size?

I know, Chrysler blocks are all over the place, and the only accurate way to tell is to pop off the heads and measure how far the factory slugs are down in the bore, and compare that to their compression height upon disassembly. I'm just trying to do a little planning ahead, and determine whether this block is worth fooling with right now.

Discussion on why I'd like to know deck height:

I'd like to use commonly available +10 or +11cc dished pistons for a Magnum engine to work well with the EQ Magnum heads I have, but if this block is at the LA deck height, that will likely take significant milling to maintain any sort of decent quench. Alternatively, I could look at something like the Icon 742 (10.1 CR with zero deck and .039 headgasket), but that's an expensive set of pistons for what I'm trying to do. I'm not having any luck finding other pistons in the +9 to +11 cc range at the LA deck height. I think KB107s (+5cc) will result in excessive compression with the 64cc iron heads (10.6CR with zero deck and .039 headgasket), while something like the KB362 (+19.4cc) would be a little low (9.1CR with zero deck and .039 headgasket). I'd really like to shoot for 9.5-10:1 static compression and .040" quench, for use of regular pump gas at 5500+ elevation.

I think of the three listed above, the KB362 is likely the right answer, but it would be better to be able to use a Magnum type replacement piston, both for the ideal piston relief size and for cost. However, if the LA roller block is at or near the old 9.599" deck height, that's going to take a lot of milling to get down to zero deck. For example, the Speed Pro H655 is a +11.23cc piston with a compression height of 1.612". For a 9.599" deck height, that would require .074" of milling to get down to zero deck. A 1.675" compression height piston like the Icon or KB would only take .011" of milling to get down to zero deck, and would actually be almost at zero deck in a 9.585" deck height (.003" out of the hole in a perfect world). I don't know what "deck height" the commonly available LA intakes are set up for. Is there a rough number of how short the deck height can be before milling the intake also becomes necessary?

I'm probably focusing too much on quench, but I really would like to run on regular pump gas while still having enough static compression to work with a decent sized cam. Proper quench is about the only way I know of to do both without going to EFI. Maybe I'm overthinking all of this.

Even if that 92 LA block does have a 9.585" deck height, your KB107 would still be only .003" out of the hole and your compression ratio with a Fel Pro 1008 would be about 10.55 to 1 with 4.03" bore.

If you are worried about that, Sealed Power H116CP pistons are 1.66 compression height, would sit about .012" down the hole, and would bring the compression down to about 10.18 with 4.03" bore.

CHRYSLER Speed Pro H116CP 30 Speed-Pro Hypereutectic Pistons | Summit Racing

Edit to add, I have a 92 LA 360 block I just assembled. It was previously decked an unknown amount by previous owner to raise compression. I had it decked again to get a smoother finish and after we took off .012" my IC742 pistons only sit .018" out of the hole. So I highly doubt the 92 LA block is shorter than an older LA block.

 

[RustyRatRod]

AN LA is an LA is an LA. The LA has one deck height. The Magnum another. PERIOD

 

[cal30_sniper]

am I missing something here? are you concerned about 0.014" difference in deck height? It seems like a lot of hand-wringing over such a small amount of material. I'm not an automotive machinist, but just a minimal clean up cut will probably take 0.004", another 0.010" doesn't seem like a big deal to me. It's not like cutting a sl/6 an 1/8".

Rusty, I don't think you're missing anything, other than that this is less hand wringing and more trying to get ahead of what combination is going to work well with this block. .014" difference is significant when talking about quench, though likely less significant from a general machining perspective. I'm an engineer with background in combustion, but not a machinist, thus familiarity with one concept leads to questions in another. 4.0" bore piston availability seems to fall into three camps: Stroker pistons, LA pistons for open chambered heads, and Magnum pistons for closed chamber heads. The deck height and balance differences in the Magnum engine complicate piston selection for an LA closed chambered head build while meeting both ideal compression ratio and quench. It seems easy to build either a motor with good quench, or a motor with good compression, but not both.

If you are worried about that, Sealed Power H116CP pistons are 1.66 compression height, would sit about .012" down the hole, and would bring the compression down to about 10.18 with 4.03" bore.

CHRYSLER Speed Pro H116CP 30 Speed-Pro Hypereutectic Pistons | Summit Racing

Edit to add, I have a 92 LA 360 block I just assembled. It was previously decked an unknown amount by previous owner to raise compression. I had it decked again to get a smoother finish and after we took off .012" my IC742 pistons only sit .018" out of the hole. So I highly doubt the 92 LA block is shorter than an older LA block.

Thanks, I had overlooked the H116CP based on small piston relief size without noting the compression height difference. This would likely be a better choice with no deck work being conducted, although it might not lead to good quench without a thin headgasket, thus raising compression again. I imagine I will end up having the deck worked on at least somewhat, if nothing else to square up the bores. That being the case, the small piston relief may be a liability in a motor built for quench (excessive compression for pump gas).

Thanks for the personal experience shared with the 92 LA block. That's what I was hoping to gain by posting here. One would logically assume that LAs would be the same, but there were other oddities with the 91-92 blocks (oil filter boss in 91, and engine mount pads in 92) that were introduced prior to the Magnum in 93. Some other posts I found claimed either that the deck height spec was revised for these late roller blocks, or at least production tolerances had tightened to the point where the motors were more closely held to the blueprint specifications. I appreciate the feedback, and would be interested to know more about your build process/combination with that 92 block.

 

[Bobzilla]

Rusty, I don't think you're missing anything, other than that this is less hand wringing and more trying to get ahead of what combination is going to work well with this block. .014" difference is significant when talking about quench, though likely less significant from a general machining perspective. I'm an engineer with background in combustion, but not a machinist, thus familiarity with one concept leads to questions in another. 4.0" bore piston availability seems to fall into three camps: Stroker pistons, LA pistons for open chambered heads, and Magnum pistons for closed chamber heads. The deck height and balance differences in the Magnum engine complicate piston selection for an LA closed chambered head build while meeting both ideal compression ratio and quench. It seems easy to build either a motor with good quench, or a motor with good compression, but not both.



Thanks, I had overlooked the H116CP based on small piston relief size without noting the compression height difference. This would likely be a better choice with no deck work being conducted, although it might not lead to good quench without a thin headgasket, thus raising compression again. I imagine I will end up having the deck worked on at least somewhat, if nothing else to square up the bores. That being the case, the small piston relief may be a liability in a motor built for quench (excessive compression for pump gas).

Thanks for the personal experience shared with the 92 LA block. That's what I was hoping to gain by posting here. One would logically assume that LAs would be the same, but there were other oddities with the 91-92 blocks (oil filter boss in 91, and engine mount pads in 92) that were introduced prior to the Magnum in 93. Some other posts I found claimed either that the deck height spec was revised for these late roller blocks, or at least production tolerances had tightened to the point where the motors were more closely held to the blueprint specifications. I appreciate the feedback, and would be interested to know more about your build process/combination with that 92 block.

Since you are getting specific about some of your thoughts on this build, please provide a little more info. What exact head gasket do you want to run and what compression ratio are you hoping to achieve. I assumed a FelPro 1008 because it is common, but since you keep bringing up quench I would now assume you will also want to limit the crevice volumes, so a Cometic MLS gasket may be a better choice if the budget allows. The Cometic is available in many different thicknesses, so you can get a thinner one to help bring the compression back up if the pistons end up sitting below the deck surface.

The 92 LA does have different connecting rods than older LA 360. The 92 connecting rods are narrowed at the small end like a Magnum, allowing you to run Magnum style pistons. These are actually same casting number and dimensions as a 5.9 Magnum connecting rod.

You mentioned worries of engine balance. Whichever piston you choose you will probably need to balance the rotating assembly anyways, so that is not an issue or concern for you. Just know that it should be factored into the cost.

 

[RustyRatRod]

I consider .014" huge in terms of engine building.

 

[cal30_sniper]

Since you are getting specific about some of your thoughts on this build, please provide a little more info. What exact head gasket do you want to run and what compression ratio are you hoping to achieve. I assumed a FelPro 1008 because it is common, but since you keep bringing up quench I would now assume you will also want to limit the crevice volumes, so a Cometic MLS gasket may be a better choice if the budget allows. The Cometic is available in many different thicknesses, so you can get a thinner one to help bring the compression back up if the pistons end up sitting below the deck surface.

The 92 LA does have different connecting rods than older LA 360. The 92 connecting rods are narrowed at the small end like a Magnum, allowing you to run Magnum style pistons. These are actually same casting number and dimensions as a 5.9 Magnum connecting rod.

You mentioned worries of engine balance. Whichever piston you choose you will probably need to balance the rotating assembly anyways, so that is not an issue or concern for you. Just know that it should be factored into the cost.

I'd love to talk specifics, just didn't want to scare people off with a thread starter that was even longer than it already is.

The engine is going in a daily commuter. Car is a '77 Volare, slant six/auto, manual everything, no A/C car. As rugged as the slant six has been, its cold weather manners are terrible, and the pathetic compression ratio is made even worse up here at a mile plus elevation. I figure it's making around 85hp up here, which is leaving a lot to be desired maneuvering in modern city traffic flow.

Powertrain upgrades going along with the engine:
-I already swapped to an 8.25" rear diff out of an an M-body. It's a 2.92 open diff currently, but will likely be getting a Cherokee 3.55 suregrip in the near future.
-Along with the V8, it's getting a Jeep 46RH trans swap (converted to 2WD). Trans is a basic rebuild with a Transgo shift kit and lockup neutral balanced converter. I believe the converter is rated for 1800-2000RPM.
-ZJ Jeep Grand Cherokee Magnum exhaust manifolds (reasonably good flow without the headaches of headers on a daily driver). Manifolds are a great fit on an F-body, but require a passenger side starter, hence the Jeep 46RH. Exhaust will be either 2.5" dual straight back, or maybe a Y into a single 3" to defeat the issues with the early F-body gas tank offset.
-ZJ Magnum Cooling and electrical system (radiator, factory trans cooler, trans lines, alternator, starter, cabling)
-I'll be keeping the manual steering and manual brakes, car will not be getting A/C. I will add a Taurus electric fan, as it's a simple upgrade, will relieve the drag of a clutch fan, and the Magnum charging system will easily support it.

And the engine:
Basic plan is for a pump-gas friendly higher-compression engine. Shooting for 9.5-10:1 to compensate for altitude. The car lives at 5500' elevation, and will see up to 10k occasionally, but rarely if ever less than 4000'. Winter temps can get well below 20F, sometimes in the single digits. Summer temps hover around 100F. It needs to start up and go in either environment.

Aside from the Magnum exhaust manifolds, I've chosen some Hughes-built Magnum EQ heads, a Weiand Action Plus intake, and an '85 Mopar quadrajet that I'll be rebuilding with a Cliff Ruggles kit and making appropriate mods to the idle fueling circuit and rod/jet combos. I've already converted the slant six to a GM HEI ignition system, and plan to carry this over to the V8 distributor.

I've got two engines available, an '88 318 and this '92 360. The 318 is low miles, and likely ready to throw in as is. If I go the 360 route, I'll be looking at a comparatively larger cam, and a B&M weighted flexplate to stay with the neutral balance 46RH converter. After a lot of research, I think the build goals would be well suited with a Lunati 20200714 cam (for the 318) Lunati 20200714 Lunati High Efficiency Camshafts | Summit Racing, or a 20200711 cam (for the 360) Lunati 20200711 Lunati Voodoo Camshafts | Summit Racing. The 318 would probably just need a basic refresh while it's out (oil pump, timing chain, gaskets, etc). The 360 has 184k miles on it, so I'm sure it's time for a complete rebuild. To me, that would entail decking the block, minimum overbore I can get away with, new rings/pistons, balanced rotating assembly, and all new bearings. Head gaskets are undetermined, but you are right, something with the appropriate bore diameter would maximize quench and combustion efficiency. I think I'd prefer a zero-decked motor with a ~0.040" headgasket, but a .027" gasket with a piston .013" in the hole, or a .050" gasket with the piston .010" out of the hole obviously accomplish the same result. Target piston to head clearance of .035-.045" to maximize combustion efficiency with the closed chamber Magnum heads.

The build is best described as max efficiency, not max effort, but I'd love to get over 350hp out of it for some decent fun in a 3200lb car. It shares a garage with a 700hp+ supercharged Holden that I finished up last year, so I've already got something for serious social work, and I'm trying to avoid going crazy with this one. I like to tinker with the unusual and I've a penchant for detail work, so my builds tend to reflect that. They also typically come together much greater than the sum of their parts.

I hope that sheds some more light on my goals. I'm in the serious planning phase right now, with a mid-spring build start date. I'm not above throwing the 318 in for the time being and taking my time developing the appropriate combo for the 360 with adequate machine work for a later exchange.

 

[cal30_sniper]

Also, that's good news on the Magnum connecting rods. If my engine shares that peculiarity, it makes some of the available piston options a bit easier to implement. Gotta love automotive transitional years.

 

[Bobzilla]

I think at this point, if you want as little over bore as possible, you need to get the 360 block measured out to see how worn it is. A 92 LA 360 probably had a TBI injection system and they often had minimal bore wear.

There are several different piston combinations available off the shelf that will get your desired compression just by moving around the numbers, with a little block decking here, or a little more or less gasket thickness there.

If the bores are straight enough with no ridge at the top, there is a forged Diamond piston available under part number 51400 that is 4.005" bore with a 9cc dish volume. That would land right at about 9.84 to 1 compressor with your 64 cc chamber, pistons .010" down, and a .030" thick 4.03" bore Cometic head gasket.

Diamond 51420 is the same 9cc dish with a 4.02" bore, gets to 9.9 to 1 compression with 4.05" bore Cometic gasket.

I looked at a lot of these pistons when I was shopping for mine, but my block was already .040" over, so I used a 4.04" IC742 piston, and with my 58cc Edelbrock heads I am coming in right at about 11 to 1 compression.

 

[AJ/FormS]

I'd really like to shoot for 9.5-10:1 static compression and .040" quench, for use of regular pump gas at 5500+ elevation.

At 5500ft, I seriously doubt that excess compression is gonna be your problem.
Scr is nothing but a tool to be used to achieve a certain pressure. A pressure known to to do what you want it to do.
Choose your cam first,calculate the Ica off the advertised duration, and plug your numbers into the Wallace calculator, and then work backwards. to your desired pressure/available fuel target.
For instance; your 360 at 5500, with a 340-type cam, will need 10.8 to achieve 155psi to run 87 with that .040 or less Q, in iron.. On 91 you can run it up to 11.0 or perhaps a lil higher.
Whereas, at 9.5 it will be a bit of a dog until around 3500 rpm.
With alloy heads, 180/185 is possible still on 87, and that might like an Scr of over 11.5
Now you got a ripper of an engine below 3500, but then you might run into a different problem, hi-speed detonation.
That 5500 ft is worth about a full Scr point over 1000ft. In other words a combo that runs nice at 9.8 at 1000, will need 10.8 at 5500.

 

[cal30_sniper]

At 5500ft, I seriously doubt that excess compression is gonna be your problem.
Scr is nothing but a tool to be used to achieve a certain pressure. A pressure known to to do what you want it to do.
Choose your cam first,calculate the Ica off the advertised duration, and plug your numbers into the Wallace calculator, and then work backwards. to your desired pressure/available fuel target.
For instance; your 360 at 5500, with a 340-type cam, will need 10.8 to achieve 155psi to run 87 with that .040 or less Q, in iron.. On 91 you can run it up to 11.0 or perhaps a lil higher.
Whereas, at 9.5 it will be a bit of a dog until around 3500 rpm.
With alloy heads, 180/185 is possible still on 87, and that might like an Scr of over 11.5
Now you got a ripper of an engine below 3500, but then you might run into a different problem, hi-speed detonation.
That 5500 ft is worth about a full Scr point over 1000ft. In other words a combo that runs nice at 9.8 at 1000, will need 10.8 at 5500.

I had some time this morning and played with dynamic compression and cranking pressure calculations. The cam I'd like to run in this motor (Lunati 20200711, advertised duration 270deg with a 106IC) should put me at 8.73DCR and 154PSI cranking pressure, assuming a 5cc Piston relief (KB107), 64cc head (nominal for EQ Mag, need to measure), and +.030 pistons set to a .040" quench. That sounds pretty solid for a street motor, and should get by on the 85-86 octane regular grade we have around here. I can always step up to a mid-grade gas if necessary, but running the cheap stuff for a daily is appealing to me. That would leave Premium fuel on the table if I need to venture to a lower altitude. I also run a GM HEI 5 pin ignition module that allows 5 degrees of timing retard when the 5th pin is grounded. I could get creative with that and a hobbs switch if I run into issues on the edge. Dehorning/polishing the combustion chambers and valve reliefs might help a little also.

Stepping up to a piston like the Icon742, with 9.6cc relief, would drop DCR to 8.3, and cranking PSI to 143. That would provide more margin for 85 octane, but is also leaving some performance on the table, especially as I travel up in altitude above 5500.

 

[AJ/FormS]

That would provide more margin

You got the idea!
Just remember; the calculator needs the Intake Closing Angle, calculated off tye ADVERTISED specs. Do NOT use the .050 specs!

Here is what it says right at the top of the calculator;
...............Dynamic Compression Ratio Calculator ...................
(Use seat to seat or advertised specs for Intake spec for best results)

For best results at altitude, To generate a smaller Ica for to trap more mixture in the chamber; I recommend a solid lifter cam, and on a tighter LSA, like 108. Do not try and use a HFT on a 115 ,lol.
The solids will let you run one size bigger cam at the ~same pressure as a HFT. As will a 108 over a 112. So by running a tight LSA, AND a solid, you can run a cam of about two sizes bigger off the after-lash advertised, than you could with a wide-LSA-hydro .
If you get the VP over 140, then you don't have to advance the cam. 140VP is plenty of VP; more just spins tires earlier and easier.

A hydraulic roller, IMO
IMO, is the wrong way to go , at altitude. They make power in the midrange all-rightee, but the Ica runs big very early, leaving you with a weak bottom end, that requires additional stall to overcome..
A solid roller, on the other hand, can be built to have very fast ramps. Faster than a Flat tappet even.

I must be a DA cuz I just can't find anything on the Lunati site anymore.

 

[cal30_sniper]

You got the idea!
Just remember; the calculator needs the Intake Closing Angle, calculated off tye ADVERTISED specs. Do NOT use the .050 specs!

Here is what it says right at the top of the calculator;
...............Dynamic Compression Ratio Calculator ...................
(Use seat to seat or advertised specs for Intake spec for best results)

For best results at altitude, To generate a smaller Ica for to trap more mixture in the chamber; I recommend a solid lifter cam, and on a tighter LSA, like 108. Do not try and use a HFT on a 115 ,lol.
The solids will let you run one size bigger cam at the ~same pressure as a HFT. As will a 108 over a 112. So by running a tight LSA, AND a solid, you can run a cam of about two sizes bigger off the after-lash advertised, than you could with a wide-LSA-hydro .
If you get the VP over 140, then you don't have to advance the cam. 140VP is plenty of VP; more just spins tires earlier and easier.

A hydraulic roller, IMO
IMO, is the wrong way to go , at altitude. They make power in the midrange all-rightee, but the Ica runs big very early, leaving you with a weak bottom end, that requires additional stall to overcome..
A solid roller, on the other hand, can be built to have very fast ramps. Faster than a Flat tappet even.

I must be a DA cuz I just can't find anything on the Lunati site anymore.

Their site went to crap a while back. I typically use summits website for the specs on their products, but their cam cards are particularly hard to find. Here’s Summits info for that cam:
Lunati 20200711 Lunati Voodoo Camshafts | Summit Racing

I’ve got the smaller 20200714 I bought on sale a while back while planning to build a roller 318. The 0714 is ground on a 106 intake centerline, which I assume is the same for the 0711. I did use the 270 advertised of the 0711 for my calculations, which gave me a Intake Closing Angle of 61 degrees ABDC.

I think I would like to get them to grind a custom one for me on a 108 or 110LSA, but I like the general specs of the cam.

I’m not sure I understand the whole difference in cylinder pressure, but I assume since the valve is closing faster, it’s valve curtain area is larger later in the closing event, which is bleeding excess cylinder pressure compared to a flat tappet with a lower valve lift at the same angle. I think that argument could be reversed though. A hydraulic roller will move more air than a flat tappet over the same duration numbers. In order to reach the same total airflow, a flat tappet would require longer duration, thus lowering cylinder pressure compared to a shorter duration roller moving the same volume of air.

 

[AJ/FormS]

The Wallace calculator has only one purpose,well two
to predict low rpm performance, and to be able to compare different combos.
The P/V numbers that it generates are directly comparable across all engine sizes, and you can work them as pecentages.
So if you have a slanty with a PV of 87 you know she's a dog. But if you have a 416 with a PV of 180, you know that's a hot engine. But you already knew that, you didn't need the PV to tell you that.
But the PVs in the middle , from 125 to 150 ish are gonna make or break your combo, and when you spend $5000 smackers on an engine, you want some performance for you trouble, am I right?

So since I have run three different cams in my engine, I can be confident in saying that I am very disappointed in a PV of less than 130; and that I really like a PV in the range of 140/150, and that more than 160,on the street is sorta killer crazy. I run a Commando 4-speed with 3.55s, and BFG 295s. .
Here are some stock PVs for Mopars at 700ft.

318 is ~113 @8.0,Ica of 48*...................... base
360 is ~123 @8.0,Ica of 52* .............. +8.84% over 318
340 is ~134 @10.5,Ica of 64*............. +7.94% over 360
My 367 at 930ft ~164 @10.95, Ica 60* +22.4% over 340
My 367 at 5500ft ~143VP ...... LOSS of 12.8% over 930 ft
440M ~146@10.5@Ica of 72*,Magnum circa 1968, FWI
Now, remember I said you can compare the low rpm performance of any engine to any engine by the percentage in PV difference. So I added another column so you can see it, under "base".

Remember this calculator has nothing to do with horsepower, which does not occur until a much higher rpm. This VP is a stall to 3000/3600 rpm number depending on what you are comparing it to.

Read about VP here
V/P Index Calculation

 

[Bronze Barracuda]

Hi, so getting back to the original question.
What is the deck height of a La Non Roller Bock (9.599)?
A LA Roller Block( )?
Magnum (9.585)?

My curiousity isn't about the final compression as .014 will not be relative to my build. But apparently may have some relevance in the valve train geometry.
I have 1974 LA heads on a 1990 block. I had the pushrod holes enlarged for pushrod clearance, and had the valve spring seats machined for new valve springs I am using the roller pushrods (which are shorter than pre 89 rods) I am trying to gather as much info as I can.
We are taking the block to get dynoed and my mechanic friend figures the deck height will be relevant, I might need different length pushrods.

So after all that rambling, what is the factory deck height of a 1990 360?

 

[Bobzilla]

Hi, so getting back to the original question.
What is the deck height of a La Non Roller Bock (9.599)?
A LA Roller Block( )?
Magnum (9.585)?

My curiousity isn't about the final compression as .014 will not be relative to my build. But apparently may have some relevance in the valve train geometry.
I have 1974 LA heads on a 1990 block. I had the pushrod holes enlarged for pushrod clearance, and had the valve spring seats machined for new valve springs I am using the roller pushrods (which are shorter than pre 89 rods) I am trying to gather as much info as I can.
We are taking the block to get dynoed and my mechanic friend figures the deck height will be relevant, I might need different length pushrods.

So after all that rambling, what is the factory deck height of a 1990 360?

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View attachment 1716265644

Deck height variance and pushrod length have very little to do with valvetrain geometry on an LA Mopar small block using factory rocker arms. The geometry is fixed since the shaft mounting and the size of the rocker arm do not change. The only thing a longer or shorter pushrod will do is set the plunger preload in a hydraulic lifter.

If the rocker arms are changed to any roller tipped rocker arm the geometry will be off and pushrod length will not fix it.

I do not know the actual deck height and the number is considered nominal anyway since factory tolerances allowed a fair amount of variance in the advertised number. This can be measured precisely by the machinist decking the block or roughly with a larger caliper while engine is apart. No real help since yours appears to be assembled already.

 

[Bronze Barracuda]

Deck height variance and pushrod length have very little to do with valvetrain geometry on an LA Mopar small block using factory rocker arms. The geometry is fixed since the shaft mounting and the size of the rocker arm do not change. The only thing a longer or shorter pushrod will do is set the plunger preload in a hydraulic lifter.

If the rocker arms are changed to any roller tipped rocker arm the geometry will be off and pushrod length will not fix it.

I do not know the actual deck height and the number is considered nominal anyway since factory tolerances allowed a fair amount of variance in the advertised number. This can be measured precisely by the machinist decking the block or roughly with a larger caliper while engine is apart. No real help since yours appears to be assembled already.

Thanks.
Yes mine is assembled, although at the very least I could remove the rocker covers. But I believe with the original rocker shafts and pushrods from the roller block everything should be ok.
I did Prime the engine and put a test pressure gauge on it was reading 65 PSI at 1600 RPM drill speed with 30 weight oil. So I'm thinking that should have pumped up the lifters I turned the crank until I had oil coming out of the rocker shafts on both sides and then turned everything back to zero I was able to rotate the pushrods when the Pistons were at top dead center on compression stroke however there didn't seem much play in the Rockers themselves. Just for consideration.

Curious what effect all machining and such may have.
As stated the block is a roller I'm assuming the deck is shorter than the LA block that had originally came on then the deck was milled .010
And the heads were milled .010 as well so with . 010 off the heads and the deck as well plus 014 shorter deck to begin with that's a total of 034
Not sure if the math is correct.
Thanks again for all the help.

 

[Bobzilla]

Some of the old LA engines came from the factory slightly higher than 9.6 deck, due to that manufacturing tolerance. Your numbers are valid on paper but without knowing actual measured specs your particular parts it is still a guess. If you remove a valve cover and find one of the rocker arms that can be pushed down on the pushrod side you can estimate how much more travel the lifter plunger has. This will only work on lifter that is not fully pumped up with oil and must done when that lifter is on the cam base circle. If you can push it down your pushrods will be fine for this application.

Most likely you are fine because there is a lot of lifter plunger travel available, the very reason the factory engines worked with so much deck height variance.

 

[Newbomb Turk]

Deck height variance and pushrod length have very little to do with valvetrain geometry on an LA Mopar small block using factory rocker arms. The geometry is fixed since the shaft mounting and the size of the rocker arm do not change. The only thing a longer or shorter pushrod will do is set the plunger preload in a hydraulic lifter.

If the rocker arms are changed to any roller tipped rocker arm the geometry will be off and pushrod length will not fix it.

I do not know the actual deck height and the number is considered nominal anyway since factory tolerances allowed a fair amount of variance in the advertised number. This can be measured precisely by the machinist decking the block or roughly with a larger caliper while engine is apart. No real help since yours appears to be assembled already.

Not exactly. As @Bewy pointed out above the adjuster length on solid lifters can and will affect geometry.

Because the adjuster isn’t parallel with the valve stem, making the pushrod shorter (causing the adjuster to be longer out off the bottom of the rocker) will reduce rocker ratio and that can and will affect geometry.

 

[Bobzilla]

Not exactly. As @Bewy pointed out above the adjuster length on solid lifters can and will affect geometry.

Because the adjuster isn’t parallel with the valve stem, making the pushrod shorter (causing the adjuster to be longer out off the bottom of the rocker) will reduce rocker ratio and that can and will affect geometry.

Totally agree on the adjustable stuff. I was responding to post 16 which reopened this thread, and I made the assumption of non-adjustable hydraulic setup based on his description of the heads and block he used. My bad.

 

[Bronze Barracuda]

Totally agree on the adjustable stuff. I was responding to post 16 which reopened this thread, and I made the assumption of non-adjustable hydraulic setup based on his description of the heads and block he used. My bad.

Yer correct, non adjustable