Domed pistons

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99dodge318La

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I am just wanting to get some feed back on these pistons before I pull the trigger and order them. The part number is
DODGE Keith Black KB Performance Piston and Ring Kits KB399KTM-020
With factory heads what compression ration would these get me up to. I have access to AV gas but I'd like to be able to run 93 if possible.

The engine is a 76 318.
 
Make sure to double and triple check piston to valve and piston to head clearance (on the quench pad as well as the dome). I have a set in my '68 318 with Indy/RHS heads. Calculated compression is close to 11.5:1, but I'd say it would measure closer to 11:1.
 
I am just wanting to get some feed back on these pistons before I pull the trigger and order them. The part number is
DODGE Keith Black KB Performance Piston and Ring Kits KB399KTM-020
With factory heads what compression ration would these get me up to. I have access to AV gas but I'd like to be able to run 93 if possible.

The engine is a 76 318.

Go back to the UEM home page, look the pistons back up in the KB catalog, in the right hand column of info there is a range listed of "possible" compression ratios based on chamber volume

There are too many variables to give an accurate "guess".......what's your deck height......what's your chamber volume.....What heads are you running, iron or aluminum.......what head gasket are you using??????????
These are "things" that affect static compression ratio, then there is the question of what cam shaft are you running, how is it degreed as that will affect dynamic compression ratio which generally is the real "tell" as to what octane gas you need to run..........if foggy memory serves me right, 180 psi cranking compression is the limit for pump gas......those smarter than me will chime in if I am wrong.
 
Appreciate the info guys. I wasn't expecting an exact number just a ball park figure. The reason I'm looking at buying these is so I can avoid having to ship the block and or heads to a machine shop to be decked. I don't have one ine local, and I assumed it would be cheaper to use these pistons then to try and find and use a machine shop I have no history with.

The motor is a 76 318 out of a M880 has been rebuilt within 2 years of me getting it. Crank has been turned and its been bored .020 over. Has summit brand headers has a stealth intake 650 eldelbrock and summit .441/.441 .218/.228 cam.....I'm wanting to step up and use a howards .510/.510 .247/.247 cam
 
Appreciate the info guys. I wasn't expecting an exact number just a ball park figure. The reason I'm looking at buying these is so I can avoid having to ship the block and or heads to a machine shop to be decked. I don't have one ine local, and I assumed it would be cheaper to use these pistons then to try and find and use a machine shop I have no history with.

The motor is a 76 318 out of a M880 has been rebuilt within 2 years of me getting it. Crank has been turned and its been bored .020 over. Has summit brand headers has a stealth intake 650 eldelbrock and summit .441/.441 .218/.228 cam.....I'm wanting to step up and use a howards .510/.510 .247/.247 cam

From KB's catalog......compression range is 12.2 with 57cc chamber down to 10.4 with a 68 cc chamber.........though as I have already stated, there are many more variables involved.

Don't forget to up grade springs with your new cam

You could up grade to a set of 360 heads
 
Is it true the cc measurements of the combustion chambers vary due to the manufacturing irregularities? I would think that would affect compression ratio. I suppose what I am trying to say is, you'd have to cc the heads to get an "accurate' Compression ratio spec.
 
From KB's catalog......compression range is 12.2 with 57cc chamber down to 10.4 with a 68 cc chamber.........though as I have already stated, there are many more variables involved.

Don't forget to up grade springs with your new cam

You could up grade to a set of 360 heads
From KB's catalog......compression range is 12.2 with 57cc chamber down to 10.4 with a 68 cc chamber.........though as I have already stated, there are many more variables involved.

Don't forget to up grade springs with your new cam

You could up grade to a set of 360 heads
I was looking for a set of 360 but everyone around where I'm at thinks there gold. For the price of them and then having them gone through and cleaned up I could buy a set of performer RPM heads. But since I can't swing that I just did a home port job followed 1 of the threads on here actually. And for valve spring I ordered
Howards Cams 98438-K34. Will I need to get the spring seat machined for these and If so is it possible to do myself?
 
It's funny when non Mopar guys think everything is gold. My neighbor ran up to me one day saying he had Mopar rallies he wanted to sell, they were wheels from a Dodge omni or K car LOL!
 
I was looking for a set of 360 but everyone around where I'm at thinks there gold. For the price of them and then having them gone through and cleaned up I could buy a set of performer RPM heads. But since I can't swing that I just did a home port job followed 1 of the threads on here actually. And for valve spring I ordered
Howards Cams 98438-K34. Will I need to get the spring seat machined for these and If so is it possible to do myself?

Instead of looking for some one who has a pair for sale, go to local junk yard and pull your own......do simple valve job, knurl the guides, at that point have the spring seats cut for springs.....it is not a home hobbiest type job, I can't see that equaling the cost of Eddy Performer RPM's.........OOTB Eddies need to be checked over, a cost you may have over looked
 
With factory heads what compression ration would these get me up to. I have access to AV gas but I'd like to be able to run 93 if possible.

The engine is a 76 318.
Appreciate the info guys. I wasn't expecting an exact number just a ball park figure. The reason I'm looking at buying these is so I can avoid having to ship the block and or heads to a machine shop to be decked. I don't have one ine local, and I assumed it would be cheaper to use these pistons then to try and find and use a machine shop I have no history with.

The motor is a 76 318 out of a M880 has been rebuilt within 2 years of me getting it. Crank has been turned and its been bored .020 over. Has summit brand headers has a stealth intake 650 eldelbrock and summit .441/.441 .218/.228 cam.....I'm wanting to step up and use a howards .510/.510 .247/.247 cam
I was looking for a set of 360 but everyone around where I'm at thinks there gold. For the price of them and then having them gone through and cleaned up I could buy a set of performer RPM heads. But since I can't swing that I just did a home port job followed 1 of the threads on here actually. And for valve spring I ordered
Howards Cams 98438-K34. Will I need to get the spring seat machined for these and If so is it possible to do myself?
I'm wanting to step up and use a howards .510/.510 .247/.247
Hang on a sec; is that 248@.050?
With stock 1976 iron heads?
Back up the bus; what are you trying to achieve? and what will this engine be going into?
It seems to me, on your budget, you are headed for disappointment.
 
Hang on a sec; is that 248@.050?
With stock 1976 iron heads?
Back up the bus; what are you trying to achieve? and what will this engine be going into?
It seems to me, on your budget, you are headed for disappointment.
It's going in a 99 swb 2wd 5speed truck. With 4.10 gears. I realize the heads aren't any where near ideal but they do have some port work done. And it's just going to be a week end toy to play with.
 
It's going in a 99 swb 2wd 5speed truck. With 4.10 gears. I realize the heads aren't any where near ideal but they do have some port work done. And it's just going to be a week end toy to play with.
What 5-speed?
Ima thinking the 5-speed is gonna be the weakest link.
Since you didn't say; Ima guessing that Howards is 248/248 advertised. Ima thinking that's gonna be the wrong cam for this application. But what do I know.
You got a link or picture of those pistons?
I think I know what you are trying to do, and with a 318LA, it's kindof hard.
 
What 5-speed?
Ima thinking the 5-speed is gonna be the weakest link.
Since you didn't say; Ima guessing that Howards is 248/248 advertised. Ima thinking that's gonna be the wrong cam for this application. But what do I know.
You got a link or picture of those pistons?
I think I know what you are trying to do, and with a 318LA, it's kindof hard.
Sorry the duration is .248 @.050 the advertised duration I believe is. 308 id have to look at the cam card to be exact and its the NV4500 . Here's a link to the pistons KB Pistons Engine Piston Kit KB399KTM.020; 3.930" Bore 6.0cc Dome for Chrysler 318 "LA" Mopar
 
KBPWKB399.jpg


The catalog says 11/1 with 64cc heads.What they don't say is that at 3.930 bore, to get 11/1 requires a total chamber volume of 65.896cc.
The cd on those 299s is 1.81, so from the piston top to the deck, not including the dome, will be ~ .0095 if the deck is 9.600;
that's 1.9cc.
the dome is -6cc
gasket (.039) is 8.8cc
and the heads could be up to 72cc for smog heads.
Total estimate is 76.7, and if correct, that will be 9.59Scr
To get to 11, the heads would have to be 61.2cc

But hang on, that's a mighty big cam for a 318, and the Ica is 80* Installed at +4, assuming an LSA of 110. And with just 11/1 Scr, the pressure is predicted to be just 149psi @500ft elevation, and the low rpm performance will be pretty doggie. It's a good thing you chose 4.10s.
Furthermore, the powerpeak of that cam is gonna be up around 5600 rpm or so. Is that what you figured? Is that what you want?

IIRC the NV4500 has ratios of 3.49-2.14-1.38-1.00-.73od Those are pretty good, but the splits are ; .61-.645-.725-.73
That means that whatever you rev your engine to, the Rs will fall to those percents at the shifts. So lets say you choose a shift of 5800. then the rpms will drop to: 3540-3740-4200-4230
With a power peak of 5600, the torque peak is likely to come in at around 4300, so for low ET, you need your drops to come in around there or higher on every shift. But the first two shifts are way off the mark. and by top of third when she finally drops in on the cam, your speed is already 85mph, and now you gotta buck the wind.with a somewhat lazy combo (irrespective now of the 4.10s, which can't help anymore.)
So what's wrong?
Well firstly; those pistons are a great choice. IDK what your head-chamber CCs will come in at, but this combo can make almost any chambers work.
But I don't like that cam; it is just too big. You need a cam to match the powerband dictated by the transmission. and a rearend to put the power where yo need it to be. While 4.10 x.73= 2.99 cruiser gear, those 4.10s are the wrong rear for at least the first two gears.
For a streeter, 3.55s are what you want; here's why; 3.55s will get you 60 mph revving 5500 in 2.14 second gear with 28" tires. So you got a bit of rpm left over. Shifting at 5500 means your powerpeak can be around 5200, and that dictates a cam of around 230@.050 or 268 to 276 advertised, on a hydro. This is still plenty big for a 318 so lets make it a solid lifter cam of 268* at .012 valve lift after lashing. And lets make it on a 112 to cover that powerband. So in at 112* I get an Ica of 66*, and now your pressure at 11/1 jumps up to 177psi which is too much for iron heads, but at 9.59 is back to 148, but now with a much stronger bottom end.
But lets get it up to 8.0Dcr; with an Scr of 10.2, and Ica of 66*, the math spits out 160 psi, to run best pumpgas at WOT. This is the best bottom end you will get on this combo, and it is over 30% stronger than the Howards cam at 11/1.
But to be clear, the 230 cam will not make the absolute power that the Howards 248 will. But I can guarantee you that the 230*cam will be WAAAAAAAAAY more fun to drive, and will probably get you to 60 mph quicker.
So how to get to 10.2 should be your next question.
At 3.93 x3.315 the required total chamber volume is no more than 71.62cc.
Subtracting 1.89 -6 +8.8=4.7, leaves 66.92cc for the heads. How easy is that.
Hang on, we're not done yet. You the piston fitter, have to make sure those 299s actually fit in the chambers without hitting anything. And if you have to machine them, then the math goes off; your head chambers will have to be adjusted for that.
BTW,
>I like your idea of not decking the block, so long as it measures useable as-is.. and so long as the 299s are not too much deeper in the holes than the math indicates. If I was building a 318, I think I would give those a try, even if I had to mill them to fit.
>I tried the .028 Gaskets but they squeezed out on me (alloy heads); others say they are fine.
> I have had no trouble with the FelPro .039s, at up to 185psi, ( the highest I have run).
> In my streeter, I have run a 248@.050 cam in my 367 (at over 185psi), and I couldn't wait to get rid of it. I replaced it right away with a 223/230/110 and absolutely loved it. When that 223 gave up, I replaced it, with a 230/237/110 and was immediately disappointed. She gave up a lotta bottom-end, and I had to really scramble to get it back. My solution was a lower gear in the trans, and a lot of tuning; but really, the shine was off the apple. I am waiting for it to die, so I can replace it, but since 2004 it just keeps on going, and going, and going...

Oh yeah, just a reminder, my gearing math was based on 28" tires, and the transmission ratios are from memory............ so you know; garbage in garbage out; but the points are the same ;
1) IMO that Howards is way too much for a street 318, and
2) IMO you need to better match your cam to whatever the gear splits that your NV4500 actually has.and
3) manual transmissions are way more fussy than automatics, cuz the tires are married to the engine by the clutch; there is no torque-multiplying fluid-coupler to help.
4) to be clear, the NV 4500 ratios, if I remember them right, are great for DRAGRACING. And the 3-4 split is great as well. But the first two splits are set up for a low-rpm small engine making lots of torque....... like a 5.2Magnum; which has a well-matched cam, and tuning that you cannot duplicate with an LA, unless maybe you put a tunnel-ram on it,lol. Or maybe a turbo.......
 
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