Rowdy and Mean 318 build

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MopaR&D

MopaR&D

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A while ago I posted a thread about my 360 having broken in my '70 Duster (busted piston). Well now I'm getting ready to send the 318 block originally out of the car to the machine shop for prepping. The bottom end will be pretty straightforward; zero-decked block, possible overbore, hone with torque plates, factory crank and rods, full rotating assembly balance. I'll be putting in a set of KB167s; even though the piston in my 360 that broke was also a KB Hyper I understand it wasn't the piston's fault it broke (too much low-RPM cylinder pressure and detonation). Question: are my 360 connecting rods any stronger than the 318 ones?

I plan to reuse the stock Magnum heads that were on my 360, depending on how much extra I can spend I may take them to a local head porter and have them checked out for damage and possibly a valve job. I may even try my hand at a light porting job if I can find a junk head to practice on first. Point being I've read that stock Magnums support up to 400 HP and I want to get my 318 as close to that level as possible. I originally thought even with my Hughes retainers the max valve lift could only be around .525"; after checking, double and then triple-checking I found with a set of calipers that the distance between the bottom of the retainer (actually the valve locks as they poke out the bottom a bit) was a smidge over .560"!! That means I can safely run a much bigger cam with these heads than I thought but I know Magnums tend to "stall" in flow when they get much over .500" lift.

So that leaves cam and valvetrain... I had the smaller 256/262 adv. duration Lunati Voodoo HFT in my 360 and it was a torque monster. The rest of the drivetrain will consist of a 2600-stall converter in front of my 904 and 3.55 gears in the 8 3/4 rear end. I'm thinking of using the 268/276 cam which is advertised to have a power range of 1800-6200 RPM but with the 1.6 rockers the lift gets bumped up to .527" intake and .547" exhaust which may 'stretch' the power band just a bit? I'm also going to take the time to get the pushrod length spot-on and I plan to use Crower (best manufacturing tolerances from my 'research') Cam-Saver lifters (extra cam lobe oiling just for reliability) so I can rev this thing solidly to 6500 RPM on a regular basis.

I'll be reusing the RPM Air-Gap intake off my 360 as well as the Hedman shorty headers going into 2 1/4" head pipes (biggest I could fit around the steering/t-bars) and 2 1/2" exhaust with X-pipe after that. I'm not sure what to do for carburetion though; my 360 had a 750 cfm Street Demon carb that was just a hair too big on the primary side and that engine pulled a LOT of vacuum which made it difficult to get the transitional response just right; it idled at 900 RPM in gear with the throttle blades closed farther than I would have preferred. The 2.94 rear gears with 28" tires and factory 2100-stall converter definitely didn't help. You think it'll be too big for this smaller-but-much-higher HP engine? I'm tempted to just get a 650 vac. secondary Holley as I don't need the "Street" aspect of the Demon carb anymore.

More ideas to come along with progress pics; hopefully when I get paid at the end of the month I'll have enough reserve cash to drop the block, crank and rods at the machine shop to get checked out and not be afraid I'll be out of money when it's all done and ready.
 
Same rods

If you plan on turning 6500 you need to do some oiling mods so that the rod bearings will survive.
And you will need some serious valve springs. With that comes a special break-in procedure and the battle for just the right amount of ZDDP so the lifters will live. You're gonna need a lot more cam than the 268 to hit 400hp, and that means a lot more rpm than 6500.And a lot more compression.And a lot more stall. And then a lot more gear.
But the 268 is a fun cam, when the compression,the TC, and the rear gear, support it. So are you willing to give up the 400 target?
The 268 in a teener will power peak at about 5400rpm, and with a 904 will want to be shifted at about 6500 into second, to drop in at 3850. You will need the oiling mods. This cam will not be satisfied with the 2600TC unless the compression is pumped up. Even then it will be iffy.
10.0 will be your Scr target, for a Dcr of [email protected] will need to get your TOTAL chamber volume down to 73.2cc.
She will want 3.91s with that 2600TC. Probably 3.73s with a 2800TC and over 3000 with 3.55s.Each of these gears is about 5% apart, and so you will need 5% more torque to happily run each lower gear.
DO-NOT-OMIT the oiling mods, unless you have deep pockets for a do-over.
Forget 400hp with a teener, it's just too high/expensive a target. This 268 will be big fun when properly supported. If not supported it will be a big fat do-over.

If you really want 400hp,rebuild that 360. Same money gets you 13% more everything. That 400hp still needs rpm, but now it is doable. Just remember you don't get it until about 5800rpm, so with 3.55s, that is about 54mph. The cam will now want to be about a 284*, and will want to be shifted at 6800 with that 904,going into 2nd, to drop in at 4000. The 360 will want lots of compression for that cam, but it's a bit easier to get. And of course the oiling mods are still mandatory.
You can go down 1 or even 2 cam sizes ,and 3.55s are just right.With enough compression the 2600TC will hang in there.
 
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early 318s had thinner and lighter rods than 360s. around 1972+ the 318 rods are the same as 360s. 1964-71 273/318 light rod, floating pin - 1618699.
 
AJ/FormS said:
Same rods

If you plan on turning 6500 you need to do some oiling mods so that the rod bearings will survive.
And you will need some serious valve springs. With that comes a special break-in procedure and the battle for just the right amount of ZDDP so the lifters will live. You're gonna need a lot more cam than the 268 to hit 400hp, and that means a lot more rpm than 6500.And a lot more compression.And a lot more stall. And then a lot more gear.
But the 268 is a fun cam, when the compression,the TC, and the rear gear, support it. So are you willing to give up the 400 target?
The 268 in a teener will power peak at about 5400rpm, and with a 904 will want to be shifted at about 6500 into second, to drop in at 3850. You will need the oiling mods. This cam will not be satisfied with the 2600TC unless the compression is pumped up. Even then it will be iffy.
10.0 will be your Scr target, for a Dcr of [email protected] will need to get your TOTAL chamber volume down to 73.2cc.
She will want 3.91s with that 2600TC. Probably 3.73s with a 2800TC and over 3000 with 3.55s.Each of these gears is about 5% apart, and so you will need 5% more torque to happily run each lower gear.
DO-NOT-OMIT the oiling mods, unless you have deep pockets for a do-over.
Forget 400hp with a teener, it's just too high a target. This 268 will be big fun when properly supported. If not supported it will be a big fat do-over.

If you really want 400hp,rebuild that 360. Same money gets you 13% more everything. That 400hp still needs rpm, but now it is doable. Just remember you don't get it until 5800rpm, so with 3.55s, that is about 54mph. The cam will now want to be about a 284*, and will want to be shifted at 6800 with that 904,going into 2nd, to drop in at 4000. The 360 will want lots of compression for that cam, but it's a bit easier to get. And of course the oiling mods are still mandatory.
You can go down 1 or even 2 cam sizes ,and 3.55s are just right.With enough compression the 2600TC will hang in there.
Click to expand...



Did we not read the 340 build just posted on this site? You are telling a guy he will have to RPM the crap out of something when he does not need to.

He has the same stroke as a 340 with a smaller bore. It will make less HP but not need more RPM.
 
yellow rose said:
Did we not read the 340 build just posted on this site? You are telling a guy he will have to RPM the crap out of something when he does not need to.

He has the same stroke as a 340 with a smaller bore. It will make less HP but not need more RPM.
Click to expand...

Not only that but I've seen numerous posts where guys put a Comp XE268 or similar cam in a mostly stock (but healthy) 318 with tall gears and stock converter and it ran better than expected when everyone (including myself) was saying it would for sure be a total dog off the line. 400 HP isn't the target, getting the most out of what I have IS. I'll look into those oiling mods btw.
 
yellow rose said:
Did we not read the 340 build just posted on this site? You are telling a guy he will have to RPM the crap out of something when he does not need to.

He has the same stroke as a 340 with a smaller bore. It will make less HP but not need more RPM.
Click to expand...
he think this guy doing it wrong im fixin to really mess up,..530ish lift in a 318 but sposed be all done by 6000 rpm...with 3000 converter and 3:91s im hoping it works..depending how heads turn out...time will tell!
 
Your tune was way off on the 262* equipped 360. Mostly I think The T-port sync was off. And the 900 idle IN-GEAR!!proves it. It shoulda been happy at 750, maybe less. With a 4speed it woulda been happy at 650/700.
The transition was hard cuz mostly there wasn't any. I bet the idle-timing was 18* or more and the mixture screws were kindof dead. If that is true, then the sync was off for sure.
The 750 is almost too small for a 360. It will be just right on a 318 with a 268 cam. The primaries will work just fine on any SBM. The smaller the better.
Forget 2.94s with any cam much over stock.

But back up the bus.
Something is going on here. If you were happy with the 360,and it's 262 cam and the 2.94s, then why the sudden desire for 400 hp. I mean that 262 mightof made 330, but it didn't arrive until 54 mph with those 2.94s
Mr.D3
You need gears before anything. If you like, put all the 360 stuff on that teener including the 262 cam.Get the compression up. Then get you some gears in the range of 3.23s to 3.91s,the higher the better, if hiway travel is not important. I guarantee you that teener in an A-body, with 3.91s and that 2600TC will be good for ear-to-ear grins! You will want to get the static CR up to 9.8, for a Dcr of 8.2@165psi This is doable. The power will be down some 13%,compared to the 360, but the performance increase with 3.91s will be some 33%, for a net improvement over the 360, of plus 20%. Plus 20% is H-U-G-E !
Your new power peak with 3.91s will arrive at around 42 mph, NOT 54 as it did with the 360.
 
yellow rose said:
Did we not read the 340 build just posted on this site? You are telling a guy he will have to RPM the crap out of something when he does not need to.

He has the same stroke as a 340 with a smaller bore. It will make less HP but not need more RPM.
Click to expand...

You lost me. The OP is the one who brought up the 6500rpm. It's right there at the bottom of paragraph 3.
so I can rev this thing solidly to 6500 RPM on a regular basis.
Click to expand...
And the title of the thread is
Rowdy and Mean 318
Click to expand...
.
And;
Point being I've read that stock Magnums support up to 400 HP and I want to get my 318 as close to that level as possible.
Click to expand...
The only way to make power is to process air. If we are limited to a certain head, then Rpm is the only other option. And the same cam in a smaller engine power peaks at a higher rpm. And if you are stuck with a shift split of 59%, then the shift rpm must of necessity increase.
Where did I goof?
 
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AJ/FormS said:
Your tune was way off on the 262* equipped 360. Mostly I think The T-port sync was off. And the 900 idle IN-GEAR!!proves it. It shoulda been happy at 750, maybe less. With a 4speed it woulda been happy at 650/700.
The transition was hard cuz mostly there wasn't any. I bet the idle-timing was 18* or more and the mixture screws were kindof dead. If that is true, then the sync was off for sure.
The 750 is almost too small for a 360. It will be just right on a 318 with a 268 cam. The primaries will work just fine on any SBM. The smaller the better.
Forget 2.94s with any cam much over stock.

But back up the bus.
Something is going on here. If you were happy with the 360,and it's 262 cam and the 2.94s, then why the sudden desire for 400 hp. I mean that 262 mightof made 330, but it didn't arrive until 54 mph with those 2.94s
Mr.D3
You need gears before anything. If you like, put all the 360 stuff on that teener including the 262 cam.Get the compression up. Then get you some gears in the range of 3.23s to 3.91s,the higher the better, if hiway travel is not important. I guarantee you that teener in an A-body, with 3.91s and that 2600TC will be good for ear-to-ear grins! You will want to get the static CR up to 9.8, for a Dcr of 8.2@165psi This is doable. The power will be down some 13%,compared to the 360, but the performance increase with 3.91s will be some 33%, for a net improvement over the 360, of plus 20%. Plus 20% is H-U-G-E !
Your new power peak with 3.91s will arrive at around 42 mph, NOT 54 as it did with the 360.
Click to expand...

I appreciate the input as always but just to clear a few things up... first off that cam was 256* advertised duration on the intake side, 262* was on the exhaust. I wasn't satisfied with the way that 360 ran, brutal torque off idle but it ran out of steam by 5200 RPM. Second regarding tuning, multiple times I reduced the overall timing due to pinging from the high cylinder pressure and last it was running it had only 8 degrees of base timing advance, nowhere near 18* like you guessed. Lastly I really really don't want to run any deeper gears than 3.55s because this will ultimately be a road race car, I'm not concerned with having a cannon-like holeshot for ultimate 60' times at the drag strip. And regarding the transition circuit, the idle mixture screws were actually SO sensitive that I was constantly adjusting them 1/16th of a turn or less at a time because even a 20*F change in temp made it idle noticeably more rich or lean. The only way I could lower the idle speed to open up the throttle plates more was to take out even more timing and with it at only 8* idle timing it had noticeably high underhood temps and I could tell the headers and exhaust were hotter than they should have been.
 
AJ/FormS said:
OH boy, I should go back to school.
Did you ever check the cylinder pressure?
Click to expand...

LOL pretty sure these problems couldn't be solved with formal education, that thing just ran odd I never could figure it out. I did check the cranking compression, IIRC averaged out to 170 psi at 5000' above sea level. SHOULD have been OK but it definitely wasn't, even with that conservative timing and 91-octane premium.
 
consider a cast crank 4.00" stroke combo, will work good with parts you have, 6500 rpm no problem, at 1 hp per cube, well tuned 400 ish hp. and more tq. i'm going this route soon for my 87 318 w150 truck.
 
MOPEkidD-3 said:
A while ago I posted a thread about my 360 having broken in my '70 Duster (busted piston). Well now I'm getting ready to send the 318 block originally out of the car to the machine shop for prepping. The bottom end will be pretty straightforward; zero-decked block, possible overbore, hone with torque plates, factory crank and rods, full rotating assembly balance. I'll be putting in a set of KB167s; even though the piston in my 360 that broke was also a KB Hyper I understand it wasn't the piston's fault it broke (too much low-RPM cylinder pressure and detonation). Question: are my 360 connecting rods any stronger than the 318 ones?

I plan to reuse the stock Magnum heads that were on my 360, depending on how much extra I can spend I may take them to a local head porter and have them checked out for damage and possibly a valve job. I may even try my hand at a light porting job if I can find a junk head to practice on first. Point being I've read that stock Magnums support up to 400 HP and I want to get my 318 as close to that level as possible. I originally thought even with my Hughes retainers the max valve lift could only be around .525"; after checking, double and then triple-checking I found with a set of calipers that the distance between the bottom of the retainer (actually the valve locks as they poke out the bottom a bit) was a smidge over .560"!! That means I can safely run a much bigger cam with these heads than I thought but I know Magnums tend to "stall" in flow when they get much over .500" lift.

So that leaves cam and valvetrain... I had the smaller 256/262 adv. duration Lunati Voodoo HFT in my 360 and it was a torque monster. The rest of the drivetrain will consist of a 2600-stall converter in front of my 904 and 3.55 gears in the 8 3/4 rear end. I'm thinking of using the 268/276 cam which is advertised to have a power range of 1800-6200 RPM but with the 1.6 rockers the lift gets bumped up to .527" intake and .547" exhaust which may 'stretch' the power band just a bit? I'm also going to take the time to get the pushrod length spot-on and I plan to use Crower (best manufacturing tolerances from my 'research') Cam-Saver lifters (extra cam lobe oiling just for reliability) so I can rev this thing solidly to 6500 RPM on a regular basis.

I'll be reusing the RPM Air-Gap intake off my 360 as well as the Hedman shorty headers going into 2 1/4" head pipes (biggest I could fit around the steering/t-bars) and 2 1/2" exhaust with X-pipe after that. I'm not sure what to do for carburetion though; my 360 had a 750 cfm Street Demon carb that was just a hair too big on the primary side and that engine pulled a LOT of vacuum which made it difficult to get the transitional response just right; it idled at 900 RPM in gear with the throttle blades closed farther than I would have preferred. The 2.94 rear gears with 28" tires and factory 2100-stall converter definitely didn't help. You think it'll be too big for this smaller-but-much-higher HP engine? I'm tempted to just get a 650 vac. secondary Holley as I don't need the "Street" aspect of the Demon carb anymore.

More ideas to come along with progress pics; hopefully when I get paid at the end of the month I'll have enough reserve cash to drop the block, crank and rods at the machine shop to get checked out and not be afraid I'll be out of money when it's all done and ready.
Click to expand...
I like it,Khalid.... My personal favorite cam, wide lobe centers ,(112...) big exhaust split, mild lifts .480" ish intake ,495 ish on exhaust.... .050 duration, 223 intake/ 233-4 on exhaust..) I have run two of these personally, seen 4 of them run low 13's - deep 12's in 360's.... I wouldn't hesitate a second, in a properly quenched 318....
Give this a read...

https://www.google.com/url?sa=t&sou...fsnM9ZW4AGS8jz3jA&sig2=tZsnlSeK7bxf3nyCW8Icog
 
MOPEkidD-3 said:
LOL pretty sure these problems couldn't be solved with formal education, that thing just ran odd I never could figure it out. I did check the cranking compression, IIRC averaged out to 170 psi at 5000' above sea level. SHOULD have been OK but it definitely wasn't, even with that conservative timing and 91-octane premium.
Click to expand...
Yeah that is on the high edge.... just the dense air with no humidity on a cool dry day could do that in. A wider LSA cam would have killed of a bit of cylinder pressure for you.... but I think you were at 112 with the Voodoo. So 114.... or some cam retard.

I think you are on the right track with the KB167's and zero decking. For road racing, you are gonna need to emphasize a wider torque band that starts well down in the 2000's range. Forget the HP numbers, and work on keeping a wide torque band. You simply can't optimize a narrow torque band for ALL of the different corners that you are going to encounter by messing with TC stall speeds on a road circuit. I would also rethink the stall speed that you have chosen; you are gonna have corners where you need to feather the throttle to get juuuuust the right amount of torque to the rear wheels. If that RPM just so happens to be where the TC is going in and out of stall, it is gonna be hard to feather the throttle properly.

Are you going to change to a 4 or 5 speed? Auto's in road race and rally suck in a certain way (beyond the TC stall speed issue above): you have to use the engine torque when accelerating AND the reverse torque when decelerating, to set the car's weight to front or rear for best handling in certain corners. Auto's like the 727/904 don't have any appreciable reverse torque ability. Plus there will always be corners where the auto gears just won't be right; a 4 or 5 speed fixes that right up, and the closer the ratios, the better..
 
Don't let anybody talk you out of the KB167 318. My teen with XE268 and 302 heads had just as much balls as the 5.9 Magnum just not as much torque which just means more spinning the tires on take off or breaking em loose punching the throttle. I think the 318 actually pulled harder at higher RPMs. Also I did not have to deck the block to get good quench with closed chamber heads. I'm not saying you wouldn't have to but that in my case I did not.
 
MOPEkidD-3 said:
A while ago I posted a thread about my 360 having broken in my '70 Duster (busted piston). 318 block:
The bottom end will be pretty straightforward;
zero-decked block,
possible overbore,
hone with torque plates,
factory crank and rods, full rotating assembly balance.
I'll be putting in a set of KB167s; even though the piston in my 360 that broke was also a KB Hyper I understand it wasn't the piston's fault it broke (too much low-RPM cylinder pressure and detonation).

Question: are my 360 connecting rods any stronger than the 318 ones?

I plan to reuse the stock Magnum heads that were on my 360, depending on how much extra I can spend I may take them to a local head porter and have them checked out for damage and possibly a valve job. I may even try my hand at a light porting job if I can find a junk head to practice on first.

Point being I've read that stock Magnums support up to 400 HP and I want to get my 318 as close to that level as possible. I originally thought even with my Hughes retainers the max valve lift could only be around .525"; after checking, double and then triple-checking I found with a set of calipers that the distance between the bottom of the retainer (actually the valve locks as they poke out the bottom a bit) was a smidge over .560"!! That means I can safely run a much bigger cam with these heads than I thought but I know Magnums tend to "stall" in flow when they get much over .500" lift.

So that leaves cam and valvetrain... I had the smaller 256/262 adv. duration Lunati Voodoo HFT in my 360 and it was a torque monster. The rest of the drivetrain will consist of a
2600-stall converter in front of my
904 and 3.55 gears in the 8 3/4 rear end. I'm thinking of using the 268/276 cam which is advertised to have a power range of 1800-6200 RPM but with the 1.6 rockers the lift gets bumped up to .527" intake and .547" exhaust which may 'stretch' the power band just a bit?

I'm also going to take the time to get the pushrod length spot-on and I plan to use Crower (best manufacturing tolerances from my 'research') Cam-Saver lifters (extra cam lobe oiling just for reliability) so I can rev this thing solidly to 6500 RPM on a regular basis.

I'll be reusing the RPM Air-Gap intake off my 360 as well as the Hedman shorty headers going into 2 1/4" head pipes (biggest I could fit around the steering/t-bars) and 2 1/2" exhaust with X-pipe after that. I'm not sure what to do for carburetion though;

my 360 had a 750 cfm Street Demon carb that was just a hair too big on the primary side and that engine pulled a LOT of vacuum which made it difficult to get the transitional response just right; it idled at 900 RPM in gear with the throttle blades closed farther than I would have preferred.

The 2.94 rear gears with 28" tires and factory 2100-stall converter definitely didn't help. You think it'll be too big for this smaller-but-much-higher HP engine? I'm tempted to just get a 650 vac. secondary Holley as I don't need the "Street" aspect of the Demon carb anymore.

More ideas to come along with progress pics; hopefully when I get paid at the end of the month I'll have enough reserve cash to drop the block, crank and rods at the machine shop to get checked out and not be afraid I'll be out of money when it's all done and ready.
Click to expand...

Wow, that was a lot.
(Even more so before I finish coffee this morning! LOL! )

If I'm reading this right, your future engine build and drive train line up will be;
318 cid + overbore
KB167 @ 0-deck on 360 rods
Magnum heads with extra clearance retainers from Hughesengines
XE268H W/cam saved lifters
EDM oiling hole for extra cam oil lubrication.
Edel. RPM intake
Shorty headers into 2-1/4 - 2-1/2 exhaust

904/2600 stall- 8-3/4 W/3.55's

IMO, this is a good combo.
You choice on carbs, but, I think the 750 will be OK up top. The Demon "Street" moniker is a well used and correct label for the carb, and as well suited to the build you have going on above.
You are WELL in the "Street" perameters.

Your combo is an excellent typical kind of street build. Not is not just a few hop up parts thrown on an engine. It is not a serious big breather stomping the streets. This build is 100% American street smarts.

"Do not "use a lower stall converter, (lower than 2400) a tall (2.96) gear &/or a 28 inch tall tire with the Hwy. gears.

"Do" have the head checked out on and off the engine for clearance.
(Spring retainer & valve to piston.) While porting would be nice, IF the pockets are shallow, don't fret and over think this. Just run it! You can save for head porting later.
(And IMO, a better head is a good idea, IF your so inclined. EQ's.)
 
MOPEkidD-3 said:
LOL pretty sure these problems couldn't be solved with formal education, that thing just ran odd I never could figure it out. I did check the cranking compression, IIRC averaged out to 170 psi at 5000' above sea level. SHOULD have been OK but it definitely wasn't, even with that conservative timing and 91-octane premium.
Click to expand...

This is what's missing in the equation. This isn't a sea level or low altitude car.
170 psi is a bit of compression for 5000 feet. ok let me rephrase that. 170 psi at sea level would be around 130-140 at 5000 feet. the 170 psi, was it in the 360?
Did you run vac. advance can on your motor that killed a piston?
Also? you were running a 360 and now you're building a 318? Why?
 
I didn't go with the hypers for exactly the reason why you are building a new motor...but I had my own problems. I went with Icon forged 1.81 CH. Decked to 0.00 the piston set .002 in the hole. My heads are Indys W/ .192-.162 valves and 62 cc chambers. Nothing done to them other than springs to support the xe268h and stock stamped rockers. Some like Aluminum heads...I don't so I didn't. CR is 9.8 now, was 9.5. at the dyno run and wasn't tuned right. With 3.23's and 2200 stall it runs 12.93 and 104 1/4 mile. Broke em loose and spun it up to 7000+ on damp pavement and galled a wrist pin. No damage other than the wrist pin. New rod and piston and it's a screamer again with a much better tune after seeking advice from those here. Since the 318 piston episode I have decided to build a 408...just waiting for the heads from Brian @ IMM and then the teener is coming out and the 408 is going in with 3.55's. Quench is your friend to help stave off some detonation. It did detonate a bit when I ran 89 ethanol free on the street...octane boost fixed that. now I run 92 e10 w/ no detonation... at the track I run 98. Here's my dyno chart at 9.5 cr and a poor tune.
dyno-sheet-jpg.1714992435

Prolly somewhere between 330 and 350 hp to the crank. It's fun like AJ says but I want more...=408. The 408's gettin Mahle forged slugs this time.
 
I haven't read all your previous posts. Why not repair the 360? Did you ruin the block? IMO with the intention of turning 6500 rpm, you should be using forged pistons. Probably a solid cam too. I don't quite understand peoples love for hyper pistons. Sure, you can fit them tighter. Big deal. A forged piston, when abused, will deform before it outright fails. A cast/hyper piston will break into pieces.
 
Hypers can be sure a ton lighter than forged units (but not always). Takes stress off the rods and crank.

- I've run both in the same engine on 14-15 psi turbo'd; both worked out fine and I put many hundreds of race miles on each.
- Caution and tuning to avoid detonation made them both work to around 1.75 HP per ci. (Knock detectors are a BIG help!)
- And I have destroyed forged pistons in even a low compression engine when the ignition advance got all whacked out.
 
forphorty said:
I haven't read all your previous posts. Why not repair the 360? Did you ruin the block? IMO with the intention of turning 6500 rpm, you should be using forged pistons. Probably a solid cam too. I don't quite understand peoples love for hyper pistons. Sure, you can fit them tighter. Big deal. A forged piston, when abused, will deform before it outright fails. A cast/hyper piston will break into pieces.
Click to expand...
"Big deal?" Why yes it is! A tighter fit piston has a chance at less blow by due to less available open area around the circumference of the piston. Which also helps with less piston rock. That helps with piston skirts and cylinder walls suffering less wear and damage.

Normally lighter and still a strong piston, a properly timed & tuned engine will not damage these slugs. Abuse will. Any piston will suffer if abused in that manor.

While the performance ceiling is limited to mostly a NA engine, there are people hitting it with NO2 or a supercharger. I haven't heard of both at the same time though.

I have previously run my hypers to 7K, no problem!

A forged slug is the slug of choice for big power. His build is far far far from that.

Food for thought .... current factory cars are making use of Hyper slugs and making some very good power.
 
MOPEkidD-3 said:
LOL pretty sure these problems couldn't be solved with formal education, that thing just ran odd I never could figure it out. I did check the cranking compression, IIRC averaged out to 170 psi at 5000' above sea level. SHOULD have been OK but it definitely wasn't, even with that conservative timing and 91-octane premium.
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I have to agree, Somehow that engine was the exception to the rule
 
A little extra piston to wall clearance is not a big deal to me. My ole forged TRWs have been bouncing around in my 440 for 25 years. Yes, it does have a little blowby now. Still runs fine and doesn't foul plugs. Again, been together for 25 years. Lots of miles in a 68 Satellite. Was a daily driver but currently shares 50/50 duty with a 73 RR. I don't own a modern car, never have. I am not opposed to a cast type piston . I have cast pistons in the bargain basement 400 in my RR. The OP mentioned square decking, torque plating, etc. Personally, if I was was spending a lot of money on quality machine work, I would opt to spend a little more on a stronger piston.
 
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