440 engine-Six Pack pistons vs lightweight pistons -all things the same...

[minnesota guy]

Question to those who have built both motors...440 motor with 6 pack pistons and factory non 6 pack rods vs. the same type motor with same deck height with a modern lightweight piston and maybe a lighter rod. All things equal if you bolted every other piece and cam from one to the other, What is the time difference in a QT mile run??

I have a 440 built with 6 pack pistons--very heavy. Wondering if it is worth a couple tenths to switch them out for lightweight pistons and rods--with same deck height--all other things being equal.

Who has done this?

Thanks!

 

[1967coronet440]

I think there's probaly an easier way to pick up a couple tenths, like a cam swap

 

[minnesota guy]

Done that already with a number of cams. I want guys who have done this and can report some numbers if possible. Thanks

 

[RT K_line]

I used to run a 6 pack engine in my GTX back in the 80s with a Cam Dynamics hydraulic 294 304 512 526 and the car would stay with cars running high 12s. I built my current engine with KB pistons with same compression as the 6 pack but the standard forged rods. the car ran 1230s to 50s depending on the weather with a purple shaft 557 lift. I think it revs better with the lighter pistons but power wise ? with different cams is hard to say. Same converter and gears though.

 

[451Mopar]

I have no direct comparison for performance, but the lighter pistons put less stress on the bottom end components like rod bolts.

 

[dieseldazzle]

Better technology and weight in my six barrel cars pistons and rods along with smaller stem valves and better rods. Zero deck etc. little bowl work better springs Every bit helps.

 

[lewtot184]

I use a set of icon 836 pistons with 440 source lightweight rods. took 3/4 of a pound off each cylinder vs stock piston and rod. think about it.

 

[493 Mike]

When I put together my Ohio Crankshaft 493 I was VERY impressed on how quick it would rev to redline. In fact it scared me-at first. Then it was just what I needed!
Mike

 

[mopar 3 B]

Would think there would be a durability factor with light rods and heavy pistons. Is there less stress in a drag car engine as compared to hours of endurance the 6 pack engine was designed for?

 

[lewtot184]

heavy pistons break rods. heavy rods and pistons beat up main caps. mopar big blocks and hemi's have heavy reciprocating parts as compared to to a big block chevy. if your going to rev the mopar up then get rid of as much weight as possible. i used to do some engine work for some bracket racers and they claimed 2-3 tenths reduction in e.t. with lightweight pistons. they couldn't tell any big difference with alum rods, but alum rods are good shock absorbers and take stress off the main caps. some people think lightweight parts add horsepower, they don't. the engines rev quicker and the bottom ends last longer.

 

[minnesota guy]

Thanks for posts. Again, all things aside regarding stress mains, rotating force, etc. Just want pure numbers from guys who have gone to lighter pistons/rods and everything else remains the same.

 

[67 coronet]

not sure you are gonna find someone who has done that much of a swap and not changed other parts at the same time. lighter parts improve the spool up speed. easy to see in your head that a faster spool up to rpm's means a faster time down the track. but, i dont think you are gonna get exact numbers.

 

[Challenger340]

Very difficult for me to give a "quantifiable" this amount of hp difference between lightweight stuff vrs the far heavier 6 pack Pistons, given, I have not done any actual "side by side" Dyno testing ?
Nonetheless,
we have built & Dyno'd many nearly identical 440 Engines using lighter aftermarket Piston offerings(ICON, SRP, ~2400 gram bobweights, etc) along a tried & true package combination, same Cam, Compression and yes Ported / Flowed Heads, to the point where it's a no-brainer for us when a Customer requests around a 540-550hp/550trq 440 using a Flat Tappet Cam on pump gas..... easy-peazee !
Imagine our surprise then....
when we had a Customer who merely wanted a set of Heads Ported/Flowed by us, and a Cam/Intake rec to do the same HP/Trq goal with a L2355 Piston'd LY Rod ~2700 gram bobweight Engine he already had ?
We supplied the Ported/Flowed Heads, with a Cam & Intake Rec as requested..... based on those goals from our prior Dyno's results.

The Customer then assembled himself on to his ~2700g Bobweight 6 Pack Piston shortblock, and showed up for a Dyno session.
We could NOT get above 510HP / 535 Ft/lbs
seeming to indicate, to me anyways, that there is a parasitic HP/Trq loss with the heavier shortblock bobweight.... versus the lighter components we typically utilize.
Granted,
his CR/DCR as installed was slightly lower than what we typically shoot for.... ~10 vrs our 10.3/4, nonetheless the breathing power/Flow, Cam & Intake was there ? and his Shortblock did seem to seal well ?

Long story short.... best guess parasitic sacrifice using the heavier stuff @ 20-25 hp and same for Trq.
Which ain't gonna set your world on fire translated to an actual E.T. drop at the track !

 

[minnesota guy]

Thanks! I guess also good to stay away from the L2295 TRW/Speedpro 11.5/1 old school piston as well.

 

[dvw]

If I were putting in light pistons and rods I'd definatly stroke it at the same time. 2.2" chevy pin, long rod. The piston won't get any lighter. Thin rings also. My .9mm/3mm ring pack was 25 grams lighter than the previous .043"/3/16" ring pack.
Doug