Author Topic: Should I?  (Read 29 times)

Offline V12T

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Should I?
« on: September 18, 2019 - 08:55:32 am »
Now considering what to do, if anything, my Challenger engine. It's a low mileage 76 440 with factory measurements and rods, pistons etc. so untouched. It runs fine, I won't do many miles (700/year) and won't overstress it with high revs, burnouts etc. I'll be keeping the car for a long time. I've had the oil pan off and the bearings and bores look in excellent condition.  Calcs show about 7.7:1 CR with stock 1.912 compression height pistons. I don't NEED any more power but........I'm only human!. I've found some stock bore pistons that will give me around 10:1 CR with 2.067 compression height (almost flush) so a lot more power - back to real muscle car days. Heads are 452's so hardened seats and 88cc capacity.  I would check the bores from the top before making a decision. So - is it realistic to only change the pistons or should I leave well alone? Advice welcome.




Offline Oldschool

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Re: Should I?
« Reply #1 on: September 18, 2019 - 09:09:15 am »
The rule of thumb is roughly 15 HP per 1 point that the CR is raised. So if you went from 7.7:1 up 10.0:1, theoretically you would gain about 35-40 HP with the new pistons and no other changes. If the work and $$$ are worth the extra HP to you, then I say go for it.
Ken  --  In Georgia

MOPAR-------"Built To Run------Here To Stay"

Offline 70chall440

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Re: Should I?
« Reply #2 on: September 18, 2019 - 11:59:42 am »
Go for it but don't go crazy and make it unusable. I'd recommend some aluminum heads and a roller cam along with EFI.
Current Mopar
70 Challenger RT 440-6 EFI, 73 Cuda 416-6 EFI
05 Hemi Durango, 01 Ram 4x4, 14 Ram 2500 4X4, 10 PCP Challenger 6 spd RT, 01 Viper GTS ACR, 52 B3B w/330 Desoto Hemi, 70 Hemi RR (under const)
Past Mopars
9 x Challengers. AAR Cuda, 4 RR, 2 GTX, 4 Chargers, etc... (too many to list)

Offline jimynick

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Re: Should I?
« Reply #3 on: September 18, 2019 - 11:11:05 pm »
" I'd recommend some aluminum heads and a roller cam along with EFI."- OH, you temptor you! That's how you begin the slide to a full monty rebuild! Something you may wish to consider is how do the weights of either piston compare? Are you into a rebalance? Same mounting, pressed or floating? Is there a wee ridge in the cylinders that that now higher CH piston ring may have a problem passing over or sealing to? Just a couple of pensees to ponder on before doing it. I'm all for more power, so good luck!  :cheers:

Online cudabob496

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Re: Should I?
« Reply #4 on: September 18, 2019 - 11:43:00 pm »
May have a valve clearance issue. Also, cam duration my be too small
for that CR, resulting in too much cylinder pressure, and or detonation.
I would think you would want to rehone the cylinders. Max CR for iron heads
and pump gas is around 9.5. Instead of new pistons, can you increase CR by
shaving heads?
72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

2011 Kawasaki Z1000