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Hemi vs Chevy wager...

General engine tech -- Drag Racing to Circle Track

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Craig J
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Hemi vs Chevy wager...

Post by Craig J » Sun Dec 01, 2019 3:33 pm

One of my best friends (8Pack) has a 472" hemi that is finally going on the dyno after complete disassembly due to a thrust bearing failure. He got the complete iron head 426 for what seemed like a very good price, but he has dumped a ton of money into repairs, in total he has well over 24K in it. He had a very reputable builder to all of the repair work, and I expect it to run very well, probably at least 650 hp.

The friendly wager we have going is for a case of cheap beer: I think I can make double the power of his super awesome hemi using a chevy for a quarter of the money...

My home made LM7 & 67 mm turbo made 480 whp @ 11 psi. I built a Volvo wagon with an L33 & 67 mm turbo made 450 whp @ 10 psi... but I do not believe I am good enough to build a 1300 hp LS based engine, so this is my plan:

I bought a Gen V 427 truck block, std rods & mains, std bore. It was an impulse buy, and $300 was probably too much, but now I am sort of committed.

Next steps.

rigid hone the truck block at home to approximately 4.257 (it measures 4.249 at the bottom & 4.255 at the top)
reuse the forged GM 427 crank
6.535 rods (used)
~30 cc dome forged 427 pistons (new)
112 cc aluminum heads (used)
454 vortec efi intake with spacers (used)
210# injectors (new)
Megasquirt (new)
solid roller (new)
two VS Racing 75mm turbos
two Tial 38mm wastegates

Questions: Who makes a cheap 30 cc dome piston for a 4.250 bore with floating pins? The Speed Pro pistons I found say they are pressed only, and I don't think I can find any 6.535 rods for press fit pins.

Thanks
Craig

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Re: Hemi vs Chevy wager...

Post by FC-Pilot » Sun Dec 01, 2019 4:49 pm

I am not a turbo genius but I might do a few things different. First thing would be to lower the compression. Lower compression opens the tuning window considerably. Also being mindful of the valve job widths will help with heat transfer to help cool the valves. Also, of running an alcohol based fuel (even if it is just E85) will eliminate the need for an inter cooler. I am sure others will give better advise and details but those are some things that I would consider in the planning stage.

I look forward to what others might say.

Paul
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Re: Hemi vs Chevy wager...

Post by PackardV8 » Sun Dec 01, 2019 7:52 pm

If one believes CarCraft/Motor Trend Road Kill, all one would have to do is pull a 5.3 LS out of the wrecking yard and bolt on a couple of eBay Chicom turbos, total cost less than $1,000 and an afternoon's work.
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Re: Hemi vs Chevy wager...

Post by Racer71 » Sun Dec 01, 2019 8:07 pm

I hope that means 30cc dished pistons not domed. You’ll want to lower the Cr not raise it, dependant on your desired boost level of course

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Re: Hemi vs Chevy wager...

Post by Craig J » Sun Dec 01, 2019 8:44 pm

FC-Pilot wrote:
Sun Dec 01, 2019 4:49 pm
... of running an alcohol based fuel (even if it is just E85) will eliminate the need for an inter cooler...

Paul

I work for an ag equipment company, so I will be using E100. I'm not sure about the intercooler yet...

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Re: Hemi vs Chevy wager...

Post by Craig J » Sun Dec 01, 2019 8:51 pm

PackardV8 wrote:
Sun Dec 01, 2019 7:52 pm
If one believes CarCraft/Motor Trend Road Kill, all one would have to do is pull a 5.3 LS out of the wrecking yard and bolt on a couple of eBay Chicom turbos, total cost less than $1,000 and an afternoon's work.
I already built & tuned two of those myself, they were a pretty easy way to get to almost 500 whp, however I don't think they will get me 2x a decent 472" hemi. I think a 427 chevy with decent aluminum heads can get the job done.

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Re: Hemi vs Chevy wager...

Post by Craig J » Sun Dec 01, 2019 8:54 pm

Racer71 wrote:
Sun Dec 01, 2019 8:07 pm
I hope that means 30cc dished pistons not domed. You’ll want to lower the Cr not raise it, dependant on your desired boost level of course
E100, 10.5:1 static CR, and 20 psi is the plan... old big block chevy stuff all has pretty large combustion chambers, so it is going to take a 20+ cc dome to get the job done.

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Re: Hemi vs Chevy wager...

Post by FC-Pilot » Sun Dec 01, 2019 8:56 pm

Craig J wrote:
Sun Dec 01, 2019 8:44 pm


I work for an ag equipment company, so I will be using E100. I'm not sure about the intercooler yet...
With e100 (Usually it is E98 to prevent consumption) you will have no need for an inter cooler. I would still like to see the compression lower than that if it were me. Lower static compression will give less of a hard pressure spike and therefore be easier on the crank.

Paul
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Re: Hemi vs Chevy wager...

Post by JodyB » Sun Dec 01, 2019 9:39 pm

Keep it simple. Add a On3 94mm or 107mm turbo for $1000-1200. Turn boost controller to 11

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Re: Hemi vs Chevy wager...

Post by turbotater » Mon Dec 02, 2019 5:10 am

I have that basic combo.
Stock 454 , vs 78/75 turbos, 210 injectors , ms3 ultimate. I am using 781 heads .
Mine is running now but I haven't made in power pulls.
4 digit power I think is reasonable but I am not sure about 1300 to get to the number you are describing .

Mike

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Re: Hemi vs Chevy wager...

Post by Craig J » Mon Dec 02, 2019 6:25 am

turbotater wrote:
Mon Dec 02, 2019 5:10 am
I have that basic combo.
Stock 454 , vs 78/75 turbos, 210 injectors , ms3 ultimate. I am using 781 heads .
Mine is running now but I haven't made in power pulls.
4 digit power I think is reasonable but I am not sure about 1300 to get to the number you are describing .

Mike
What fuel are you planning to run? E85? Roller cam?

Thanks
Craig

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Re: Hemi vs Chevy wager...

Post by midnightbluS10 » Mon Dec 02, 2019 9:35 am

Anybody that pay $24k for 650hp has more money than brains. That's just ridiculous. I guess he paid that so he can say it has a hemi?


My money is on the Chevy.
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Re: Hemi vs Chevy wager...

Post by lefty o » Mon Dec 02, 2019 9:53 am

cant you just buy a 632 crate motor from gm that makes that and then some , and save a few grand?! :roll:

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Re: Hemi vs Chevy wager...

Post by Elroy » Mon Dec 02, 2019 9:59 am

Hemis are most definitely niche. Especially when looking at efficiency/dollar. But to be fair most of all this stuff is. Hemi is just a more extreme example. If a big chevy is the more efficient option that says a bunch.

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Re: Hemi vs Chevy wager...

Post by Craig J » Mon Dec 02, 2019 12:10 pm

midnightbluS10 wrote:
Mon Dec 02, 2019 9:35 am
Anybody that pay $24k for 650hp has more money than brains. That's just ridiculous. I guess he paid that so he can say it has a hemi?


My money is on the Chevy.
It started out as a lot less money... he bought the complete iron head 426 with single 4 bbl for under $12K

add dual quad setup
add new solid lifter cam
add new springs

then the thrust bearing failed...

new crank
machine block to use 440 main bearing with larger thrust surface
new pistons
aluminum heads
Stage V rocker arms
new cam
new springs to match new cam
new pushrods to match new heads
balance
etc
etc
etc

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