'Best' donor for a tow engine swap to get converted to EFI

grendel

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I think you need more cofee or less, not sure... but nothing wrong with anyone in either thread.
 

gary kosier

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Well, here's my take on this this thread. For Lil John, for your use, you need low speed torque! To get
that, you need cubic inches. That means a 500 or bigger. That's pretty much a given fact.
On the EFI, I have a headroom problem in the motor home, so I'm stuck with the factory manifolds. I rather like
stuff that's been engineered by smarter people than me. I have an GM 7730 ECM with a mod by Dynamic EFI
that allows programming with a laptop. I have a wiring harness that's made for that ECM in a street rod. The EFI
has been converted to TPS & IAC that match the ECM. I also milled the exhaust crossover off the bottom of the
manifold to reduce weight. I was going to remove the metal around the runners, but decided not to.
I like to let other people work out the big problems and then refine the solutions. LOL

Gary Kosier
 

Roy Heisenberg

The 472 Crank is stronger due to overlap
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What vehicle(s) do you drive?
472 Caddy in a ‘75 Jeep J-20 TH-400 Dana-60 100LL
500 is great for Torque, but if the 472 is within 4%, and the crank is stronger, and a 472 is way cheaper to build???

I say a 472 with 425 heads makes awesome low end grunt. Super low buck, crank lasts for 100 years, and you can recycle or UpCycle some 425 heads.

Are small port heads the magic for some builds??

Best HP and Torque,
Roy who dances only with 472
 

Lil'John

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71, 72 Toyota FJ55s
Are small port heads the magic for some builds??
In reading the Big Inch Cadillac book, the early 76cc(??) heads were not cast for EGR. My understanding is this meant not having that in the combustion chamber that needs to be closed up. And the head apparently lighter than a head with the EGR casting. Not sure how much lighter.

A question about the smaller heads. My understanding is they give ~10 to 10.5 to 1 compression. Is it possible to use a thicker head gasket to get the compression down to allow non-premium gas?
 

Roy Heisenberg

The 472 Crank is stronger due to overlap
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472 Caddy in a ‘75 Jeep J-20 TH-400 Dana-60 100LL
Yes, thick head gasket, and a big cam with big duration, and you are set.
 

kzhurley

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I would not use a thicker head gasket to lower compression unless you verify proper quench area.
Id rather have a 10.5:1 with proper quench than a very detonation prone 9.5:1 due to improper quench.
These engines seem very timing sensitive to begin with.
 

kzhurley

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I also don't believe that a 472 is any cheaper to build if you're starting from scratch either way. Unless of course you cannot find a 500 core. Seems that 472s cost 1\2 as much as a 500 core. I feel that theyre both close enough that youd be happy with either 1 and it would be very hard to tell them apart if built the same.

And also, 500 heads already would be considered a "small port" build on a big cad to begin with. I would think that the smaller port 425 head would be even more of a choke on any larger engine..
 

Lil'John

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71, 72 Toyota FJ55s
I would not use a thicker head gasket to lower compression unless you verify proper quench area.
Id rather have a 10.5:1 with proper quench than a very detonation prone 9.5:1 due to improper quench.
These engines seem very timing sensitive to begin with.
Isn't this going to be the same issue with machining down large chamber heads down for higher compression than 8:1?
 

Roy Heisenberg

The 472 Crank is stronger due to overlap
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472 Caddy in a ‘75 Jeep J-20 TH-400 Dana-60 100LL
That is great info, and makes me a big fan of 2618 Alloy forged pistons...

Thanks for the cool link to Grumpy,
Bro. Roy
 

blue68deville

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I'm running a 454 TBI unit on top of my 472, using the EBL flash computer. I went with an MSD distributor (got it cheap), locked it out and have the GM spark module mounted externally. It has been working great for 4+ years now. I started with a 7747 computer and did the chip thing for a bit, the EBL is much easier, faster, and has a wideband input to do some self learning VE to help get you in the ballpark.
 

Lil'John

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71, 72 Toyota FJ55s
In further reading, it looks like the small chamber(76cc) heads went from high compression(10:1) to low compression(8.5:1) around 71.

What about the engine changed to allow this?

My understanding is from a 'super high hp' stand point, the high compression is desirable but requires higher octane gas. I am trying to avoid going to higher octane gas.
 

gary kosier

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Your compression is usually changed by varying the piston dish or dome as needed. Being lazy, I usually go into Summit's website and dial up a piston. Then go to details and click
on check compression. This will give a chart where you punch bore, stroke, head CCs, deck height, piston dish or dome and no. of cylinders. Hit calculate and it will give you
displacement and compression ratio. Don't like the answer, back up and change the numbers and try again. I like to look at different combinations and see how they work out.
When you can't do anything, it helps to while away the time.

Gary Kosier
 

Roy Heisenberg

The 472 Crank is stronger due to overlap
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472 Caddy in a ‘75 Jeep J-20 TH-400 Dana-60 100LL
It is ALIVE !!
 

Roy Heisenberg

The 472 Crank is stronger due to overlap
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What vehicle(s) do you drive?
472 Caddy in a ‘75 Jeep J-20 TH-400 Dana-60 100LL
Why not also try a water/Methanol injection system ??? This helps with bigger smoother torque and you can bump up the timing right to the ragged edge !!!

Thanks,
Roy
 
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