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carb head on efi motor?

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mattri
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carb head on efi motor?

Post #1 by mattri » Sun May 10, 2009 11:10 am

I know this has been discussed, tried a search. Can I use a carbed head on an EFI motor? I have a rebuilt head with a 3 angle valve job thats been milled true and port/polish that came off of my old bronco, can I swap it into my 95 F-150? Think not but heres to hoping.

Lazy JW
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Re: carb head on efi motor?

Post #2 by Lazy JW » Sun May 10, 2009 11:33 am

Bad Idea. :evil: Sorry.

Yes, it will bolt on and run, but the computer/timing/fuel curves are programmed for the "fast-burn" characteristics of the EFI head. It won't run properly and will likely be down on power and economy.
Joe
"The White OX" 1974 F-350 300-6, Stock single exhaust, Carter YF, T-18A, Dana70 w/4.11, Flatbed dually w/dump bed. "Where no oxen are, the crib is clean, but much increase is by the strength of the ox" (Proverbs 14:4)
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krobert56
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Re: carb head on efi motor?

Post #3 by krobert56 » Tue May 12, 2009 3:28 am

what if you just use the efi short block with a carb head and intake system and change the cam
basicaly use a yard EFI motor to get a little higher compression
1984 Lil Ranger -cop car 351W - C-4 - 8.8
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1982 f100 step side I6 4spd od -- Mrs Kitty's truck

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StrangeRanger
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Re: carb head on efi motor?

Post #4 by StrangeRanger » Tue May 12, 2009 6:48 am

You're going to get LOWER compression with the carby head. The EFI head has a smaller chamber
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Lazy JW
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Re: carb head on efi motor?

Post #5 by Lazy JW » Tue May 12, 2009 8:38 am

krobert56 wrote:what if you just use the efi short block with a carb head and intake system and change the cam...


In essence this is what I did on my 81 F-150 TorqueMotor®. I used EFI pistons set to zero-deck with a mildly ported carby head and stock carby manifolds plus a torque cam from www.reedcams.com

As StrangeRanger pointed out, this combo gives LOWER compression ratio than stock.
Joe
"The White OX" 1974 F-350 300-6, Stock single exhaust, Carter YF, T-18A, Dana70 w/4.11, Flatbed dually w/dump bed. "Where no oxen are, the crib is clean, but much increase is by the strength of the ox" (Proverbs 14:4)
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American Thunder
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Re: carb head on efi motor?

Post #6 by American Thunder » Sun May 17, 2009 11:25 pm

Use a 240 head for the same compression as efi head?
1977 530hp 302 Mustang II videos:
Smokeshow at 8000 rpm
0-90 mph speedometer view

1983 4x4 Bronco - '95 300 converted to carb, 5-speed, 3.55 gears and 9" rear.

Lazy JW
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Re: carb head on efi motor?

Post #7 by Lazy JW » Sun May 17, 2009 11:46 pm

Lazy JW wrote:Bad Idea. :evil: Sorry.

Yes, it will bolt on and run, but the computer/timing/fuel curves are programmed for the "fast-burn" characteristics of the EFI head. It won't run properly and will likely be down on power and economy.
Joe


Even using a 240 head still loses the fast burn for which the EFI is programmed; this could work with an aftermarket EFI I suppose.
Joe
"The White OX" 1974 F-350 300-6, Stock single exhaust, Carter YF, T-18A, Dana70 w/4.11, Flatbed dually w/dump bed. "Where no oxen are, the crib is clean, but much increase is by the strength of the ox" (Proverbs 14:4)
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American Thunder
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Re: carb head on efi motor?

Post #8 by American Thunder » Mon May 18, 2009 10:59 pm

I wonder if a milled 240 head with around 9.5 compression would respond similarly to the stock ignition timing curves that the stock efi fast-burn head does with 8.8 compression.. hmmm.. With some experimentation, that could work well.
1977 530hp 302 Mustang II videos:

Smokeshow at 8000 rpm

0-90 mph speedometer view



1983 4x4 Bronco - '95 300 converted to carb, 5-speed, 3.55 gears and 9" rear.

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