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Old 06-11-2012, 05:36 PM
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Cleveland 4V

Can't really call my car a hotrod. Just a '71 Mustang with 351C 4V quench
and cam. We measured valve lift at 0.58 which is a result of a rebuild before
I bought the car. Yesterday installed a Holley 770 cfm which is way too big
for 351ci engine if you do the math. Car loves it, so there is something else
going on here. Just need a different slant on advice/experience. The stock
valve lift for a 4V Cleveland is ~0.43

Thanks for the welcome.

mike
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Old 06-11-2012, 05:59 PM
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My thought is that with the extra lift from the cam/valvetrain it needs the extra cfm. 625 CFM should be close to what that engine requires( as stock)IIRC. The extra lift could be the reason.
Did you degree the cam to see what duration you have @ .050?
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Old 06-12-2012, 07:48 AM
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Quote:
Originally Posted by goodnigh
Can't really call my car a hotrod. Just a '71 Mustang with 351C 4V quench
and cam. We measured valve lift at 0.58 which is a result of a rebuild before
I bought the car. Yesterday installed a Holley 770 cfm which is way too big
for 351ci engine if you do the math. Car loves it, so there is something else
going on here. Just need a different slant on advice/experience. The stock
valve lift for a 4V Cleveland is ~0.43

Thanks for the welcome.

mike
The vacuum secondary/air valve type carbs are much more forgiving when sized too large than if you'd have put a 4779 Holley DP on it, for example.

I don't know which 770 you have, but if it has 4-corner idle like the 83770, it should work very well on an engine cammed like yours is, especially if the intake is a dual plenum.

If you've not already done so, be sure to dial in the advance curve. If it hasn't been done yet (unless it just happened to be close) you still have some power/drivability left on the table.
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Old 06-12-2012, 07:04 PM
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Cleveland

The carb is a Holley 86770. Since we have aluminum valve covers, a blue
block and intake plus chrome air cleaner, we went with the 86xxx job.
Something I noticed today when driving home from work in hot weather, the
engine would idle at ~400 rpm, but when you tap the gas it would jump to
3000 in a blink.

We never measured the duration but if it is the cam descibed in a Cleveland
book I recently purchased (great book) then it would be .248/.258 @ 0.050.
We bought this as a long block to replace a Cleveland with a cracked block.
Long story. I would post a picture if I knew how.
The car is a 1971 Grande w/toploader and 2.75 posi. If it had a 3.50 rear,
it would barely be streetable

mike
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Old 06-12-2012, 07:15 PM
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Quote:
Originally Posted by goodnigh
The carb is a Holley 86770. Since we have aluminum valve covers, a blue
block and intake plus chrome air cleaner, we went with the 86xxx job.
Something I noticed today when driving home from work in hot weather, the
engine would idle at ~400 rpm, but when you tap the gas it would jump to
3000 in a blink.
Hard to say exactly what is causing that but it could be the timing needs sorted out. If the mechanical advance is right at the verge of advancing, when the engine speed is increases even a little the advance could be kicking in, raising the idle speed. Or it could be just the nature of the beast.
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