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Check fuel pressure? Motor might be making a little steam, and now has a fuel supply issue?

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I would look at the fuel supply

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We had just finished installing a 440 in my friends' '65 Coronet. We pulled his 383 that ran a best of 12.5 something. Using the same cam, heads, carb, headers and drivetrain, we were looking for at least a .5 decrease in ET. The car ran the same as with the 383. We picked up .3 only when we dropped the exhaust at the collectors. It has a 3500 stall converter, 4.30 gears and 28" tall slick. The car launches a lot better, but seems to slow down from around half track on. I'm thinking this thing should be 60'ing in the low 1.6 range instead of 1.7-1.8 and running at least low 12's to high 11's. Any suggestions?

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Several thnings, on the cam did you install it at the same lobe centers on the 440 Or did you advance, retard or just stick it in on the dots If you guys just stuck it in you need to degree it or at least check and set the intake lobe centers Second thing ,what do the spark plugs look like now from the 440, if you put new ones in Lots of ways to slow cars down, even when your not trying to do that Let us know what you find and do to correct it

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The car launches a lot better, but seems to slow down from around half track on.

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The car launches a lot better, but seems to slow down from around half track on.

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Your heads will only support so much power , by raising your cubic inches you are making it sign off earlier.

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Cam was degreed to a 105* on a 106* recommended. My first thought was fuel pressure, but he doesn't have a guage visable from the cab, so it could be monitored. He runs a blue pump with 3/8"
line. If it would go low 12's we both would be happy. This is, as I stated, where we were hoping to be on the first outting. Trap RPM is 6000, but it takes a seemingly long time to gain rpm between shifts. Plugs looked good, no fouling or over rich indications.

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I would NEVER drive or race a car w/out a fuel pressure gauge visible. If I didn`t have my gauge in view, my car would be jacked staying in it at ZERO pressure. I`d mount in in view and go from there.

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Never ran with the exhaust uncorked with the 383 as far as I know. We wanted to keep everything the same just change engines. Of course the intake had to be changed. The 383 had an M1. The 440 has a Torker II. Carb is a Demon 850. Valve springs are Comp 928. 150 closed 371 open. Cam is also a Comp. Solid flat tappet, 252* @.050 with .540I lift. The 383 had dome pistons at 11.2:1 compression. The 440 is .030" over and has flat tops at 10.5:1 compression. Quench is .054". Pistons are .015 in the hole and .039" gasket. I think he should go a little bigger with the cam, maybe to a 259* or 260* and more closer to .600 lift. He does run race gas.

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jmo bet the 440 has 9.1 comp add the weight of the 440 over the 383,
point comp , yep ran the same or close , the 383 should been quicker
see previous post

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You left out the head info

And the MPH change between the 1/8 and 1/4.

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Sorry 'bout that. Heads are 906's with home port and big valves. 2.14/1.81. Only slightly shaved to get them level. MPH at 1/8 was around 88. 1/4 MPH was 110-111.
Like I said, everything was the same as with the 383,except for the intake. We wanted a true comparison. When it ran the same, this is what was dissappointing. Ya' the 440 is slightly heavier, but it also gives 53 more cubes and a bunch more torque.

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Did he ever run the 383 with open exhaust? Most likely the 383 would not pick up as much. Some of these guys that think a 383 is a better motor than a 440 are off base. Your buddy made the right move. Dollar for dollar the 440 will out run the 383.
The exhaust is what is restricting your 440. The 440 is exhaling more than the 383.
I have full 3 " exhaust on my 850 horse Cuda and uncapped I only pick up less than a tenth.
If he wants to run through the exhaust he should start by upgrading the exhaust.
By the way I am running Magnaflow mufflers. They are straight through.

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really hard to say why either motor dont/didnt run,
for the straight across trade he did no he would run really close,
the 383 had compression, yes lighter , ,wether it 5# or 500 #
the addiadge was you could take 20 # battery out of the front of the car, take it put it in the back and thus lose 100# out of the car,
(rumor)
he used the same came heads carb, i have done this with not much pickup for the work involved.
now he can work on the combo he has , yes to me that combo should be mid 11 car, , that being said,, the 383 should be real close as well
i have done this deed, several times only to be disapointed at the end result,
did the exact thing when i ran small blocks , took out 360 270 h comp cam 8.5 ccp , put in realy swell 340, 10.1 nice pistons , warmed up heads solid cam ld 340 intake race gas the whole deal,
didnt pick up squate, ran it tune it, sold it , put 360 back in changed intake from the 340, ran faster , everyone said the 340 would flat out run that stock 360 didnt wouldnt , couldnt ,
why idono,
as for this poster , wish you the best, hope you do see that 12.0 11.90 ticket, or faster
good luck, dennis

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Do the math. Hes nowhere near 10.5 to 1. Lucky if its 9.5 to 1.
Probably 2 points down from the 383.

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I did the math as you suggested.

With slightly shaved 906,s you can expect 88 cc chamber volume or higher.

using.

87cc chamber
4.36 bore
4.50 gasket bore
4cc valve reliefs
.015 in the hole
.039 gasket ========= 9.75 comp.

With only a slight shave on the 906,s the Comp,s probably even less then that. More like 9.5


There are no measurements to estimate the 383,s true comp. I based my opinion on the stated 11.2 and 10.5 comp difference.

The 906,s chamber would need to be around 79cc or less to hit the 10.5 comp mark.