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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.