Just returned from the track....Something is wrong!!!

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The only thing I changed was I went from a Action Plus to the X-celerator manifold, and installed a new timing set.

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I dont get where the vacuum leak would be coming from though. I have had two different intake manifolds on here. I forgot to add I am still running the stock stamped steel rocker arms. I figured Id throw that in as well

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You can cut the timing back 3-4 degrees, but it's not gonna help you out much. You need atleast a 3/8" fuel line - and thats out of the tank. To run in the low to mid 12"s, which is where you should be running, your fuel pump should be able to fill a one gallon can in about 30 seconds - minimum - and thats measured from where the fuel line connects to the carb. Forget what the pump MFG. tells you. You need to actually check it to be sure. Your 60 foot times are off about a tenth and 1/2 also, indicating you have a traction problem.

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Interesting thread. Lotta experts here. I didn't say he didn't have a timing problem. I said cutting it back 3-4 degrees wasn't going to solve his problem. Neither is degreeing in his cam - if his marks are lined up correctly. His problems are much bigger than 3-4 degrees in ignition or cam timing. If he doesn't have a fuel delivery problem now, he definately will when/if he gets his "other problem(s)" sorted out. And speaking of fuel, we just got a lot more to feed this thread - "used cam". Gee, I wonder if that's when his problems started??? "140 psi cranking compression" - A tired 8:1 360 motor will deliver 20 PSI more than that - unless of course the cam timing is off, he only let it register one pump, cranking speed was 300 rpm, etc, etc, etc. " timing marks won't line up - off 1/2 tooth" - Pretty remote guess that the gears are miss-marked. R-U sure you are lining up the "0's" and not any other marks (advanced / retard marks) on the gears?? Here is a good tip: Go back to the last thing you changed that made the car have 3-5" of vacuum at idle and you will find your problem!

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I'm running a 260/266 @ .050" cam and I've got 6 1/2" of vac.

As mentioned, I'd degree the cam first [ EDIT: set the timing] then check for vac leaks.

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Cranking compression (especially with a performance duration cam) and static compression are two very different things. Don't let that throw you off.

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Its not a low compression engine. Its 11.26 to 1. The compression test was done with 5 hits on the gauge, all plugs removed. From the day this motor was built, it never had any vacuum at idle, and always ran like a rat.

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Cranking ( dynamic) compression pressure is way too low for that cam. Should be in the 180psi range. Not likely your C.R.is 11.26:1. This would explain poor vacuum and soft bottom end while still having a decent speed - 106mph. The slugs are probably .015 - .020" down in the holes. BTW, most reputable cam Mfg's will give you a suggested dynamic compression pressure for a particular cam. It is much more important than the static number - but much less impressive

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"The 5/16" fuel line you are running is too small"
I'll say it again your fuel line is fine. You can run 11's w/ a 5/16 ine and mech pump...even w/ a 440-6 in a B-body. If it's fuel issue you either have a clogged filter or you car is lean. changing the line to 3/8 won't do squat.

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If you have 140 across the borad you have a compression problem...either your valves are a tad open or you don't have the 11:1 you thought you had.

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I'm not sure what a decent CR means,

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overkill = cheap security. If you are pushing the edges of the envelope, you will only go lean once! Could I see a show of hands of those on this thread that even have a fuel pressure guage in their car?

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for two cars

but I've seen many a car run 11s with just 5/16 lines

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Theyre not flat tops. They have a .050" quench dome, and a .039" head gasket, sitting .009 in the hole...with a .050" recess machined in the chamber

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I've also supported 550hp with a factory mechanical and 5/16 line. Many lines now have kinks and guy dont cut them properly so the flow is much lower than it should be. That fact is, overkill sells, and in many cases, meaning a car that runs in the 12s or high 11s, they simply dont need that much pump or line. In somecases, you add so much volume in the line the milder pumps have trouble pumping against the inertia of the fuel in the line in first gear.

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Im working on getting a degree wheel. But heres another "long shot". Edelbrock recommends the use of adjusteble rocker arms when using cams with a greater-than-stock lift. There has to be a reason for this. Since Im running the MP509, is it possible the rocker stands themselves might not be machined at the same height as say a stock cast iron head, therefore causing the valves to "hang open"? Much like a Chevy with the rockers adjusted too tight? I do have experience with that scenario and the effect is great. I should have a degree wheel tomorrow and Ill take a crack at it.

But who here thinks I could benefit from an adjustable rocker setup? Id like to rule that out as a possibility as well. I appreciate all of the replies. Its all very interesting. I just hope I can get to the bottom of this.

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So you checked preload and adjusted it by using shims?

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I've always check the geometry, adjusted the pushrod length accordingly, and used adjustable rockers to set preload.

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Im working on getting a degree wheel. But heres another "long shot". Edelbrock recommends the use of adjusteble rocker arms when using cams with a greater-than-stock lift. There has to be a reason for this. Since Im running the MP509, is it possible the rocker stands themselves might not be machined at the same height as say a stock cast iron head, therefore causing the valves to "hang open"? Much like a Chevy with the rockers adjusted too tight? I do have experience with that scenario and the effect is great. I should have a degree wheel tomorrow and Ill take a crack at it.

But who here thinks I could benefit from an adjustable rocker setup? Id like to rule that out as a possibility as well. I appreciate all of the replies. Its all very interesting. I just hope I can get to the bottom of this.

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The engine wouldnt have to be running for an accurate test? I mean so the lifters would be completely pumped up

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The rocker arm geometry will be screwed up in what way? I did verify it was the .509 when I got the cam. I did mic the lobes

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Ok, but how will the geometry be screwed up?

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Whoops! Mine is a -2

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power valve = 8.5 ( BTW, @ 3-5" yours is open ( dumping fuel )all the time - not good, and a contributing factor to your other problems...

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No, just rebuilt it. Has 74/77 jets in it. I have a 61-99 jet kit, but I guess with the low vacuum it would be hard to tune correctly

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Dispite everyones "expert" input on this thread, try to stay focused on your known problems

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Incorrect moper. A cam with a different base circle diameter will change the valve train geometry. So will head milling, blocking decking, head gasket thickness, etc. Running too small a fuel line won't affect it though.

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When finding TDC with the piston stop make sure to go VERY SLOW as you come up to the piston stop. You do not want to create any new problems.

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What... like breaking the stop off in the cylinder?

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Yep been there done that!

Although I was not laughing when it happened 15 years ago.