HELP ! New motor won't rev past 2000 rpm

[FasterCat]

67 Cougar, new 306 roller motor, new duraspark distributor, all wiring re-done, carb rebuilt, pretty much everything is new Calculated compression ratio is about 9.7:1. (oh ... Trick Flow Twisted Wedge Heads) ... still has the old coil ... maybe I'll swap that too (new one is in the trunk) ... Started her up, let her idle up to temp. She idles great, sounds nice ... but only revs to about 2000 rpm ... ... ideas ? What should I check ? ... before you ask ... duraspark ignition retard (white) is disconnected. Not sure what the Vacuum s/b for the cam I have (Trick Flow Twisted Wedge - Stage 1), but I measured it: 500 rpm = 7 in HG 1000 rpm = 12 in HG From my experience (with basically stock 60-70s V8s) this seems VERY low ? ... oh yeah ... the Vacuum readings listed above are both with and without all vacuum lines connected Doesn't misfire or act up at all ..... "feels" strong up to 1500 rpm ... Dist is "stock duraspark" with "stock" box. Initial timing is 10 BTDC at just over 1K rpm it has advanced to 34 BTDC (with ported vac advance re-connected) I also did the old fashioned vacuum leak search: ... spraying carb cleaner all around the capped off vacuum fittings, carb base, and all around the intake .... no change Help ?

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[crunchyskippy]

I apologize in advance if you've already checked these items, but I like to start simple:

[1] Is choke disengaging?
[2] Replaced fuel filter?

[boogerschnot]

Throttle linkage?

Does the throttle keep moving back and you get no more? or is that with it pulled all the way? Are your "butterflies" opening up? Crunchyskippy might be onto something.

10 inches is pretty low. I get about 19-20 at idle.

[Gun Jam]

Yeah you need to take the air cleaner off and look down the carb with the engine off and move the throttle to wide open do you see the plates at the front of the carb open all the way so they are straight up an down?

What ignition system are you using? Did someone install a 2k rev limiter for run in purposes?

At 2k does it still run fine or is it popping or surging?

-Gun

[kalli]

what happens at 2 grand? she just stuck there, no sputtering or misbehaving. that nearly sounds like a rev limiter.

---->at just over 1K rpm it has advanced to 34 BTDC (with ported vac advance re-connected)
disconnect vacuum advance, plug the hose so carb can't suck air through it and check again. 34 at 1000 is way too much if it's caused by mechanical advance

even with choke fully engaged the engine should rev all the way to sudden death when you floor it as the choke is usually pulled open a bit when flooring.

when you open the throttle fully you should see 0" vacuum, can you confirm that as well?

with the vacuum I'm not sure:
hefty cams have less vacuum, but the vacuum is usually in relation to throttle position, so I don't understand why your vacuum is higher at 1000 rpm than it is at 500

Kalli

[Gun Jam]

-Kalli

my vac reading is also higher at greater rpm no load.

I get about 12 or 13 at 700 rpm but close to 20 at 2000 rpm

If im going 60 mph in 5th im getting about 15 but if I go up a hill and maintain 60 by applying power vac will drop off...the bigger the hill the more vac drops

-Gun

[kalli]

ah ya ... the load .... still would be interested to hear what actually happens at 2000rpm. is it a specific rpm it won't go past, is it sputtering, misfiriong ... ?

[kalli]

.wrong thread ... was tired

[boogerschnot]

good info Kalli.

[RWP289]

Have you considered blockage in the exhaust?