351 Windsor wont pull after 3k...help

[cobra351w]

Recently rebuilt windsor,performer edelbrock heads and inlet package, roller rockers, mallory DP dizzy, and edelbrock 1405 600 cfm carb

Cam...?? measured lift and duration, similar to performer.!!

Problem: will not pull in any gear above 3000....nothing happens at all, just fluff.!!

I think it fuel related, but the lambda probe reads 13AFR cruise , 14 when I throttle.

Jets: Main 98 needle 70/47 secondary main 95 springs , tried blue, pink, now on orange.

Odd thing is that there is no registered idle vaccum???, increases as throttle opens (out of gear)

I wondered if I'm way out on secondary main??

[wilf]

First,

You are measuring vacuum at the wrong port - what you are seeing is "venturi effect" induced vacuum - will increase with airflow. Opposite almost of manifold pressure. Use the other port.

Secondly - do you have a vacuum advance on the dizzy? If so disconnect, reset static timing, and try again with it disconnected.

The advance curve you want is 34 degrees total at 3000 rpm, start advancing around 1500, all in by 2500 - 3000.

Go back to the standard springs etc. on the carb once you are SURE the ignition is OK.

[cobra351w]

Re the vacuum port, I thought that too, but I am measuring the inlet side, not the carb side.

vacuum is zero at tickover (butterflies almost shut), then increases to about 16 HG .

The dizzy has no vacuum advance, so have set about 12 deg initial advance, total should go to about 34 ish degrees.

I guess it could be that I have a massive air leak elsewhere ??

thanks

[TINKA]

Have you had a look to see what the timing is when it is at 3,000rpm is it actually advancing properly at all.

[cobra351w]

Tinka,

I was going to do that next, as I still can't believe the carburation is that far out.

Perhaps the plate stops have moved.??

I read that the mallory condensors are also prone to failure??

[tonym]

Originally Posted by cobra351w

I think it fuel related, but the lambda probe reads 13AFR cruise , 14 when I throttle.

I run 15 at cruise and 12.7 at wot, if it's any help

[wilf]

Ah - Mallory DP distributor eh? Throw it away! Or at least fit a pertronix conversion, or fire a MSD or similar sparkbox from it. That distributor will NEVER allow your engine to run properly for more than 5 minutes. The condensor is also highly suspect - swap it out and see if it cures your problem.

For now though - is the dwell set properly on both sets of points?

[cobra351w]

Funny that, I was also thinking that too!!

This build has a chequered history, as when I first fitted the engine, I had a similar issue, went through all the same pain, even stripped down to block, at this point fitted the new heads and manifold and carb, the problem appeared to improve, but not been able to drive the car, could not check fully.

Common components:-
Mallory Dizzy (new cap/rotor fitted) initially replaced condensor, but fitted old one back as no improvement.

Mallory HO Coil

Camshaft (fully checked and timed)

I'll check points and dwell.!!

I'll be shopping tomorrow for breakerless ignitions I think!