Having trouble pulling vacuum at idle. Need some help!

[miller]

Put a new carb base gasket on, and see if any change.

 

[Dad's69RR]

Ok here is what I have learned. I installed gaskets on valley pan and the vacuum came up a little. Timing right at 36 deg with vac adv. I swapped out my 750 carb and put on 650 just to see if it would improve, still only about 6.5 in of vac. I did a compression test and was only getting around 110 on a supposedly fresh rebuild? Should this be a concern?

The next thing I called the guy I purchased from to try to get more info on the rebuild and cam specs. He gave me the number of the shop that did the rebuild and I checked them out and they have a good reputation in the engine building business but the owner does not keep very good records and I still do not have the cam specs. All I know from the previous owner is that a purple cam was put back in but have no clue which one? The car idles and I can bring to temp but it should be a little smoother than it is. Once the rearend gets serviced I will get to drive on the road for the first time and hope to troubleshoot more.

 

[bm02tj]

cam one tooth out that could lower cranking compression and lower vacuum

 

[Ron Ward]

Wondering....

Which intake manifold are you using on the car? The reason I ask is if you are using a manifold designed for a spread bore carb (like a Thermoquad) the Edelbrock or any other square bore carb may encounter sealing issues under the base. Edelbrock offers a plate to help seal the base of the carb to the manifold.

Here's what it looks like.

 

[nm9stheham]

What type of lifters? Hydraulic or solid? If the valvetrain is not right for either, or the lash is too tight for the solids, and a couple of intakes are hanging open a bit, then this will behave as you are finding.

 

[Dad's69RR]

OK I am convinced that the cam is out of time. How do I check this when I do not know what the cam specs are?

- - - Updated - - -

What type of lifters? Hydraulic or solid? If the valvetrain is not right for either, or the lash is too tight for the solids, and a couple of intakes are hanging open a bit, then this will behave as you are finding.

I am not sure on the lifters but will be pulling covers off and checking tonight.

 

[Dad's69RR]

OK haven't posted much lately and here is the status. Went through every scenario possible and pulled the heads. Found 5 bent push rods and a lifter stuck in the bore. High lift cam was installed with the stock valves, valve springs, and lifters. Cam was wiped and hopefully nothing else damaged! This was supposed to be a newly rebuilt engine with "no miles" well now I know why there wasn't any miles on it. I keep wanting to believe it was an honest mistake but just goes to show that doing things the right way doesn't overtrump slapping something together to make $$.

 

[Hemi Rebel]

OK haven't posted much lately and here is the status. Went through every scenario possible and pulled the heads. Found 5 bent push rods and a lifter stuck in the bore. High lift cam was installed with the stock valves, valve springs, and lifters. Cam was wiped and hopefully nothing else damaged! This was supposed to be a newly rebuilt engine with "no miles" well now I know why there wasn't any miles on it. I keep wanting to believe it was an honest mistake but just goes to show that doing things the right way doesn't overtrump slapping something together to make $$.

Damn, sorry to hear this. Thats a real kick in the nuts. On the bright side you know what the problem is and can move forward now.

 

[Dad's69RR]

69 Driver coming along

Been a while since I have posted just not enough time in the day. Since my last post I have pulled the engine, did a total rebuild, replaced the lower radiator support, prepped and painted the engine bay, rebuilt z-bar assembly, and had exhaust manifolds ceramic powder coated. I just buttoned up the engine so need to paint and put back in. I hopefully will have it running within the next couple of weeks and to paint after first of the year. Hopefully Dad will get it back by the time it gets warm out. Here are some pics of the progress. Will post more later.

 

[Sixpactogo]

I'm guessing the cam was not properly broke in to start with. Starting a new engine up and not keeping the revs up for the 1st 20 minutes will wipe the cam lobes in a hurry.

 

[Dad's69RR]

My thoughts exactly! Proper break-in most important with a new engine.

 

[mopar 3 B]

Check the bottom of intake for cracks.

 

[Dad's69RR]

Need some more help! Have went through everything I can think of and still have an issue at idle. I tried two different carbs, have new module, wires, cap, rotor, engine harness, and the car will cut out around 1000-1500 RPM's at idle. Runs awesome above that but have to pedal the car to keep it above idle rpm? The only thing I can think to do is change the electronic pick up. Anyone have suggestions? BTW I broke down and bought a new 670 street avenger carb(electric choke). Not sure what else it could be everything is new?

 

[dieseldazzle]

Do another compression test. What oil did you use during your break in? You said bent push rods on first motor? Then how did the heads check out? The wrong machine shop doing mass work will send heads home with bent valves I've been down that road before.

 

[Dad's69RR]

Do another compression test. What oil did you use during your break in? You said bent push rods on first motor? Then how did the heads check out? The wrong machine shop doing mass work will send heads home with bent valves I've been down that road before.

Used Brad Penn Oil, Had the heads machined compression is good!

 

[Dennis H]

Ignorant me. I thought that there is more vacuum at idle than any other time. My Dad's 60 Falcon had vacuum wipers. When he stepped on the gas, the wipers stopped. At idle, wipers went fast again.

 

[coloradodave]

Ignorant me. I thought that there is more vacuum at idle than any other time. My Dad's 60 Falcon had vacuum wipers. When he stepped on the gas, the wipers stopped. At idle, wipers went fast again.

You are correct Dennis. The highest vacuum reading will be at idle when the throttle blades are nearly closed...