Ok I need some help big time... :banghead: i feel like I'm chasing my tail!

To start, this is what I have...1969 383 h code .40 over, Holley 650 cfm, mech secondaries. Mopar heads, Edelbrock performer intake. Melling 23302 cam straight up. Fresh rebuild (although I didn't do it, so there could be ??)

Vacuum is a huge issue or should I say lack of. Off the intake three different gauges read 5 inches with steady needle. Give some throttle up it comes to 17 or so then smoothly back to 5". I obviously suspected vacuum leak. I've tried the propane method nothing, the brake cleaner nothing, the starter fluid (very carefully) nothing and even blocked off the air to the carb and stalled immediately!

I should mention timing, and vacuum advance, the Initial at 11 and all at 38. Vacuum advance unhooked because when the engine gets throttle, revs up but only drops back to about 1100-1200 rpm. Unhook vac line to advance drops right back to idle at 750 rpm.

I thought might be leaking at brake booster if not installed correctly. Bypassed that. Checked vacuum lines to headlights and door actuators all seemed hooked and correct. But getting vacuum right off Edelbrock bypasses all of that anyway.

Where / what else could cause only 5 inches of vacuum? Do I see a rebuild coming up? What do you guys think?

Thank you!! And hopefully you guys can stop the bleeding!!

Myraman

 

My 2 cents........
Too much duration on the cam.....
Didnt build enough compression in the short block....

 

X2 What are the specs of the cam?? what piston were used??...Bill

 

Where are you attaching your vacuum hose exactly?

 

Cam specs are attached with the pic. I figured that would be the easy way.

Pistons....don't know I didn't do rebuild, previous owner couldn't tell me. I haven't been that deep yet.

Vacuum hose from intake splits and goes to brake booster and to headlights (69 charger) I did unhook both of those and checked vacuum right off intake. As far as vacuum advance, the line come off the ported line from Holley (top) not the base of the carb. That I had not changed it was that way when I got it.

The engine had blue permatex all over it. I knew this was gonna be an issue.

Thanks for the help!!

 

Those cam numbers show more duration, valve openings/closings and overlap than I'd run in a street 383. Here is a hughes recommendation chart for some examples.

http://www.hughesengines.com/TechArt...lattappets.php

 

Ok if there is more duration than it should have, besides ripping the cam out and going less duration and starting over again, what are my options, if any?

Thanks for the help! Much appreciated even if it is going to cost me more money.

 

If it is idleing down with the vacuum advanced hooked up like you say, it must like more initial advance. I would first try unhook vacuum advance, add more initial but restrict centrifugal first so your total doesn't get too high. This just might raise your idle vacuum.

Next step would be to decide if you want to go to the next level of pertformance to match the camshaft.

 

I already unhooked the vacuum advance due to high idle after throttle up.
I can add more initial but is the centrifugal within the distributor with the weights/springs etc?

What would be the next level of performance? Heads etc?

 

I'm surprised it will idle under 1500.

 

The centrifugal advance (mechanical) is inside, the weights ands springs won't limit the amount of advance. The type of distributor will have some means of stopping the mechanism from moving fully. If it is a Mopar style then the slots can be welded to limit movement, there is plenty of info on this if you search.

As far as the next level I would look at a higher stall torque converter if automatic transmission equiped. Higher numerical rear axle gears to have it in the operating rpm of the engine. Headers and a higher operating rpm range intake manifold with a larger carb.

 

Coronet500 and everyone, thanks for the help The folks I got this car from weren't much help in identifying what it had for stall converter on auto 727 transmission, pistons, and cam specs. It was a very rough idle and hardly any vacuum. They thought the tranny might have an upgrade but we know how that goes. It has 4:11 in rear from what I can determine no sure grip. Original exhaust manifolds and an Edelbrock performer dual plane 383 intake. I guess I'm off to the next level! But I think I'll tear the whole thing apart and start from scratch so I know exactly what I have! Again thanks for all the assistance from all! I'll post how things are going once I figure out how to poop $100's

 

Your very welcome. Check out this article. http://www.moparmusclemagazine.com/t...nition_system/

Before tearing it apart I would try this or buy one of the newer distributors that have easily adjustable mechanical advance with bushings.

At the very least I would try (without vacuum advance connected) adding advance with a timing light and vacuum gauge to see how much the vacuum will increase.

 

Give Mike a call and chat with him...... Tell Him RacerHog sent you...
He will point you in the rite direction.....
He is just around the water from you.....

http://www.mrlperformance.com/

 

You need to give that bitch all the initial it wants. Use your vacuum gauge, and time the engine for max vacuum. Keep turning down idle speed if necessary, and make sure that once you get timing "roughed in" that you reajust idle mixture and speed for best vacuum and best idle.

Do this with engine fully warm. Then start several times to check for "starter kick." You might want to retard timing so vacuum drops off the peak a couple of inches Hg.

If it doesn't kick, note what that timing is, and recurve the distributor.

You'll have to play with total for max HP to determine what that end wants, but 34-36 or a hair more.

 

Advance the valve timing, buy a timing gear set with different crank gear options. You will still need to punch a couple of small holes, 1/16 to 3/32 in the primary throttle plates so you can back the idle adjust down enough to bring the holly idle circuit in. Then work with the ignition timing to achieve good throttle response.

 

Another way is to crack the secondary's open with the set screw on the bottom of the carb
Try adjusting the mixture screws for highest vacuum reading

 

Man...This is getting ugly....

 

Not quite as ugly as the wife will be when she sees how much money I'm gonna spend fixing this / these issues! LoL

But really she'll be ugly but hey....it's my car!! What does she expect?

 

Ok update, get ready for this... Well as I started to tear things apart last night, I noticed that the rocker arms are not sitting on the valves correctly. The wear marks are around the edge not in the middle as should be. The pushrods and rockers are the stock ones for the engine. However, apparently when the heads were redone the valves were redone as well. I then went to all the paperwork that I did get with the car. I had a machine shop receipt that listed
Intake valve cut down 2.140
Exhaust valve cut down 1.810
"Open up valve job for bigger valves"

I'm willing to bet the pushrods are not the correct length for the valves now making geometry all wrong.

Did I mention that I also think the rockers are not on correctly. Isn't there a "right and a left" the are all over the place.. Don't appear to be correct.

Thoughts? Getting these issues straight should make a pretty good diference.

Thanks....

 

Yes there is a right & Left to the rockers If that is the case ? I would NOT trust any work they did

 

Stamped Rockers will very in lift... There just all over the place when you measure them.

Get a good set of rockers and shafts..(I'm a Harland Sharp Guy).. And then you can measure for the right push

Mopars are finicky with there valve train. But once it set up rite... It's a win win.

And like Lynn said.... Get someone that knows Mopar to do the head work for you....

http://www.harlandsharp.com/sb_mopar.htm

 

That is the case!! I am learning fast that I am not trusting anything they did. I made this decision after posting this morning to pull the engine and completely re-do everything. Then I will know for sure.

I do have a great machine shop here in town that has a guy that know his stuff. Already spoke to him. He was the one who pointed me in this direction...

stay tuned

again thanks!!

 

Here's a couple pics of the top of the valves with rockers flipped up out of the way. Looks to me like the rockers aren't sitting squarely on the valves. Bit of a problem? Pushrods issue, spring tension etc? Thoughts....

Thanks...

It only let me upload 1 pic. But they're all very similar!

 

Update, Guy at machine shop looking at heads thought the marks on valve stems were not outrageous. Little off, but not as bad as I thought. However, on all but 2 cylinders the intake valve had burnt exhaust all over it. He did test the springs and the were a little weak. New ones going in. His thought is the intake valve staying open longer than should. Could it be from those weak springs or maybe pushrods too long? Pushrods appear to be in that stock range. 8.56"

Or could there be another issue?

We still haven't figured out why only 5" of vacuum! Could that cause the issue?

Another thought on lack of vacuum... With the Edelbrock performer 383, has that port that runs underneath the carb traveling to other side. The heads have that port right in the center that actually comes from one cylinder. If vacuum/air etc is traveling straight across into the other head, could it be choking itself out not producing / maintaining vacuum? I don't know!

I know that's a lot in the early a.m. But I think of this stuff all night!

 

That cam you installed is a 302* cam.... It's too large for an old 9.0.1 C/R motor....

Have your engine guy put in some 12.5.1 and that should give that cam some bang for it's buck....

 

call me clueless but I don't get the 12.5.1?

 

m -

Bob means 12.5:1 compression pistons or machine work to raise the comp ratio.

Definitely have the engine looked at by some one who know what they are doing.

If you decide to keep that cam, the build problems corrected and the vacuum remains that low, you are looking at secondary vacuum pump - among other things.

Archer

 

Archer, thanks! had a brain dead moment..Been a long week and only Wednesday....

 

Thanks Archer....

Myraman... I think you just a little to big of a cam for the motor....
I would have made a recommendation of something in the 260* or 270* at most for that stock motor.

just my two cent...