70 Challenger T/A - No Idle, runs poorly after lifter/pushrods replaced

[Russ Furchner]

Long story here.... Seemed like a simple job, but I did a lot of things at once and want to verify if I'm on the right track. I had a lifter that was making noise, I could not stand it, so I replaced the lifters and pushrods. The cam showed no strange wear and compression was 150psi+ per cylinder, so I decided to just do the lifters and pushrods, it's the original engine, so I made sure I got the overall length right. I also replaced the metering block on the center carb with a new part from Holley (suspect) and re-assembled the top-end. I set and re-checked the lifter pre-load, so I'm confident that I did that right. On initial start-up, the engine would not idle and backfired through the carb if you let the RPM's get too low. I went ahead and ran it for 20 minutes @ 2000 (ish) as has been suggested to break everything in. I suspected vacuum leaks, so I checked the carbs and they seemed to be fine. I then pulled it all back apart and it looked like the manifold gasket had not sealed properly, so I started again. Once again on re-start, same issue. On the accelerator pump, it will rev smoothly, but not hold RPM. So I adjusted the idle mixture richer, and it helped a little. I decided the the intake ports did not seal again, so back apart it came. I have ordered new (different) manifold gaskets and am going to eliminate the cork gaskets after testing the seal with masking tape and marker. Will use a bead of RTV as others have suggested in place of the cork. I did not remove the distributor and firing order checked/rechecked. No soot on the plugs, I'm pretty sure I'm dealing with a lean condition, probably vacuum leak, but I'm also suspicious of the new metering block. I'm going to use the old one unless I can convince myself that the new one is OK. Someone along the way deleted the vacuum advance on the car and I want to put it back to stock. I'm suspicious of the new metering block because in addition the the vacuum advance port, it has what appears to be metering rods behind the jets in the supply tubes. The plugs on the top of the metering block are marked with "50" and the old metering block has nothing like that. Many questions here, but I would appreciate the opinions of those with more experience than me.

 

[Chryco Psycho]

Wow where to start .
Cam wear can be a problem with newer oils so possibly the new lifters tore up the old cam , if you are pulling the intake measure the lift of each lifter & visually inspect the cam , I assume the lifter noise is gone ?
What is the new metering block from ? it could have corrosion or dirt inside , causing issues or it could just be an incompatable part for that carb . if you swap the metering block & the problem disappears you know you found the gremilin at least !
Any evidence of the intake gaskets not sealing when you removed the intake ? intakes generally are not hard to get to seal if you use good gaskets

 

[Russ Furchner]

Thanks for the reply, the cam is good, first thing I checked. No issues with the valve train, very quiet now. On the manifold gasket, I think the cork bits that seal the galley are thicker than necessary. Probably 3 to 4x the resting gap of the intake to the block. The evidence was a oil past the sealing point and in a couple of intake ports. I am also suspecting the metering block, I bought it as an engineering part, looks like the right one, Holley told me it was the right one, but it could be defective or they made a mistake. I used Fel-Pro gaskets, got a different set, maybe a bit better on the way. I am pretty convinced it's fuel, either a vacuum leak or the metering block. Eliminating both next time it's back together.

 

[moparleo]

Adjustable rockers, right ? Besides the carb problems I would check the cam lobes. You said original engine and a lifter was making noise? Replacing all the lifters and the push rods without checking lobe wear just seems odd.

 

[moparker]

Needle valve in the carb might have some dirt

 

[Ralph]

Unplug the vacuum advance and see if it runs without the backfire

 

[DetMatt1]

What brand are the new lifters? last set of Comp Cams lifters I bought were bad out of the box and it took me a while to figure it out As the issues started out rather intermittently.

 

[Russ Furchner]

Comp Cams lifters and pushrods. I did check the cam completely and did a compression check before I made the decision to proceed. That was the decision point between a rebuild, full timing set and this fix. I measured and inspected the cam first thing, no pitting, no flat spots, normal wear pattern. The lifter noise was one lifter, must have been an internal issue, there was no cupping or any unusual wear on the old lifters and it was only under certain conditions. The engine ran well, too rich, but well before I started. I checked the cam again after I took it apart and checked the pre-load again, that part of the job I'm pretty certain was done right. Assembly lube was used on all the moving parts and after the initial lifter pump-up, perfectly quiet. I did more research on the center carb metering block last night, I had the vacuum port sealed since I don't have a distributor to support it yet. I'm pretty focused on that as the issue right now. I've not seen any other examples where there are brass rods (looks like restrictors) in the main ports with "50" on the plug on top. I might be a correct block, but the set-up is for something else. I just don't think I'm getting enough fuel on the idle circuit or main jets. It's happy when the accelerator pump is providing fuel.

 

[oldkimmer]

U don’t have any plug wire crossed do ya? Kim

 

[Russ Furchner]

One more point. I purchased this car as a survivor, advertised as un-touched. It is numbers matching, build sheet and fender tags match the car. Someone has messed with the top-end before for sure, the silicone was a dead give-away and the center carb is not original. I'm suspicious that the engine was also re-built at some point, it would be rare to have a 50 year old engine have compression between 150 and 152 psi per cylinder on all 8. That's the big reason I did not change the cam, given what I saw, the general lack of wear, almost impossible for a 50 year old car with 70k miles on it.

 

[Russ Furchner]

U don’t have any plug wire crossed do ya? Kim

I've checked that soo many times...... Good call. I even checked each wire in case I messed one up during the process.

 

[70chall440]

After reading this my initial feeling is that it is carb related, however it could also be a vacuum leak or a combination of the two. The six pack (carb) I had on my 70 Challenger was somewhat similar; always was a battle to get it run right, I rebuilt the carbs I don't know how many times. I always suspected there was something going on with the metering value (bad passages, drilled passages, etc.) but since you replaced that you should be good.

2 other things come to mind; first is jets and second the butterfly set up on the outboard carbs (if it seems lean they they might be set too tight).

 

[Russ Furchner]

After reading this my initial feeling is that it is carb related, however it could also be a vacuum leak or a combination of the two. The six pack (carb) I had on my 70 Challenger was somewhat similar; always was a battle to get it run right, I rebuilt the carbs I don't know how many times. I always suspected there was something going on with the metering value (bad passages, drilled passages, etc.) but since you replaced that you should be good.

2 other things come to mind; first is jets and second the butterfly set up on the outboard carbs (if it seems lean they they might be set too tight).

Good to hear this. I love the idea of the six pack, but keep 3 carbs in sync is not easy. I've rebuilt them as well, so the outboards seem to be working well and the are probably original, The center carb has been messed with for sure, so I have no idea of a baseline. This weekend, I'm using the old metering block, which lacked a vacuum advance, but worked. Replacing the .070 jets/power valve delete with .061 and a 7.5 power valve. I'm also suspicious that the block may have been decked given the tolerance between the block and intake manifold on the block ends, it's only about .070, so very tight for cork gaskets. Going with the black RTV instead, just to guarantee a seal. Because I'm OCD, I'll re-check everything along the way. 3rd time is the charm.

 

[budascuda]

I have never had any luck replacing a leak free intake manifold with the distributor still in!
Nevvver......
Didn't the motor run fine before the "procedure" ?

 

[70chall440]

Good to hear this. I love the idea of the six pack, but keep 3 carbs in sync is not easy. I've rebuilt them as well, so the outboards seem to be working well and the are probably original, The center carb has been messed with for sure, so I have no idea of a baseline. This weekend, I'm using the old metering block, which lacked a vacuum advance, but worked. Replacing the .070 jets/power valve delete with .061 and a 7.5 power valve. I'm also suspicious that the block may have been decked given the tolerance between the block and intake manifold on the block ends, it's only about .070, so very tight for cork gaskets. Going with the black RTV instead, just to guarantee a seal. Because I'm OCD, I'll re-check everything along the way. 3rd time is the charm.

I don't know that I would use RTV on the carb, I think I would try and get/make a paper gasket before that. As I recall, Holley has some blue fiber gaskets that might work better.

 

[NoCar340]

I don't know that I would use RTV on the carb, I think I would try and get/make a paper gasket before that. As I recall, Holley has some blue fiber gaskets that might work better.

I think (hope) he's talking about using it as a replacement for the cork end gaskets between the intake manifold and block, which are generally more of a problem than a solution. I haven't used 'em in decades. Just run a bead of silicone between the intake flange gaskets, let it skin over, and install the intake without those end pieces.

I'd be willing to bet those intake end gaskets have been the problem all along. They almost always are.

 

[Russ Furchner]

I don't know that I would use RTV on the carb, I think I would try and get/make a paper gasket before that. As I recall, Holley has some blue fiber gaskets that might work better.

I meant at the ends of the intake manifold in place of cork.

 

[Russ Furchner]

I have never had any luck replacing a leak free intake manifold with the distributor still in!
Nevvver......
Didn't the motor run fine before the "procedure" ?

Yes, it ran well. The power valve delete made it run too rich and the lifter noise bugged me, but it ran well.

 

[Russ Furchner]

I think (hope) he's talking about using it as a replacement for the cork end gaskets between the intake manifold and block, which are generally more of a problem than a solution. I haven't used 'em in decades. Just run a bead of silicone between the intake flange gaskets, let it skin over, and install the intake without those end pieces.

I'd be willing to bet those intake end gaskets have been the problem all along. They almost always are.

Exactly.

 

[AUSTA]

Did you do a compression test after the installation of new pushrods