Have you tried putting the "old" carb back on to make sure it's not the new carb?

The fact that it's a new engine makes me think that it might be a vacuum leak.

Reason why I say that is that the intake (and exhaust) manifold needs to be retightened after installation.

Mine was WAY LOOSE after just a couple hundred miles.

Use a 1/4 inch drive click wrench and some wobble extensions, and you can retorque the whole thing in about 5 minutes. As you know - 10 foot pounds, or 120 inch pounds.

If that does not fix it - then I guess you'd have to start looking for other likely places for a leak...

The carb might also be loose. That happened to me once, and it puzzled the heck out of me till I figured it out.

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1963 Dodge Dart, motor by Doug Dutra, Offenhauser two carb intake, Pertronix, Clifford 6x2, Flowmaster 40's, Erson RV15/295 RDP, head work. Addco anti-sway bar, urethane suspension bushings, KYB's, racing leafs, SSBC discs. Need ZDDP? Get STP.

from your vacuum readings, i don't think there is a leak. 18-20 inches of vacuum at idle is normal. what is your timng set at? i had mine at 0* and it was okay, every once in a while it would miss, but only one cylinder. i have base timing set at 10* now and it idles great.

what spark plug gap are you running? i wasn't paying attention when i put mine in and the gaps were all over the place. after resetting the gaps to the same gap, .035-.040" that really helped out too.

go through the basics and make sure everything is correct and adjusted properly.

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

...you got vacuum accesories like the heater controls or power brakes hooked up? If so, try disconnecting or blocking them temporarily and see what happens...

D/W

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If it ain't broke, fix it!

I replaced the carb in an effort to solve the problem. I have one vac line to the vac advance on the dist. which I disconnected and capped. No other vac. accessories on the car.

Initially I gapped the plug to 45 as suggested by a friend who also has a Pertronix systems. Thinking that the gap might be the problem, I re-gapped them to 35.

I'm a victim of the Damper Dudes, so my timing mark is not correct. In any case, I've advanced and retarded the timing with out being able to eliminate the miss.

I've re-torqed the manifolds to 130 inch. I'm afraid to over tighten the bolts. I used gasket sealer on both sides of the manifold gasket. The sealer was rated hi-temp to 700 . I

I take it from the responses that I should be looking for a vac. leak.

The one thing I did not do when rebuilding the engine was to re-surface the manifolds. I placed a straight edge along the ports and I could see that each port was flush against the face of the straight edge.

The end ports on the exhaust manifold where about an 1/8" out of alignment with the other ports. I ground/filed the place where the two manifolds mount to compensate.

I not seeing or hearing an exhaust leak.

I'm just at a lost. I don't know what else to try. I contemplating digging out a rocker arm from my parts bin to clean-up and re-place with the rocker on the engine. I know it's not the problem, but it's about the only thing I have not done.

Thank for the suggestions.

I'll double check my bolts holding down the carb.

See also:

http://www.slantsix.org/articles/manifo ... ctions.jpg

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1963 Dodge Dart, motor by Doug Dutra, Offenhauser two carb intake, Pertronix, Clifford 6x2, Flowmaster 40's, Erson RV15/295 RDP, head work. Addco anti-sway bar, urethane suspension bushings, KYB's, racing leafs, SSBC discs. Need ZDDP? Get STP.

Wish I could help but I'm having a very similar problem with my /86 D-150. I'll keep an eye on this thread to see how you get it taken care of and maybe I can solve my problem as well. I've replacee the carb, fuel line, fileter, pump, dist. cap, coil, plugs, cables, and it still stalls and dies after it gets warmed up.

My new rebuilt developed a stumble yesterday. Just for kicks I removed the idle jets and one of them was plugged. My carb is a Holley 5200 so the idle jets are accessible from the outside. I pushed a guitar sting through the jet and a piece of brass was plugging it up. Reinstalled and it's much better but not perfect so I think I might have more crap elsewhere in the carb system.

Now one other thing you might try is to look at the hoses on the fuel delivery system. I was having problems a while ago with fuel delivery and pulled my hair out until I discovered I had a kink in the hose at the fuel tank. Got the kink fixed and it cured that problem.

This problem really sounds like fuel delivery system to me. You might measure your fuel pressure for kicks.

Good luck.

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Sweet Emotion

Last night I torqued the manifold nuts for the third time and discovered that the one under the center intake ports was stripped. So, I purchased all new grade 8 nuts and replaced all.

In order to eliminate the leak, I had to tighten them to 150 inch pounds. I am not happy with that, and I'm afraid that the manifold will crack when it heats up and tries to float.

At least the stumble is gone.

Meanwhile, I sent an e-mail inquiring about the Dutra Duals. I'll either purchase these, or remove, resurface, and replace my manifold.

Thanks for all your help.