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Old 05-05-2010, 09:38 PM
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273ci falling flat under load..what gives?

Hey Gang...

Been having some trouble getting the 273 in my 41 Plymouth Rod project running properly...maybe someone can help me out.

I had to rebuild the engine after discovering worn rod bearings last year, so she's all new inside. The only non-stock items are the 468 lift cam and hydraulic lifters (with new push rods, of course...)

Engine starts and idles fine, but when I get out to drive, it start to accelerate, and then at about 1800 rpm, it starts to sputter and bog. Can't accelerate thought it either.

Thought it was fuel, so I rebuilt the carb, and inslled a new electric fuel punp..so it's not fuel. Then I thought it was plugs...so I put new plugs in..nope, not that either! So I figured that it was the original points/condenser distributor that I was using. Soooo I bought a new Mopar Perfomance electric distributor...tried it today, still the same!

I am stumped! Any ideas would be great!

Ty

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Old 05-06-2010, 04:29 PM
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perhaps timing chain maybe a tooth off

can you do a compression check?
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Old 05-06-2010, 05:12 PM
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Quote:
Originally Posted by Tyroma
The only non-stock items are the 468 lift cam and hydraulic lifters (with new push rods, of course...)

Engine starts and idles fine, but when I get out to drive, it start to accelerate, and then at about 1800 rpm, it starts to sputter and bog. Can't accelerate thought it either.
I'd be interested to know what the vacuum was, when the sputtering began and during it. If possible, mount a vacuum gage where it can be read during a drive and see what the results are.

There's a pretty good chance that the ignition advance will need to be increased over what it now is- but the TOTAL advance can't be too much, or detonation will occur. Just to see if more timing will help, increase it about 10 and drive it gently (do NOT run it up high RPM, this is just to see if the bog/stutter is lessened or eliminated) and note what happens to the stutter.

What is the initial timing and the total w/o vacuum advance added in? Is the vacuum advance hooked up to a manifold or ported source? It should be manifold, if the cam has much duration and overlap.

What are the cam specs, as they appear on the cam card?

What type carb and intake are you using, and what is the carb set up like?
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Old 05-06-2010, 05:16 PM
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Quote:
Originally Posted by cobalt327
I'd be interested to know what the vacuum was, when the sputtering began and during it. If possible, mount a vacuum gage where it can be read during a drive and see what the results are.

There's a pretty good chance that the ignition advance will need to be increased over what it now is- but the TOTAL advance can't be too much, or detonation will occur. Just to see if more timing will help, increase it about 10 and drive it (do NOT run it up high RPM, this is just to see if the bog/stutter is lessened or eliminated) and note what happens to the stutter.

What is the initial timing and the total w/o vacuum advance added in? Is the vacuum advance hooked up to a manifold or ported source? It should be manifold, if the cam has much duration and overlap.

What are the cam specs, as they appear on the cam card?

What type carb and intake are you using, and what is the carb set up like?
I'll try advancing the timing, and get you the cam specs. I am using a stock 4 barrel cast-iron intake manifold and a thermoquad 4 barrel carb. The vacuum for the distributor is comming off the carb.

Ty
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Old 05-06-2010, 05:23 PM
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Quote:
Originally Posted by Tyroma
I'll try advancing the timing, and get you the cam specs. I am using a stock 4 barrel cast-iron intake manifold and a thermoquad 4 barrel carb. The vacuum for the distributor is comming off the carb.

Ty
The vacuum off the carb can be either/or (ported or manifold). What you will want to see, is if there's vacuum at idle or not. If not, you'll want to try a different port. But this likely will not make any difference as far as the stutter- the ported vacuum will be active at 1800 RPM, but it may make the engine more responsive otherwise.

If adding 10 to the base timing doesn't help matters, you're probably looking at a carb tuning issue. Or a vacuum leak, if it was bad enough. Do you have access to a vacuum gage and an accurate dial back timing light? If you just have a regular timing light, that's cool- just make a quick, temporary TIMING TAPE.

Hopefully like va4cqd mentioned, the timing set was installed correctly...
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