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Discussion Starter #1
Hey guys,

i have a 383 stroker, and a th350 transmission. not sure what the lockup is on the torque converter.

i am using a street demon 750 carb.

the car runs great idles around 1000 RPMs when in park, and idles without issue in neutral.

However when i put it into gear it drops idle down to around 600 usually.

I also am having an issue that when i cruise down the road, and start to slow down pressing the break that the car will stall out.

In all cases if i give it a little bit of gas when it starts to stall it stays running.

What would you do to trouble shoot this? I did pull the carb and make sure floats are right and everything seems to be setup correctly.
 

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Discussion Starter #5
It uses a vacuum line for power brakes, pcv, and then a line going down to the transmission.

I'm using a msd distributor that does not rely on vacuum to advance so the nipple for that is caped off.

It has the original transmission, this is my first automatic so I'm not really sure what the vacuum line is for and what the right terms are, stall may be the correct term to use here instead of lock. Po said it was a th350 transmission. It's a 3 speed automatic.

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^^

Ah, yep simple old TH350 with a vacuum modulator. Likely a 1200-1800 rpm stall speed, if its a GM or stock replacement torque converter.

Still thinking vacuum leak, which could be the carb, intake, booster or any hard/rubber lines. BTW, what carb are you running?

Sounds like they locked out your MSD advance, I prefer to run vacuum advance. Is it a stock or radical running engine?
 

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Discussion Starter #7
^^

Ah, yep simple old TH350 with a vacuum modulator. Likely a 1200-1800 rpm stall speed, if its a GM or stock replacement.

Still thinking vacuum leak, which could be the carb, intake, booster or any hard/rubber lines. BTW, what carb are you running?

Sounds like they locked out your MSD advance, I prefer to run vacuum advance. Is it a stock or radical running engine?
It is supposed to have a higher stall than stock.

It has a mild street cam, but I don't have any specs for it. Also has stock heads on it. The PO had planned to build it as a 400-500 hp street car, and then ran out of money so it's got a 383 bottom end that could breath alot more with the proper top end on it. Im Planning on getting a top
Kit in a few months so that I'll know what I've got.

Is is possible to drive if I disconnect the vacuum goin to the transmission?

I was thinking I should just pull all the vacuum lines and just cap them to see if it fixed the issue, and then connect 1 at a time back on to see if anything makes the stalling return.


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Sorry, forgot you mentioned a 383 already. You should be able to cap off the vacuums, you will not have good brakes (very hard) and the trans will shift at very high rpms, I do not suggest you drive it. Might be able to see about putting it in gear (chock tires), you can also use some carb or brake cleaner to spray around fittings, bolts etc.

Do you know what your timing is set at by chance? Would think it would be 12 or so BTDC and 32-36 at rpm.

I have seen timing being set wrong and idle adjusted to compensate, leading to similar situations. People do some weird stuff prior to selling or when finances become an issue.

Check your booster fitting and rubber grommet too.
 

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Discussion Starter #9
Sorry, forgot you mentioned a 383 already. You should be able to cap off the vacuums, you will not have good brakes (very hard) and the trans will shift at very high rpms, I do not suggest you drive it. Might be able to see about putting it in gear (chock tires), you can also use some carb or brake cleaner to spray around fittings, bolts etc.

Do you know what your timing is set at by chance? Would think it would be 12 or so BTDC and 32-36 at rpm.

I have seen timing being set wrong and idle adjusted to compensate, leading to similar situations. People do some weird stuff prior to selling or when finances become an issue.

Check your booster fitting and rubber grommet too.
So when I unhooked the booster there was air that it released, so it seems to hold there. Grommet is good.

If I wanted to test the lines couldn't I just hook up a hand pump and build it up to Round 25 psi, then if it starts to drop that's a bad line.

No timing tape on the motor so not sure what the initial is set to, and I'll have to open the distributor to see what springs are in it to get the advance

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