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Discussion Starter #1
I have a 73 corvette. Car would randomly loose power or stall while idling, highway over bumps etc. Was able to put car in neutral and restart. Then could not do this and and to stop and put in park. Due to other reasons have had a new 350 small block installed with thumper cam, Holley 1850c (600cfm) edelbrock 7501(sbc intake man) all out of box. Problem is it still stalls! Have found trace residues of rust in gas. Wondering if this could be the culprit. There is no spacer between carb and intake so hood would close. My mechanic believes there to be a vaporize issue because of this. I've been driving in sub freezing temps and still stalling. Neutral safety switch? If anyone has any ideas...
 

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if you see rust in the fuel, my first thought is a clogged fuel filter or line or sock in the tank..check your fuel pressure[should be 3-6psi] somethings cutting off fuel flow.. the lack of a phenolic spacer under carb, won t affect the engine while running.only percolation after shut down when hot... if all is ok,Then, check wiring to distributor , the distributor itself, and possibly for a bad coil. good luck and welcome to SV
 

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It does sound fuel related and Fish is probably right. But a new Holly may need some float adjustment. Do they still have the plastic view plugs that rot away?
 

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I have a few ideas to offer but wanted to find out a little more about your car. Is your transmission an automatic or manual? When the stalling occurs is it at idle speed immediately or takes a few seconds, minutes? If an auto does it do this in gear only? in Park? both?

Since it sounds like the stalling is the same now with the new engine as it was before I would look at any and all parts that were reused ex. fuel pump, distributor and other ignition parts, fuel lines, things like that just to help find a common denominator if there is one.

Lastly something I would look at that could have existed before is a vacuum leak. I would look at hoses to and from the engine going to the headlights.

On another note just FYI, I have a Thumpr cam and the carb your using is a universal carb and you'll probably going to find it to be too small, especially with a single fuel inlet versus a dual feed. If you need any help tuning it let me know since I've tried a lot of different things trying to get everything out of it and can offer the things that didn't work and what has.

Good luck and keep us posted, Welcome to SV
 

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it does sound fuel related and fish is probably right. But a new holly may need some float adjustment. Do they still have the plastic view plugs that rot away?
I just unscrew the brass plugs in the float bowls
they make clear ones ?
cool
won't use them for racing though....
 

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I just unscrew the brass plugs in the float bowls
they make clear ones ?
cool
won't use them for racing though....
I wouldn't use them for anything!(well maybe a display engine) exposure to fuel clouds them for one and then they freeze up forcing you to have to remove the bowls after they break off when you try to remove them then you have to knock out the threaded area. Not worth the hassle, nice idea but flatout don't work.
 

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Demon carbs have glass plugs that don't cloud or deteriorate. Best to leave in the brass unless the glass Demon plugs fit.
 

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Discussion Starter #10
I have a TH400 trans which was just rebuilt with B&M shift kit. The fuel pump has been changed, inline filter, msd distributer, wires and plugs. The headlights have been converted to fixed. Car stalls at idle on occasion. Typical example is car drives fine for 20 min. Park to go into a store come out and hit the gas a little heavy. Next couple minutes it starts to sputter cuts off and on. Then starts dying every other block till I get it home. Also when I'm cruising on the hwy at left off the gas to get off, Trans down shifts and car dies. It always starts right back up. I use to stick it neutral and restart. Wont start in neutral any more and i have to stop in the middle of the freeway and restart. Thank to everyone for the advice.
 

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I heard demon just closed it's doors
 

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I have a TH400 trans which was just rebuilt with B&M shift kit. The fuel pump has been changed, inline filter, msd distributer, wires and plugs. The headlights have been converted to fixed. Car stalls at idle on occasion. Typical example is car drives fine for 20 min. Park to go into a store come out and hit the gas a little heavy. Next couple minutes it starts to sputter cuts off and on. Then starts dying every other block till I get it home. Also when I'm cruising on the hwy at left off the gas to get off, Trans down shifts and car dies. It always starts right back up. I use to stick it neutral and restart. Wont start in neutral any more and i have to stop in the middle of the freeway and restart. Thank to everyone for the advice.
Based on this info I would say it is Fuel related. Almost sounds like the choke is acting up in some way causing a rich condition which will stall as would a lean condition. You might need to pull the spark plugs and see what kind of color you have to indicate which way the fuel mixture is going.

Fuel pressure would be another thing to check at idle when the engine is cold then hot. Location of the fuel filter could cause a vapor lock condition, type of filter can hamper things as well. I would certainly double check the float levels. Mine were a bit low at one time and heavy acceleration then stopping for a light with a heavy brake would cause it to try and stall out, feathering the throttle would save it in neutral but after raising the floats the problem stopped.

On the old engine, what carb did you have? I know you said you have a 600 cfm 0-1850 now, just curious since it's doing the same thing.

Did you increase the compression any with different cylinder heads? again just curious
 

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I m with PBV, It sounds like a flooding condition..floats not set right or too much fuel pressure forcing needle and seat open..Holleys don t like more than 6psi.. I would still check the coil too..
 

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Just had a thought- check the wire between the distributor and the coil. It flexes everytime the vacuum advance moves the breaker plate in there. If it hits just right, it'll pull the break apart and shut you down. As soon as it quits, the break goes back together and away you go.

Fish- Demon filed bankruptcy and closed the doors.
http://www.hotrodders.com/forum/barry-grant-goes-bankruptcy-166809-2.html
:doh:
 

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Wow! I had no idea they were going under! Its a shame, they had some pretty good stuff. I guess hi-perf carburetors are a dying art, eh? Everybody wants fuel injection, now.
 

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Discussion Starter #17
On my way to the shop armed with all of your ammunition on troubleshooting this problem. I will post the outcome soon. Thanks again to everyone that responded.
 

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I have a 73 corvette. Car would randomly loose power or stall while idling, highway over bumps etc. Was able to put car in neutral and restart. Then could not do this and and to stop and put in park. Due to other reasons have had a new 350 small block installed with thumper cam, Holley 1850c (600cfm) edelbrock 7501(sbc intake man) all out of box. Problem is it still stalls! Have found trace residues of rust in gas. Wondering if this could be the culprit. There is no spacer between carb and intake so hood would close. My mechanic believes there to be a vaporize issue because of this. I've been driving in sub freezing temps and still stalling. Neutral safety switch? If anyone has any ideas...
my 78 vette vette started doing this and my guy said same thing...vapor lock. So we put on a phenolic spacer 1/2 inch..still did the same thing. Had a 795cfm rochester carb on it. We bought an Elderbrock top end kit (carb included) replced the old. It ran gr8 25-35 miles than all of the sudden I was having to drive 2 footed! Took it back to out guy and don't ya know the distributor went bad. We had it replaced and now she purrs. He believes the distributor was the original or 80's era replacement.
 

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Just had a thought- check the wire between the distributor and the coil. It flexes everytime the vacuum advance moves the breaker plate in there. If it hits just right, it'll pull the break apart and shut you down. As soon as it quits, the break goes back together and away you go.
good one
It's been years since I dealt with points type distributors.....
I do remember that happening to me back in the early 80's

I feel old......thanks.....:smilielol5:
 

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I have a 73 corvette. Car would randomly loose power or stall while idling, highway over bumps etc. Was able to put car in neutral and restart. Then could not do this and and to stop and put in park. Due to other reasons have had a new 350 small block installed with thumper cam, Holley 1850c (600cfm) edelbrock 7501(sbc intake man) all out of box. Problem is it still stalls! Have found trace residues of rust in gas. Wondering if this could be the culprit. There is no spacer between carb and intake so hood would close. My mechanic believes there to be a vaporize issue because of this. I've been driving in sub freezing temps and still stalling. Neutral safety switch? If anyone has any ideas...

Stalling can be caused by a number of things. It's nothing unusual for a fuel pump to bind up inside and suddenly quit pumping (I had that happen recently). And stalling can be the result of a bad electrical connection at or in the distributor. Or in the ignition switch. Cars don't vapor lock anymore as we don't have the cheap fuels anymore like we did in the 50's. If it feels like you're losing power right before the engine dies that is most likely being caused by a fuel delivery problem. You can tee a mechanical fuel pressure gauge into the gas line right at the carburetor and then tape the gauge to the outside of your windshield..........then observe your fuel pressure while you're driving.
 
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