Low RPM Hot Restart

[Nfg]

Hello I'm hoping someone can point me in the right direction here. I'm having an issue with warm restarts after my car sits for 10mins or longer. When I turn the key (No gas) The car fires after slight delay but only at 100rpm then after about 15-30 seconds will hit 550 rpm (base idle is 700)

The car is a fresh 355 roller vortec heads comp XR264Hr 110lsa 1.5 rockers. Running manifold vacuum base timing 14 deg. The carb is a brand new jet stage 2 800 cfm https://www.summitracing.com/parts/jet-36002/overview/

I have full control over mixture screws and can stall the engine. I have 15.5" of vacuum at 700 rpm at 4.25 turns. Idle is 575-600 rpm in drive. Float level is in spec, fuel pressure is 5.5psi. from my untrained eye I see no nozzle drip. Carb does not leak down and cold starts like a dream.

I think its a carb issue because my old quadrajet does not have this problem. This is my 3rd Jet performance quadrajet in a month. The first one leaked down. The 2nd was a whistling peat. This one seems ok, But they ALL did this exact same hot restart problem.

Thanks for any help

[Frank400]

Do you have a return line ?

[Cliff Ruggles]

Three in one month?  Time to get something else.  I see WAY too many of those sent here for similar issues, and other problems as well.  They aren't much if any better than the commercially "remanufactured" stuff, and the clear epoxy they use over the bottom plugs leaks and peals right off with a pocket knife!.....Cliff

[Nfg]

Do you have a return line ?

No return line.

[Nfg]

Three in one month?  Time to get something else.  I see WAY too many of those sent here for similar issues, and other problems as well.  They aren't much if any better than the commercially "remanufactured" stuff, and the clear epoxy they use over the bottom plugs leaks and peals right off with a pocket knife!.....Cliff

Yes the biggest mistake I made was buying this carb for $400. Unfortunately I was un aware of your services when I bought this thing  I ordered your book the other night and look forward to figuring this thing out.

I'm not sure if I should rebuild this carb with one of your kits and recipes or find a good used core. I have another carb that doesn't do this but someone has monkeyed with it and drilled the stamped holes on the primary butterfly's. Does jet do any funny stuff internally that would make this a poor candidate? Also not sure if this 800cfm carb was the best option to get.

Yes this is my 3rd carb in one month! The only positive from this experience is Summits customer service is top notch! The first carb I received would leak down overnight and poor cold and hot restarts. I first called Jet and some guy who sounded like he was not supposed to answer the phone told me to just stick it in a box with my receipt and a note whats wrong. When i asked for the address he wasn't sure and said to verify it with google. Knowing I would probably never see the carb again if I did that, I called Summit and they sent me out a new carb the same day no questions asked.

I tore down the first carb thinking the welch plugs were leaking. they were ok but I did see the clear stuff they put over them and yes I could scrape it off with my finger nail. The issue was 5 pin holes in the bowl, porous casting?

The second carb didnt leak down but the passenger side mixture screw was cross threaded, the air horn leaked and it would whistle like a banshee at 1500rpm and hard hot restart. Called Summit and they sent me out a new one the same day.

The 3rd carb seems ok and runs good but still having the same hot restart issue. Will start after slight delay but barley run. If I touch the gas before I start it, it will flood.

I'm pretty sure they don't test any of these carbs at least non of the ones I received. junk!


 

[Frank400]

What is the carburetor number on that Jet carb ?

[Cliff Ruggles]

We get calls in here all the time from folks who bought those and want us to crawl thru the phone and fix them.  I don't really want any sent here, nor do we want anything purchased over the counter from an auto parts store.  Much better end result to start out with an unmolested core and completely/correctly rebuild it exactly for the application....IMHO....Cliff

[Nfg]

What is the carburetor number on that Jet carb ?

17083222

[von]

I had the same problem and it turned out to be too much fuel pressure from a stock replacement parts store fuel pump, Airtex brand. I tried two of them with the same result. Stock 350 Chevy engine. I got an AC Delco pump from a Chevelle repro parts house and problem solved. I put a fuel pressure gauge and then a fuel pressure regulator on it to verify the cause. After it was shut off hot the fuel pressure would rise even higher for a little while, overcoming the needle and seat and cause flooding, which caused the hard start. If it would sit long enough for the engine to cool some, the pressure would drop enough and excess fuel in the intake would evaporate and engine would start OK.

[Nfg]

I had the same problem and it turned out to be too much fuel pressure from a stock replacement parts store fuel pump, Airtex brand. I tried two of them with the same result. Stock 350 Chevy engine. I got an AC Delco pump from a Chevelle repro parts house and problem solved. I put a fuel pressure gauge and then a fuel pressure regulator on it to verify the cause. After it was shut off hot the fuel pressure would rise even higher for a little while, overcoming the needle and seat and cause flooding, which caused the hard start. If it would sit long enough for the engine to cool some, the pressure would drop enough and excess fuel in the intake would evaporate and engine would start OK.

Thank you for posting this. I had a Delco pump that was putting out 9 psi. Thinking that was the problem I installed a carter pump that is rated at 5.5 psi but really is just under 6 psi and still had the same exact issue. After reading your reply I hooked up the pressure tester and after shut down fuel pressure goes over 8 psi with in 10 mins.

My fuel lines are not close to any heat sources and running a plastic spacer. But I will install a regulator and see if it helps.



 

[Frank400]

That is a case where a return line would REALLY (read solve) the problem.

  Frank.