390 hard starting-warm engine

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Jul 18, 2005 | 08:19 PM

highrider76

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390 hard starting-warm engine

The vehicle is a 76 f250 w/ 390, auto tranny.
It has a new comp 252H cam, A 1968 (I think) gt 4 barrel intake and a 650 holley. No egr.

It is hard starting with a warm engine,if i get it started at all. It pops right off when its cold and idles well.

According to the trouble shooter in my holley book i think it has a sticking "exhaust-manifold heat control valve" that routes exhaust through a passage in the intake to create a "hot spot". (found on most vehicles prior to 69).

I have no clue what i am looking for or how to fix the problem?
DID i miss something when i didnt put egr on the vehicle?

thanks
Highrider76

Last edited by highrider76; Jul 18, 2005 at 08:21 PM.

Jul 18, 2005 | 09:07 PM

ford390gashog

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From: Brentwood,CA

does the engine turn over slow when hot? it could be your base timing is way to far advanced.

Jul 18, 2005 | 09:16 PM

highrider76

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Quote:

Originally Posted by ford390gashog

does the engine turn over slow when hot? it could be your base timing is way to far advanced.

The truck is set a around 15-18 cant remember, prolly closer to 18. Tommarow I am goin to try about 12 i found that number somewhere this evening. yes it cranks alot slower hot

Last edited by highrider76; Jul 18, 2005 at 09:38 PM.

Jul 18, 2005 | 09:36 PM

stretch351c

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From: Stanton,Ne

A couple of things come to mind.You might have a vapor lock problem due to the fuel line routing on the 390's. It runs up right next to the drivers side exhaust manifold. Or, if your not getting spark your coil could be getting hot and not working right. I had both problems on my F250 with a 390. I moved the fuel line by lengthing it and re routing and replaced the coil. I still have a bit of a problem warm but nearly as bad. Usually I treat it like it's flooded, put it on the floor and hold it til it starts.

Jul 18, 2005 | 09:39 PM

ford390gashog

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From: Brentwood,CA

18 is way too much base timing for your engine. thats the reason why its hard to start when warm. bring it down around 12 or 10 btdc.

Jul 19, 2005 | 12:07 PM

76supercab2

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Wouldn't it be a much better idea to have a very low inital timing. Then have the active advance (centrifugal and vacuum) activate at a very low rpm (say 900 or 1000). That way you'd have easy starting and good power. How? Because you don't drive at idle (800 RPM) and expect a lot of power. If the advace came on quickly off idle it would be similar to having an high initial advance.

Jul 19, 2005 | 01:42 PM

highrider76

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Quote:

Originally Posted by highrider76

According to the trouble shooter in my holley book i think it has a sticking "exhaust-manifold heat control valve" that routes exhaust through a passage in the intake to create a "hot spot". (found on most vehicles prior to 1969.)

Ok the timing @ 12 fixed the hot start problem but still will the exhaust crossover cause problems? This vehicle doesnt have the valve the book talked about? I put plugs in the extra fittings on the intake that i think may lead to the crossover.

I read somewhere that you can put block off plate on the intake gakets to block these off or will i be alright leaving it as is?

i'm already over budjet for the project so i dont want to spend much more .

Last edited by highrider76; Jul 19, 2005 at 01:46 PM.