Motor cut off in drive/reverse

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Coolio

Not-quite-so-new-guy
Apr 23, 2018
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I have a Pontiac 400 with 700r4 an Holley 600 carburetor. Car idles pretty good but when I go to put it in drive it just cut off. Not sure what it could be ,any help would be appreciated.
 

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pontiacgp

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Mar 31, 2006
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Kitchener, Ontario
You're missing a power wire on the electric choke which means the choke will always be on. Have you checked all the vacuum lines?
 
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Coolio

Not-quite-so-new-guy
Apr 23, 2018
31
9
8
You're missing a power wire on the electric choke which means the choke will always be on. Have you checked all the vacuum lines?
I will install the power wire. I'm not to sure what to look for when checking the vacuum lines.
 

pontiacgp

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Mar 31, 2006
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Kitchener, Ontario
One other thing I would do is hook up your pvc to get rid of some of the pressure built up

pcv.jpg
 

MrSony

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Nov 15, 2014
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Des Moines, Iowa
That port on the carb is where the distributor vacuum advance plugs in, for ported vacuum, or "timed vacuum", as it were. From the looks of it, you have your vacuum advance plugged into the base plate, for manifold vacuum so you're getting extra timing at idle, instead of at cruise speeds when vacuum is low. PCV should be hooked up, get whatever the parts store says for a valve for like a... 77 grand prix with a 400 (6.6L) or something. Sites like Year one or whatever might have pre-molded PCV hose that hugs the engine and looks tidy. They are different sizes of valves, so one in the "help" section may not work 100%, but I've been using one of those and been just fine. What's your idle speed? If it's too high (high idle on, like with your choke not being hooked up), it will kinda "startle" the engine when you put it into gear. I dealt with that on my car forever until I made the choke work. idk about pontiac engines, or where the oil pressure port is, but on my Buick 350 (car was originally a 3.8, same engine +/- 2 cylinders), I teed off the factory port location and as well as running a mechanical gauge I have a little two prong sender (and a two female slot 3 wire factory plug I cut off a 3.8 at a junkyard) to get power from the fuse box, the wire from the light, and a wire from the middle prong to the choke. Works like a charm. The switch is normally open, closes with 4psi of oil pressure, ergo, car on = choke power. It's a neat little setup, I like it better than the alternator method or splicing into whatever other switched 12v there is.
 

pontiacgp

blank
Mar 31, 2006
29,270
20,391
113
Kitchener, Ontario
That port on the carb is where the distributor vacuum advance plugs in, for ported vacuum, or "timed vacuum", as it were. From the looks of it, you have your vacuum advance plugged into the base plate, for manifold vacuum so you're getting extra timing at idle, instead of at cruise speeds when vacuum is low. .

Ported makes the engine run hotter burning off more pollutants. Before the emissions crunch the vacuum advance was hooked to the mainfold vacuum which will give you better performance and gas mileage if the timing is set up properly.
 

MrSony

Geezer
Nov 15, 2014
6,793
6,679
113
Des Moines, Iowa
Ported makes the engine run hotter burning off more pollutants. Before the emissions crunch the vacuum advance was hooked to the mainfold vacuum which will give you better performance.
Kinda depends on the engine as well. My 429 BBF from '70 didn't like manifold at all, but ran like a top on ported. My 8:1 SBB could have really given a damn either way, and my 10:1 '70 SBB likes ported as well. My uncles stock 307 Chevy C/10 liked manifold though.
 
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