Propane question

pplblazerdude · Sep 19, 2017

Currently on my buggy I have a impco 425 with a adaptor to quadrajet baseplate on top of a adaptor to square bore. This is the way it was when I got it. I have had trouble with off idle power and have found that I have a vacuum leak around the throttle shaft and can't seem to get all the carb gaskets to seal good. Has total of 4 with all the adaptors.

I am wanting to switch to a Holley throttle plate to eliminate all the extra crap. What throttle plate are your guys running? Did you have to do any mods to it to make it work with propane?
I have been looking at this one
http://www.jegs.com/i/Holley/510/112-118/10002/-1

Only thing I have seen people possibly do is plug the small hole in the center of the ports.

Please let me know your thoughts as I'm sick of this mess.

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ForMud · Sep 20, 2017

I don't remember what model Holly carb I used the base plate off, but it was a 600 cfm "Throw away" we used to get for $145 way back when ( Their $320 now ). I don't remember clogging off any holes.
On the Qjets, We used to reaming out the holes where the shaft ran though the base and put bushing in there to tighten them up.

pplblazerdude · Sep 20, 2017

ForMud said:
I don't remember what model Holly carb I used the base plate off, but it was a 600 cfm "Throw away" we used to get for $145 way back when ( Their $320 now ). I don't remember clogging off any holes.
On the Qjets, We used to reaming out the holes where the shaft ran though the base and put bushing in there to tighten them up.

I've got a Holley base coming. Should fix me up

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deranged57 · Sep 27, 2017

Seems I am a little late to the party - on my propane setup I used the holley 850cfm mechanical secondary (double pumper) base plate. This is the exact piece i have http://www.allcarbs.com/detail.php?pid=489&gb=1&ctgn=4&stt=0 it is also available in red.

pplblazerdude · Sep 28, 2017

deranged57 said:
Seems I am a little late to the party - on my propane setup I used the holley 850cfm mechanical secondary (double pumper) base plate. This is the exact piece i have http://www.allcarbs.com/detail.php?pid=489&gb=1&ctgn=4&stt=0 it is also available in red.

I ended up going with a Holley 4150 600cfm base. This is on a 4.3 and also the impco only
Flows 425. Going this weekend to ride so hopefully I will be pleased. Seems from the little running around the neighbor hood I will be.

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Rockwells607 · Oct 3, 2017

Will Changing the base plate increase the cfm ? I thought you had to go with two units to do so? In interested as m wife is still running propane on her 347 stroker

pplblazerdude · Oct 4, 2017

Rockwells607 said:
Will Changing the base plate increase the cfm ? I thought you had to go with two units to do so? In interested as m wife is still running propane on her 347 stroker

I don't see how it could. I do know that my buggy runs much better now since i got the holley on it and got everything sealed up good. Very happy with it.

paradisepwoffrd · Oct 4, 2017

From my understanding, the most restrictive piece is the limit. If the mixer is 425cfm and baseplate is more, changing it wouldn't change much unless you went to <400.

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