holley 2 barrel conversion

[frost66gmc]

I am ready to the 2 barrel Holley conversion on my 66 gmc. I have rebuilt the original Stromberg carburetor and still not running right. I just want to make sure I get the right carburetor and adaptor plate. I have a 66 gmc with a 305e v6. Below are the links to the carburetor and adaptor plate I had planned on getting.


http://m.summitracing.com/parts/hly-0-4412s
http://www.jegs.com/webapp/wcs/store...=&pgGrp=search

Coul someone verify this would be the correct setup and what else I would need. The carburetor is a Holley 500cfm. It says it has a Ford downshift. I'm assuming this doesn't matter I just won't connect this linkage. Thanks so much for the help.

[bigblockv6]

Those are the correct parts so you're all set there, you may want to consider enlarging the manifold base opening to match the bigger ports of the carburetor and adapter so there's no restriction in the flow of fuel.

[frost66gmc]

Thanks big block v6, could I just use a small grinder on the intake manifold. I just need to make sure I don't grind too close to the bolts on the manifold. The adapter will align up with these bolts. Right?

[bigblockv6]

A small die grinder with a bit, just mark out how much area you want to clean out, it's relatively easy task. The bolt holes will line just fine.

[frost66gmc]

Thanks again !!!!

[Andice]

I did this conversion a few years ago and did not do any grinding or port enlargement and have had no problems. The truck runs great. Best of luck!

[frost66gmc]

Thanks Andice, I''ll try it without grinding first. If I grind I'll probably go ahead and take the intake manifold off and replace the intake gaskets. All the gaskets on the truck are dry rotted I think. The transmission is leaking and the differential. I am assuming it's the seals where the drive shaft enters both. I have been trying to replace seals and gaskets as I go along.

[frost66gmc]

Ok, I got the new carburetor on the truck. It is spitting up gas and shooting fire. Do I need to adjust the distributor for the timing? How did the timing get off or was it off to begin with?

[jrmunn]

Hello Frost66,

I see that none of the more experienced forum members have replied to your post about problems after installing a Holley carburetor, so I will relate my experience. I converted my 64 GMC 3/4 ton pu with a 305E v6 from the stock Stromberg two-barrel carburetor to a Holley 500 last year, without making any changes to the intake manifold. It ran great afterward without any changes in ignition system settings. But I had just replaced ignition parts because of another problem that turned out to be worn out points, with symptoms that included hard starting, backfiring, and engine dying at low speed. I recently found that the resistor wire is delivering a full 12 volts to the coil (this doesn't make sense, but I know that my voltmeter is working) that burns up points faster than expected. I had also replaced much of my fuel delivery system because of this.

Both power and general performance is better with the Holley. My only concern is that the truck seems to run rich.

I have purchased smaller jets for the Holley, a Pertronix ignition to replace the points, and a Pertronix coil that is supposed to give better long-term operation at 12 volts. These will be installed when time and weather permit.

Good luck with your truck.

JRMunn

[frost66gmc]

Thanks for the information. I went ahead and adjusted the distributor about a 1/4 turn counter clockwise and this stopped the fire in the carb. Mine maybe running rich too. I now got some smoke out of the tail pipes. I am hoping this is just condensation because it has been raining while I've been working on it. It is white smoke but it's coming out of both tail pipes so I think my head gaskets are good.