Installing new Holley 3810 - options for heat shield

[Alexander D.]

A new Holley 3810 will arrive shortly for my '67 300hp engine. My car is stock, with cast iron OEM manifold (with the smiley face heat slot under the carb).

I've read various threads where advice is given around using an aluminum 'heat shield' under the carb to reduce the chances of percolation on hot days.

The stock setup was: bottom 4-hole gasket on cast iron manifold, followed by stainless heat shield, with carb bolted on top.

Carb expert Lars recommends a 3-gasket sandwich consisting of two 4-hole gaskets with the heat shield sandwiched between. The carb then gets mounted on top.

Note I will be plugging the smiley face heat slot using Dorman 7/16" plugs before I install the new carb.

My questions:

1. Where do I get the OEM type stainless heat shield? I see plenty of heat shields, some sold by Holley. But, these are much larger than the OEM shield, and extend way beyond the base of the carb. I get it that these are designed to reflect additional heat by insulating the fuel bowls. But, these large shields don't look stock. Also note it rarely gets super-hot in the coastal PNW area where I live. I only experience percolation during the occasional road trip to warmer places south or inland. So, I'd rather stick with a stock looking configuration, or close to it, if I can.
2. Is there any merit to using a 1/2" phenolic carb spacer instead of the OEM type stainless heat shield? Will I have hood clearance issues if I install one of these? Can the stock choke rod setup be modified to work properly with the carb being mounted 1/2" higher?
3. Or, will the "Carburetor Heat Dissipator-Holley/AFB-1/4" kit made by Mr. Gasket and listed on the Holley website do the trick? The description states each aluminum plate is 1/16" thick (i.e. two together = 1/4" thick). Will that work with the stock choke rod?

I don't know how to insert a screen shot here, so here's the link to the Holley listing for the Mr Gasket kit:
https://www.holley.com/products/fuel_systems/carburetor_components/carburetor_gaskets_adapters_and_spacers/adapters_and_spacers/parts/97

Thanks for your help.

[Joe L.]

Re: Installing new Holley 3810 - options for heat shield

A new Holley 3810 will arrive shortly for my '67 300hp engine. My car is stock, with cast iron OEM manifold (with the smiley face heat slot under the carb).

I've read various threads where advice is given around using an aluminum 'heat shield' under the carb to reduce the chances of percolation on hot days.

The stock setup was: bottom 4-hole gasket on cast iron manifold, followed by stainless heat shield, with carb bolted on top.

Carb expert Lars recommends a 3-gasket sandwich consisting of two 4-hole gaskets with the heat shield sandwiched between. The carb then gets mounted on top.

Note I will be plugging the smiley face heat slot using Dorman 7/16" plugs before I install the new carb.

My questions:

1. Where do I get the OEM type stainless heat shield? I see plenty of heat shields, some sold by Holley. But, these are much larger than the OEM shield, and extend way beyond the base of the carb. I get it that these are designed to reflect additional heat by insulating the fuel bowls. But, these large shields don't look stock. Also note it rarely gets super-hot in the coastal PNW area where I live. I only experience percolation during the occasional road trip to warmer places south or inland. So, I'd rather stick with a stock looking configuration, or close to it, if I can.
2. Is there any merit to using a 1/2" phenolic carb spacer instead of the OEM type stainless heat shield? Will I have hood clearance issues if I install one of these? Can the stock choke rod setup be modified to work properly with the carb being mounted 1/2" higher?
3. Or, will the "Carburetor Heat Dissipator-Holley/AFB-1/4" kit made by Mr. Gasket and listed on the Holley website do the trick? The description states each aluminum plate is 1/16" thick (i.e. two together = 1/4" thick). Will that work with the stock choke rod?

I don't know how to insert a screen shot here, so here's the link to the Holley listing for the Mr Gasket kit:
https://www.holley.com/products/fuel_systems/carburetor_components/carburetor_gaskets_adapters_and_spacers/adapters_and_spacers/parts/97

Thanks for your help.

Alexander------


The stock, thin stainless shield heat shield is all you need, especially if you eliminate the heat slot. You can use it as Lars suggests with 2 gaskets or just a single gasket in the stock configuration.

If you use any gasket/shield configuration other than stock and thicker than the stock gasket/shield, you will need to fabricate a new choke rod for the divorced choke. You cannot modify the stock rod to work.

[Alexander D.]

Re: Installing new Holley 3810 - options for heat shield

Hi Joe!

Any tips on where I might buy a stock OEM style stainless heat shield?

Will the 1/16" thick aluminum plate sold with the Mr. Gasket Kit be a suitable substitute?

Will the choke rod work properly if I install the carb onto a single 1/16" thick alum plate, sandwiched between 2 regular carb gaskets as recommended by Lars?

Thanks,

Alex

[Joe L.]

Re: Installing new Holley 3810 - options for heat shield

Hi Joe!

Any tips on where I might buy a stock OEM style stainless heat shield?

Will the 1/16" thick aluminum plate sold with the Mr. Gasket Kit be a suitable substitute?

Will the choke rod work properly if I install the carb onto a single 1/16" thick alum plate, sandwiched between 2 regular carb gaskets as recommended by Lars?

Thanks,

Alex

Alex------


The stock heat shield is available from any of the major Corvette parts vendors like Dr. Rebuild, etc. The stock gasket is an insulating type gasket and can also be obtained from the same suppliers.

If you change the thickness of the stock gasket/shield to any other thickness, then you have to fabricate a new choke rod if you want the choke to function properly. A new choke rod can be fabricated from welding rod. However, my suggestion is to just use the stock gasket/shield. With the heat slot decommissioned by plugging the holes at either end 90%+ of your carb heat problems will be solved by this alone.

[Alexander D.]

Re: Installing new Holley 3810 - options for heat shield

Thanks again Joe.

Based on your advice I'll just go with the heat slot blocked, and the single carb gasket and heat baffle under the carb. That way I won't have to modify the stock choke rod setup for it to operate as it should.

Cheers, Alex.

[Edward D.]

Re: Installing new Holley 3810 - options for heat shield

Alex,
You will still have to bend the rod a bit to adjust choke correctly. I have yet to see a new rod that didn't require bending to adjust. Follow the procedure in the service manual. Hold choke butterfly closed, pull rod up to stop on spring housing, bottom edge of top of rod should be just above top of hole in butterfly arm. Thats the correct adjustment. You should also plan on adjusting high idle to spec which is done by bending the tab that rests on a notch of the plastic high idle cam. Also check the choke vacuum break which is adjusted (if necessary) by bending the little rod that the vacuum break diaphragm pulls. Check your accelerator pump adjustment as well. All of these adjustments are simple and covered in your chassis service manual.