Cali,68,L-79

Well after installing the BG carb and experiencing flooding after shutdown and constantly changing idle speed I chased down the gosts to no heat shield.

As per LARS
BG and Holley carbs need a reflective heat shield installed under the carb: The accelerator pump wells are close enough to the hot manifold that the fuel in the pump wells will boil after hot engine shutdown. As the fuel boils and vaporizes, it pushes fuel out the accel discharge nozzles, flooding the engine after shutdown.

Well I tried to follow his example.

Holley builds a shield, but it does not fit correctly. Seen here is a modified Holley shield: I have trimmed about an inch off the forward edge so it will clear the thermostat housing. The rear edge has been trimmed forward. The right side of the shield has been cut inwards to prevent the throttle shafts from binding on the shield. The right corners have been trimmed at a 45-degree angle to clear the carb inlet line. Finally, the shield has been bent downwards and “jogged” so that the accel pump levers will not hit the shield: If you install a flat shield, the accel pump levers will hit the shield, and will be partially depressed. This will cause an off-idle flat spot and stumble.

And I ended with this.

Holley Heat Shield (with gaskets): HLY-108-70 $35.95 and 2 days wasted away.

Cali,68,L-79

The expensive Holley shield bottomed out on the manifold runners and was impossible for me to create so I went to Home Depot and for $4.71 I bought



In order for the “jogged” shield to clear the base gasket, the gasket “ears” must be trimmed. Shown here is a trimmed base gasket that will allow the bent shield to fit properly.



Engine used to run cold idle 850RPM and warm idle 1200RPM. Now it's always 850RPM. Thanks LARS!

bobs77vet

your bends came out great!!!!!!! mine are about 5/8" in height i was shooting for 3/8" but that didn't happen... i am thinking about a 1/2 phenolic spacer to go along with this, what are you going to do?? paper gasket or something else?

Cali,68,L-79

I ran the 1/2" Holley gasket and then took the heat shield sandwiched between to 1x4 wood blocks then put the whole thing in a vise and made a small bend. Took the contraption apart and checked it under the carb to make sure it cleared the acel pump rods on both ends. the "jogging" LARS refers to above is impossible without the proper tooling and as expensive as that would be I'd go for a simple bend. If you look at the last shot the heat shield is just about invisible. There is the 1/2" on the manifold then the heat shield then another thin holley gasket.

David

Brettmc

How did it run after?

Brett

Cali,68,L-79

Flooding after shutdown gone. Idle is stable at 850RPM. Ran car thru the streets 30 minuts and idles 20 minutes after that and it never creeped over 180 degrees and 850RPM. Also for the first time was able to get a nice screech at 60mph when shifting into 2nd gear, so yeah runs alot better than with that torquerII/ Eldebrock 600cfm carb.

bobs77vet

i hope mine comes out as good looking as your stuff, i pick up my engine and 700r4 at the end of this week i'm psyched...does that "jog" in the front go up? (it may be an optical illusion) thks bob

Cali,68,L-79

No Bob both go down about 10 degrees, just enough to clear the acl. pump rods. The difference in space between the runner and the pump rod is tight so go with a little bend, mock it up and if not enough do another bend. P.S. what kind of shield are you goin with?

David

bobs77vet

16 ga stainless steel, all the cutting, holes and bends are done and it looks great on the carb, manifold is with engine builder so i just have to wait a couple or more days to see if my handi work was upto the challenge and do some finish trimming.

Cali,68,L-79

BOB what's the story with the engine? i.e. you building a stroker?

Jughead

Nice fabricating.

bobs77vet

no this is a father/son project and my 17 yr old will also be driving it so i'm keeping it tame, i went for the 350/350 with the 700r4 and steeroids i figured that should be enough fun.. i do have a roller block, vortec head engine in my garage that i'm saving for a stroker but i figured i didn't want too much power for Jr.... i can still remember being 17 even though it was 30 yrs ago!!!! this has been a great two year project so far and the best part has been my availability (nights and weekends)conflicts with the local teenage party schedule so any time we are working on the vette is time well spent. we have also pulled his friends into the project. i figured if i could come up with something fun and constructive between 15 and 18 it would be too my advantage in the long run... hopefully the engine and trans will arrive by friday. bob

norvalwilhelm

You did a nice job of fabricating the heat shield but I am suprised that it made that much difference. I have run big blocks forever and never experience fuel perculation.

Fevre

Is pretty amazing that little heat sheild makes a diff, might do one up for my vette. What would be best is a return line like an EFI system has, just got done with a new manfold install on my formula, the fuel rails get hot as heck after shut down but are cool to the touch when the car is one with 50 lbs of pressure.

DJ Dep

Nice fabrication Dave! Just curious...did you try the factory heat shield Chevy makes for Holley carbs? Part #3969835. And yes, it is made for a double pumper. Thry also make one for the Quadrajunk #3982944.

Dep

SmokedTires

Nice job

rainman69

Where would one find one of these Part #3969835's? I tried a Google search and only found one for $325...

DJ Dep

YIKES!!! You don't need the solid gold version!!!!
Check with Scoggin Dickey...

http://www.sdpc2000.com/

Dep

Cali,68,L-79

Dep yes I did you can see it up there about the 2nd or 3rd photo and I destroyed it plus wasted $36 and 2 days. This plate cost under $5 and 4 hours to make.

David

Jughead

I think that's the one I have. You can have it for a lot less tham $300.
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