Do Carb Heat Shields Work?
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
Do Carb Heat Shields Work?
To prevent fuel bowl boiling?
http://www.jegs.com/cgi-bin/ncommerc...20&prmenbr=361
http://www.jegs.com/cgi-bin/ncommerc...20&prmenbr=361
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Re: Do Carb Heat Shields Work? (paul67)
NO, not for a street driven car....IMO the only thing to do is pull the manifold and clean it up, and pour plaster of paris down the heat crossover passageway, thereby blocking it completely, and same with the EGR if you want, at least get rid of the EGR at any rate...blocking all passages....
nice if you can somehow keep engine oil off the bottom of the manifold....
Pontiac and BB Mopar used to do their manifolds in a spyder web design and use a valley pan for that reason....someone tooled up and did the same concept for SBC also....
but there is no other cure....might want to run engine at lower temp if you cooling system is up to the task....
GENE
nice if you can somehow keep engine oil off the bottom of the manifold....
Pontiac and BB Mopar used to do their manifolds in a spyder web design and use a valley pan for that reason....someone tooled up and did the same concept for SBC also....
but there is no other cure....might want to run engine at lower temp if you cooling system is up to the task....
GENE
Thread Starter
Team Owner
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From: Ontario
Re: Do Carb Heat Shields Work? (mrvette)
I hesitate to go in that direction as temperatures during the driving season here (April to October) can vary from 25-100F and I prefer to retain the crossover for quick warmup at the lower temps. And to block the crossover would mean that the heat riser would have to be removed as well: when it is closed at start-up where would the passenger side exhaust go? So the heat shield seemed to offer cheap insurance against fuel boil.
The intake in the pic is the same as the unit (GM #3890490) on the car. It does have the crossover passage but no EGR. And an oil splash shield is installed.
The intake in the pic is the same as the unit (GM #3890490) on the car. It does have the crossover passage but no EGR. And an oil splash shield is installed.
Melting Slicks
Joined: Apr 2002
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From: Tucson AZ
Re: Do Carb Heat Shields Work? (Double Aught)
Paul,
I clipped this from a post Lars wrote in another thread:
Finally, the BG is very sensitive to manifold heat: The heat coming off the manifold will easily boil the fuel in the big accelerator pump housing, causing the carb to flood out after shutdown. To prevent this, yu need to use one of the Holley reflective heat shields between the carb and the manifold - a carb spacer will NOT solve the problem - you need the reflective shield.
While I have little experience in this area, common sense would tell me (as would Lars I think) that the benefit of a heat shield will be dependent on several circumstances including the carband intake used. I can easily see some carbs being more susceptible to the "boil over" issue based on their design (size and location of components, material used - aluminum manifolds dissapte heat faster than iron and should prevent less issues).
Would I just throw one on, yes if the cost was minimal; if the cost was great or originality a concern, not without testing my set uip through a little trial and error.
I clipped this from a post Lars wrote in another thread:
Finally, the BG is very sensitive to manifold heat: The heat coming off the manifold will easily boil the fuel in the big accelerator pump housing, causing the carb to flood out after shutdown. To prevent this, yu need to use one of the Holley reflective heat shields between the carb and the manifold - a carb spacer will NOT solve the problem - you need the reflective shield.
While I have little experience in this area, common sense would tell me (as would Lars I think) that the benefit of a heat shield will be dependent on several circumstances including the carband intake used. I can easily see some carbs being more susceptible to the "boil over" issue based on their design (size and location of components, material used - aluminum manifolds dissapte heat faster than iron and should prevent less issues).
Would I just throw one on, yes if the cost was minimal; if the cost was great or originality a concern, not without testing my set uip through a little trial and error.
Thread Starter
Team Owner
Joined: Aug 1999
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From: Ontario
Re: Do Carb Heat Shields Work? (Robert N)
Thanks Robert. I do not know what a BG but here is my setup. The carb is the stock Holley 4160. I dropped by a local speedshop today to see if the Holley shield is available in Canada. It is and I will have one on Monday. I can't see that it will do any harm. And the price is reasonable as I do not have to pay shipping, brokerage fees, etc. There may be a fitment issue with that rear vacuum fitting. If yes, I will improvise.
Melting Slicks
Joined: Apr 2002
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From: Tucson AZ
Re: Do Carb Heat Shields Work? (paul67)
BG = Barry Grant.
I have a 650 DP Holley on thge stock high rise aluminum intake with no issues and no heat shield. Summer temps here are like your winter lows - 110+ is not uncommon with a avergae at 100+ degrees.
I agree that for the price, the shield cannot hurt and I will probably add one as well when the time comes.
I have a 650 DP Holley on thge stock high rise aluminum intake with no issues and no heat shield. Summer temps here are like your winter lows - 110+ is not uncommon with a avergae at 100+ degrees.
I agree that for the price, the shield cannot hurt and I will probably add one as well when the time comes.
Le Mans Master
Joined: Apr 2003
Posts: 7,154
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From: I blame my Dyslexia MD
Re: Do Carb Heat Shields Work? (Robert N)
i would think oneof those 1/4 inch thick heat disapating spacers woudl do alot more
its a thin layer of aluminium then a layer of a composite or somehting that doesnt transmit heat well and then another layer of aluminium
or a thin wood spacer also some composite thin spacers and other types of heat disapating gaskets. They just limit the heat transfered to the carb by the intake manifold.
MAtt
its a thin layer of aluminium then a layer of a composite or somehting that doesnt transmit heat well and then another layer of aluminium
or a thin wood spacer also some composite thin spacers and other types of heat disapating gaskets. They just limit the heat transfered to the carb by the intake manifold.
MAtt
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Racer
Joined: Dec 2003
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From: Livermore CA
Re: Do Carb Heat Shields Work? (paul67)
Paul
I've used the original GM heat sheild that looks very much like the one you posted a link to. I've had the same setup on 3 cars (2 BB & 1 SB) now all with aluminum manifolds and dual feed Holley carbs. and have had no boiling problems at all.
I've used the original GM heat sheild that looks very much like the one you posted a link to. I've had the same setup on 3 cars (2 BB & 1 SB) now all with aluminum manifolds and dual feed Holley carbs. and have had no boiling problems at all.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
Re: Do Carb Heat Shields Work? (paul67)
Sorry Paul, didn't notice Canada there on your addy.....
in that climate, I would take off any heat risers, and just run open passages under the carb....and call it quits....
GENE
in that climate, I would take off any heat risers, and just run open passages under the carb....and call it quits....
GENE
Thread Starter
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From: Ontario
Re: Do Carb Heat Shields Work? (mrvette)
Thanks Gene. That is an option as well. Those heat risers do tend to freeze up with time. I think muffler shops have the replacement spacers.
Le Mans Master
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From: delmont pa
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Re: Do Carb Heat Shields Work? (paul67)
chevy used them on some engines so i would guess they work. they do not spend a $.01 they do not have to. it keeps the heat from the float bowls when the engine is shut off.
[Modified by clem zahrobsky, 4:02 PM 1/17/2004]
To prevent fuel bowl boiling?
http://www.jegs.com/cgi-bin/ncommerc...20&prmenbr=361
http://www.jegs.com/cgi-bin/ncommerc...20&prmenbr=361
[Modified by clem zahrobsky, 4:02 PM 1/17/2004]
Safety Car
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From: St Louis MO
Re: Do Carb Heat Shields Work? (paul67)
I have the same Holley heat shield and it didn't help my randomly-occurring problem of fuel spitting out the air bleeds after the car is turned off.
Brett :thumbs:
Brett :thumbs:
Race Director
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From: Forked River NJ
Re: Do Carb Heat Shields Work? (Brettmc)
I have the same problem of teh fuel spitting out of the air bleeds. I have no heat crossover in my heads. It is just the heat from the manifold tha tboils the fuel when it is shut off. I would like to find a cure for this. Every time I go to start it after sitting for 15 minutes it is flooded due to the fuel in the intake. It is a pain to start.
Drifting
Joined: Nov 2002
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From: Loveland, CO
Re: Do Carb Heat Shields Work? (paul67)
paul67, I also see from your carb photo that your Holley has a divorced choke, which will also not work if you plug the heat crossover passages. Why is it that one thing always leads to another.
Racer
Joined: Jul 2002
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From: South Bend, Indiana
Re: Do Carb Heat Shields Work? (paul67)
I used the actual Chevy heat shield plus insulator spacers on a Victor JR and still had heat problems. My solution was to go with a Carter Competition Series 750 and never had another problem.
1976 406 TH400 3000stall 4.11 gears
[Modified by jimtreber, 4:25 PM 1/18/2004]
1976 406 TH400 3000stall 4.11 gears
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