Carb spacer question

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cjperformance
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Re: Carb spacer question

Post by cjperformance »

GRTfast wrote: Thu Mar 15, 2018 7:44 am
cjperformance wrote: Thu Mar 15, 2018 6:49 am
GRTfast wrote: Thu Mar 15, 2018 6:42 am The issue that led to phenolic spacers was boiling fuel in stop and go traffic. I’ve since converted to a return line fuel system, but I’m reluctant to get rid of the thermal isolation a phenolic spacer affords for the carb. It gets hot in central Florida, and it seems the pump gas these days boils easily.
Gets hot here too, Adelaide, South Australia.
I use phenolic, plastic, wood spacers with fiber washers under the carb retaining nuts to isolate the studs from the carb.
Exactly what I did... and I thought I was being clever. Looks like I'm not the only one. :D
:D works well under intake manifold bolts too. Use a temp gun as the engine is warming up and you can see the hotter areas around the intake bolts. Use fuber washers and make sure the bolts dont contact the intake and the difference is quite noticeable
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Re: Carb spacer question

Post by groberts101 »

Here's what I was trying to convey earlier. If you use a solid block type spacer the radius into each end of the short side can be pushed almost all the way out to the manifolds carb pad so long as there is enough material left to weld the spacer on. Luckily I'm better at porting than photography but it gets the point across.
DSCN9559 crop.jpg
Here it is welded in place and all buttoned up in the engine bay. Helped this 11.5:1 pump gas 385" motor reach 7000+ during shift point overrevs and made the truck faster without giving up any bottom end above 2000-2200 rpm or so.
blazer engine crop.jpg
PS.. notice the square up widened radius on that short plenum side. That is a VERY high speed area that needs all the help it can get. treat it like the SSR in a squashed port head and it will pay dividends!
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Re: Carb spacer question

Post by GRTfast »

Beautiful work.
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Re: Carb spacer question

Post by cjperformance »

Yes nice. And yes the "ssr" area you widened from carb to runner is of big help.
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Re: Carb spacer question

Post by sanfordandson »

This spacer will work well in your combo.


Image

http://highvelocityheads.com/ss4150-1al ... ies-carbs/
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Re: Carb spacer question

Post by GRTfast »

sanfordandson wrote: Sat Mar 17, 2018 8:52 pm This spacer will work well in your combo.


Image

http://highvelocityheads.com/ss4150-1al ... ies-carbs/
..except that my fuel will boil in the carb in traffic. That why I blended my 4 hole phenolic spacer, and tried opening up the high plenum side holes into an oval. Looking for the best of both worlds.
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Re: Carb spacer question

Post by BOOT »

They call the spacers with cut outs like that weight reduction but really it reduces the heat transfer by reducing the path/material it can travel. No1 says you can't use a 1/4" phenolic on top either. I've also used the fiber washer as other have mentioned, plus I'll use stainless studs or bolts.
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Re: Carb spacer question

Post by sanfordandson »

GRTfast wrote: Sat Mar 17, 2018 10:23 pm
..except that my fuel will boil in the carb in traffic. That why I blended my 4 hole phenolic spacer, and tried opening up the high plenum side holes into an oval. Looking for the best of both worlds.
I'd be looking into why your fuel "boils over" then.
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Re: Carb spacer question

Post by GRTfast »

sanfordandson wrote: Sun Mar 18, 2018 9:22 am
GRTfast wrote: Sat Mar 17, 2018 10:23 pm
..except that my fuel will boil in the carb in traffic. That why I blended my 4 hole phenolic spacer, and tried opening up the high plenum side holes into an oval. Looking for the best of both worlds.
I'd be looking into why your fuel "boils over" then.
I know exactly why it was boiling. The carb (and consequently the fuel) was getting too hot.

Scenario where fuel boils:

No phenolic spacer, 100+ degree weather, stop and go traffic, dead head fuel delivery setup.

Solutions successfully implemented: return line fuel delivery setup, phenolic spacer.

I Identified the problem, and fixed it.

It is possible that i could use an aluminum spacer with the circulating fuel delivery system, but I have no plans to go back towards the configuration that caused the problem. I’d rather keep the carb as cool as possible, and modify phenolic spacers to achieve the optimum induction path geometry. I think a cool carb and cool fuel are two desirable things to have, especially for a Florida street machine.
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Re: Carb spacer question

Post by sanfordandson »

GRTfast wrote: Sun Mar 18, 2018 11:05 am dead head fuel delivery setup.
Thats was you #1 problem.
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Re: Carb spacer question

Post by groberts101 »

GRTfast wrote: Sun Mar 18, 2018 11:05 am
sanfordandson wrote: Sun Mar 18, 2018 9:22 am
GRTfast wrote: Sat Mar 17, 2018 10:23 pm
..except that my fuel will boil in the carb in traffic. That why I blended my 4 hole phenolic spacer, and tried opening up the high plenum side holes into an oval. Looking for the best of both worlds.
I'd be looking into why your fuel "boils over" then.
I know exactly why it was boiling. The carb (and consequently the fuel) was getting too hot.

Scenario where fuel boils:

No phenolic spacer, 100+ degree weather, stop and go traffic, dead head fuel delivery setup.

Solutions successfully implemented: return line fuel delivery setup, phenolic spacer.

I Identified the problem, and fixed it.

It is possible that i could use an aluminum spacer with the circulating fuel delivery system, but I have no plans to go back towards the configuration that caused the problem. I’d rather keep the carb as cool as possible, and modify phenolic spacers to achieve the optimum induction path geometry. I think a cool carb and cool fuel are two desirable things to have, especially for a Florida street machine.
Another trick or two is to run a very cold t-stat to increase coolant flow. More flow = better cooling capability with smaller peaks and greater margins. Which I usually then try to take advantage of with more aggressive tunes. I always thought adding safety margin was for pussies and people that don't know how to tune! :lol:

Next trick to lose some heat buildup in the induction would be to use exhaust coatings and/or header wraps. I usually do both because every little bit helps, IMO. Voids the coating warranty though.. so there's that.

Then from there.. wrap/insulate ALL your fuel lines in the engine compartment. Again.. every bit helps in cumulative manner.
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Re: Carb spacer question

Post by GRTfast »

sanfordandson wrote: Sun Mar 18, 2018 1:28 pm
GRTfast wrote: Sun Mar 18, 2018 11:05 am dead head fuel delivery setup.
Thats was you #1 problem.
I’m sure it was part of the problem, but I wouldn’t say is was the prime contributor. My engine compartment is completely open, and my fuel line is routed in such a way that is isn’t exposed to the headers at all really. When I was having the problem, I used one of those point and shoot thermometers and the carb was in the 190F range, which is right at or above the boiling point for today’s pump gas from what I understand. I added the phenolic spacer and the fuel boiling issue was solved. I switched to the pump around style fuel supply setup later on to ease the load on the electric fuel pump. I didn’t measure the carb temp after I started using the spacer, but it feels cool to the touch.

Long story short, I think the carb was getting the majority of the heat through conduction from the intake. The fuel line wasn’t hot except for the last foot or so leading to the carb.
Last edited by GRTfast on Sun Mar 18, 2018 3:44 pm, edited 1 time in total.
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Re: Carb spacer question

Post by GRTfast »

groberts101 wrote: Sun Mar 18, 2018 1:36 pm
GRTfast wrote: Sun Mar 18, 2018 11:05 am
sanfordandson wrote: Sun Mar 18, 2018 9:22 am

I'd be looking into why your fuel "boils over" then.
I know exactly why it was boiling. The carb (and consequently the fuel) was getting too hot.

Scenario where fuel boils:

No phenolic spacer, 100+ degree weather, stop and go traffic, dead head fuel delivery setup.

Solutions successfully implemented: return line fuel delivery setup, phenolic spacer.

I Identified the problem, and fixed it.

It is possible that i could use an aluminum spacer with the circulating fuel delivery system, but I have no plans to go back towards the configuration that caused the problem. I’d rather keep the carb as cool as possible, and modify phenolic spacers to achieve the optimum induction path geometry. I think a cool carb and cool fuel are two desirable things to have, especially for a Florida street machine.
Another trick or two is to run a very cold t-stat to increase coolant flow. More flow = better cooling capability with smaller peaks and greater margins. Which I usually then try to take advantage of with more aggressive tunes. I always thought adding safety margin was for pussies and people that don't know how to tune! :lol:

Next trick to lose some heat buildup in the induction would be to use exhaust coatings and/or header wraps. I usually do both because every little bit helps, IMO. Voids the coating warranty though.. so there's that.

Then from there.. wrap/insulate ALL your fuel lines in the engine compartment. Again.. every bit helps in cumulative manner.
Engine compartment is 100% open, fuel line is routed away from the headers. I run a 180 T-stat and an electric fan that kicks on at 195 and off at 185.

Bottom line is, I have no issue with fuel boiling now. Car is totally happy in Florida summer bumper to bumper traffic. With no A/C, I can’t say the same for myself, lol!
Take the risk of thinking for yourself, much more happiness, truth, beauty, and wisdom will come to you that way. -Hitchens
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