Carb spacers on a Streetmaster

[jholmes217]

I am running a port matched Streetmaster 390 on my 428 Cobra Jet with 4 speed.  While the car hasn't died on me, the idle gets a little erratic when I'm sitting at a stoplight on hot days, so I'm thinking it is caused by heat in the engine bay.  My current spacer is a 1 inch aluminum open spacer.  I am thinking about getting one of the plastic 1 inch Super Sucker plastic spacers, or a plastic, wood, or phenolic open spacer.

Does anyone have dyno or track comparisons of a Super Sucker vs Open spacer on a Streetmaster?

[jholmes217]

I am running a port matched Streetmaster 390 on my 428 Cobra Jet with 4 speed.  While the car hasn't died on me, the idle gets a little erratic when I'm sitting at a stoplight on hot days, so I'm thinking it is caused by heat in the engine bay.  My current spacer is a 1 inch aluminum open spacer.  I am thinking about getting one of the plastic 1 inch Super Sucker plastic spacers, or a plastic, wood, or phenolic open spacer.

Does anyone have dyno or track comparisons of a Super Sucker vs Open spacer on a Streetmaster?

Disregard.  After further research, I see lots of complaints about the plastic ones melting.  I will probably go with a wood open spacer.

[Joe-JDC]

I've never seen a super sucker type spacer lose horsepower on dyno testing.  I always prefer anything besides aluminum for the spacer if heat is the problem.  On the Streetmaster you can't go wrong with either the open or super sucker one inch spacer.  Joe-JDC

[Yellow Truck]

I'm running a 1 inch Super Sucker on a Street Dominator. I haven't put it on a dyno yet and when I do I will probably do an on/off comparison.

Having said that - no heat problems with it, and I've had not issues with boiling the fuel in the carb. I used to have problems on warm days at traffic lights with the old 410 running an iron intake and an aluminum spacer. Having said that I also re-routed the fuel line up through the passenger side frame (on a 4WD it is boxed) and up the firewall to a filter and then into the back of the carb. This keeps the fuel away from the engine heat, so it may be the routing that stopped the boiled fuel problem.

[jholmes217]

I'm running a 1 inch Super Sucker on a Street Dominator. I haven't put it on a dyno yet and when I do I will probably do an on/off comparison.

Having said that - no heat problems with it, and I've had not issues with boiling the fuel in the carb. I used to have problems on warm days at traffic lights with the old 410 running an iron intake and an aluminum spacer. Having said that I also re-routed the fuel line up through the passenger side frame (on a 4WD it is boxed) and up the firewall to a filter and then into the back of the carb. This keeps the fuel away from the engine heat, so it may be the routing that stopped the boiled fuel problem.

Are you using a plastic or aluminum Super Sucker?  How long have you been using it if plastic?  I've been reading of people having issues with the plastic ones warping and/or melting.

[jholmes217]

I came across this while searching today.  I could experiment with open and tapered with this.  Thoughts?  http://www.jegs.com/i/Proform/778/67160C/10002/-1

Also considering this one.  I could use the PCV since the original 735 cfm Cobra Jet Holley didn't have a PCV port, and the Streetmaster doesn't have the holes for it like on the Cobra Jet manifold.  http://www.jegs.com/webapp/wcs/stores/servlet/SearchResultsPageCmd?Ntt=Trans+Dapt+2545&requestYear=&storeId=10001&catalogId=10002&langId=-1&year=&make=&model=&submodel=&engine=&Nrpp=&No=&persistYmm=false

[scott foxwell]

The last super sucker I tested made absolutely no difference on a 532 ci 840hp BB Chev on a ported Super Victor intake, 1050 carb. I have seen 12 hp gain with a 1" open spacer at the 700hp level, 509ci engine, 4150 carb, stock Air Gap. I've seen as many different results as different spacers I've tested... open, four hole, cone type, 1", 2", on ported intakes, on stock intakes. I have seen nothing in the way of any consensus. It seems every combination will react differently to different spacers. You just have to test and find out. Fortunately it's one of the easiest parts to test and get immediate results.

[Yellow Truck]

Jeff - mine is plastic. I specifically wanted the heat protection. I've had it fully hot on a hot day, and had it on and off a few times since then with no evidence of damage.

Having said that the engine does NOT run hot as a rule. As per Scott's comments - I didn't do it for performance primarily. I did it because the previous 410 in the truck (also didn't run hot as a rule) tended to boil the gas in the carb and coming to a light after a drive of 10 or 15 minutes would idle rough, lose RPM, and be balky off the line.

Mine has a taper and holes that match the bottom of the carb. I have no evidence about it but I'll get it on a dyno eventually and test it with/without the spacer.

My understanding is it makes a difference what intake is under it.

[scott foxwell]

Phenolic is probably the best insulator and best suited for a spacer. I would guess an open spacer would work best for power on an open plenum/single plane like the Streetmaster... a four hole would probably increase throttle response and off-idle performance but again...you really never know till you try.

[Yellow Truck]

When I say "plastic" I mean phenolic resin. Mine is a four hole over an open plenum single plane. I don't plan to try an open and a 4 hole, but I will try with and without. The things are almost $100 and I'm not that curious.

I got a little thrill when I got it and opened the package and it had a label that said "Drag Race Only". They probably say that to all the boys...

[jholmes217]

The Super Sucker carb spacer I ordered from Jegs came today.  Anyone know why it says "Drag Race Only" on it?

[gdaddy01]

to dodge emission control cars ?

[Yellow Truck]

I thought it was there to give us a little thrill.

[Drew Pojedinec]

I use both the plastic and phenolic.

A little clarity......
Plastic is Delrin
Phenolic is Micarta

To avoid confusion I like to refer to them this way.
I've had a delrin spacer on a daily drive 390 for 7 years with no issues.  I like it as it is rock hard and a great surface for a good gasket seal.  It doesn't insulate as well as Micarta, but it's durable and that engine doesn't have heat soak issues.

My Galaxie I use Micarta spacers due to it running much hotter (mostly due to the more enclosed engine bay).  They work very well too, but are somewhat easier to break.  They also absorb fuel if it boils out, so there is that.

I wouldn't consider running a carb down here in the deep south without a spacer.


Jeff what carburetor are you running?

[jholmes217]

I'm running a 735 cfm Holley Cobra Jet carb, but thinking of trying a Summit Racing 750 cfm VC carb like this.  https://www.summitracing.com/parts/sum-m08750vs/overview/