Which Carb Spacer? - Weiand Stealth

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73Swinger18

73Swinger18

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I have a 318 with a Weiand Stealth intake and Holley 600 carb. I had percolation issues after shutdown and purchased a 0.5" Summit open phenolic spacer which helped. I had a carb shop take exhaust readings and tune it appropriately after the install and am now wondering if a four hole spacer would have been the better route. I ask this because I noticed the 2-8 (passenger) bank exhaust runs a lot richer on warm up than the other side. I think this may be due to the design of the intake and open spacer allowing more fuel to be drawn over to that bank. The car runs just as good (seat of the pants) as it did without the spacer. Do you think I should try a four hole spacer?
 
mopowers said:
How do you know the pass side is richer? How much richer is it?
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When started on cold mornings (full choke), it leaves a little black soot on the concrete. I have turn-downs right before the rear axle. Works great as a street sweeper and creates a nice dusty mess!
 
73Swinger18 said:
When started on cold mornings (full choke), it leaves a little black soot on the concrete. I have turn-downs right before the rear axle. Works great as a street sweeper and creates a nice dusty mess!
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A while back I was tuning on a Weiand Stealth to see if I could make it work better than a Holley Strip Dominator. Despite my best efforts, the Holley remained the faster intake for my particular race only combination, but I found out some interesting things. I always used a 1", 4-hole tapered spacer so I can't say if an open or 4-hole straight would have helped or hurt, But while checking the plugs one day, I noticed that the cylinders fed from the shallow side plenum were running richer than the ones fed by the deeper side. When I adjusted the jetting by (I believe) 2 numbers from square (no PV) with the shallow side leaner by 2, the car picked up about .05 in ET. (Forgot if it was 1/8 mile or 1/4 .

My theory is that perhaps the shallow side has less volume, so the vacuum signal is stronger, thus running a bit richer. Not sure if this would apply to all dual plane intakes, but it's something to think about. But on the street, I'd consider a straight 4 hole or tapered 4 hole. But recheck the a/f ratio with each change.
 

Locomotion said:
A while back I was tuning on a Weiand Stealth to see if I could make it work better than a Holley Strip Dominator. Despite my best efforts, the Holley remained the faster intake for my particular race only combination, but I found out some interesting things. I always used a 1", 4-hole tapered spacer so I can't say if an open or 4-hole straight would have helped or hurt, But while checking the plugs one day, I noticed that the cylinders fed from the shallow side plenum were running richer than the ones fed by the deeper side. When I adjusted the jetting by (I believe) 2 numbers from square (no PV) with the shallow side leaner by 2, the car picked up about .05 in ET. (Forgot if it was 1/8 mile or 1/4 .

My theory is that perhaps the shallow side has less volume, so the vacuum signal is stronger, thus running a bit richer. Not sure if this would apply to all dual plane intakes, but it's something to think about. But on the street, I'd consider a straight 4 hole or tapered 4 hole. But recheck the a/f ratio with each change.
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I run a china airgap and 1" 4 hole on my Magnum 360 and stagger jet also. The shallow side also has a sharper turn and my guess is some fuel drops out at lower rpm. Deep side larger plenum nice easy entry. I also run a heat shield under the bowls and added a 90* angle shield to keep the radiate heat from the upper radiator hose off the front bowl.
I tuned a 3310 this week to try at the track and noticed the accelerator nozzle barely dripping fuel after shutdown. Ended up drilling a .021 hole in the diaphragm well to allow the damn ethanol fuel to expand back into the fuel bowl. Had to up the nozzle size from 30 to 35 since the volume dropped with the bypass hole drilled. Carb was not even warm to the touch.

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Insexond what Locomotion said. The more plenum there is, the leaner the mixture will be. Vacuum or extra space or both, it doesn't matter.

His fix was to "Stager jet" the carb. A common practice for racers to get the engine running and producing max power evenly on each cylinder. This can be read about in the MO engines book and other race type productions.

I'd try a 4 hole spacer, non tapered.
 
Locomotion said:
A while back I was tuning on a Weiand Stealth to see if I could make it work better than a Holley Strip Dominator. Despite my best efforts, the Holley remained the faster intake for my particular race only combination, but I found out some interesting things. I always used a 1", 4-hole tapered spacer so I can't say if an open or 4-hole straight would have helped or hurt, But while checking the plugs one day, I noticed that the cylinders fed from the shallow side plenum were running richer than the ones fed by the deeper side. When I adjusted the jetting by (I believe) 2 numbers from square (no PV) with the shallow side leaner by 2, the car picked up about .05 in ET. (Forgot if it was 1/8 mile or 1/4 .

My theory is that perhaps the shallow side has less volume, so the vacuum signal is stronger, thus running a bit richer. Not sure if this would apply to all dual plane intakes, but it's something to think about. But on the street, I'd consider a straight 4 hole or tapered 4 hole. But recheck the a/f ratio with each change.
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Good info! The purpose of the spacer for me was to reduce heat only. I wasn't too concerned with any performance gain from it. I was thinking that with the spacer, some of that fuel may be drawn over to the other side with less resistance. I might just get a thinner spacer/gasket like this one https://www.summitracing.com/parts/hly-108-18/overview/ and keep it divided between the manifold/carb. I didn't notice the passenger side running rich until after I added the open spacer. I'll take it back to the carb shop and have them stick the probe in each tailpipe to see if there is a difference after I decide which route I am going to go.
 
this is what i've done , this was in my daily driver dart . its a sandwhich of gaskets and metal plates . all so block the heat crossover from head to head . i've used the ford hotwater plate under the carbs in colder weathered machines .

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pomonamissel said:
this is what i've done , this was in my daily driver dart . its a sandwhich of gaskets and metal plates . all so block the heat crossover from head to head . i've used the ford hotwater plate under the carbs in colder weathered machines .

View attachment 1714997958
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I blocked my crossover. Did you use open gaskets or ones with a center divider?
 
bore holes in the plates . my intake is a rpm performer , its divided . electric choke is required on the carb . very cold blooded , that to fatten up the carb jetts n rods . almost 10 percent . but i added headers to the mix when it went into the p/u .
 
Have you tried the "Thick" gasket from Edelbrock at approximately .333 thick?
Works for me!
 
Installed the Edelbrock divided heat insulator gasket today and it definitely made a difference in low speed torque/responsiveness. The 2-8 bank isn't running rich like it was before either. Picked up one more inch of vacuum too. Thanks for everyone's inputs! The half inch open spacer will sit on the shelf for another day/project.
 
For insulation, use a phenolic spacer. I don't care for the black "plastic" ones, but use the ones that look like wood/epoxy. They both insulate better than aluminum. Canton has a line of open, 4-hole and tapered 4 hole spacers, which is what I use, and they tend to be less expensive. (But I haven't made any performance comparisons.)
 
A 1" bottom milled/tapered 4 hole, the HVH model in particular, has made 10-15 bolt on hp and the same in tq on every dyno test I've seen done with one.
 
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