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Underside of Intake manifold
#1
What's the bulge under the intake manifold that goes on the across the bottom of it and has a small port on each side, also does a cleveland have to be run with a lifter valley pan?

Gas is for cleaning parts, alcohol is for drinkin, nitro is for racin
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#2
if it's what i think your talking about it's for attaching a pan/shield onto the bottom of manifold to provide heat shield to carb. so it don't vaporize fuel before getting into cyl's.
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#3
The bulge is a heat cross over. It uses exhaust heat to heat up the intake manifold. You do not have to run a valley pan, I do not run one but I have my heat crossover blocked off.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
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#4
(04-30-2018, 08:00 AM)73pony Wrote: The bulge is a heat cross over. It uses exhaust heat to heat up the intake manifold. You do not have to run a valley pan, I do not run one but I have my heat crossover blocked off.

so need to worry about that port causing a vacuum leak?

Gas is for cleaning parts, alcohol is for drinkin, nitro is for racin
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#5
Correct. It allows exhaust gasses to cross through the intake to heat up the intake manifold. When you set the intake manifold what did you use for the end seals?

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
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#6
(04-30-2018, 09:42 AM)73pony Wrote: Correct. It allows exhaust gasses to cross through the intake to heat up the intake manifold. When you set the intake manifold what did you use for the end seals?

I bought gaskets from summit and it came with cork end gaskets

Gas is for cleaning parts, alcohol is for drinkin, nitro is for racin
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#7
(04-30-2018, 09:51 AM)Studdley Wrote:
(04-30-2018, 09:42 AM)73pony Wrote: Correct. It allows exhaust gasses to cross through the intake to heat up the intake manifold. When you set the intake manifold what did you use for the end seals?

I bought gaskets from summit and it came with cork end gaskets

I always ditch the end gaskets and run a fat bead of RTV black silicone across the ends.

Kevin

1971 Mach 1
408C Stroker
C4 w/3,000 stall
8.8" Rear w/3.73's
Disc brakes all way around.

[Image: 28ivsix.png]




                                                                                             
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#8
(04-30-2018, 09:54 AM)turtle5353 Wrote:
(04-30-2018, 09:51 AM)Studdley Wrote:
(04-30-2018, 09:42 AM)73pony Wrote: Correct. It allows exhaust gasses to cross through the intake to heat up the intake manifold. When you set the intake manifold what did you use for the end seals?

I bought gaskets from summit and it came with cork end gaskets

I always ditch the end gaskets and run a fat bead of RTV black silicone across the ends.

+1. that's why I asked. I have never had any luck getting the cork end seals to seal properly.

73 Grandé H Code. Headman long tube headers, T-5 Transmission, 3.70 Traclok, Lowered 1" all around, Aussie 2v heads w/ 2.19 intake, 1.71 exhaust, screw in studs, full roller cam 608/612 lift 280/281 duration LSA 112, Quick Fuel 750 CFM double pumper, AirGap intake.

- Jason


[Image: 082-hot-rod-power-tour-2017-1970-1970s.jpg]
  Reply
#9
This is what I did, not saying you have to, but I carefully "hand milled" a step about .080" deep and cut some 1/16" SS, then using a center punch, stitched the plate in place using some high heat exhaust paste to seal it. I also had previously inserted 5/16 set screws into the holes in the carb mating surface, see pic.
By doing this I practically eliminated any heat getting to the underside of the Holley 670 carb. This heat riser was intended for the Autolite 4300 carb only. My car was experiencing a huge amount of fuel vaporization causing hard hot starting until I "fixed it"
Also, when I install a valley pan, I do NOT use RTV. It's expensive, but well worth it to use Permatex "The Right Stuff" on the manifold ends. Do NOT use any silicone based product around the intake ports. Here I use Permatex 2 non-hardening gasket maker/sealer. Just a small bead around valley pan port grooves. There are other products that can be used here, but I have had no issues with P 2. There was another precaution I took, but then I'm a bit anal that way, was to cut and insert a .020" SS plate into the paper gasket to act as a double block-off for the heat cross-overs. The paper is slightly thinner than .020", but on the VP, I flattened that groove to allow for it. Tighten according to pattern and spec. There is a "trick" you can use and that is cut the heads of a couple of long 5/16" bolts, screw them into the head holes at center. These will act as a guide when lowering the manifold, just make sure they are long enough to remove!! Another tip is to get a couple of eye bolts that can be screwed diagonally into the carb mounting holes, then use a rod of some sort as a handle. Help from a buddy is a GOOD idea here!!
Hope that helps.
Geoff.
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#10
(04-30-2018, 10:49 AM)Stanglover Wrote: This is what I did, not saying you have to, but I carefully "hand milled" a step about .080" deep and cut some 1/16" SS, then using a center punch, stitched the plate in place using some high heat exhaust paste to seal it. I also had previously inserted 5/16 set screws into the holes in the carb mating surface, see pic.
By doing this I practically eliminated any heat getting to the underside of the Holley 670 carb. This heat riser was intended for the Autolite 4300 carb only. My car was experiencing a huge amount of fuel vaporization causing hard hot starting until I "fixed it"
Also, when I install a valley pan, I do NOT use RTV. It's expensive, but well worth it to use Permatex "The Right Stuff" on the manifold ends. Do NOT use any silicone based product around the intake ports. Here I use Permatex 2 non-hardening gasket maker/sealer. Just a small bead around valley pan port grooves. There are other products that can be used here, but I have had no issues with P 2. There was another precaution I took, but then I'm a bit anal that way, was to cut and insert a .020" SS plate into the paper gasket to act as a double block-off for the heat cross-overs. The paper is slightly thinner than .020", but on the VP, I flattened that groove to allow for it. Tighten according to pattern and spec. There is a "trick" you can use and that is cut the heads of a couple of long 5/16" bolts, screw them into the head holes at center. These will act as a guide when lowering the manifold, just make sure they are long enough to remove!! Another tip is to get a couple of eye bolts that can be screwed diagonally into the carb mounting holes, then use a rod of some sort as a handle. Help from a buddy is a GOOD idea here!!
Hope that helps.
Geoff.
Very helpful

Gas is for cleaning parts, alcohol is for drinkin, nitro is for racin
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