Intake Manifold question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

skokie · 06-03-2005, 12:53 AM

Ok here is a dumb one. What are the center ports on a intake manifold for? Reason I ask is because I am going to be taking off my 2101 to get it cleaned and the new gaskets I bought (fel pro 1205) has no hole in the center.

Thanks

Dick Dale · 06-03-2005, 12:57 AM

Pictures?

**kwmech** · 06-03-2005, 12:59 AM

Heat crossover?

Old Yeller 1970 · 06-03-2005, 01:32 AM

Sounds like the heat riser. If you're still running the factory heads and intake you'll probably want different gaskets so it will work properly.

On the other hand I did the same thing you're contemplating and ran the gaskets without the heatriser openings when I replaced my old intake with an Edlebrock Performer.
When I took it off to do my engine rebuild I discovered that the heat had blown a hole through it anyway so I had the heat riser operational even though I had intended to block it off.

So maybe it really doesn't matter if you get different gaskets. The exhaust heat may burn a hole through them anyway.

**pjmoreland** · 06-03-2005, 02:07 AM

If you have a heat-activated choke (bimetallic coil), the heat passing through the center ports on the manifold will help open up the choke.

skokie · 06-03-2005, 02:13 AM

Here is the pic of the intake with the port circled in red. If those ports are the exhaust ports then the gaskets look to be the wrong ones. Or are they supposed to be blocked off? Engine is a 350 target master crate.

**pjmoreland** · 06-03-2005, 02:23 AM

That's the heat riser port.

fastwillie 696969 · 06-03-2005, 03:01 AM

me myself and irene would use hi temp rvt

skokie · 06-03-2005, 11:30 AM

HMM i cant remember if the gaskets I put on there had a center hole or not.

**VetteVet** · 06-03-2005, 12:03 PM

Being that you are in So Cal,Brad, you won't need the heat riser and it would help to
prevent carb overheat and boil over. Just my .02

68Stepbed · 06-03-2005, 02:39 PM

I use a Fel-Pro 1204. It has a metal block off plate. The 1205 just has regular gasket material and will burn through.

I agree with VetteVet about your SoCal location. It just depends what carb you are running. If you have a hot air choke you need a gasket with the hole in it. If an electric choke I would use the 1204.

Gas burns better when it's cooler. Blocking off the heat riser will improve throttle response unless it's really cold. Cooler temps will cause the fuel to wash the cylinder walls because a cold engine can't burn cold gas fast enough.

Good luck. Hope this helps.

skokie · 06-03-2005, 02:57 PM

I called edelbrock and they said the correct part is a 1256. Also I am not in so cal. I am in no cal but it does get kinda warm up here

**VetteVet** · 06-03-2005, 05:57 PM

Quote:

Originally Posted by skokie

I am not in so cal. I am in no cal but it does get kinda warm up here

Sorry Brad, I should have checked. When you live in Mich anywhere in Cal. is warm. LOL

06-03-2005, 12:53 AM	#1
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Intake Manifold question Ok here is a dumb one. What are the center ports on a intake manifold for? Reason I ask is because I am going to be taking off my 2101 to get it cleaned and the new gaskets I bought (fel pro 1205) has no hole in the center. Thanks __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

06-03-2005, 12:57 AM	#2
Dick Dale Excelsior, You Fathead. Join Date: Jun 2004 Location: Valparaiso, In Posts: 937	Pictures? __________________ Go Navy. The Sea Is Ours. Budget 350 Build http://67-72chevytrucks.com/vboard/s...38#post2264638

06-03-2005, 02:13 AM	#6
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	Here is the pic of the intake with the port circled in red. If those ports are the exhaust ports then the gaskets look to be the wrong ones. Or are they supposed to be blocked off? Engine is a 350 target master crate. Attached Images __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234 Last edited by skokie; 06-03-2005 at 02:13 AM.

06-03-2005, 03:01 AM	#8
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	me myself and irene would use hi temp rvt __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

06-03-2005, 11:30 AM	#9
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	HMM i cant remember if the gaskets I put on there had a center hole or not. __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

06-03-2005, 12:59 AM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,630	Heat crossover?

06-03-2005, 01:32 AM	#4
Old Yeller 1970 DON'T TREAD ON ME Join Date: May 2005 Location: Crosby County, TX Posts: 989	Sounds like the heat riser. If you're still running the factory heads and intake you'll probably want different gaskets so it will work properly. On the other hand I did the same thing you're contemplating and ran the gaskets without the heatriser openings when I replaced my old intake with an Edlebrock Performer. When I took it off to do my engine rebuild I discovered that the heat had blown a hole through it anyway so I had the heat riser operational even though I had intended to block it off. So maybe it really doesn't matter if you get different gaskets. The exhaust heat may burn a hole through them anyway.

06-03-2005, 02:07 AM	#5
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,982	If you have a heat-activated choke (bimetallic coil), the heat passing through the center ports on the manifold will help open up the choke.

06-03-2005, 02:23 AM	#7
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,982	That's the heat riser port.

06-03-2005, 12:03 PM	#10
VetteVet Msgt USAF Ret Join Date: Jan 2005 Location: Kalamazoo, Michigan Posts: 8,718	Being that you are in So Cal,Brad, you won't need the heat riser and it would help to prevent carb overheat and boil over. Just my .02 __________________ VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative.

06-03-2005, 02:39 PM	#11
68Stepbed Registered User Join Date: Mar 2005 Location: 10-Uh-See Posts: 5,609	I use a Fel-Pro 1204. It has a metal block off plate. The 1205 just has regular gasket material and will burn through. I agree with VetteVet about your SoCal location. It just depends what carb you are running. If you have a hot air choke you need a gasket with the hole in it. If an electric choke I would use the 1204. Gas burns better when it's cooler. Blocking off the heat riser will improve throttle response unless it's really cold. Cooler temps will cause the fuel to wash the cylinder walls because a cold engine can't burn cold gas fast enough. Good luck. Hope this helps. __________________ Matt 68 C10 stepside, LS1/700R4, TCI Engineering suspension system

06-03-2005, 02:57 PM	#12
skokie Registered User Join Date: Oct 2003 Location: San Jose Ca. Posts: 3,354	I called edelbrock and they said the correct part is a 1256. Also I am not in so cal. I am in no cal but it does get kinda warm up here __________________ RIP to my son Dylan. 5/17/2002 - 8/18/2018 If you want to know more about rare forms of pediatric cancer or if you want to help fund pediatric cancer research, please check out the website for the non-profit I started. https://slothforpedcancer.org 68 build thread http://67-72chevytrucks.com/vboard/s...d.php?t=223234

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