Lars87

I am replacing a L98 intake gasket, and notice that the rear coolant ports are covered with and aluminium blind, as a part of the gasket.

This a a Victor Reinz gasket set. The one I removed also had the blinds, but I belive this has been done before, as the RTV on the china walls did not look factory.


So, should a 87´L98 have the rear coolant ports in the intake/heads blinded off?

Joe C

aluminum head L98's should have restrictors in the rear water ports of the intake manifold gaskets. some members have opted for open ports. I'm probably going to get some negative comments, but I used iron head gaskets on my 90, thus opening up the rear water passages. I've driven about 1000 miles so far, and haven't notices any water temp issues.

WW7

When I put in my new 383 I used restrictor gaskets, but form what I have read it's only neccessary if you have the original heater setup from the factory with the small tube coming off the manifold... There are many on here who have stopped using the restrictors and I've never heard of any problems....WW

BOOT77

It's a 5/16 line out and lets trapped air out from the back of the heads. I've noticed air trapped on iron heads when just pulling the intake, I saw dry pockets 3-4" deep on each head. I've always used felpro 1204 on all my stock/smallish intakes, it has open rear ports and 99% of the time the intake that fits that port size doesn't. I even have a 1204 set I'll be using on my C4 when I mild port the intake. Pretty sure the C4 tpi is the only intake that has a rear factory vent line other than a C1 I once saw in a picture.


Does the alum blind have holes? If not just drill a hole in each side, they don't have too be big the line out is only 5/16.

SunCr

The Restrictors are there to keep coolant at the rear of the heads longer to prevent hot spots. They are not used on the F-Body (and if the gaskets don't have them they may be intended for that application and not the L98 Vette). The ZZ4 Long Block, which uses the 113 Aluminum Heads, doesn't use the Restrictors either. To provide a sufficient amount of coolant, a bypass runs from the heater core outlet to the rear of the heads. Trapped air is not an issue; never has been an issue and never will be unless you used an incorrect procedure to change out the Coolant. Air doesn't cool anything and if you have air in the cooling system, you need to bleed it out using one of the procedures that have been posted a gazillion times around here. If you run without the Restrictors, you can remove the Bypass Hose.

rochhound

i have a 86 c4 i just got back together,had never been rebuilt.the front and back water ports
where both restricted from the factory.my gasket set didnt have these blocked,so far after burping it runs cool around 215 f or lower.

BOOT77

Steam pockets I've read that's why the alum headed corvettes have that line out.

vetteoz

http://forums.corvetteforum.com/c4-s...-question.html

BOOT77

I didn't read all that but as I got down I do rem that people who use large lines have slow warm up. And that's why I used 1/4" lines on my C3 and I'd bet that's why it has the restrictor plates have small holes so it doesn't slow down warm up with the bypass. Still that's why I thought my 86 had the heater core valve or w/e.

Edit: Also on my C3 I have the bypass at the pump blocked, so the rear intake lines + a small hole in my t-stat are the only bypass until the stat opens.

Lars87

Thanks guys. Got the info I needed. Staying stock on the 87´.

Cliff Harris

The water pump puts water into the front of the block on both sides. The basic flow pattern is rearwards through the block and then frontwards through the head, where it then goes into the front of the intake manifold and out through the thermostat. There are a bunch of holes along the flow path between the block and the head.

The rear passage in the intake manifold seems to be there to balance out any pressure differences between the two sides. I wouldn't think the pressures would be too different, so you don't need a large passage, thus the small holes in the gaskets.

WW7

When I was putting my 383 together back in 2010, I asked on here if I should use the restricted or unrestricted intake gaskets, I eliminated the small tube from the heater hose and put a plug in its place on the Edelbrock 3860 intake, then installed the restrictor gaskets.. The answers I got back then were just like we're getting now, (mixed and confusing).....I have checked a few times with a infared heat gun and haven't noticed much temperture difference between the front and back of the heads...I have noticed that some of the intakes used on 350 engines around the time that our cars were built have no holes for coolant in the back of the intake manifolds at all , so how important can the rear ports really be to the cooling of the engine?...All I know is my 383 now has over 30,000 miles on it and it still runs as good today as when I first put it in........WW

SunCr

More of an explanation is here: http://www.hotrodlane.cc/PDFFILES/TPIStory.pdf

If there's steam in your cooling system there's a problem - probably should retake HS Chemistry.

BOOT77

What about those who run straight water as per racing rules? Or when using lots of nitrous and boost making lots of heat.

From the pdf
"and has a water cross over at the back of the intake to relieve hot spots on the back of the heads similar to the later LT-1 engines"

I coulda swore hot spots cause steam? The line could be since gm knew the corvette would be used for racing for all we know.

Prob shouldn't make blanket statements!