Rear coolant passages
05-05-2008, 02:02 AM
#1
Rear coolant passages
Why is the rear coolant passages plugged on the intake gaskets for an L98? The gaskets I'm removing from my 89 have a small hole in a metal plate (which can also be removed for more coolant flow.) Wouldn't it be better for these to be opened up? The new gaskets which are the same felpro number don't even have a metal plate, but just gasket materal altogether. Can someone explain? Thanks!
05-05-2008, 10:17 AM
#2
Race Director
Are you sure you have the right gasket? I think that some of the earlier year engines don't have that back port and use the closed gasket. I have the Fel-Pro 1256 on mine with wide open ports.
05-05-2008, 12:28 PM
#4
Race Director
The 1256 matched fine on mine, it just has the rear water passages full open. There is another gasket with the small holes in it, I don't remember the number.
05-10-2008, 05:15 PM
#6
Instructor
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Hey - I'm doing my intake gasket for an 89 L98 and have the same scenario. The gasket's have the rear water jacket blocked with an exception of a seep hole (about 1/8") and are stamped as rears. My FSM tells me to put the blocked port in the front. This does not make sense.
What did you end up doing?
What did you end up doing?
05-10-2008, 08:02 PM
#7
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My gaskets kinda came apart during disassembly. I did find a piece of rectangle metal with a tiny hole in it but I'm not sure which passage was block, front or back so I believe I had the restricted.
05-10-2008, 08:41 PM
#8
Race Director
My stock '88 intake gaskets had the small hole in the rear port. No troubles using the gasket with fully opened ports. I've debated deleting the steam vent hose but haven't.
05-10-2008, 10:02 PM
#9
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I was about to post and ask the same question. The FelPro overhaul gasket set I just bought has the restrictor plate and the directions from FelPro say to use it in the back. The gasket kit I bought off ebay from some guy down in Texas had fully opened ports. I see the topic is still up for debate???
05-11-2008, 10:59 AM
#11
Race Director
05-12-2008, 03:00 AM
#12
Le Mans Master
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No , I bought a job lot of full TPI gaskets sets so have only ever used the factory type with restrictor.
As with the other comments , are at a loss to explain why rear port is not used in our setups but have never had any cooling probs.
Touch wood.
As with the other comments , are at a loss to explain why rear port is not used in our setups but have never had any cooling probs.
Touch wood.
05-12-2008, 07:59 AM
#13
Racer
My friend had his 88 motor completely rebuilt, it always ran hot. He installed a low temp fan switch and a 160 stat and it did not help. One day he decided to do a head swap. we noticed the rear water ports were restricted with a 1/8 hole. I drilled a 1/2 inch hole in the new metal block offs. The car has run cool ever since.
05-12-2008, 10:37 AM
#14
Melting Slicks
I always wanted to ask to you gurus..
.. I have Brodix heads with the rear coolant passages BIG and OPEN (if I correct remember..)
The Superram baseplate HAS also the rear coolant passages (if I correct remember..
).
Obiouvsly I used gaskets (felpro 1206) with the BIG rear coolant passage OPEN.
But what I ask to myself....
What'S if I use an intake manifold without the rear coolant passage?
Where's going the coolant if the manifold don't allow the passage?
Which part of the motor will not be cooled anymore?
Thanks
-Beppe-
.. I have Brodix heads with the rear coolant passages BIG and OPEN (if I correct remember..)
The Superram baseplate HAS also the rear coolant passages (if I correct remember..
).Obiouvsly I used gaskets (felpro 1206) with the BIG rear coolant passage OPEN.
But what I ask to myself....
What'S if I use an intake manifold without the rear coolant passage?
Where's going the coolant if the manifold don't allow the passage?
Which part of the motor will not be cooled anymore?
Thanks
-Beppe-
05-13-2008, 09:31 AM
#15
Le Mans Master
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Where does the rear passage go?
Only from one head to the other.At best it might pickup some heat from oil splash under intake; at worst it is adding unwanted heat to the intake.
Neither my Edlebrock Torker or Vic Jnr manifolds ( both popular performance intakes ) have rear coolant crossover.I don't believe my HSR has it either.
A SBC enters water into the block at the front (waterpump ) and exits from the heads via the front intake crossover to thermo housing.The water circulates in the block meanwhile.Nothing is setup to particulary direct flow across the rear crossover from one side to the other.
Some racers run hoses direct off the rear coolant ports to get better
( more even ? ) cooling .
The LTX engines have superior cooling because the coolant is directed to the heads first where the major heat is.
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Nilak (10-25-2023)
05-13-2008, 09:39 AM
#16
Melting Slicks
Beppe , consider this.
Where does the rear passage go?
Only from one head to the other.At best it might pickup some heat from oil splash under intake; at worst it is adding unwanted heat to the intake.
Neither my Edlebrock Torker or Vic Jnr manifolds ( both popular performance intakes ) have rear coolant crossover.I don't believe my HSR has it either.
A SBC enters water into the block at the front (waterpump ) and exits from the heads via the front intake crossover to thermo housing.The water circulates in the block meanwhile.Nothing is setup to particulary direct flow across the rear crossover from one side to the other.
Some racers run hoses direct off the rear coolant ports to get better
( more even ? ) cooling .
The LTX engines have superior cooling because the coolant is directed to the heads first where the major heat is.
Where does the rear passage go?
Only from one head to the other.At best it might pickup some heat from oil splash under intake; at worst it is adding unwanted heat to the intake.
Neither my Edlebrock Torker or Vic Jnr manifolds ( both popular performance intakes ) have rear coolant crossover.I don't believe my HSR has it either.
A SBC enters water into the block at the front (waterpump ) and exits from the heads via the front intake crossover to thermo housing.The water circulates in the block meanwhile.Nothing is setup to particulary direct flow across the rear crossover from one side to the other.
Some racers run hoses direct off the rear coolant ports to get better
( more even ? ) cooling .
The LTX engines have superior cooling because the coolant is directed to the heads first where the major heat is.
05-13-2008, 10:26 AM
#17
Le Mans Master
Design was to keep the coolant at the rear of the heads longer to enable better cooling (and given the number of head gasket failures at #7, I often wonder how effective it was). To ensure adequate flow, coolant is delivered from the bypass at the heater core outlet. Design is unique to the Vette and wasn't used on the F Bodys, so when shopping for manifold gaskets, you need to specify that it's for a Vette, (though many have done away with it and when you do, you can plug the bypass). '91 is particularly difficult to find as the heads were also redesigned to accept intake gasket retainers and the F Body and/or ZZ4gaskets (without the restrictors) are generally all that's available. Also, for '89, ignore the Service Manual as it has the install backwards (corrected by a Bulletin).
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Nilak (10-25-2023)
05-13-2008, 10:48 AM
#18
Le Mans Master
