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one Intake manifold gasket set has a restrictor port on the ends of each gasket while another gasket has no restrictor plates. The restrictor plate cover over a port. I've been told the gaskets without a restrictor port adds performance and cools down the heads. Which one should I go with for my 1990 corvette l98 motor? Taking it apart tonight. Do these motor have the restrictor ports originally from the factory?
Thanks Dave c
Not a great pic on my 88 L98. You will see a small black metal pipe that runs from the coolant/heater hose that connects to the back 2 cylinders, 7 & 8. I am sure there is some coolant value on the back of the intake but it has to be minimal.
I chose NOT to use manifold gaskets with the restrictors on my 90. after reading much on the forum on this subject, it seemed like a 50/50 mix going both ways. I did have a set of felpro's for an iron head 85 and used them on my 90. no other changes. it's been about 3-4K miles, and I have NOT noticed any temperature issues - the 90 seems to run just fine. as a side note, FWIW, it seems like most blown head gaskets on the aluminum head L98's occurs at either #7 or #8 cylinder - back by the restrictors. if down the road, I have issues because of the non-restrictor gaskets, then I'll admit i screwed up, and write it off as a learning experience, but so far so good.
So will putting a gasket without a restrictor port cause problem ? I'd think It will add to the performance and cool down the heads?
as I said, hasn't seemed to cause any temperature issues on my 90 in several thousand miles of DD. everything seems normal. as far as performance gains - I doubt it - nothing I can feel by the seat of my pants.
no flames or anything like that, but why? i'm still trying to figure out why the general put restrictors there in the first place.
It's a mystery to me. I just stated what the stock configuration was.
When I replaced my head gaskets recently I used the restricted gaskets because I have the steam tube. I figured there must be a reason for those gaskets, whatever it might be.
If you look at the aftermarket manifolds made for the Chevy small block engines you will notice most don't even have holes in them for the rear coolant to flow through.. I know Dart intakes don't have rear crossover cooling for any of their Chevy manifolds, just solid metel in the back...If rear cooling was important then they would have rear holes for the coolant to flow through ...The tech guy at Dart heads told me they don't put coolant crossovers in their SBC manifolds because it's not necessary, and they don't need it...WW
Here are some SBC intakes on Summit, use the 360 degree view button and look at the bottoms of the manifolds...No rear coolant crossovers on them.....Neither Dart of Edelbrock use them on most of their intakes......So, I would say if your car is stock with the stock manifold, and the little steam release hose coming off the manifold, keep using the gaskets with rear restrictors...If you car is modified like mine is using a different manifold, then it doesn't make much difference what you use...
just seems to me, that if the coolant gets hot enough to create steam, boil, or whatever, and there's a need for a steam tube, that can't be good - . I would really like to see some real engineering data - flow vs temperature for the rear ports of the heads/manifold. I may be out in left field here, but that whole configuration just doesn't make sense to me -
just seems to me, that if the coolant gets hot enough to create steam, and a need for a steam tube, that can't be good - . I would really like to see some real engineering data - flow vs temperature for the rear ports of the heads/manifold. I may be out in left field here, but that whole configuration just doesn't make sense to me -
Joe, It seems like GM really went out of their way to do little afterthought fixs on the C4 Corvettes, some helped, some didn't ...Do you remember the "Frizbee".........I know quite a few guys who use standard open gaskets on their stock Corvette motors and have never had a problem... Pete K, the guy who built my engine told me "Use either gasket and you'll be fine", of course I have a 4 bolt truck block in my 89 so who knows...............WW
Joe, It seems like GM really went out of their way to do little afterthought fixs on the C4 Corvettes, some helped, some didn't ...Do you remember the "Frizbee".........I know quite a few guys who use standard open gaskets on their stock Corvette motors without a problem... Pete K, the guy who built my engine told me "Use either gasket and you'll be fine", of course I have a 4 bolt truck block in my 89 so who knows............WW
- as I said, I used non-restrictor gaskets on my 90, and haven't noticed any ill-effects.
right now, I'm glad I went that route.
Lower intake gasket
. I would really like to see some real engineering data - flow vs temperature for the rear ports of the heads/manifold. I may be out in left field here, but that whole configuration just doesn't make sense to me - 
..
..I know quite a few guys who use standard open gaskets on their stock Corvette motors and have never had a problem... Pete K, the guy who built my engine told me "Use either gasket and you'll be fine", of course I have a 4 bolt truck block in my 89 so who knows....
- as I said, I used non-restrictor gaskets on my 90, and haven't noticed any ill-effects. 