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What do I do?! Should ports match on a supercharger intake manifold?
I bought a Cadillac CTS-V LSA supercharger to put on my small-bore cathedral port engine. My original plan was to make a couple adapter plates out of 1/2" thick aluminum that blend the square ports from the supercharger manifold into the cathedral ports on my heads.
Well the supercharger came and I measured the port size on the supercharger manifold. The ports aren't that much different than the cathedral ports.
Supercharger manifold (measured myself)
H: 2.53" at highest, 2.45 at lowest (shape is slightly irregular at the top)
W: 1.16"
Cathedral heads (from a website)
H: 2.75"
W: 1.00"
That's a really small difference We're talking less than 3/32" on each side for the width, and less than 1/4" inch in overall height.
Then there's the intake manifold gasket. It doesn't match the supercharger manifold very well. Based on these numbers, that gasket doesn't match the L92/LS3 head ports either.
Supercharger manifold intake gasket (measured myself)
H: 2.82" at highest, 2.76 at lowest (shape is slightly irregular at the top)
W: 1.57"
L92/LS3 square port head (from a website)
H: 2.475"
W:1.25"
Here's a pic of the LSA supercharger manifold and gasket. The port is significantly smaller than the outside perimeter of the gasket.
I guess it's not all that unusual. It looks like Magnuson does the same thing - though I'm not sure if it's for performance, efficiency, or cost reasons.
So it seems like GM and Magnuson aren't that concerned about matching the port size/shape between their intake manifold and heads. Should I be concerned about it?
Here are my best ideas so far:
1) Just use the head gasket that's on the supercharger manifold and bolt it down to my cathedral port heads - no adapter plate
2) Make a 1/2" adapter plate and that blends the square port on the supercharger into the cathedral port heads - I would also use gaskets - it would go (intake manifold - gasket - adapter plate - gasket - head)
3) Forget the intake manifold gaskets: Make a 1/2" adapter plate that blends the two ports together, coat the perimeter of each opening on the adapter plate with silicone gasket maker and let it dry before putting it together - I might even put a shallow rut in the plate to help the silicone bite. The final product would be a 1/2" adapter/gasket plate
4) New idea: The gasket in the picture is 1/8" thick. I could make small liners/inserts, 1/8" thick, to put inside the port. These liners would sit entirely inside the gasket hole, but be shaped to blend from the square port to the cathedral port.
Depends on if you want to get 100% out of the combo . From what I just read your height, the inlet port of the head is higher so no LIP thus would be acceptable .
As far as the width , The inlet port is narrower then the blower so it will have a LIP , this should be addressed. Maybe just a slight hit with a diegrinder to blend the head in this area.
I like number 3 as far as execution goes, but that gasket maker might not be quite up to snuff on a boosted app and you might get a vacuum leak. Although I guess it could happen with an oem gasket also...just stuff to think about...
i think the 1/2 plates would cause a problem. it going to make the supercharger sit higher, and it probably wont fit at all. imagine the distance between bank 1 and bank 2. you just lessened that number by an inch. you'd theoretically need to cut the supercharger in half and take an inch out the middle. You should just do this the right way and buy some cheap LSA heads. problem solved!
This is a good point. For the sides, blending the head would be a good option. I do need to take a good look at the top of the square port and see how that matches up with the top of the cathedral port.
Originally Posted by VUSS383
Depends on if you want to get 100% out of the combo . From what I just read your height, the inlet port of the head is higher so no LIP thus would be acceptable .
As far as the width , The inlet port is narrower then the blower so it will have a LIP , this should be addressed. Maybe just a slight hit with a diegrinder to blend the head in this area.
Yea, I'm having second thoughts about the gasket maker too.
Originally Posted by Fbodyjunkie06
I like number 3 as far as execution goes, but that gasket maker might not be quite up to snuff on a boosted app and you might get a vacuum leak. Although I guess it could happen with an oem gasket also...just stuff to think about...
The plates will make the supercharger sit about 3/4" higher, which will add height to the engine and also throw off the stock CTS-V belt drive. I could definitely line up the ports, but I'd have to adjust the angle of the ports on the plate.
Unfortunately, my car is a 3.9" bore, not a 4.0" bore, so the L92/LS3 heads won't work. The cheapest heads available are from GMPP, and they're about $1,450 per set. That's about half of what I'll spend for this whole setup!
Originally Posted by KILLER-LS1
i think the 1/2 plates would cause a problem. it going to make the supercharger sit higher, and it probably wont fit at all. imagine the distance between bank 1 and bank 2. you just lessened that number by an inch. you'd theoretically need to cut the supercharger in half and take an inch out the middle. You should just do this the right way and buy some cheap LSA heads. problem solved!
I am leaning towards option #4, which is to make liners out of 1/8" aluminum plate that actually sit inside the gasket holes and blend the square port into the cathedral port. I guess I'll make one and see how durable it is.
Nice job!! I too have one of these blowers and I am going to make adapter plates , plan so far is 1/4 inch aluminum sandwiched between cathredal gasket and lsa gasket but I do like the silicone idea! if silicone can handle cooling system psi I don't see why it cant handle 15 boosted psi....but who knows more research is needed
Do not use silicone rtv ect on anything to do with fuel. This is one of those ideas that can snow ball. Like if I was doing it, most likely it would devolve to a head swap eventually. That blower would be great torque and loads of fun in your car.
My maggie manifold wasn't exact
I doubt it makes much of a difference unless your looking for 100% of what the blower can make.
It'll turn into a heater before that small amount of boost lost would mean something power wise.
I'd bolt it on and let er rip
I haven't fit one personally
If the manifold/gasket seals around the intake port of the head and of the supercharger I don't see why not
Might not be ideal, but like I said, the maggie manifold doesn't line up perfectly with the heads, hasn't made a difference for anyone running one that I inow of
Might have to pick one up for giggles haha If anything it would be a great desk ornament all polished up.
I almost think that the hardest part would be driving the darn thing, My truck has an aftermarket serpentine set up which complicates it even more...
Think the pulley can be pushed out however far to line up with the belt right above the waterpump outlet with some sort of adaptor or even a longer shaft made? I understand belt wrap wouldn't be super good but if only a few psi would it be bad?
NOT looking to push the limits, just extra looks and some speed. Tired of people saying "dude, that's gotta be 500hp right?" and saying "no just 350" They always look a little disappointed. ~430 hp would be sick.
EDIT!
I looked up LSA belt drives and it almost looks doable! If the pulley can be spaced out that is... THe belt would have quite a bit of wrap doing basically this with my drive kit in the first pic. stolen from here http://www.superchevy.com/how-to/eng...ory-drive-kit/
This next kit is a real for blower aftermarket set up that has even more belt wrap but isn't cheap...
from here http://www.c1pulleys.com/chevylsvictory-sc03.html
Aren't there any other heads that will work? I've been looking into doing an lsa top end on one of my engines but hood clearance is ridiculously tight as it is. I'll be lucky to squeeze the blower in there let alone the extra ~1" from the spacers.
There are no OEM heads that I'm aware of that will fit on any bore smaller than a 6.0. Mast motorsports sells a small bore ls3 head, that might be the only option, but by then just buy a 6.0 and a set of ls3 heads.
08-19-2011, 05:56 PM
What do I do?! Should ports match on a supercharger intake manifold? 
