FastKat

iTrader: (10)

Do the LS1 (cathedral port) and the LS3 (square port) heads have the same intake manifold bolt pattern? I don't have any LS3/L92 stuff, so I can't check it out for myself. Looking at the pictures below, it really looks like the pattern is the same. Also, if you look at LS1 and LS3 intake manifolds, the bolt pattern (going straight down through the intake manifold) still looks the same.

If there is a difference, can someone explain exactly what it is? The only difference I can see from the pics is that the LS3 head has an extra bolt hole.

(BTW, I know the ports don't match up.)

the_merv

iTrader: (88)

No difference..same bolts too. That extra one on the LS3 is for a little dimple on the Intake Manifold..my L76 has it on it.

GNXClone

iTrader: (7)

Interesting...that hole for the dimple on the LS3 head.

I have an L76 intake I bought to install with LSA heads. The LSA heads are LS3/L92 style, but do not have the hole for the dimple. Guess I'll just have to cut the dimple off.

1CAMWNDR

iTrader: (21)

They are the same as far as number of bolts and which port gets 2 bolts. But otherewise they have nothing in common.

joe.broderick.sr

The question I have is will a LS3 intake manifold work on a GM L59 5.3L vin-Z out of a '04 Yukon? I have been reading where I can use a LS6 or LS1 but the LS3 seems to be a little less expensive. Thanks in advance. Joe

the_merv

iTrader: (88)

No.

Cathedral to Cathedral, Square to Square.

joe.broderick.sr

I am learning. Thanks again

FastKat

iTrader: (10)

Just to clarify, 1CAMWNDR is correct. The bolt pattern is the same, so it will bolt up.

However, the ports are not a perfect match... though much closer than you might think! It's also worth noting that none of the OEM manifolds I've run into are a perfect match on the heads.

With all that being said, it would probably still be best to use a cathedral intake on cathedral heads, and a square port intake on square port heads... unless you were using a CTS-V LSA supercharger on cathedral heads... but that's an entirely different issue that I know nothing about...

joe.broderick.sr

So what I am hearing is that either will work together but the best performance is to match types. Until this post I didn't even know that there were two types of intake ports. Now I have seen pictures of them. Thanks, again

the_merv

iTrader: (88)

IMO if you criss-cross them then you are half-assin it..

Do it once, do it right.

v8mgbgt

Hi
Just measured my Cathedral ports on my 317 heads and they are around 80mm.
My LS9 intake which should be the same as the LS3 dimensions has a seal which is less than 80mm.

So I would conclude that the LS3 square intake seal may not have enough height to enclose the cathedral port.

Hence I am looking for a set of LS3 heads in the UK if anyone has any for sale.

http://www.mgbv8.co.uk/

FastKat

iTrader: (10)

My goal is to put a TVS1900 supercharger from a Cadillac CTS-V on a set of cathedral port heads. The Cadillac engine uses the square port head design. The correct heads for my 5.7L small-bore LS engine are about $1,500 from GMPP which is just too much money. That leaves me with a square port supercharger (manifold) and cathedral port heads.

There is a twist though. It looks like the square ports on the supercharger are a little smaller than the ports on the square port heads. You would think they would be an almost perfect fit, but they're not. I've seen this on Magnacharger kits, too. I don't know if there's a good reason for this or if it's a cost issue, but their kits seem to work pretty well.

With all that being said, I am debating whether I should make a 1/8" aluminum spacer to "blend" the two port shapes together, or just put the square port supercharger on the cathedral port heads and see how it does.