Does anyone possibly have the flange riser measurements for the imco risers to manifold on a LS engine. They look fairly close to the ones I have for my bbc, could be wrong. Getting rid of all my big block stuff and going with a LS.

Appears the LS Powerflow system uses the riser gaskets on the Thumper series of bbc exhaust systems.
Appear both use Imco gaskets 11-1007
See individual parts of bbc system here:
https://imcomarine.com/cal_store/thu...kit-black.html

snd then:

Thank you! I didn't think of looking it up that way. Those are different then my power flow gaskets. Was trying to use my risers i have now and just get new manifolds for the LS but looks like I'll be having to buy manifolds and risers for the LS.

29 bucks for a 2 dolla gasket

Sounds like a Mercruiser move.

Speaking of money and exhaust - i have seen others mention the low cost of ls exhaust systems from crusader marine but nothing if fitment to existing tailpipes, performance, etc, etc ..

Nice move I did this. I bought Hardin marine exhausts. I had to custom mill my own 6” risers out of billet aluminum.

post a link to yours. I’ve been consumed by weight reduction everywhere I can aluminum exhausts, plastic intake. But in retrospect would’ve been easier to go with crusader exhausts. Of course vp is doing Ls based now too.ever need to talk hit me up.

my engine is broken in on the stand but my b3 outdrive isn’t finished. I hope to do 60 top speed. We’ll see

Your inbox is full. How does that cam sound that you are using? Can you measure the flange bolt hole dimensions for me?

Sorry cleaned it out. I posted it on YouTube let me see if it’s still there

i will try but I put it together already. I made my own gasket using roll of paper and rtv

Thanks. Just measuring the bolt distances will work.

Outside of bolt approx 3.380 x 5.115

Looks like what you need
https://www.hardin-marine.com/p-1045...ld-system.aspx

this is what I have. All I could get during pandemic.
https://www.hardin-marine.com/p-110032-exhaust-manifold-to-riser-gaskets-ls-manifolds.aspx

https://www.hardin-marine.com/p-104504-ls-m-marine-aluminum-exhaust-manifold-system-for-gm-48-53-60-62.aspx

had to custom fab my own risers to get the proper height for my situation