porting injector housings to 36MM

[wfot]

Ok, I have heard that 36MM is "the" number to get to when going all out.

My questions is that 36MM throughout the entire injector housing?

For example, if you drop a 36MM ball down the top, would it drop out the bottom? I am aware the injector bosses get in the way on the secondaries.... I am working on a solution to that....

When is 35MM good enough?

Can the housings take 36.5MM?? or 37MM?

When do the welded housings need to be done? 750HP??

Inquiring minds need to know.

any thoughts or findings or pics would be appreciated

[Paul Workman]

No, nothing sacred about 36mm. But, it does depend on what you are trying to accomplish - specifically - before porting anything.

That said, there are many successful runner examples of builds that are far larger. But!! Runner dimensions are but ONE part of an overall LT5 performance build, AND there are some quirks with regard to the castings of LT5s to be aware of and avoid - or else you may breach the coolant jacket.

For example, many have "siamesed" the intake plenum AND the input to the injector housing. And, the gen-III LT5 did away with the dual runners entirely - secondaries non-existent, i.e, the septum between runners completely gone, thus leaving a wide oval runner, divided just at the dual intake valves.

If you're not a mechanical injuneer, then I would suggest researching extensively what others have done and what the results have been before (and I mean no offense here) "willy-nilly" opening up this and modifying that.

All that said, there is a TON of performance left on the table when the LT5 left MerCruiser!!!

[wfot]

thank you paul,

this is exactly why I am asking this here. I would like real world examples of what people have done/used and what the results were. and please I would appreciate to hear what a dyno shows vs what does it feel like driving vs actual track numbers.

I am looking for real world HP numbers vs actual runner size...
IE can a 35mm runner support 450 hp?
can a 36mm runner support 550 hp?
I think a 36mm can got a 415 CID motor 600 HP on a dyno

What HP level does it become necessary for the siamesed runners or welded runners?

I think I saw on post somewhere by Pete and he stated that he can actually get the runners to 36.5mm, can the 36.5mm get 650HP?

any input or experience, good or bad, is appreciated.

thank you all again

John

I am also working out a way to be able to port the secondary injector boss just like the primary boss on the 90 housings. I am hoping if I an get the secondaries to flow as much as a fully ported primary, that this would get a full 36mm port on all 16 runners to go over 600hp..

I made a oring bung that is welded on top of the secondary port that lifts the oring point higher just like the primary port. this allows primary orings to be used on all runners and hopefully an excellent balance of flow for over 600 hp and be able to keep the low end torque.

[Pete]

John
Drop a 35mm gauge ball straight thru the port they call this 36mm dropping a 36mm gauge ball straight thru they call this 37mm.
I also have a 36.5mm gauge ball.

Your question about the power level.
You can't get the intake big enough for it to hurt driveability of course alot is also in the tuning.
My lil 350 intake was more or less what they would call 38mm no divider in the plenum with no secondaries made 330 rwtq @ 3k rpm 410 peak car would run 11.0's @128-129 mph ran 154mph 1/2 mile.
Car drove like a stocker would drive it to BG,car shows etc,
My ports are 38mm+- but went into oil same port on 1 on each IH i do not reccommend this for the faint lol

Like i mention its also in the tune.
Hope this helps you with your venture.
Pete

[Pete]

There are a few 350 ZR-1's running around with ported top ends to 37mm some with stock cams some with performance cams
That make good HP/TQ #'s they might come on here and reply on the driveabilty.

I have done hours and hours and lots of $$$$ research on cams on the LT5.
If going with performance cams gotta pick the right set of cams price is irrelevent in this case you get what you pay for.

Pete

Originally Posted by Pete

John
Drop a 35mm gauge ball straight thru the port they call this 36mm dropping a 36mm gauge ball straight thru they call this 37mm.
I also have a 36.5mm gauge ball.

Your question about the power level.
You can't get the intake big enough for it to hurt driveability of course alot is also in the tuning.
My lil 350 intake was more or less what they would call 38mm no divider in the plenum with no secondaries made 330 rwtq @ 3k rpm 410 peak car would run 11.0's @128-129 mph ran 154mph 1/2 mile.
Car drove like a stocker would drive it to BG,car shows etc,
My ports are 38mm+- but went into oil same port on 1 on each IH i do not reccommend this for the faint lol

Like i mention its also in the tune.
Hope this helps you with your venture.
Pete

[Corvette95]

So ....I know there are a few Gen3 plenums out there...cannot they be reproduced in a limited run? I wonder the costs of something like that....would a group pre-purchase make it happen? Thinking out loud.

[Pete]

Originally Posted by Corvette95

So ....I know there are a few Gen3 plenums out there...cannot they be reproduced in a limited run? I wonder the costs of something like that....would a group pre-purchase make it happen? Thinking out loud.

3D printing.
What would be the purpose for this Gen 3?
More volume?

Pete

[Corvette95]

Originally Posted by Pete

3D printing.
What would be the purpose for this Gen 3?
More volume?

Pete

My thinking was that the higher CU builds all have the Siamese plenums and as I understand was going to the the stock plenum had the LT5 not been discontinued (OBD2). Does the Siamese plenums not provide more clean flow and volume? Again, thinking out loud. From the appearance and appearance alone perspective , I think the standard plenum provides more of a visual impact than the Siamese plenums, but we are talking HP and flow, right? BTW, Pete, I am more than completely happy with the top end work you did on my car. Thanks again!

[grahambehan]

Originally Posted by Corvette95

So ....I know there are a few Gen3 plenums out there...cannot they be reproduced in a limited run? I wonder the costs of something like that....would a group pre-purchase make it happen? Thinking out loud.

Gen 3 plenum, really?

Graham

[A26B]

Originally Posted by Corvette95

So ....I know there are a few Gen3 plenums out there...cannot they be reproduced in a limited run? I wonder the costs of something like that....would a group pre-purchase make it happen? Thinking out loud.

Really?? Where are they at? I only know of 1.