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#1 |
![]() Join Date: Jan 2009
Location: New jersey
Posts: 156
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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 |
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#2 |
![]() ![]() Join Date: Nov 2007
Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri
Posts: 6,493
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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!!!
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Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry |
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#3 |
![]() Join Date: Jan 2009
Location: New jersey
Posts: 156
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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. |
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#4 |
![]() Join Date: Dec 2003
Location: Chicagoland,IL
Posts: 2,679
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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
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'91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage Last edited by Pete; 03-05-2021 at 06:06 PM. |
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#5 |
![]() Join Date: Jan 2006
Location: Decatur, AL
Posts: 1,112
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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.
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Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454 |
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#6 | |
![]() Join Date: Dec 2003
Location: Chicagoland,IL
Posts: 2,679
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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 Quote:
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'91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage |
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#7 | |
![]() Join Date: Dec 2003
Location: Chicagoland,IL
Posts: 2,679
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3D printing. What would be the purpose for this Gen 3? More volume? Pete
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'91 #1635 PoloGreen 350 LT5 11.09 @ 129.27 11.04 @ 128.86 474RWHP 400RWTQ http://www.youtube.com/watch?v=SFNFOhGGlR4 http://www.youtube.com/watch?v=ZlRIOMwaDYY https://sites.google.com/site/peteszr1garage |
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#8 |
![]() Join Date: Feb 2013
Location: New Concord Kentucky
Posts: 179
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#9 |
![]() Join Date: Jan 2006
Location: Decatur, AL
Posts: 1,112
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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!
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Corvette95 Registry and Forum (*************) 1989 C4 Conv Wht/Gry Auto Hardtop Top Flight SOLD 1995 C4 Coupe Purple/Blk 6 Speed 1989 C4 Conv Wht/Red Auto SOLD 1996 C4 Conv Black/Tan Auto SOLD 1994 C4 Coupe Wht/Blk SOLD 1995 C4 ZR-1 White/Gry #278 Dual Dunn Head SOLD 1986 C4 Coupe Black/Red 4+3 SOLD 1990 C4 ZR-1 Red/Red #0454 |
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#10 |
![]() Join Date: Dec 2003
Location: Arcadia,OK
Posts: 3,385
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Really?? Where are they at? I only know of 1.
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Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. |
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