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#21
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Ha.....Mick above mimic'd about identical to what I just said about the M20 gear ratios.
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#22
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Edelbrock intake Cam: Xtreme Energy XE274H 274/286, 230/236, .488/.491, 110 Hyd They have been tuned. Should be scary to drive, right!
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1970 Tempest (428 Whitmore, Cliff Q-jet, Doug Nash Five Speed) slowly coming back to life 1965 Lemans (462 Butler, Cliff Q-Jet, Muncie M20 with 3.55s) |
#23
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Edelbrock intake Are those carbs way too small in your opinion?
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1970 Tempest (428 Whitmore, Cliff Q-jet, Doug Nash Five Speed) slowly coming back to life 1965 Lemans (462 Butler, Cliff Q-Jet, Muncie M20 with 3.55s) |
#24
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For sure too small for the CI and really not a good 2-4 intake.If you want more power a QJ and a good modified stock intake would be better.If you like the eye candy and performance a Offy intake and a pair of 3705 max wedge AFBs properly jetted for a in line intake would be my choice.Progressive linkage for the street and solid at the track.Tom
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#25
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My setup is mild 400/M20/3.55 rear/26 tall tire and I’m pretty happy with overall driving manners.....but I usually don’t push it much over 65 mph
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#26
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Burns the tires in 1st, 2nd, and 3rd with factory traction bars. Blew away a turbo diesel last night and that was going from a light up a bridge. It's near perfect up until I need another gear, 5th. However, that keeps me out of trouble with speeding tickets. 25" tires though. And a very happy engine. Since the question was asked with 3:55 gears in mind, that should make up for the 25" tires. Last edited by TAQuest; 07-18-2019 at 08:44 AM. |
#27
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Thanks. I am thinking maybe carbs are the issue. I am taking off the way you described in your 462 paragraph. I was thinking the tranny and gears were my issue! Sent from my iPhone using Tapatalk
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1970 Tempest (428 Whitmore, Cliff Q-jet, Doug Nash Five Speed) slowly coming back to life 1965 Lemans (462 Butler, Cliff Q-Jet, Muncie M20 with 3.55s) |
#28
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Fixed that and the car is happy with the ratios. I think a lot of folks that have issues with the m21 ratio are really having issues with their engines and passing the buck to the ratios. A happy engine gives you more flexibility with trans and gear ratios. When you get it right you need those ratios or you just sit and spin. |
#29
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I had a close ratio Muncie four speed with a 3.55:1 rear in my car for many years - from what I have come to understand, it wasn't ideal, but it was fine for me.
I also had compression on my side, which helps torque numbers... Pontiac did build some cars with a close ratio Muncie and 3.42:1 - so that's honestly the lowest (numeric) gear ratio I would use with a close ratio transmission - but even then I'd suggest only doing it with a higher torque engine...
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1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
#30
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Lets pursue this a little further. I always thought that the Offy manifold was limited by the runner design of the manifold -- basically carbs sit really low and runners have to go uphill and make the sweep into the head. The Edelbrock "looks" like a better design since carbs sit higher and ports look to have about the same angle as a normal 4-barrel manifold.
I sold my Offy dual quad manifold and carburetors a few years ago and recently picked up an Edelbrock dual quad manifold with almost new 625 cfm Edelbrock carbs in exchange for doing some engine work. Thought it was going to be a step forward, but wouldn't be the first time I've made a move backwards based on what looks like it would work better. Thinking about putting them on my son's 65 2+2 421 engine. He doesn't race it anymore and pure street duty now, but I'm interested to hear whether the Offy would have been a better choice.
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Mick Batson 1967 original owner Tyro Blue/black top 4-speed HO GTO with all the original parts stored safely away -- 1965 2+2 survivor AC auto -- 1965 Catalina Safari Wagon. |
#31
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When I first bought my car, the M21 was paired with 3.31s in the rear. After I worked on the tune a bit, it ran great and - with the lousy tires on it - spun the tires in all 4 gears.
During restoration, I switched to 3.73s and good rubber - that REALLY woke it up.
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1965 Pontiac LeMans. M21, 3.73 in a 12 bolt, Kauffman 461. |
#32
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An M20 with it's stock gears will have zero problems taking off from a stop, even with a 3.08 rear gear, which was optional. I suspect you have a swapped in M21 right now, or else you have engine/tune problems. Have owned/driven many GTO's with M20's with rear ratios from 2.56 to 3.90, and the only one I had to feather the clutch on was the car with the 2.56 swapped in. The original M-20 in my '65 (the one with the small countershaft) has a lower 2.56:1 first gear than the later '66-up 2.52 geared boxes.
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Jeff |
#33
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Mick,look at the placement of carbs on a factory 421 SD intake,then look at the placement on the E intake.The factory spend maybe millions on dyno work as did chevy on their dual quad intakes.Chevy found theirs were better with the carbs close together like the E.The Offy is like the factory pontiac 2-4s.Also the E AFBs although they race well at WOT just dont seam to drive as well as other AFBs without a lot of tuning work.As said I have been doing the 2-4 stuff on pontiac for over 55 years and have tried virtually all AFBs.The factory SD pontiacs are by far the best.Buick 60s and the 348 chevys are very good for 625ish replacements.For 750s the factory SDs are the best,the single 4 409s are good and my choice is 3705 mopars with jet changes as they come jetting for a Xram intake and have staggered jetting.Have not tired the new E AFBs I think they are the AVS?Tom
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#34
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#35
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Muncie M20 Users: Love or Hate
Update: I just switched my setup to a single carb and intake. Cliff’s Q-Jet and a Performer RPM. This really worked well. It really woke up with lots of low end power and responsiveness. No track yet and only a few miles into it, but thinking the tranny wasn’t the core issue as many of you suggested. Thanks for all the help!
Sent from my iPhone using Tapatalk
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1970 Tempest (428 Whitmore, Cliff Q-jet, Doug Nash Five Speed) slowly coming back to life 1965 Lemans (462 Butler, Cliff Q-Jet, Muncie M20 with 3.55s) |
#36
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The transfer from idle to main jet is a very important area for drivability and ET. and light throttle pinging
And the hardest area of most carbs to modify
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If your not at the table you're on the menu A man who falls for everything stands for nothing. |
#37
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It was the idea you had of going with an M-21 that would have made what you were complaining about worse for you. |
#38
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Yes still have the M20 and 3.55s. It was the duel carbs not tuned correctly. Sent from my iPhone using Tapatalk
__________________
1970 Tempest (428 Whitmore, Cliff Q-jet, Doug Nash Five Speed) slowly coming back to life 1965 Lemans (462 Butler, Cliff Q-Jet, Muncie M20 with 3.55s) |
#39
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M21 would work fine also.
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#40
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Just saying.
__________________
1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
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