Hello gang, i'm new to this forum, and actually a Small Block Chevy visitor. I was posting over at Camaros.net and someone suggested I ask this question here, so here goes. i've got a 64 corvette 327 -365 Horse numbers matching combination. the motor is now .030 over with correct 11 to 1 pistons. Stock fuelly heads, 4speed with the wide ratio muncie (2.56) 1st gear and 3.70 posi out back. i'm running the hp ramshorn manifolds with a 2.5 chambered system out the back. I have the dual plane aluminum intake, and my goal is to run a 12.90 with all stock appearing componants. I tried running an ISKY solid roller cam with ported 461s but it actully hurts becasue the manifolds choke that intake system. I originaly had the old LT-1 cam in the car with a 2.20 1st gear muncie and it ran pretty good,but I never had it on the track and I'm sure that it wouldn't turn a 12. I guess my question boils down to... what cam will make the most power through those manifolds, get me into a 12.90 with my combination, and still be drivable? or is this even possible? I'd appreciate any help and guidance. Thanks for your time. Aaron
Wow, we must have quite a good reputation for people to refer your Vette to a Buick BBS. The people here are very good, and many know about different makes. Be patient, someone will probably have some good advice.
Someone rattle Donny's cage and wake him up... The small block guys can chime in here and agree/disagree with this, but I think the M20 wide box is gonna hurt ya...the drop down from 3-4 is hard for a small block to do and keep pulling. There was a thread on this around here just recently, and I believe it was Mark that said he tried an M21-M20 swap on a big block car, and it had trouble with the 3-4 jump...and I think you're gonna need a bit more gear out back. Oh, and that chambered exhaust SUCKS...been there, done that. Get a good mandrel 2.5" system. BTW: we had a '64 327/365 vette for several years...I grew up with that car and hated to see it leave...but long story short, not even the birdcage survived! :ball:
There's an LT1 Vette in the 12.60's so other than being tire restricted I don't see why this guy shouldn't be able to get there. I do agree with putting the M20 in storage while sticking an M21 and 4.56's or so in it. The rams horns supposedly flow pretty well for cast manifolds, so get the exhaust in order with a good 2.5 inch mandrel system with an x pipe and you should be on your way.
as far as my chambered system goes, its not the same system on a camaro. it has one bend in it aside from the head pipe and the chambered sections are through design so there is no restriction.... i'm sure its gonna be loud but shoudl be very minimal back pressure. Its a 2.5id all the way so i am not too worried about it. as far as the M-20 vs M21.... if you are shifting at 5500 then the 3-4 shift is a little rough... but if you grab 4th gear at 6800 or 7000 it puts you right at about 5000 which is fine for a cammed smallblock... i shoudl also mention that i'm not going to be racing this car on a regular basis, its a pure stock looking show car... i just want to put it on the track once or twice, turn a 12.90 and then just drive it from stoplight to stoplight on friday or saturday nights... in fact, i'll probably only grab 4th gear at 7000 when its on the track... at that point the car is well above 100 mph with the 3.70s. thanks Aaron
Aaron, there is a pure stock race coming up in Stanton Michigan September 16th and 17th. If there is any way you could make it there, you could probably get more tips than you would believe. The Richards bros show up with 57 and 62 Corvettes that they flog pretty hard. A couple of 66 Vettes there too. The Stanton p/s race is really a car show and drag race all in one, so that sounds like what you are wanting to do. There are even small block Oldsmobiles that run in the 12s so it shouldnt be too hard to do with a Corvette. Oh yeah, chambered sucks. It costs you about 3 tenths over a mandrel bent / Flowmaster system. A X pipe should be good for another tenth. And get yourself a 4.56, because the biggest gains in et are in the first 60' .
Greg Gessler...... Specializing in Stock Appearing Heads, Intakes and Exhaust Manifolds. We look forward to helping you get to the finish line first!
Keep in mind porting and roller cams are not allowed at the Pure Stock race. At that point you are in F.A.S.T. territory. :Smarty:
true, but i'm trying to appear pure stock, not trying to win races in a pure stock class.... i suppose a thin headgasket and headders woudl solve my current problem, but that would take away from the beauty of a stock appearing engine compartment.
aaron, you need to get your terminology down Pure Stock: exactly the way it left the factory: .070 max over bore and factory stroke, stock uncut heads with proper casting numbers, stock cam, stock bottom end, stock carb, stock exhaust manifolds. Factory Appearing: looks exactly the way it left the factory: unlimited boring and stroking, heads ported but with proper casting numbers, trick roller camshaft, lightweight rods, stock carb, extrude honed exhaust manifolds. If I were building a Factory Appearing small block vette, I'd go with at least 406 cid..........
:laugh: :laugh: :laugh: :laugh: :laugh: How many small block cars (other than the cajun Vette) are certified pure stockers and run in the 12's? Anyone? Beuhler? Crickets? I'm not there........yet..........But the doctor is in! :bglasses: Was going to post another Olds pic here, but don't want to upset Brian when he's at work.
12.90's? I am the "Mark" that swapped M20's and 21's around. Both of my cars I tried this on would not pull the M20. One a RA IV Judge that runs well into the 12's as a pure stocker and the other car a L89 Camaro had even worse luck trying to pull the M20. Both have far more torque and gear than what you have in your Vette. Both motors are also shifted north of 6000 rpm, so your idea of shifting at 7000 is not enough for a small block to pull that trans. My '69 Z with a stock M20 and 3.73 gears is a dissaster when you make the shift at 7000 and try and pull that big drop. Chambered exhuast create tremendous back preassure. Every dipple creates a sizeable loss in flow. If I remember my physics correctly every 90 degree bend in a pipe creates a 15% loss in efficiency. How many bends do the gasses believe they are taking with all those dipples? Beniot are you out there? You can give him more help than anyone. Beniot runs a LT1 certified pure stocker that has done some 12.50's. He runs 4.56's and a M21. With your exhuast, trans and gear I do not believe you will get to 12.90's without major motor work. With the above changed you should be able to get there as a pure stocker. Mark
"Chambered exhuast create tremendous back preassure" I agree with this 100%. I had a 427 chambered exhaust Camaro, that I always felt was corked. I did replace it with just standard exhaust (not mandrel bent & 2 mufflers not a crossflow) and felt there was a big improvement. Although I cannot confirm it with track times. My own 69's RAIV Judge Hardtop & Convert both had used standard 2 1/4" exhaust and the best ever I could get out of both of them was a 13.10's I switched to mandrel bent 2 1/2 " exhaust and they both run high 12's, in otherwise stock condition.
i'm not sure i follow you... what do you mean... "would not pull the m20" also, i'm not worried about the 3-4 shift.... if that is what keeps me from the12 second mark... then i'll live with it to have more fun on the street. regarding the chambered pipes.... the sections enlarge to 3 inches where the dimples are... so i'm surprised that it has that bad of an effect on the exhaust flow.
With the goals you have laid out, I would say what you really need is more cubes. You don't wan't to hurt the streetabilty with deeper gears and a close ratio trans. So poke it and stroke it! :3gears:
Pulling The M20 What I meant is the rpm drop is so large on the M20 that the motors lay flat after you shift into 4th for a long time. You can hear them fighting by the exhuast note change and the fact that the Judge lost 2+ mph with the change. And the air was better on the day with the M20 than it was ever with the M21. Both cars were about 0.1 faster to 60', but were off by .02 by the end of the 1320. I have several cars with M21's and they perform well on the street. My 455 HO has an M21 with 3.73 gears and it is very nice to drive. It has a bunch more torque than a small block but that could be offset by how much lighter your Vette is. I hope this helps. Mark
