Flywheel weight determination UPDATE

[1983calais]

Last winter I converted the Monte Carlo to a manual trans with the Camaro T5. John B pedal, Camaro hydraulics, Zoom clutch, and a light weight (16 lbs) flywheel. I also put the Holley Sniper EFI on my 327 sbc I built for the car. I know little about the EFI but from the research I did on the internet, it is a real easy application and simple tuning. My car takes off in first gear like crap. I have to feather the clutch and give it more throttle so it won't stall or jerk you to death. I have been driving stick shift vehicles my whole life (only way to go in my opinion) and have never drove anything like this. I thought it was the EFI having issues. I am rebuilding the T5 now and doing more research and found out the lightweight flywheel is more than likely my issue. This is a street car and not a drag car. Drivability is a must. I am going to get a new flywheel and there are different weights. Does anyone know how to determine the weight, 26 lbs, 30 lbs, or ? I will need? Thanks for the input. Thinking about the 26 lb McLeod flywheel.

 

[bracketchev1221]

The short stroke isn't helping you. What gear is in the rear? Assuming 3.73, that and a 2.95 at least first gear, you shouldn't be having a stumble problem to get it moving. A heavier flywheel, will help overall driving with a short stroke though. I used a 30 lbs Hays wheel with my 2.56 first gear Saginaw and 3.42 gears and the car drove fine.

 

[1983calais]

The short stroke isn't helping you. What gear is in the rear? Assuming 3.73, that and a 2.95 at least first gear, you shouldn't be having a stumble problem to get it moving. A heavier flywheel, will help overall driving with a short stroke though. I used a 30 lbs Hays wheel with my 2.56 first gear Saginaw and 3.42 gears and the car drove fine.

The T5 has a 2.95 1st gear and the 3.73 posi rear. I didn't think I should have a problem either but from what I've read on the internet this may be my issue. Your 30 lb flywheel is twice the weight as mine and I think I might be better with something like that. I don't have enough mass there to get the car moving from a dead stop with the lightweight flywheel.

 

[pontiacgp]

You're correct that the flywheel is causing the problem.

 

[1983calais]

You're correct that the flywheel is causing the problem.

Thanks for the reply. Any idea what weight (lbs) I should use? just as long as it is an internally balanced one of course.

 

[pontiacgp]

I use a 52 tooth 26.5 lbs flywheel in between a 355 and a T5 WC that works great. It revs up and down faster than a 30 lb flywheel I tried when looking for a vibration. To drive with a light flywheel the clutch is almost like an on/off swith and you need to be on the gas.

 

[1983calais]

I use a 52 tooth 26.5 lbs flywheel in between a 355 and a T5 WC that works great. It revs up and down faster than a 30 lb flywheel I tried when looking for a vibration.

The 26 lb flywheel, like yours, is the one I was leaning towards. My setup is close to yours so I should have about the same results. I didn't want one to heavy but one heavy enough to get rid of the stalls and jerks. Thanks Mr. Prime Minister!

 

[pontiacgp]

We had a tiny flywheel in our circle track car and it was a b!itch to get that car moving from a stop. You can't feather the light flywheels and they are not made for stop and go traffic. They are great for changing gears at 6 or 7000 rpm or on a circle track when you don't change gears. It's surprising how fast the rev drop without a heavy flywheel's momentum keeping the engine spinning. We depended on the flywheel set up to save our brakes from over heating.

 

[1983calais]

We had a tiny flywheel in our circle track car and it was a b!itch to get that car moving from a stop. You can't feather the light flywheels and they are not made for stop and go traffic. They are great for changing gears at 6 or 7000 rpm or on a circle track when you don't change gears. It's surprising how fast the rev drop without a heavy flywheel's momentum keeping the engine spinning. We depended on the flywheel set up to save our brakes from over heating.

That's what I found out. A b!tch indeed! Drivability just sucks. I was to the point last summer I didn't even want to drive it because of this issue. When I get the new flywheel in and back on the road, I will report back. By the way, the headers you turned me on to did work in my car but I modified them just a little to get more clearance for the slave cylinder. I cut the collector, bent it down so it was level and welded back together. I had to weld my o2 sensor bung in there anyway so a little more welding wouldn't hurt. Worked out great. Thanks again for the help.

 

[Mike T]

I don't mean to swim upstream against popular opinion but i don't believe that a 4 lb difference in flywheel weight will make a drastic difference in first gear take off. Between gear shifts and when you get off the throttle, maybe but not from takeoff. The 327 was all about hp not torque. In order to achieve the best possible hp curve, the engine has to have high air/fuel velocity. Unless I'm missing something, the Holley Sniper 4bbl EFI is rated at 800 cfm, way, way to high for a 327 unless you built it out of some monster expensive internals. (cam, valves, etc.)

The air/fuel ratio that promotes good cylinder burn, flame propagation and power is around 14.7 parts air to 1 part fuel, or very close. In order to stay in that neighborhood, the 327 at 7,000 rpm has a theoretical air capacity of 621 cfm. That's at 100% volumetric efficiency. For a "street" modified engine the maximum cfm rating drops to 540 cfm (+/-) (*click on image below) (stoichiometric air–fuel mixture is about 14.7:1)

If you have the 4 bbl Sniper, I don't think the 327 can keep the air/fuel velocity high enough when pulling it through the big 800 cfm bores. Remember, the EFI doesn't use vacuum to meter in fuel, so you are probably running real rich, especially at low rpm. I would be willing to bet that if you ran the engine at idle for about five minutes and then pulled the EFI, you would find gas puddled in the bottom of the manifold plenum. The rich mix and low air fuel velocity would make for very, very weak performance, especially to get a 4,000 lb +/- car moving from a dead stop.

Borrow a 650 cfm - bbl from someone with 60-64 jets and i think the 327 would wake up. Just a thought.