TTop Tony

Last spring when I rebuilt my stock engine I put on a Holley with mechanical secondaries. When I took the car to the dragstrip no matter what rpm I dropped the clutch at (I tried 1000, 15000 and 2000) The rear wheels would spin, catch and then the car would bog and finally pick up again. The mechanic who tuned the carb said it was my 3.08 gears causing the problems. I was wondering since this is my first mechanical secondary carb would going back to a vacuum secondary carb cure the bogging. Anybody else have this problem? Is there anyway to tell what gear to go to to cure the bog. Would a 3.36 suffice I was thinking 3.55's but I'm not sure. The track at Bowling Green is almost an hour away so theres some interstate driving involved. Any thoughts are appreciated.

page62

Your gears?!?!? I could be wrong here, but methinks your mechanics has been spending too much time picking "weeds" out of the tobacco field... :crazy:

TTop Tony

huh? I trust my mechanic. Why do you think they recommend higher stall torque converters with more potent cams.

redwingvette

Your mechanic is saying that because of the gears your engine is not in its power band when the tires hook up. The engine can't build RPM's fast enough so it boggs. Vacuum secondaries will compensate some what because they won't open unless there ids enough flow to alow them to. Changing gears will help but as you stated the RPM's will increase at crusing speeds. I run 3.55 gear with a stock convertor and see about 3200RPM's at 70mph. Thats not bad for trips. 3.73 gear would help your 1/4 times but you would see higher RPM's at 70.

Alwyn678

Not sure it would cause a bog......But one thing is for sure....3:73 rear gear and 2400 stall and a Transgo shift kit will eliminate any launch problems....Except for tire smoke and spin. I went from a 3:08 to a 3:73 and noticed quite an improvement.It revs higher but is not that bad...i still run 80+ all day long on the watermelon 500

TTop Tony

Thanks redwing thats basically what I wanted to know. A friend of mine has a vacuum secondary carb I might try it but I think its a good excuse to go to taller gears. 3.55 would probably be a good compromise with my 4 speed.

gkull

The real problem is your car weighs to much! So you don't have the brute power to keep it going after the flywheel inertia wares off. Instead of using a crutch with a gear change attack the problem with higher compression and or a stroker kit.

I also have a very poor opinion of performer intakes. They max out on flow and hp below a 600 cfm carb.


[Modified by gkull, 3:37 PM 12/12/2002]

TTop Tony

Odd you say that gkull. I have a set of performer rpm alum heads and was planning on getting a perf rpm air gap intake to go with it this summer. The heads should boost my compression to 10:1. It sounds like I should do that first and it might improve the bog some.

Langadorf

Changing to different gears may help get rid of the bog, but first I'd check the easy things - accel pump shooter size and cam. When I put a 750 DP on my 383 w/ 3.55 gears (auto w/2500 stall), it would bog off the line also. By changing shooter sizes and pump cams I was able to get rid of the bog completely. I'd try tuning your carb before I started switching gears. I'd also try launching at 2500-3000 RPM - you may just be launching too low. I think by doing these two things you could get rid of the bog although lower gears wouldn't hurt either for other reasons.

TTop Tony

Good point I did install the carb out of the box.

chewy

3.08s and a double pumper are not exactly the hot set up as you found out. When you hit the throttle you have the full airflow of the carb. and with 3.08s the engine doesn't need or want it. Try the vacuum carb they are very forgiving for size and gearing you should like it.

glen242

Did you throw your Q-Jet away?

TTop Tony

No actually I have the original QJet, Its in good condition but a bit out of my league to rebuild and rejet with the new motor.