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Username Post: which rear end gear        (Topic#361973)
Posts: 68

Reg: 09-16-17
07-31-20 12:29 PM - Post#2800005    

I just got my car all back together and it runs great. I am having 1 issue though. My car likes to bog down when i role out of first gear.

I have a 505hp 427 big block, backed by a TKO600 and 3:73 gears. I am running a comp cams mother thumpr cam #11-601-8

Should I be running a 4:10 of 4:30 gear? or should i take a little longer and just get used to the car?


"11th Year" Gold Supporting Member
Posts: 477
Loc: Oakland Co., Michigan
Reg: 10-12-08
07-31-20 01:39 PM - Post#2800015    
    In response to jeff198901

With that trans & that rear gear the problem in the engine not the gearing.

Carb or timing.

Edited by sz0k30 on 07-31-20 01:40 PM. Reason for edit: No reason given.

Frequent Contributor
Posts: 2107

Loc: Lake George, NY
Reg: 11-11-15
07-31-20 02:31 PM - Post#2800019    
    In response to sz0k30


Posts: 68

Reg: 09-16-17
07-31-20 02:39 PM - Post#2800021    
    In response to sz0k30

The car just came back from a very respectable race shop In Ottawa Ontario. I’m currently breaking in a new McLeod twin disc as well. This set up feels a lot different than the old motor and worn out clutch

The car goes like crazy that’s for sure! Maybe it’s all in the driver!

Posts: 43

Reg: 09-03-18
07-31-20 03:34 PM - Post#2800024    
    In response to jeff198901

Hi from Ottawa, as well! Which shop did it?

Mcleod twin? Rev it more, it won't bog, and it won't slip.


65 Impala convertible 327/250 Maderia Maroon/black California black plate car

Posts: 68

Reg: 09-16-17
07-31-20 04:00 PM - Post#2800026    
    In response to jayoldschool

D&D performance! In chesterville to be more specific, just outside Ottawa. I am from Kingston

"10th Year" Gold Supporting Member
Posts: 643
Loc: Albuquerque, NM
Reg: 02-09-06
08-01-20 06:18 PM - Post#2800108    
    In response to jeff198901

JEFF! You need a bigger motor! Drive it like you stole it. Bill

Bill Wilhelm
1965 Impala SS
1966 Corvette, ordered for my 23rd. birthday

"3rd Year" Silver Supporting Member
Posts: 407
Loc: Langley BC
Reg: 02-09-13
08-02-20 01:21 AM - Post#2800112    
    In response to jeff198901

Hey Jeff.

I built a bunch of small blocks and big blocks in the early to mid 90’s when those Thumper Cams came out. You didn’t mention what heads you have, compression ratio, or carb or intake .
Did you dyno the engine?

The big deal on those Cams was that they were “choppy” at idle. That was mostly because they had 107° lobe separation angle and a bunch of overlap but they fell flat after 4800 RPM. Great for the street scene when you pulled up and everybody’s listening to the rapity-rap of your engine at idle but when it came to power they seem to fall off after 4500 rpm depending on, of course ,on which Version of the Thumper you had.

There are so many variables but the combo you have mentioned with a 2.87 first gear in that TKO 600 and a 373 rear gear should be in the effective driveline ratio of 12.5 depending on your rear tire diameter.

After a couple of dyno tests I stopped using those cams in my engines and went to the Edelbrock performer RPM or Comp Cams Magnum series. IMO hydraulic roller is the only way to go for a street engine. Flat tappet is 1940’s tech. There is a reason the OEM WENT TO ROLLERS......!!

Your combo should scream out of first gear! I suspect carb tuning is the problem, and possibly ignition timing. I still don’t like those Thumper cams and would never use them again..

I grew up in Ottawa! I remember as a kid in the late 70’s the street scene on Carling Ave near MR. Donut! (Woodroffe and Carling and is now a Tim Horton’s)
They used to bring out the water trucks late to hose down the roads to discourage street racing.....

There was a shop on Richmond Road near Lincoln Heights shopping center that used to work on all the hot car at that time..... I lived closed by but was always fascinated by the cars I saw back then. Early influence on my life that led to me being a gear head!Lol!

Moved to the West Coast in early 80’s but I clearly remember the Street scene in Ottawa back then!

Golden Palace Egg Rolls! I always get a few dozen to bring back if I’m ever back there! You know what I mean!!
Let us know what you figure out!

Still a 17 year old delinquent Hot Rodder

Posts: 68

Reg: 09-16-17
08-02-20 05:37 AM - Post#2800117    
    In response to 66SS632

I will have to pull up a build sheet for the motor when I get home. It made power right until 5600rpm And is a hydraulic roller motor. The car does go like crazy that’s of sure. I think a lot of it is just me getting used to it. The motor was dyno tuned at D&D performance and fine tuned with some road tests

This motor runs so differently than the poorly built motor that cam in the car, it seems to like it’s rpms a lot more and keeping it mind the motor and clutch only have about 50 miles on them

Edited by jeff198901 on 08-02-20 06:16 AM. Reason for edit: No reason given.

"16th Year" Platinum Supporting Member & Senior Moderator
Posts: 14693
Age: 74
Loc: St. Louis, MO
Reg: 12-11-03
08-04-20 02:38 AM - Post#2800261    
    In response to jeff198901

If you have a GM distributor, make sure the advance plate (inside) and the vacuum dashpot is hooked up and working.

Check the timing.

Tom 65-70 Full Size Team Moderator

View My Photos Here

65 Impala SS Tahitian Turquoise

"6th Year" Silver Supporting Member
Posts: 1436
Loc: No. Virginia
Reg: 01-18-13
08-04-20 06:22 AM - Post#2800270    
    In response to jeff198901

The 'weight' of the flywheel and the new clutch may be factors. They possibly need some 'break in/getting used to' time.

The 3.73 should be just fine. IF you are trying to shave time off you ETs, a lower gear may help.


Edited by japete92 on 08-04-20 06:26 AM. Reason for edit: No reason given.

Posts: 68

Reg: 09-16-17
08-04-20 11:58 AM - Post#2800294    
    In response to japete92

I got quite a bit of seat time this weekend. Everythibg is a-o-k!

Clutch is taking some getting used to but I’m getting a lot more familiar with it!


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