New rear diff
Thread Starter
Instructor
Joined: Oct 2014
Posts: 143
Likes: 24
From: Prince George BC
New rear diff
Ordered new rear diff yesterday for my 75 vette . Car has rebuilt 350 motor with around 370 hp . Has rebuilt turbo 400 with 2400 2600 stall convertor . Stock rear end was 3.08 now going with 3.55 gears . Also will change all u joints , side yokes , mounting bushings and cross member cushions .
Hoping to make car quicker in 1/4 mile times . Have had car to track first time this year and ran best 14.17 at 97 mph and 2.15 60 ft time . Thinking I can get car in mid 13 seconds . Does this sound like a time I should be able to reach after some more trips and practice at track ?
Also wondering about how much my speedo will be out with new gears ? Will I need to change speedo gear and does anybody know what color gear would be right for 3.55 gears ? Have been looking in Ecklers catalogue and does not give me answer to this .
Thanks to all for any advice and help with questions
Hoping to make car quicker in 1/4 mile times . Have had car to track first time this year and ran best 14.17 at 97 mph and 2.15 60 ft time . Thinking I can get car in mid 13 seconds . Does this sound like a time I should be able to reach after some more trips and practice at track ?
Also wondering about how much my speedo will be out with new gears ? Will I need to change speedo gear and does anybody know what color gear would be right for 3.55 gears ? Have been looking in Ecklers catalogue and does not give me answer to this .
Thanks to all for any advice and help with questions
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
Ordered new rear diff yesterday for my 75 vette . Car has rebuilt 350 motor with around 370 hp . Has rebuilt turbo 400 with 2400 2600 stall convertor . Stock rear end was 3.08 now going with 3.55 gears . Also will change all u joints , side yokes , mounting bushings and cross member cushions .
Hoping to make car quicker in 1/4 mile times . Have had car to track first time this year and ran best 14.17 at 97 mph and 2.15 60 ft time . Thinking I can get car in mid 13 seconds . Does this sound like a time I should be able to reach after some more trips and practice at track ?
Also wondering about how much my speedo will be out with new gears ? Will I need to change speedo gear and does anybody know what color gear would be right for 3.55 gears ? Have been looking in Ecklers catalogue and does not give me answer to this .
Thanks to all for any advice and help with questions
Hoping to make car quicker in 1/4 mile times . Have had car to track first time this year and ran best 14.17 at 97 mph and 2.15 60 ft time . Thinking I can get car in mid 13 seconds . Does this sound like a time I should be able to reach after some more trips and practice at track ?
Also wondering about how much my speedo will be out with new gears ? Will I need to change speedo gear and does anybody know what color gear would be right for 3.55 gears ? Have been looking in Ecklers catalogue and does not give me answer to this .
Thanks to all for any advice and help with questions
Thread Starter
Instructor
Joined: Oct 2014
Posts: 143
Likes: 24
From: Prince George BC
My 78 with a stock ZZ383 ? HP using RPM air gap 7516 with TH350 stock 1800 converter with 3.08 at 2200 ft elevation auto shifting @ 5000 RPM, best run @ 13.84 at 101 MPH. Will you loose .5 sec ,would depend at where your engine makes HP. and if your transmission shifts just before max HP. At what RPM does it shift now ?
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
On the three runs I made I was shifting around 5000 rpm . Motor is supposed to make max hp at 5300 . My very first time running down 1/4 mile so was a little nervous about revving at over the 5000 rpm range . The shop that built my motor said should be no problem running up to 5500 range . Also was around 4500 at trap and figure that with 15% change with 3.55 gears that should get me closer to max hp at trap .
http://www.zeitronix.com/
Carb stock settings were very rich for 2200 ft. I went down from 70-75 jets to 67-70 jets (Primary - secondary) and then tuning timing curve. You may have more than .5 to gain yet.
Thread Starter
Instructor
Joined: Oct 2014
Posts: 143
Likes: 24
From: Prince George BC
Have you had the carb AFR tuned. I started at 14.3 runs and got down to 13.84 by AFR tunning the carb with O2 Wideband monitor.
http://www.zeitronix.com/
Carb stock settings were very rich for 2200 ft. I went down from 70-75 jets to 67-70 jets (Primary - secondary) and then tuning timing curve. You may have more than .5 to gain yet.
http://www.zeitronix.com/
Carb stock settings were very rich for 2200 ft. I went down from 70-75 jets to 67-70 jets (Primary - secondary) and then tuning timing curve. You may have more than .5 to gain yet.
I have not had the carb ARF tuned . I have trusted my motor builder to do my carb tuning so far . Once I get new rear diff installed will look at more fine tuning of carb as well . Thanks for the info
