After switching out rear ends in my car it now goes slower.
Went from 3:31 with 28" tire and 12.39 @110.6 mph to 3:73 same tire and 12.47@109 even. Changed nothing else except put on a K&N air filter lid.
It 60ft a bit better @1.80 over a 1.86, but what happened? Everyone at work kept say put more gear in it so I did and this happened :confused::confused:

where the weather conditions the same on both trips to the track?

I'd say your engine is more of a "torquer" & does not make much high end HP

If the 60' was better, my guess would be worse air(weather).

most likely weather. Even Canada gets hotter in the sumer. ;) Did you change your shift points any? Might want to play around with that some. I like to short shift 1-2 and ride out 2-3 a little longer than most.

But if you can't get quicker, then maybe I need to just drop down to a 3.31 rear gear and go run quicker than you again!! :D

If the 60' was better, my guess would be worse air(weather).

I second that. :thumbsup:

In the same air I would say its a low 12.30 high 12.20

:sad:
Sounds strange but it's possible, Shaun. I found the same thing a few years back...
My '80 Camaro ran slightly slower after I changed from a 3.73 posi gear to a 4.10 spool.
The motor (383) never seemed to be able to stay in 1st or 2nd gear long enough to "pull" like it wanted to with the 3.73.
It had nothing to do with the weather, either.

My best prior was a 12.40 @ 110.00 with a 1.89 and a DA @ -800'. I made some tuning changes and went 12.37 @ 109.41 with a 1.76 and a DA @ +1800'.

MPH down and better ET and 60' ... 75% of it was weather, could have been better with the right air ???

You lost .1 ET so I would say it was the air. Might get .3 better with the right combo ?

331 to 373 is a fair amount of gear change,not knowing what your cam/motor setup is i'd guess you simply ran out of cam/motor.

The 331's were a better match for your current cam/motor setup,it's likely as simple as that.

Any time you go for a significant gear change you have to make sure the componants in your motor are capable of matching the additional rpms needed to just be topping out rpm & power wise just a few feet before or best case when crossing the finish line. Running out of cam/motor before the finish line kills et/speed.

By the way when cruising on the road @ 60-65mph are you happy with the additional motor rpm/noise,heat,and inceased fuel consumption that the 373's give you when compaired to the 331's you had prior?

I feel the 331's are a very good COMPRAMISE (eps fpr BBC) when it comes to street cruising and decent perf including occassional strip runs which a lot of people dont understand and think 373 is the only way to have decent perf which is not always the case. It totally depends on the setup which you proved here in your post and unless you have plenty of motor that will top out at a farily high rpm moving up to 373's was not good as you learned.

2600 rpms @ 60mph is liveable with 331's but 3,000 rpms @ 60mph for any length of time with 373's is not comfortable on the street unless your an 18 yr old youngin that stays close to home and races all the time pounding their car to death with dad bankrolling the fuel bill/repairs.

I guess you can tell i dont care for 373-410 gear on the street,gear like those is useless for any kind or reasonable driving IMHO but i am sure many would disagree with me but thats ok,it's a free country.

Scott

What's the full combo? (When I post a question like this on the board I post my full combo that I keep in a spreadsheet so I can simply cut and paste it right into my post. Makes it easier for people to see what I'm trying to do.)

Rod

Thanks guys for the replies.
I'll give it another shot if I get a chance before I consider going back to the 3:31 ( If I can find a set).
It was getting quicker.

1st 12.8 2nd 12.66 3rd 12.54 4th 12.52 and the last one 12.47

Weather this weekend would have been close to when I ran my best. It was slightly cool , tail wind with sun shining on the track.

As far as extra rpm at crusie I have a hearing problem so it does not bother me :). Gas mileage I'll find out how bad it really is in a month after I make a trip to Detroit then home (260+)then to Grand Island and home (300+) and The topper within a month a trip to Syracuse (600+). All driven.

As far as my combo It was built with the intention of stepping up in gears some where down the line.
454 +.30
781 heads 1.88 & 2.19 valves
compression around 9.8 - 10:1
RPM air gap with 750 holley dp (soon to be a Demon)
cam is a 402a2lun
HEI & MSD ignition.
Tranny is a 350 turbo, shift kit and a 10" 3000 converter.
Full exhaust 3" to the muffler and 2.5" mandrel bent over the axles.

Thanks again

TAIL WIND!?!?! :eek:

:D

slight tail wind

How did the shift RPMS change Shaun, especailly at the stripe? And I hope you kept thsoe 331s; they dont make those anymore you know!

I'm trying to reckon why you lost 1.5 mph.?

Shaun,what tires are you using? a 1.80 60 ft. is pretty decent

The brand new BFG's he bought here last year!!! As in radial TA's!!

Shaun,forget about street tires...I would be some drag radials and start getting some 1.7X 60 ft.

Chris, it's on the list of things to get, but everyone said change one thing at a time so that was what I did :)

Gene Tried to keep rpm's the same, but did hit the limiter on one pass :eek:.
Was hoping to give you a little surprise with the new gears at the track this year but I guess it will not be one now.
We are going to the track on Sunday after the show ....RIGHT!

And no I do not have the 3:31 anymore. I'll know better after a couple of HWY trips if I like them or not. The trip back from Detroit after installing the rearend was not to bad, but I have to sort the speedo out (+6 I think).

I have not set the valves since I put the inner springs in after break in last year. Can not hear any rattleing:). But is it possible for them to get tighter?

We are going to the track on Sunday after the show ....RIGHT!

Hmmmmmm.....;)

Shaun,man you do some seroiuos cruising with 1,200 miles of trips planed not counting your local crusing at home.

With that said why in blazes would you change from a farily street friendly gear like 331 to 373 when you do alot of trips/cruisning miles,doesnt make sence unless your a die hard strip racer but i dont get that impression from your posts.

Anyway i still feel your simply running out of motor and you will get a small imporvement from all these things your doing to better dial in the motor/car but nothing major because your bigest problem is your simply running out of motor on the top side with the 373's as compaired to 331's IMHO.

Good luck and let us know what the fuel & OIL usage is with the old 331 gear vs the new 373 gear after your 1st trip,it will be interesting to see just how much more fuel & OIL the 373's will use vs trhe 331's.

Scott

stay tuned :D