stock 88 mustang cam

cobra1540

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Sep 9, 2009

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#1

• Sep 9, 2009

• #1

My father and I are trying to get his 88 coupe into the 12's without any
major engine work. We have improved everything else on the car. Only
thing we've changed on the engine is a 65mm T.B..
Last year at the dragstrip his best time was 13.26 @ 103.4 mph w/ a
1.92 60'. This spring we put 4.10 gears in it ,from 3.55's. We were at
the dragstrip for the first time this year with the new gears. Our
results were good, but not expected. His 60' dropped to 1.83's - 1.85's
(that's great), but we are now going through the traps at 5800 rpm,
instead of 4700 rpm. Too much for the stock cam. quater mile times have
slowed to 13.34's - 13.4's @101.5 mph.
I'm looking for facts not guess's. I've heard that advancing the cam
improves low rpm torque and retarding it raises the rpm band. My
question is, is this true? I see a lot of seat of the pants answers on
different places, but that doesn't mean much.
I can give a list of modifications to the car, if it would help. There
are so many I hate to try to list them all. These times are all with
the car fully intact,not gutted.
Thanks in advance to any helpful
replies.

 

rbonella

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Dec 15, 2008

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Sep 10, 2009

#2

• Sep 10, 2009

• #2

true

 

Dino Dino Bambino

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Sep 10, 2009

#3

• Sep 10, 2009

• #3

Your problem is that with the 4.10 gears (are you sure your old gears weren't 3.27?), you're achieving 5800rpm at the trap when your engine cannot breathe well beyond 5000rpm. The result is your engine's gasping for air from about 90mph to the trap speed, and that's slowing you down.
Retarding the cam will sacrifice a little torque at lower rpm and add a little higher up, but that won't come anywhere near to solving your problem. I only recommend 4.10 gears for 302/306 H/C/I combos that can breathe at higher rpm and produce maximum HP close to 6000rpm. You're not even close to that so you'll either need to change your H/C/I combo or change the gears again. The aim will be to hit the 1/4 mile trap with the engine at peak HP rpm.

 

J

Joey7508

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Oct 23, 2005

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Kerrville TX

Sep 10, 2009

#4

• Sep 10, 2009

• #4

why not shed some weight? DOn't gut it but move some around. Battery in the trunk that type of thing,take out "extra stuff" for the track. There is always a turbo, they work well with stock cams.

 

cobra1540

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Sep 9, 2009

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#5

• Sep 10, 2009

• #5

The original gears were 2.73's, we changed them to 3.55's and again to 4.10's. I understand that peak hp on a stock 5.0 is around 4600 rpm. I used a drag calc online a while back to find rpm's at the traps with MT Et street drag radials (255/60/15 I believe is the size) at 27.1" tall it showed rpm at ~5400. He is shifting at 5250 -5500 anyway, so I thought the 4.10's would be best. Somewhere I must have screwed the numbers up. I have 3.73's I could install ( possibly the best compromise ). We were looking for another 3-400 rpm's without getting into the engine. He only has 53,000 miles on it and it runs great for a full weight coupe.

 

cobra1540

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Sep 10, 2009

#6

• Sep 10, 2009

• #6

Thanks for your thoughts/ replies guy's.
If we can get to 13. teens we will start to pull seats, go with a tubular k-member or lighter wheels. Right now we are trying to recover what we lost.
He'll never go F.I.

 

Dino Dino Bambino

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#7

• Sep 10, 2009

• #7

cobra1540 said:

I have 3.73's I could install ( possibly the best compromise ).

Click to expand...

Might be a good idea. It'll get the engine back in the rpm range where it's producing the most torque.

 

cobra1540

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#8

• Sep 10, 2009

• #8

Thanks for the replies. I appreciate you thoughts on my problem.

 

CRASH7772

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Apr 27, 2003

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Sep 10, 2009

#9

• Sep 10, 2009

• #9

Did you ever try shifting around 5k with the 3.55's? Or even lower 4800ish?

Also did you try shifting before the line with the 4.10's (don't know what trans your running)?

I know this doesn't apply to your question but just curious...

 

cobra1540

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#10

• Sep 10, 2009

• #10

Yes we've gone from 4800-5500 rpm shift points, 5300-5500 seemed to work the best so far. Last wed. he hit 5th. gear 1 time, just to see, and lost 2mph and 3 tenths in that effort. We'll keep trying to improve our launch technique.

Edit : the rpm's I'm giving you are from the stock tach, so take them with a grain of salt.

 

CRASH7772

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Sep 10, 2009

#11

• Sep 10, 2009

• #11

Thanks for the response and I know what you mean by the stock tach...Mine was off 300 rpms but always shifted @ 5k on the stock tach.

 

ddonaca351

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Dec 1, 2002

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Camas Washington

Sep 12, 2009

#12

• Sep 12, 2009

• #12

Put the 3.73's in it.

Remove the front sway bar and end links, then drive *very carefully* down to the track and leave on your way to a 12.9

If that's not enough, go to a set of drag shocks (90/10 front and 50/50 rear) and some lightweight big-n-littles.

...but without a h/c/i swap you're never gonna get the stock intake track to breathe above 5500.

It's just not made to do that.

Oh and leave it in 4th through the traps (on the limiter if you have to) you'll lose too much time with the shift to high gear.

 

Dino Dino Bambino

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Sep 12, 2009

#13

• Sep 12, 2009

• #13

ddonaca351 said:

Put the 3.73's in it.

Oh and leave it in 4th through the traps (on the limiter if you have to) you'll lose too much time with the shift to high gear.

Click to expand...

If he swaps in the 3.73, he'll still have rpm to spare when he hits the trap and won't need to keep the engine bouncing on the limiter.

 

cobra1540

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Sep 12, 2009

#14

• Sep 12, 2009

• #14

The sway bar and end links have been gone for a while now. I've been talking to people about this and I think we're going to try some 28 x 9 slicks on lighter rims. Maybe we can kill two birds with one stone. The slicks should grow a little, lowering our rpm at the top and should help out 60' times ( I hope ) . We don't want to go the long tube route yet I've had two different kinds on my 79 and they were a pita to work around. We already have adj. front ( AGX I think ) and QA1"s in the rear. We set the rears to the 3rd setting from soft, any stiffer and the tires hook then unload and spin ( bounce ) and softer doesn't help either.
I'm going to look for some big-n-littles to put the slicks and skinny's on