Genesis or Survival Motorsports crate

[olddog]

Grubby

I have a TKO-600 with the .64 5th. I have 26.3 OD tires. I have everything mapped out in a spread sheet. So all I had to do is change the rear ratio, to see what you will have. If your tire diameter is different, the speeds will change by the ratio of OD change.

3rd gear 3000 rpm = 55 mph
4th gear 2340 rpm = 55 mph
4th gear 2975 rpm = 70 mph
5th gear 1500 rpm = 55 mph
5th gear 1900 rpm = 70 mph

With a .82 5th gear
5th gear 1920 rpm = 55 mph
5th gear 2425 rpm = 70 mph

I don't like the .64 5th gear, as I feel the step down is too big. It you shift at 3000 rpm the engine speed in the next gear is listed below.

-------shift RPM - RPM after shift
1st ----- 3000
2nd ---- 3000 --- 1976
3rd ---- 3000 --- 2031
4th ---- 3000 --- 2344
5th -------------- 1920
The .82 the would give.
5th ------------- 2460

[Grubby]

This is a good discussion.

I will spend a considerable amount of time driving at highway speeds and keeping rpms down is a big plus. The .64 5th seems almost mandatory. If I was doing more slow speed driving or hard core road racing then I would go with the .85. Lower rpms = much less noise and much happier wife, and the mileage will improve some.

For rear end ratio - I would have thought 3.54 would be almost too much for the massive torque a stroker will put out. What are most of the guys with big FEs running? My guess is the 3.54 would still be OK for highway driving, if I have the .64 5th gear.

Patrick,
Have you driven or rode in a Cobra similar to yours with less gear ratio than you have?

#178 has a 400hp small block with 3.54 rear end. It is not quite enough torque multiplication for the car. 3.73 or so would probably be better.

John

[RodKnock]

Barry just had a customer back out of his 482 build and has some brand new parts available including a Genesis block for $3,600. The Stage 3 KCR heads are sold.

http://www.network54.com/Forum/75943...diate+shipment

[patrickt]

Originally Posted by Grubby

Patrick,
Have you driven or rode in a Cobra similar to yours with less gear ratio than you have?

Yes, I have, but I'm not sure how I would compare the two. Remember that in RodKnock's neck of the woods he can not cruise much at speeds above the high 60s. Here in my state we're now moving our posted limits up to 70. Which means casual, light highway cruising is now 80+. Here, this post Transmission Choice has the 24k gold analysis on .64 versus .82 -- and I can't remember anybody posting that they wanted to move numerically down from a 3.54 to a 3.31 or thereabouts. You might want to post a thread soliciting replies to that very issue. But I will tell you that it is an absolute joy to cruise along in the 70s or 80s with your big FE making less noise than the wind.

[RodKnock]

Originally Posted by patrickt

Yes, I have, but I'm not sure how I would compare the two. Remember that in RodKnock's neck of the woods he can not cruise much at speeds above the high 60s.

Uh, when were you here last? Our Cobra breakfast was off 101, so driving speeds tend to be less because of additional traffic, but we're still talking light in the AM on a Saturday. Nonetheless, driving was "spirited." Legal is what you're allowed.

[undy]

I'm running a 3.25 with my KC Pond 482. It's cam is similar to Rodknock's and the car has a .64 OD equipped TKO600. I'm actually very pleased w/the rear and overdrive ratios. Once the engines up to temp I can cruise at 60+ in 5th. Acceleration requires a down-shift below 65 though. If I roadraced it I'd probably have opted for the 82.