Build Validation

[DrGuy]

Hey Guys, looking for comments pro or con on my build. I'll start with what I'm looking to get out of my build first. Must be reliable, must run on pump gas, and ass puckering fast.
Now the build. Powdercoated PPMC Chassis, Jag IRS 3.31:1 rear gears, 64 427center oiler, JE Pistons 10.5-1 CR, Comp Cam FB 284B-8 Intake Lift 284-.564 / Exhaust Lift 294-.590, Edelbrock RPM heads, Erson Roller Rockers, Edelbrock manifold, Holley 750 DBL Pumper. I'm thinking Tremec 5 speed TKO 600? I'm hoping to generate approx 480HP FW?
Any thoughts on the tranny selection, clutch, or HP generation would be appreciated. Photos of the build can be seen in the build section of the gallerys under Mikes PPMC

Buildhttp://www.clubcobra.com/photopost/showgallery.php/cat/2

Thanks

[Roscoe]

Cup holder?

[blykins]

That cam is not a good match for 3.31 gears. It will be a little on the radical side, with a peak at around 6400-6500. If you go with a TKO 600, I'd step up to a 3.70-3.89 gear.

The TKO 600 is only about $90 more than the TKO 500, so it's really a no-brainer.

For the clutch, I would use a RAM Powergrip clutch kit, 11" Long, rated for 550hp.

I think your 480hp estimate is a little conservative, but it will depend on which intake you use and how detailed the engine build is.

If you have questions on the engine build or drivetrain selection, I'll be happy to help you out.

[NRP/MN]

Brent, no disrespect intended, but I disagree on your final drive gear ratio. My car with a TKO II ( 3:27 1st gear) and a 3:73 rear makes first gear almost useless. His application should be be fine with a taller rear end gear. Mike

[blykins]

None taken.

As you know Mike, the newer TKO 600's don't share the same gear ratios as the older 3550's. The 1st gear ratio in the 600 is 2.87:1 instead of the granny-gear 3.27.

I try to match all of the drivetrain components with each other. A cam that is still inefficient at 2000 rpm doesn't need a higher gear ratio that puts the rpms right in that range while cruising.

A larger duration solid cam like he has chosen, especially with a tight LSA and lots of overlap, will not be as friendly as some of the more streetable camshafts out there.

With the TKO 600, you have either a choice of a .64 or a .82 overdrive.

With a 3.31 rearend and a .64 overdrive, you would be taching 1500 rpm @ 55.
With a 3.31 rearend and a .64 overdrive, you would be taching 1900 rpm @ 70.

With a 3.31 rearend and a .82 overdrive, you'd be at 1900 @ 55.
With a 3.31 rearend, .82 OD, you'd be at 2400 @ 70.

I personally wouldn't match that particular engine setup with anything that would allow it to cruise under 2000 rpm at the normal driving speed.

With a revvier engine and less than desireable low-rpm street manners, I would rather have the lower rear gears.

[bret a ewing]

This is what I used in determining my ratios.

http://www.secondstrike.com/technical/GearingHelp.pdf

[blykins]

Any chart/software program that takes into account the rear tire size (I used a 295/50-15), gear ratios, and rearend ratio should give a pretty nice estimate.

[DrGuy]

Mike, Bret, Brent, thanks for the info. Brent, If I dont change my rear gears are you saying I should be looking at the TKO 600 with the .82OD? Should I reconsider using a toploader due to my tall rear? The reason I was going with a 5 speed was so I would'nt have to listen to the engine rpms at highway cruise speeds 70-75. I was planning on using the Edelbrock dual plane intake with an operating range of 1500rpm-6500rpm can't remember the Summit code # does this help with a HP estimate
Bret, thanks for the calculator I used the TKO 600 .82 with the 3.27 rear and the 295/50 15 tire size. I'm not sure I was making sense of the numbers though.

Speed (MPH) in Gears at RPM

Gear 1st 2nd 3rd 4th 5th 6th
Trans Ratio 2.87 1.89 1.28 1.00 0.82
Overall Ratio 9.38 6.18 4.19 3.27 2.68
Split 1.52 1.48 1.28 1.22
Rev/Mile 7,369 4,853 3,287 2,568 2,105
1500 12 19 27 35 43
2000 16 25 37 47 57
2500 20 31 46 58 71
3000 24 37 55 70 85
3500 28 43 64 82 100
4000 33 49 73 93 114
4500 37 56 82 105 128
5000 41 62 91 117 142
5500 45 68 100 129 157
6000 49 74 110 140 171
6500 53 80 119 152 185
7000 57 87 128 164 199

[blykins]

Yes, I would go with the .82 overdrive either way you go....

If you would like to fine tune your engine parts choices, shoot me an email or give me a call. I can walk you through some different scenarios. All of the parts need to work together, from the cam, to the intake, rearend gears, transmission, etc.

With that solid cam that you listed, the engine will have higher hp and tq peaks. That's perfectly fine with a high performance lightweight car like a Cobra. However, you have to choose the rest of your parts to work well with the lack of bottom end power and the tendency for that engine to be a little on the fussy side at off-idle and low rpms.

[YerDugliness]

Originally Posted by DrGuy

Mike, Bret, Brent, thanks for the info. Brent, If I dont change my rear gears are you saying I should be looking at the TKO 600 with the .82OD? Should I reconsider using a toploader due to my tall rear? The reason I was going with a 5 speed was so I would'nt have to listen to the engine rpms at highway cruise speeds 70-75. I was planning on using the Edelbrock dual plane intake with an operating range of 1500rpm-6500rpm can't remember the Summit code # does this help with a HP estimate

I have a 1989 T-5 with the 3.35 first gear and a 3.70 in the differential. First gear is almost useless, unless you plan on using your car to pull floats in a parade. I have what I think is a "box-stock" 1989 5.0 HO engine from a Mustang GT and I can idle away from a dead stop in 2nd, 3rd, and 4th. I seldom use first, most of the time I only use 2nd, 3rd, and 4th in town. My .675 OD (5th gear) is useless for anything other than highway cruising, but b/c my engine isn't tuned for high RPM use (yet) I can comfortably cruise at 70 MPH at less than 2,000 RPM's and get close to 25 MPG (YEAH....gotta love that!!!). With your cam, you'd not want to do that, it would "lug" the engine and kill your gas mileage (not to mention that the rich fuel mixture at those low RPMs might well wash the oil off your cyllinder walls, and you certainly don't want to invite early ring wear).

Bottom line, I'm glad you're listening to Brent! You won't be sorry.

Cheers from Dugly

[D-CEL]

Brent is on the money.

You need to match the cam and the rear gear. Change one or the other. I would say go with the lower gear, the car will be a hell of a lot more fun to drive. Traction is not a problem just get the right tire. Drag radials or Big letter Goodyears will hook the car nicely.

Jason

By the way, I just saw that M/T is now making a 295/55-15 (28x12.5x15) ET street radial. That is a great Cobra size

[blykins]

That's a very good summary.....I'm not a very good "explainer" of things sometimes.

I also would go for the lower gear, especially with a 5-speed between the engine and the rearend.

[DrGuy]

Brent, BTW thanks for the offer regarding the help with the motor. I already had the short block built by a local performance shop. I did tell them that I wanted a lopey cam so I think I'll change the rear gears. The other choices for the jag rear are 3.54 and 4.11. Can the rear gears be replaced with the rear suspension already attached to the frame? Also the rear that I have is a limited slip rear if that makes any difference? I hate to think of taking everything apart i.e. inboard brakes, stub axles to get to the diff. I've replaced the stub axle bearings and installed a new pinion seal so far.

[blykins]

Unfortunately, you have to remove everything from the rearend to swap gears.....brakes, half shafts, and even remove the center section from the car.

I think I would give myself two options in this scenario:

1. If the engine is still in short block form, then I would swap to a smaller camshaft. A cam swap would be super easy if the front of the engine isn't buttoned up, heads are not on, etc. Also, you can still have a very nice sounding, lopey camshaft without having a wild, temperamental camshaft. You could cut the duration down some and help with the low/mid range manners while still having a thumpy sounding engine.

2. Run everything as is and just see how you like it. You could always swap parts later down the road.

I would still go with the TKO 600 and the .82 overdrive....and picking a suitable clutch kit is simple.