Thread: Torque Converter recommendation - '78 Chevy / Jaguar XJS

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Recommendation on torque converter stall speed?

Application is a 1978 Jaguar XJ-S w/ a 1st Gen Small Block Chevy.
Currently has crate/smog motor that was swapped in place of the V12 in 1988.

I'm pulling the current engine to install another 1st Gen 350 that I had built up years ago and month-balled - new engine specs:
- 350 bored .060 / decked & line honed.
- Double Hump Heads (Ported - 2.02/1.60)
- 9.8 Compression - flat tappet cam
- Dur 288 Int / 292 Exh (224 @ 050) - Lift .450 Int/.460 Exh - Lobe Ctr @ 114
- 377 hp @ 5500 / 395 Tq @ 4500
- TH350 Transmission w/ 3.31 rear-end

Intent is street driver / cruiser - looking for reasonable pep / reaction times but street-able.

Stall speed recommendations?

I would think that a 2200 to 2400 stall speed would be about right for the specs you listed. The 3.31 rear gear and 4500 peak torque points to a lower stall speed. Let's see what others think!

Welcome to CHR, Steve:

I’ve always liked Jags and the Chevy V8 swap seems like a natural. You now can tune up for less than $100 bucks versus the $500 plus from your local Rover/Jaguar dealer.

Your cam specs are spot of for a Howard’s 117091-14 or the GM #3896962 which was used in the 350HP 350 quite successfully. I’m in agreement with Roger but would shade toward the 2,400RPM, reason being that while the wide lobe separation (114 degree) has some real advantages (nice idle, good vacuum) it also pushes the overall torque curve higher. You’re working with a 4,000 pound car and it does take a bit to get her moving from a dead stop and at 2,400 you’re coming onto the torque curve that will pull strong for another 3,000RPM. Both Hughes (Part #HUP-GM20) and B&M (Part #20412) have 2,400 stall speed offerings – either would be a good fit for this application.

That said, with the 3.31 gears and assuming a stock tire size – 70 series 15 - once you get rolling and nail the pedal you’ll be very pleased between 2,000 and 6,000RPM. Won’t be a barn burner from dead stop but will certainly be respectable. If you stomp hard and force a 3rd to 1st downshift at 35 you will hear a real squeal of tires and you will get a glimpse of God when she shifts from second to third at about 90MPH - from 45 - 120 MPH your Jag will flat fly.

Fun project – hope you stick around and let us know how you progress. Pictures are always appreciated.

Regards,
Glenn

Thanks for the input.
For some added info/input I called tech support w/ B&M, Hughes and FTI - following is what each recommended.
B&M 3000 (20413)
Hughes / 2500 (GM25)
FTI / 2800 (ESR3082) or 3200 (ESR0082)

Yes, very pleased with the purchase of this car so far. Pulling the lo-performance smog motor this week and looking forward to turning wrenches with my teenage son and daughter - I'll post some pics to share.

NOTE regarding tires; FWIW I have changed from the stock 215/70/15 (26.85" dia) to 245/70/17 (26.65 dia) so tire ratio is pretty much a wash.

Right now I'm leaning towards the Hughes GM25 for a 2500 stall.
Still open to any other bench-racing thoughts?

Best