The Stovebolt Site Forums The Shop Area The HiPo Shop 250 engine /th350/3.08 rearend

I have some questions. Is this a good combination? Anyone running this in their truck? What is a good/ ideal highway rpm for a 250? I can plug in the numbers with 26.3" tires for my rpm but don't know what ideal window is to high for the 250.
Thanks Dan


55/2165, 60/2362,65/2559, 70/2755.

The 250 has a 7 main bearing crankshaft and stronger connecting rods and bigger wrist pins than a 216 or a 235. It's also got lighter weight pistons than the earlier engines. 3K RPM or more won't hurt it at all. I'd think a 3.08 with normal-size tires will be a good highway cruiser, but it will be a bit too high for load hauling or towing. A 3.30 to 3.50 ratio would be better if you plan to do more truck stuff than cruising to a tailgate party somewhere.
Jerry

For comparison, a 1978 Camaro with 250 (L-22) and automatic transmission came stock with 2.73:1 rear axle. Tires were (I think) F78-14 which would be 26.5" dia.

So, you should be good for cruising as Jerry said.

https://nastyz28.com/camaro/camaro78.php

I think it is a good combination if not load hauling or trailer pulling. I went all over the place with my 37 Buick with a straight eight. Factory gears were 4.44; WAY to deep. Next was Turbo 350 trans with 2.73 gear; fine on Texas flatland but not good in Ozarks. On to a 2004R with a 4.11 rear gear; turned out I should have followed warnings on the 200. Finally a 3.08 rear with a Turbo 350 and all is smiles. Pulls hills in top gear and 65mph is around 2400rpm with 28" tall tires.

Thanks for all the help and information, much appreciated everyone. I think this will be a good fit for my 51. I already have the engine and rearend ,now to look for a th350 short shaft to get rebuilt. What stall converter would you recommend?

Whatever converter came standard behind a 250 with a 350 turbo should work well. Don't get conned into installing some trick high stall speed converter at three times the price of a standard one. All that would do is create a false neutral at idle and make the tires chirp every time you try to take off from a stoplight.
Jerry

Back in the day, the stock Vega converter added some useful stall at a low price.
Aftermarket TH350 converters have their advertised stall speed based on the torque of a 350" V8 engine, and will have much less behind your 250.

I run a stock 250 engine, stock T350 automatic with stock inline six converter, 3.08 rear axle from a Firebird with 235/75R15 radials ( 28" tall ). The truck weighs 3580 with two people and full of fuel. Mine is a '37 so not very aerodynamic, but it will run 70 mph all day long and still get 20 mpg. I can keep up with traffic in town or on the road. It will chirp the tires form a standing stop and has plenty of pull. I have pulled a small trailer filled with heavy antique single cylinder engines without any problem. I used to have a 3.42 gear ratio, the 3.08 is much better.