1970 Motor Replacement

[Bill S.]

I am planning on replacing a base motor 350 / 300 HP
in a 1970 Vette with a 350 HO base motor (330 HP with iron VOTEC heads) from GM performance Parts. Rumor has it that there will be a performance problem because of the new torque and horsepower figures. Is this true?
Will the M40 turbo hydromatic hold up to the new found ponies?
Thanks
Bill

[Steven B.]

Re: 1970 Motor Replacement

Bill, as for the M40 I don't believe there will be any problem as the M40 has been used in a number of higher HP and torque cars. I have over 400 lb/ft and over 400 HP (dynoed) with a 3.90 rear and the transmission has been the least of my worries. You should experience some more HP and torque, noticeable but not real drastic.

[Joe L.]

Re: 1970 Motor Replacement

I am planning on replacing a base motor 350 / 300 HP
in a 1970 Vette with a 350 HO base motor (330 HP with iron VOTEC heads) from GM performance Parts. Rumor has it that there will be a performance problem because of the new torque and horsepower figures. Is this true?
Will the M40 turbo hydromatic hold up to the new found ponies?
Thanks
Bill

Bill-----


I don't think you'll have any problems, at all, as a result of the horsepower/torque increase. As a matter of fact, the torque rating of your new motor, 380 lb/ft and the most important parameter with respect to transmission/driveline capability, is identical to that of the original one. The new engine you have is very similar in performance characteristics to the L-82 used for 1973 to 1980 Corvettes.

[Jim T.]

Re: 1970 Motor Replacement

Bill I installed a GM crate ZZ motor in my 1970 Corvette several years ago and have not done any damage to my original factory installed turbo 400 with over 160K miles on it.
Make sure you buy a new 14 inch flex plate for your GM 350/330 HO engine. The one piece rear seal crankshaft design will not permit using your 350/300 14 inch flex plate. The turbo 400 torque converter will not bolt up to the smaller flex plate that came with my ZZ crate motor.
Although the 350/300 was a good performer in my 70, I like the extra HP of the ZZ crate engine. The 350/330 crate engine is a great choice to have some driving pleasure.

[Joe L.]

Re: 1970 Motor Replacement

Bill I installed a GM crate ZZ motor in my 1970 Corvette several years ago and have not done any damage to my original factory installed turbo 400 with over 160K miles on it.
Make sure you buy a new 14 inch flex plate for your GM 350/330 HO engine. The one piece rear seal crankshaft design will not permit using your 350/300 14 inch flex plate. The turbo 400 torque converter will not bolt up to the smaller flex plate that came with my ZZ crate motor.
Although the 350/300 was a good performer in my 70, I like the extra HP of the ZZ crate engine. The 350/330 crate engine is a great choice to have some driving pleasure.

Jim-----


The GMPP 350/330 hp engine, GM #12499711 or 12496968, is supplied with a 14" flexplate which will be compatible with a THM-400 transmission. The ZZ4 350 is supplied with a 12-3/4" flexplate. In the event that one purchases a less complete version of the 350/330 which is supplied with no flexplate, the 14" flexplate to use is available under GM #14088761.

[Steven B.]

Re: 1970 Motor Replacement

Bill, to gain a litttle extra performance I added a B&M TH400 Shift Kit to my transmission. It allows for shifting "manually" or just putting it in gear as usual with an auto. It isn't too extreme for the street but shift improvement is noticeable.