Pros and cons of switching motors

[Chris L.]

Thinking about taking the stock 350 out of my 70 and replacing with LS2 or LS7. Looking for pros and cons and what else besides the motor and ECM would have to be replaced? WIll it bolt up to an M21? Cost?? Thanks
Chris

[Patrick H.]

Re: Pros and cons of switching motors

What is your goal?

Power?
Fuel mileage?
Both?

My response would be the same as it is to those who want to install a 5 or 6 speed manual in their vintage Corvette - it will take a lot of miles driven to "make up" the cost of the conversion. With the cost of C5s into the mid teens it's probably easier and not much difference in cost to buy a "complete car" in the form of a 97-00 Corvete and just drive it.

If you just want power, it's a lot less expensive to drop in a ZZ4 crate motor.

Patrick

[John M.]

Re: Pros and cons of switching motors

As far as cost and investment. I'd build the original motor to a 400HP 383 stroker looking totally stock from the outside and gear the rear end accordingly.

You'll reduce cost and maintain investment value on the car if your forced to sell.

just an opinion.

[Jack H.]

Re: Pros and cons of switching motors

One caveat to either building your existing engine into a 'stroker' or installing a higher HP crate motor: you'll be dissipating more underhood BTU's. That could push the factory stock radiator beyond its cooling capacity (especially if there's an aging factor).

But, there ARE alternatives should you face that situation...

[John M.]

Re: Pros and cons of switching motors

Alternatives that alter from the appearance of Stock?

I did the rebuild option and am pushing 400HP and 460 Ft. Lbs out of a stroker kit.

I haven't run her in the car yet but temperature is a concern. I saw a radiator shop tag on my radiator so believe it may have been re-cored.

We'll see how it holds up.

[John H.]

Re: Pros and cons of switching motors

Thinking about taking the stock 350 out of my 70 and replacing with LS2 or LS7. Looking for pros and cons and what else besides the motor and ECM would have to be replaced? WIll it bolt up to an M21? Cost?? Thanks
Chris

Chris -

It will cost about three times the price of a crate engine change, and not using an overdrive 5-speed with an "LS" engine (instead of a Muncie) wastes the potential for major fuel economy improvements. Add $3700 for the 5-speed, and you're looking at around $12K-$15K just for parts.

[Patrick H.]

Re: Pros and cons of switching motors

Chris -

It will cost about three times the price of a crate engine change, and not using an overdrive 5-speed with an "LS" engine (instead of a Muncie) wastes the potential for major fuel economy improvements. Add $3700 for the 5-speed, and you're looking at around $12K-$15K just for parts.

See.

Buy a C5 and have 2 Corvettes.

[Jim C.]

Re: Pros and cons of switching motors

I'm always gonna opt for leaving it original if possible.

[Dale S.]

Re: Pros and cons of switching motors

They are only original once. Dale

[Chris L.]

Re: Pros and cons of switching motors

Thanks guys for the input. I'm not sure just what I'm going to do as I want a good dependable driver as well as a showcar with a WOW factor.
I had a C5 (04) and was not impressed with the LS1 as it seem a bit sluggish. I always had big blocks and couldn't get use to the small block. THat's part of the reason for doing what I;m thinking about doing. Would love to put the LS9 in it , but $$$$$ a bit too high on that motor right now. I'm sure it will be cheaper next year. May wait on that one.

[Jack H.]

Re: Pros and cons of switching motors

Two Rocky Mtn members went the route of building 383 stroker engines for their SB cars. One had a '70 SB A/C car while the other had a '72 base engine car. In BOTH cases, they experienced problems with cooling capacity using their factory stock (but aged) radiators.

In one case, the owner bought a custom, high capacity aluminum radiator from Howe to fit the dimensional constraints of his existing radiator core support. In the other case, the owner changed the original SB radiator & core support over to a factory BB cooling system. Both alternatives solved the problem...

[Jim T.]

Re: Pros and cons of switching motors

Chris with your funds for an engine change for show and dependability and one that will bolt up to the M21 transmission, how about the ZZ572? It will bolt into your 70 frame with no modifications. Will the M21 handle 620 horsepower and 650 lb ft of torque?
Hope GM never quits making the ZZ crate engines.

https://store.gmperformanceparts.com/store/SelectProd.do?prodId=7655&redir=true&manufacturer= GM&name=ZZ572/620%20Deluxe%20&model=<!--19201333-->

[Patrick H.]

Re: Pros and cons of switching motors

Chris with your funds for an engine change for show and dependability and one that will bolt up to the M21 transmission, how about the ZZ572? It will bolt into your 70 frame with no modifications. Will the M21 handle 620 horsepower and 650 lb ft of torque?
Hope GM never quits making the ZZ crate engines.

https://store.gmperformanceparts.com/store/SelectProd.do?prodId=7655&redir=true&manufacturer= GM&name=ZZ572/620%20Deluxe%20&model=<!--19201333-->

I'm not sure the 572 will fit easily.
I know that they had a heck of a time fitting one under a big block hood in the King Ray.

Patrick

[Erik S.]

Re: Pros and cons of switching motors

Patrick - is this the engine from Werner's car? I am considering putting this in a C3 project myself with L88 hood, which should solve the clearance issue right?

[Steven G.]

Re: Pros and cons of switching motors

Money invested and resale are factors one may consider, another idea, is a local parts store re-manuf. 454ci long block, 3 year warranty, unlimited milage, 275-300 H.P.? @ $2072.00 + 675.00 core, there are many other items required for bb transplant. Watching resale sm vs bb, I think future retreving investment might be closer this way since #'s matching is not a factor, or is it ? Have fun with your corvette!! Steve