SBC 350 crank face distance

[Linlor]

Evening all;

I am new here and actually looking for a specific piece of information. I have a mid engine project car that currently has an SBC 350 mated to a Porsche 915 transmission through a custom adaptor, flywheel and clutch setup. I would like to see if I can swap in an LS while using as much of the adaptor as I can (adaptor plate, clutch and pressure plate) and make a new flywheel with the correct dimensions for the LS vs SBC.

I would like to ask if anyone that has an SBC out of their project is willing to take a measurement from the crank face to the bell housing mount surface. I don't know for sure if the SBC has different crank face distances between the split rear main seal or solid main seal.

Thanks very much
Don

A quick image of what I am asking for.


Also a couple pics of the flywheel setup for reference

[glennsexton]

Welcome to CHR:

Sounds like you are undertaking a avery ambitious project and your up-front research is certainly warrented and will prove to be well worth the time. Here's an article that may give you some of the information:

https://www.novak-adapt.com/knowledge/gm-crank-spacing

It has additional links that may prove helpful. Good luck and let us know some specifics of what your building.

Regards,
Glenn

[Linlor]

Thanks Glenn;

Yes it is an ambitious project. Lamborghini Countach replica with a custom frame. I am just finishing my Ferrari 308 replica project on a Pontiac Fiero frame (again full custom throughout) and now getting all my info ready for the Countach.

Thanks for the link as well. I had landed on that page as well and I see short and tall faces being used but I did not find an actual measurement anywhere on the site. I could well have missed the measurement though. Only item I saw was a reference to 'LS can be up to 4/10" shorter than an SBC crank' but the up to got me thinking I still need the actual sbc face distance. I have the LS distance already so once I get the sbc distance, I can make up a flywheel with the correct bolt pattern and spacing to still use the rest of my gear I already have.

A couple companies already make an LS to 915 adaptor but when I added it all up, it was over $3k USD and I am Canadian so add another grand to that with exchange and shipping.... If I had a big enough lathe, I could turn my own but I will get a machine shop up here to run one off for me for way less that $4k.

I could always try to sell the adaptor but I would have to say it is a VERY limited market for this setup.....

Thanks again for the link and I will go back in and have a much closer look as well to see if I missed what short and tall actually are for measurements.

If anyone else has an SBC and a straight edge handy, the measurement would be very much appreciated.

Cheers
Don

[jyardgirl]

welcome to chr

[Linlor]

As an update and recording for any future searching, I have had a local seller who graciously measured the distance on an SBC for me. It looked like the split rear main seal in the pic but I do not believe the distance changed between the one piece and split seals. If it did, then that would be a bit more problematic as I would have to figure out which crank the flywheel setup was originally made for.....

So, the distance measured for the SBC was 17mm from bell housing mount surface to crank face. The measurement I took previously from a 4.8L LS (short crank face) is 7mm so I have a distance of 10mm to make up to use my existing parts.

In the novak link that Glenn provided above, they state about 4/10" difference in the LS to SBC faces but I can now say that the 4/10" (10mm) is for the short crank LS face which is the automatic in the 4.8L LS.

Given everything is internally balanced, I can make a 10mm spacer to mate the LS face to the flywheel and rotate the bolt patterns to be able to bolt into the crank in the spacer and then bolt the flywheel to the spacer.

First hurdle solved so I guess I better go buy that 4.8l LS I saw last weekend....

Thanks all and continue to enjoy our hobby.
Cheers
Don