I am starting to build a 70 ss chevelle.the car was an original big block car .Is there any way to know if it was a 396 or a 454?

If front fenders are original, the 396 (402) will only have the SS emblem, 454s have SS454 emblems.

The drivesahft and rear end are unique to the 454 cars and will be different then a 396 car though that is not proof positive as these could have been replaced. Also, if it is a manual trans and the VIN matches, the M-22 was the only manual used behind the 454 cars and was not used behind the 396.

Dale, I am confused. Both the SS396 and SS454 used the corresponding emblems on the front fenders. Only the 71-72 SS350 cars came without numerals or did I misunderstand your answer?

Wasn't the tach's also different between the 396 and the 454? They redlined at different RPMs

Really, the only way to know for certain is if you have the build sheet. Everything and anything else could have been, and likely was, replaced over the years by other owners doing their thing.

If front fenders are original, the 396 (402) will only have the SS emblem, 454s have SS454 emblems.
Really, my 70 SS 396 has the SS emblems and 396 below them. Mine may not be all original but every 70 SS I've seen has had either 396 or 454 underneath the SS.

All 70 cars had the engine designation emblems under the SS fender emblems. Only the 454 cars in 71-72 had the engine designation. The LS5 and L34 cars had 5000 RPM tachs while L78 and LS6 cars had 6500 RPM tachs IF EQUIPPED.

All 70 cars had the engine designation emblems under the SS fender emblems. Only the 454 cars in 71-72 had the engine designation. The LS5 and L34 cars had 5000 RPM tachs while L78 and LS6 cars had 6500 RPM tachs IF EQUIPPED.
Thought it was 5500 and 6500 RPM tachs, don't have a stock tach so I'm not sure.

The drivesahft and rear end are unique to the 454 cars and will be different then a 396 car though that is not proof positive as these could have been replaced. Also, if it is a manual trans and the VIN matches, the M-22 was the only manual used behind the 454 cars and was not used behind the 396.

Thought it was 5500 and 6500 RPM tachs, don't have a stock tach so I'm not sure.

I never had any doubt my NOM ElCamino was a real SS454 because as Rick said the M22 was only available behind the 454 and the 454 was only available in the SS. While my original engine is gone, it does have the matching number M22. That is enough for me.

Also, some LS-5's in '71 got the 6500 RPM tach. I have no idea why, but mine is not the only one I have heard of. Maybe they were just using up what GM made for the failed '71 LS6? It is a correctly date coded, white faced 6500 RPM tach in my car.

Weird things happened.

so what was the difference in the shaft and the rearend?The drivesahft and rear end are unique to the 454 cars and will be different then a 396 car though that is not proof positive as these could have been replaced. Also, if it is a manual trans and the VIN matches, the M-22 was the only manual used behind the 454 cars and was not used behind the 396.

Dale, I am confused. Both the SS396 and SS454 used the corresponding emblems on the front fenders. Only the 71-72 SS350 cars came without numerals or did I misunderstand your answer?

Hey wait a minute. The Chevelle has the original gauges in it. The red line on it is 6500 and its an LS5 car. :confused:

My bad, I was thinking of 71/72. :clonk: