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This is a follow-up from last week where one of the forum members was weighing a iron block LS and some transmissions to see what the difference was between them. That sparked my interest to finally see what the difference in weight between my LS and SBC in similar configurations actually is. So here we go, knowns on each engine: (Note the SBC has alum heads and alum intake so the real only difference is the block material and the LS7 intake is plastic)
LS is a actual LS7 427 CID with an F-Body wet sump so I can mount it in my 1986 vette. Engine is complete minus starter motor, throttle body, flex plate, engine mounts
SBC is 1971 400 block bored and stroked to 436 CID ready to be installed in my 1988 Firebird. Engine is complete minus starter motor, flex plate, engine mounts.
In both situations the engine have around 10 lbs extra weight on them from the engine stand mount that I did not remove before I weighed them. (No fluids)
I weighed them on my car scales which are very accurate.
The 436 SBC weighed 424.5 LBS and is shown on the scales as LR and RR
The 427 LS7 weighed 365.5 LBS and is shown as LF and RF
Difference is 59 LBS is similar configurations.
Last edited by bjankuski; Nov 22, 2021 at 01:56 PM.
Good test! Aw man drooling over those motors. I don't think I'll be doing well drag racing your Firebird anymore! A 400 something is a goal for mine someday.
My first ride (in the 80s) in a 400ci car was impressive as far as torque goes.
59 lbs isnt worth putting tons of $ into to swap. However an all alum 427 for sure. Amazing how far engine tech has come
Cars that can run 11s with the AC on knocking on the door of 30mpg with a warranty..GM has done the hot rodding for us
I'm the guy who made the other thread about weighing stuff. I'm surprised that the LQ4 I weighed with an iron block was less than 100 more than your LS7. I figured it would be more of a difference then that.
I'm the guy who made the other thread about weighing stuff. I'm surprised that the LQ4 I weighed with an iron block was less than 100 more than your LS7. I figured it would be more of a difference then that.
IIRC the crank in an LS& is about 7lbs heavier... I'm sure the differences can be totaled to account but yes, surprising indeed. I was under the impression LQ4s were much heavier but again, I could be remembering the iron headed ones... which are very heavy.
Sort of an unrelated item but after 24 hrs work I have the 436 SBC installed back in the car and running and it sounds great, no leaks and no smoke! Now to finish the tune and add a 4" intake track and larger dual exhaust.
!
Sort of an unrelated item but after 24 hrs work I have the 436 SBC installed back in the car and running and it sounds great, no leaks and no smoke! Now to finish the tune and add a 4" intake track and larger dual exhaust.
!
Save another 5lbs by changing that water pump to an aluminum pump. I just installed and measured an aluminum to reduce weight by 4.9lbsAluminum Water pump - 4.9lb loss
Aluminum 6.6lbs
Cast Iron 11.5lbs
then add 5lbs to the LS for the throttle body and we just closed the game another 10lbs!
I’ve been toying with going LS for a long time, and weight was a big factor, fun is another. BUT I wonder what a lightweight 383 rotating assembly looks like in terms of comparisons.
SBC weight VS LS weight
