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I have this posted in the C3 section also. What are the differences in part numbers/design of the internal motor parts. In particular the cam and pistons. Where they the same motors what just the air cleaner assembly changed? I am only looking at the short block and not the heads or intake.
I am wanting to build a motor for auto crossing. In my class I have to keep stock parts but can intermix between the years. Since both the 82 and 84 have the crossfire, I was wondering if I can use the 84 motor as a base. I see a ton more of them on Ebay than the 82 motors. As long as the parts are the same between the two, I can use it.
Last edited by vettehardt; Jan 31, 2018 at 02:28 PM.
Pistons are the same I'm quite sure, the GM SPO service numbers match. By part # the camshaft carries a different number. Do you only need to satisfy a 'block casting' ID or do you need to go much deeper. Essentially the 2 are close enough I'd think to be considered 'identical'. Cylinder heads are the same also.
Just a block casting number. The pistons have to be the same configuration as stock and must be stock weight or heavier. The cam must have the same lift and durration.
Just a block casting number. The pistons have to be the same configuration as stock and must be stock weight or heavier. The cam must have the same lift and durration.
Compare then only these camshafts '82 - 14044613 and '84 - 14088843
Block casting numbers on both I'd think to be 14010207
I know that you are looking at the short block basically, so the biggest difference between motors, which was the holes in intake runners connecting adjacent runners in 1984 does not apply (I believe that was the defining change 82-84). If you are interested, I have a full set (8) of factory oversize forged 1984 pistons in the boxes. These were use by the engine plant when the blocks had minor issues and were honed to a larger bore. The are between stock bore and 0.030 oversize.
I know that you are looking at the short block basically, so the biggest difference between motors, which was the holes in intake runners connecting adjacent runners in 1984 does not apply (I believe that was the defining change 82-84). If you are interested, I have a full set (8) of factory oversize forged 1984 pistons in the boxes. These were use by the engine plant when the blocks had minor issues and were honed to a larger bore. The are between stock bore and 0.030 oversize.
The pistons you have then should be part #'d as 474191 which I believe were spec'd as 3.9990 - 4.0000 when stock were spec'd as 3.9980 - 3.9990. Older piston charts just referenced them as +.001
Those pistons would do also '78 - 80(L82) then '82(L83), & also '84(L83) + '85(L98) C4.
The pistons you have then should be part #'d as 474191 which I believe were spec'd as 3.9990 - 4.0000 when stock were spec'd as 3.9980 - 3.9990. Older piston charts just referenced them as +.001
Those pistons would do also '78 - 80(L82) then '82(L83), & also '84(L83) + '85(L98) C4.
I know that you are looking at the short block basically, so the biggest difference between motors, which was the holes in intake runners connecting adjacent runners in 1984 does not apply (I believe that was the defining change 82-84).
Since you brought that up (even though it doesn't apply to the OP's question), have you figured out a reason for those holes between the runners in the '84 intake manifold?
Since you brought that up (even though it doesn't apply to the OP's question), have you figured out a reason for those holes between the runners in the '84 intake manifold?
A little more air flow?
As far as differences, I don't believe there is much if any. For all we know gm could have just updated the part numbers for the new model on say the cam. The couple horsepower difference may be in the intake port holes or it could be in the newerish ecm... Maybe a slightly better spark advance. Who really knows. They're both l83s so... you could get them on that...
Since you brought that up (even though it doesn't apply to the OP's question), have you figured out a reason for those holes between the runners in the '84 intake manifold?
A long time ago, I believe I read that the holes were there to improve cylinder filling, taking advantage of the pressure waves in the adjacent runners in the intake manifold. Unfortunately, I can't recall the source of that enlightenment. There was some work, also years ago, in changing the size of the holes in the stock intake passages to gain further advantages. I must admit that switching from the '84 with 205 HP to the '96 with 330 HP kind of erased my memory banks!
By the way... nice port matching job!
Last edited by 1984Z51auto; Feb 2, 2018 at 12:23 PM.
Reason: Addition.
Thanks, but that was only the first cut to a very extensive porting job. If the holes were there to improve air flow, why the h*** were the ports made so small? And those weird holes are only in four of the eight intake runners!! Somehow, they must have improved the torque curve characteristics. Opening up the ports for good port matching was a MUCH better answer to that situation!!
Sorry for the diversion. Let's get back to the OP's question.
I wouldn't be surprised if there was more than 5 RWHP diff between an '92 and an '84. There isn't a lot of rwhp data for CFI cars...on cars that are running correctly, but the 1/4 mile data seems to show that the '84 was a good bit stronger.
Motorweek ran the 1/4 mile in 16.0/84 with the '82...15.8/89 with the '84....C&D did 15.2/90 in their '84. That is more than 5 hp, IMO.
82 and 84 motor differences
