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4.3 GM engine internal parts skematic

8K views 16 replies 5 participants last post by  1Gary 
#1 ·
Was looking for an internal engine parts skematic
 
#4 ·
Guys have been saying for yrs a 4.3 is a engine with the two cylinders cut out of it. Facts are the only common thing about a 4.3 with a 350 is the bore size.4.3's have split crankshaft journals and the rods are offset to the bore centerline. The cylinder spacing is completely different.

I bought/built a never used Bowtie 4.3 with a common pin crank when NASCAR ended using them.Spent three times what it would have cost to build a 350 SBC.A real a screamer but expensive $$$$$
 
#5 ·
Guys have been saying for yrs a 4.3 is a engine with the two cylinders cut out of it. Facts are the only common thing about a 4.3 with a 350 is the bore size.4.3's have split crankshaft journals and the rods are offset to the bore centerline. The cylinder spacing is completely different.
Bore spacing is common between the 90 degree V6 engines (200/229/4.3L) and the SBC at 4.4".

Actually most of the architecture is similar: The deck height (9.025"), valve train, pistons, main bearings, cam bearings, oil pump, flex plate, damper, accessories are basically the same. There are some differences w/the oiling system galleries and the later engines have balance shafts, etc. and the 4.3L rod's big ends are bigger and the smaller V6 engine's rods are narrower on the big end, but there are many similarities.
 
#6 ·
I cover the differences in 4.3 in the provided link. Thing is when I went to the Bowie common pin crank is was in part because of the OEM split crank which only leaves you with two choices.Center the rods and have the pistons wear on the thrust side of the bore or center the pistons having the rod bearings create fiction on the side. The bore spacing on the Bowtie/common pin cranks resolve that problem.
 
#10 ·
Just so you know who you are dealing with. I worked at the engine plant for Chevy.Some of that was in the dyno rm. I owned and built a Bowtie common pin crank 4.3 V6 with Brodix heads. It was about 500 hp. I am ASE master. I have spent my entire life in hot rodding which amounts to about 40 yrs. I have dealt with the 4.3's in Astros for about 8 yrs. Sooooooooooooo yey we all know how the casting and machine work dictates the bore spacing.Really kind of elementary info. Ya know??.

So given a lifetime in the business,I disagree with you about the casted bore spacing of the 4.3's being the same as the V8. I already told you you can clearly see it in the lay-out of the heads.

Now can we get this thread back on topic??.:spank::D
 
#14 ·
Please 'splain further as i am not trying to argue nor undermine your credibility (as if??) but rather to learn about this engine as Chevrolet themselves state that the bore centers are identical to the 8 cylinder block. Chapter 4, pg. 1 of the Chevrolet power manual.

a) i think the bowtie versions have siamesed cylinders. But then again, the 8 cylinder blocks do too? (pretty sure).

b) i thought any 90 degree v-6 block could accept a common pin crank?

One thing many people may not realize is this small block engine is still being installed in new vehicles---the base 1/2 ton gm pickups 58 years later! Although this year will probably be last.
 
#15 ·
The primary reason behind the common pin cranks aside from them being a forged crank was it relieve the problem of the off-set pistons fiction robbing power.
The stuff I bought was a ruff forging because the NASCAR race shops wanted to finish machine the way they wanted it. Spendy McFersion (SP??) spend alot of time with me helping me get it to a finished engine.
It was a stroker with a 273 ci.I had it in a Chevette and on the throttle stop it would run the number of 10.90 like clockwork.
My partner told me not to build a odd combo.That things that are not common place costs tons more.This was a race operation that we have been together for 14yrs racing running a number of 9.90 cars and vending SBC small parts for about the same time.

Bottom line is I lost my butt on it when we have been buying distress incomplete race cars,racing them for a yr after finished them out,selling them for a profit.I think we have been together for 40yrs now and to this day he still reminds me about that loss.

If I was to advise someone about a 4.3,I would suggest building to the extent of a turbo version or marine version.If you step beyond that you enter a arena the gets expensive in a hurry.
 
#16 ·
i am in no way trying to dislodge, discredit anyone but my general consensus ,at this point, is until there is further solid proof otherwise, the 90 degree v-6 engines have identical bore spacing with the 8 cylinder blocks.

i base this upon several things:

1) Gm themselves have stated this in writing in many places. One example is above.

2) If, let's say, a common pin crank is put into a stock 4.3 engine, then what needs to be done to the block? Specifically concerning the cylinders?

Note, my intention of the discussion at this point is not to discredit, but rather to learn more about this engine.
 
#17 ·
It does seem my memory of the bore spacing of the 4.3's was in error. While I focused on the off-set rods due to the split crankshaft design,I did forget the block casting. It has been about 15 yrs since I was in that deep into the very expensive Bowtie block and the research for the same with many SBC/BBC's engine in-between. Yeah we do buy/sell a bunch of that.

Well I have always told myself it takes alot to admit a mistake. Sorry guys..............
 
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