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wre46 01-11-2009 11:23 AM

Engine Specs
 
Anyone know why 2.000 rod journals are not in the rules? It let you build a 302ci using a 327 crankshaft. I am going to petition the CRB for a change, but wanted to ask the fourm first

jimwheeler 01-11-2009 11:59 AM

Jeff,
Another item about which I'm not sure. I'll put it on the list for the ASAC.
wheel

John Rissberger 01-11-2009 08:42 PM

I think it is covered on Page 474

CRANKSHAFT
MAIN JOURNAL DIA(MIN): 2.2182"
ROD JOURNAL DIA (MIN): 2.0690"

John Rissberger
# 10 Camaro Oregon

jimwheeler 01-11-2009 08:57 PM

I know what the specs are, I am just not sure that I remember why they were spec'd that way or what the reaction would be to changing them. The ASAC discussed all this extensively when the rules were being written, but that was many months, if not years, ago. I'm sure one of the guys will have some notes on it.
Certainly, Jeff can ask the CRB to consider 2.000" rod journals. I just try to stay ahead of this stuff, if it is sent in for consideration.
wheel

kbsmith1 01-11-2009 10:03 PM

I'd guess that would be because allowing the big end of the rod to be smaller will lighten up the rotating assembly more, and therefore might be an advantage.

Looking at my chevy engine data, I think maybe Jeff means that you could build a 302 using a 283 crank shaft. Orignally 67 *& 68 302 engines were effectively 327 blocks (4.00" bore, 2.30 main bearings) with a 283 crank (3.00 stroke, 2.30 mains, 2.00 rods). I suppose using a 283 crank might be even doable using a newer 350 large
main journal block (2.45" mains). 69 chevy 302 used 2.45 main journal block and crank and interestingly, these cranks seem to have used 2.00 rod journals even though all other chevy small blocks seem to have used 2.100 rod journals.

My recollection is that many 283 engines, even relatively low performance ones used a forged crank.

Last 283 I had was in a '65 impala station wagon, in the early '90s. It was a lot funner once a 396 got transplanted into it :-).

I was looking at what it takes to build a 302 chevy, and what off the shelf parts can be used and it's interesting all the unique possible combinations. With 5.7 rods, you can use a 3.00 crank and domed pistons.

With 5.94 rods (a stock part in 262 or soemthing small blocks in the '90s) and a 3.00 crank you can use any standard 350 piston. To get really nice rods in this length they'd have to be custom, but the stock chevy ones in this length are pretty good (supposedly) PM rods. And then you'd have a huge choice of pistons. Of course to make that combo work, you'd have to get down to about a 56-58cc combustion chamber to get compression up to 10.3. Still, this sounded like the lightest weight rotating assembly maybe, and nicer to have a longer rod engine.

King Matt 01-12-2009 11:28 AM

Quote:

Originally Posted by kbsmith1
Last 283 I had was in a '65 impala station wagon, in the early '90s. It was a lot funner once a 396 got transplanted into it :-).

Hey, me too! Except mine was actually a 65 Bel Air wagon and I swapped in a 383. I think you are right on all the details of the journal sizes. This would only make sense if someone was to build a new AS motor with a 40-plus year old block and crank. Pretty unlikely when there were about 10 million small-block 350s built since then. A 3-inch-stroke forged large main crankshaft is not very hard to find or more expensive than any other common option used in AS.

BTW WRE, a 327 crank in a 350 block is a 327, not a 302 (4.00 bore, 3.25 stroke). ;)

jimwheeler 01-12-2009 11:39 AM

I found some notes about our engine discussions. All of that was discussed extensively and the 2.0690" was where it ended up, which covered almost all Chevy cranks. While you are free to request 2.000" journals, my guess is that a change in the rules is not in the cards. I think that the rules are going to stay the way they are for some time to come, unless there is some critical reason to change them.
There may be some adjustment on spec lines, weights, etc., but the basic rules probably won't change. I am sure that a spec line will be added to get the limited prep Cam/Birds in. Since they have a different engine than the earlier cars, the spec line will be different.
wheel

wre46 01-12-2009 12:26 PM

Quote:

Originally Posted by King Matt

BTW WRE, a 327 crank in a 350 block is a 327, not a 302 (4.00 bore, 3.25 stroke). ;)


Sorry, I meant to say a "small Journal 302" crank.

thomas toth 01-12-2009 12:56 PM

Jim...you mentioned weight, how about a 80# weight reduction for everyone? These cars are getting too heavy especially the 350 cars.....way, way too much ballast needed. From what I remember the reason we didn't want to go below 3,280#s was that the Camaro's and Firebirds were difficult to get below that number. Now with the removal of the dash, misc bits, column and head lights it should be pretty easy to get to 3,200#s.

Just a thought....

Tom

jimwheeler 01-12-2009 01:00 PM

Tom,
The this is a very weighty issue. Ehem! I'll throw your comments into the hopper.
wheel


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