sbc 302 Rod bearing trouble

[jimt]

I'm building a sbc 302. I have a crankshaft from a 283 with rod journal dia ground 0.10 undersize ( 1.990 ) and rods with the dia of 2.230 I have been told the Crankshaft has small journals for the rods and the rods are for large journal crankshaft. Are there bearings available for this combination?

[Saltmine]

I don't think so. But maybe some of our Dr. Frankenstein engine builders could come up with a combination that would work.
Normally, you don't use large journal rods on a small journal crankshaft.

[olddog]

The small journal cranks were replaced with large journals for a reason. The cast iron small journal cranks could not hold up to high Hp engines. The high performance small journal engines had to use steel cranks to keep from breaking them.

You can use small journal rods on the small journal crank. You just have to have them pressed onto your pistons. Back in the day many poor boys made there own 302 doing exactly what you are doing. Saltmine is right there is no way to use large journal rods on that crank.

If you do not mind the asking, why build a 302? Unless you have some racing rules that forces you to that displacement, there is no advantage. If you are looking to build a small engine for MPG savings a 305 would be better.

[olddog]

I just remembered something. The only small journal block with a 4" bore was the early 327. If I am remembering this correctly the main journals are smaller too. So all the large journal blocks will not work. I suppose you could use a thick shell bearing like they did when they put a 350 crank in a 400 block, but I never heard of anyone ever making such a bearing.

After market cranks are cheap for a SB chevy. You can get any combination you want for around $300 or less. That is cast steel not cast iron. A much better crank.

PS: you know I just don't trust my memory on this anymore. I cannot remember for certain if the small journal cranks had a smaller main journal too.

[Daniel Wood]

If memory serves me right, GM had a 302 and didn't know it. There was a racing series called Trans Am racing I believe an GM wanted to be a part of it. The drawback was engine displacement. The highest you could go was a 305. So GM went to the drawing board with their engineers and started doing their homework.

They realized they already had the parts to do it. They took the 283 small journal crankshaft along with the 327 rods and pistons, solid lifter camshaft with solid lifters and put it in a 327 block or vice versa that was made for a small journal crankshaft which in turn, turned it into a 302. A high winding fast engine. Like I said, if memory serves me right.

The only reason why GM went to a large journal crankshaft was to save money because it was made of cast-iron. They did try a small journal cast-iron crankshaft but it would break every time.

So olddog is correct. I'm going to check up about the 283 and 327 parts though because I want to make sure I'm right on that. But I believe I am.

[Daniel Wood]

Click “ here ” and read for yourself.

[carsandcycles]

Can't help with the original poster question, but thanks Daniel; great article on one of my all time favorite cars. (make mine a '69)

[justen]

You guys are right on your history. And far as I know I haven't seen aftermarket bearings for a setup like that. But the 302 in it's day was loved by camaro owners. They could get 7000-8000 rpm out of that engine and once in a while they blew.. but not often. I think it was the teenagers who blew them up.

[jimt]

Thank you very much for the information. I knew there was away to make the 302. I have the original 327 rods that will fit the 283 crank. I wasn't sure if the 327 rods were the same length until I read the responses and article.

I'm building the 302 for nostalgic reasons, I had a original 69 Z-28 when I was 19. Now I have an original 69 SS without a numbers matching motor that needs replacing, so I'm just reproducing good times. Thanks again.

[olddog]

In case you didn't know, SB Chevy used the same rod length on all, but the 400. To accomodate the different strokes, the wrist pin hieght is moved in the piston. So you have to use 302 pistons and standard length rods to put a 3" stroke into a 4" bore.

If you use 327 or 350 pistons, the Piston will not come up to the top of the deck resulting in extreamly low compression, and very little power.

Cranks can be very cheap today. Speedway sells a cast steel crank for about $175 new. I would absolutely not use a small journal cast iron crank for anything other than a restoration, where originallity was crucial. The steel small journal will hold up, but why bother, when better material is available?

The 302 is a good high winding engine for racing, but honestly it is not a good street engine compared to other SB Chevy engines. For the same money you can build a 383 stroker (350 -any 4" bore block - and 400 crank). You can turn them 6000 RPM all day with factory rods and a cast crank. Go steel crank and H beam rods and you can turn them 8000 rpm. A 302 will reliably go 7000 with a cast large journal crank and factory rods. I would not turn a small journal that high even steel.

A 302 at 8000 rpm will not be able to make the power a 383 can make at 6000 (all else equal). To get an engine to breath above 6000 rpm requires cam shafts that run like crap bellow 2000 rpm and a very good set of heads. Now me, I love the sound of an engine like that, but I want you to understand just how much of a pain in the but such an engine can be to drive on the street. Not to mention that engines turned at high rpm do not last as long and when they fail there isn't much left. My point is that you can make more power and have a more street friendly engine by going with more cubic inches. The more you do to make power with small inches, the more unfriendly the engine.

I don't want to rain on your dream, but I don't want you to wake up in a nightmare either.

Good Luck

[Saltmine]

I really am having a problem with all of this "swapping around", and looking for special bearings and such.

If the engine in question was going into a matching numbers, restoration, I could understand it, but it's usually the case, a guy finds (or buys) a used engine block of questionable origin, and scrounges up a crankshaft here, and so on...
If you want a small-block Chevy, go buy one. But, buy one that's complete. Then, you can take it apart and rebuild it without all of the hassle of trying to match this with that, and grind down this to fit that...What you usually end up with is a mongrel, that doesn't perform well, and won't last very long.
At least with a complete engine, you have a combination you already know works, and anything you do to it, is going to make it run better.(within reason)

Last time I ran into a situation like this, a co-worker told me he had an "original 327 high-po" engine, complete, sitting in his garage. Yeah, it turned out to be a 327...but the heads were wrong, and the crank was a small journal. I asked him what he was going to do with it, and he said he was planning to sell it for $1200 to a "hot-rod collector"
Unfortunately, the "Hot-rod collector" he was waiting for never materialized. He offered to sell the engine to me, but at $800, the price was too steep, especially for an engine with such limited usefulness. He's still got the engine, probably rusted solid, by now, and he still thinks somebody will pay him $1000 for it...
I told him had I needed an engine, I would have bought a new GM 350, in the crate, for less than $1500, with a warranty, and it would perform better and last longer than any "home built" conglomeration of engine parts. "But it's not a 327." He replied...."Who cares" was my answer.

[dougbfresh]

Really-327's are boat anchors by todays standards. Crate engines are the way to go-you know what your getting EXACTLY and you have a FACTORY warantee. Why fool around with unkown trash and have to pay to have them checked out and or repaired. The only time I would use a 327 for ANYTHING is a correct resto-if you not doing that, don't waste your time on the tiny beasty.

[olddog]

Well I didn't keep up with the chevy changes, but I think the large journal engines came out around 67 or 68. I think the factory 302 were all large journals. Up until they changed to the one peice main seal in the 1980's, I think the blocks and cranks were relatively all the same design - except the 400. I would guess that there may have been accessory attachment design changes through the years, but for the most part, the SB Chevy was the most interchangable parts engine ever made, when compared to all the others.

I know the 305 with its tiny bore had to have special heads with small valves, to fit over the tiny bore. I'm sure there are other things I don't know about, but I would bet there are several books out that will list what interchanges with what. I have some books on Fords, but not Chevy.

I know in my puppy days, I bought a block here and a crank there. A set of LT1 pistons and a set of camel hump heads off a 327/375hp vette engine. I managed to build a fairly strong 350 that would pull the front wheels of my 69 Chevel off the ground. I did have a good book on the SB Chevy back then, but it got lost over the years.

No doubt Saltmines idea is easier, and Dougs easier yet, however if you are willing to work at it, it can be done. Some people get real satifaction out of building their own engine. Sure its easier to walk into a furniture store and write a check for a table and chairs, but some people would rather make them from scratch. To them its means so much more and their friends look on in awe. Same with car guys.

[dougbfresh]

Originally Posted by olddog

No doubt Saltmines idea is easier, and Dougs easier yet, however if you are willing to work at it, it can be done. Some people get real satifaction out of building their own engine. Sure its easier to walk into a furniture store and write a check for a table and chairs, but some people would rather make them from scratch. To them its means so much more and their friends look on in awe. Same with car guys.

Hey, most people know squat even about carbs anymore. Without a dyno, piecemealing this stuff together is a shot in the dark. Maybe a combo that's been tried and TESTED would be worth it but buying it built and TESTED, you know exactly what your getting, dyno sheet and all-gives you more time to do REALLY time consuming stuff like body work/paint. The machine shop in his case would end up doing most of the hard work anyway. Most of the old head designs are junk compared to the modern designs too. Costs more in most cases to build a basket case than buy a great engine ready to rock.

[olddog]

Doug - your point is vallid. The vast majority of people would be better off to pay a pro to assemble their engine.

Crate engines I guess can mean different things. Not all companies selling a complete engine package are a good deal. There are places out there that do not deliver on time (6 months late). There are ones that do not use the quality parts that they advertise. There are ones that do not stand behind their product when things go wrong. Some of the prices are steep, too.

The very well known crate engines that are trust worthy tend to sell pretty mild engines at a moderately high prices. I would say Ford, Chrysler, and GM fit into this catagory.

However with that said there are plenty of great high performance engine builders that do a super job and stand behind their product. You have to do your home work and be careful in my opinion. Nothing is ever as easy as it seems.

As far as the OEM parts go, you can build a Ford or Chevy engine and not use a single OEM part. I think the block is about the only OEM part I would use. Even then you only save about $1500 by using a factory block, figuring in the machine work. The aftermarket blocks are a huge step up and likely worth every penny. Well Ford roller lifters are about the best, so I would use them.