Hey guys, I was recently given a 1969 327 (618 block) and I'd like to rebuild it as a 302 that will eventually find its way into a 1969 z28. I plan on making 450HP at max with this motor, looking as factory as possible with an offy cross ram intake, and fuelie heads. Right now my main concern is which crank shaft I should be using because I do have the medium journal block, and its hard to locate a medium journal forged 3.000" crank. My options are a nodular iron 4.3 crank that has been modified to fit the 2 piece seal ($225) or Use a small journal forged steel 283 crank with bearing spacers (I believe these are the ones http://www.race-mart.com/items/products/callies/list42.htm) for a total of 175+ the cost of a redone 283 crank. I could also use the eagle forged crank that will drop right in but thats around $600, and I think is a bit over kill for this application. Old timers / pros WHAT SHOULD I DO!

First off, I would not used bearing spacers. Its done but there are heat transfer problems doing this.

Second, if you are going for a custom crank , why not go for a forged drop in assembly and get it done right the first time. These nodular cranks are good and do live well but the choice is there and yours to make for a few dollars more.

Third, are your sure your block will not need line boring? Now is the time to think about all this .

A medium journal 327 crankshaft is quite rare also. You may be able to use it as a bargaining chip for a 302 crankshaft.

A medium journal 327 crankshaft is quite rare also. You may be able to use it as a bargaining chip for a 302 crankshaft.


Now that you mention it I guess it is pretty rare.

First off, I would not used bearing spacers. Its done but there are heat transfer problems doing this.

Second, if you are going for a custom crank , why not go for a forged drop in assembly and get it done right the first time. These nodular cranks are good and do live well but the choice is there and yours to make for a few dollars more.

Third, are your sure your block will not need line boring? Now is the time to think about all this .

Ok, spacers are out of the question in that case, I was kind of suspicious of them in the first place.

Even though its a very clean motor The block is defiantly getting completely redone, Line bored and punched out, as well as what ever else it needs. These are added costs that make budgeting the parts a little bit harder. I need to call the machine shop that I have picked out fairly soon (Its in NY and I live in NC) and get a price on all of it.

I know that all the orignal 302's came with forged steel cranks. I cant say that im a complete and total purest because I'm not starting with a numbers matching z/28 but I do like to keep things as original as possible. The difference is about $300-350 to use the eagle, minus the cost of the spare parts I wont be using on this motor and it seems pretty reasonable, and the piece of mind being able to say that I have forged internals makes it seem cheap at the price at the end of the day.

Why not look for a small journal 327 block and use a 283 crankshaft?

I'm not a fan of bearing spacers for the same reason Don states, the heat transfer is critical into the mainwebs. However a lot of guys run them with no issues, many on this site and maybe they'll chime in with why they like them.

If you do go with spacers there is only one manufacturer that I would even consider, King. They make their spacers from hardened steel tube and not modified main bearings. Comp Cams, Jegs, Summit, Manley and all others are simply soft modified main bearing with the full grove running through them. The groove serves absolutely no purpose on a spacer, but verifies that you are dealing with a very cheap excuse of a spacer.

The Eagle crank would be a good way to go. I also like Chris (Smits 67) idea of a small journal build. It's easy to find the parts and it's the least expensive and least troublesome way to go. Just use good SJ rods, which there aren't many as most SJ rods were inferior in strength and quality (small cross section beam, very little material on the big ends and very small diameter bolts) other than 67 SJ rods or aftermarket.

I'm not a fan of bearing spacers for the same reason Don states, the heat transfer is critical into the mainwebs. However a lot of guys run them with no issues, many on this site and maybe they'll chime in with why they like them.

If you do go with spacers there is only one manufacturer that I would even consider, King. They make their spacers from hardened steel tube and not modified main bearings. Comp Cams, Jegs, Summit, Manley and all others are simply soft modified main bearing with the full grove running through them. The groove serves absolutely no purpose on a spacer, but verifies that you are dealing with a very cheap excuse of a spacer.

The Eagle crank would be a good way to go. I also like Chris (Smits 67) idea of a small journal build. It's easy to find the parts and it's the least expensive and least troublesome way to go. Just use good SJ rods, which there aren't many as most SJ rods were inferior in strength and quality (small cross section beam, very little material on the big ends and very small diameter bolts) other than 67 SJ rods or aftermarket.


We'll the reason I want to use this block is because it shares the same casting as a 1969 302, so it adds a little flare to what I'm trying to get done. Also this block was given to me in pretty excellent condition, It would be hard to find an even older block in such good shape.

If it isnt the numbers motor for the car,why not build it better internally?A forged 350 crank would rev just as hard as the 302 and make more power.Since you are even looking into non original setups like main spacers,it is obvious that you arent looking for something that can be torn down and be confirmed as 100% original.Do justice for the Z/28 name,and make it as fast as possible by making your date/casting correct 302 into a bigger and badder monster then the factory ever did.Even if it were torn down,it is just as believeable to a future buyer that and original 302 was rebuilt as a 350 as it would be to belive that an orginal 302 was rebuilt with main spacers an a 283 crank.

Good luck.

If it isnt the numbers motor for the car,why not build it better internally?A forged 350 crank would rev just as hard as the 302 and make more power.Since you are even looking into non original setups like main spacers,it is obvious that you arent looking for something that can be torn down and be confirmed as 100% original.Do justice for the Z/28 name,and make it as fast as possible by making your date/casting correct 302 into a bigger and badder monster then the factory ever did.Even if it were torn down,it is just as believeable to a future buyer that and original 302 was rebuilt as a 350 as it would be to belive that an orginal 302 was rebuilt with main spacers an a 283 crank.

Good luck.


Im not interested in a 350, I have a 357 built in my garage right now that should make over 400hp. I have a 1970 Chevelle SS with a 402 bored .030 over that makes plenty of torque. I want to build a 302, Im not saying that I want to trick anyone into believing its an original DZ motor. I just want something different. The z/28 name is justified in its own right, and thats with the 302.

Vinnie I understand. Spacers aren't a problem if you get the good ones, Kings. That's the only way I'd do a spacer main setup. The alternatives are the Eagle crank at just under $600 or the thick spacer main bearings that Federal Mogal or Clevite make. The thicker bearing eliminates the need for spacers. They aren't cheap, I've seen them for just under $200 a set. Be careful because they are offered in 400 block/MJ crank sizes as well as 4.00 bore MJ block/SJ crank sizes.

KB makes a great forged FT piston with a comp height of 1.261. That'll allow you to run a long rod 6.250 and still be .014 in the hole, or deck .014 to bring the piston to the top of the bore, which is what I'd do. What ever way you go I would run FT piston for better flame travel than the domes, but you'll need a very small chamber head to get the compression up. Even the GM aluminum bowtie phase 6 heads at 55 cc chamber are only going to put you around 10.5:1, but you can flat mill them, or any 23 degree head, .030 before you need to worry about cutting the intake. .006 flat milled on a 23 degree head = approx 1 cc, so .030 would be -5cc or 50 cc chamber. A good DCR calculator will help you figure out what exactly you end up with.

As far as spinning it high and hard I've blown up a lot of 350-355 SBC trying to run them like my 302s. The most recent was a 12.5:1 355 with bowtie 6.00 7/16" capscrew rods and all of the rods were out of round after only a few months of hard use. The rods hung in there though, it was 2 pistons that came apart and split the block open in the process. I never hurt a 302 and spun them much higher. They won't take the same abuse over time that a 3.00 stroke will IMO. They will have more grunt though like Rich points out for sure! The short stroke motor doesn't have much grunt below 4K at all. If you run a 3.00 plan on 4 series rear gears, no fun otherwise! Little motor needs all the help it can get. Like others point out you can get more bang for the buck with the 355 build and build more easy horsepower. That doesn't translate to more fun necessarily, it really depends on what you plan to do with the car.

Their is one way to build an 8500 rpm engine and that is the right way.Buy the Eagle forged crank good rods and lightweight forged pistons.If you build it cheap it will come apart and then you get to do it again.In the long run it's cheaper to do it right the first time than to do it twice.While the KB flat tops maybe fine I would be looking at Ross or Wiseco pistons.RHS has 50cc chamber heads 200cc runners with 2.02in. 1.6ex. http://competitionproducts.com/prodinfo.asp?number=RHS12333K2 Dart also has them but they are angle plug http://competitionproducts.com/prodinfo.asp?number=10310010PFK3 .Find a machine shop in your area that does circle track engines and talk to them about building an engine.


PS. Something to think about the last 283 forged cranks were made in 65- 66 that's 40 plus years ago.You want to rely on that at 8500 rpms?If you are lucky you blow the engine if your aren't you blow the engine and crash the car when oil gets under the back tires.

Vinnie, Chad makes a good point. There are a lot of good pistons out there, just make sure to use a forged piston and you probably can't go below a flat top because you won't find heads with small enough chambers to keep the CR up. So a flat top or small dome, but I'd personally stay away from the dome. The RHS may be the best bet with 50 cc chamber.

One word of advice if you plan on running a manual trans, I assume with the short stroke you are, be very picky on your flywheel selection. This is no place to save $$ you'll need a very good quality flywheel to spin it high without worrying about it failing. I'd also run a scattershield. I've seen what happens when the flywheels fail and come through the floor with GM aluminum bellhousings. The flywheel I pulled out of my 68 scared me pretty bad when I saw all the stress cracks propogating in it. It was an uncontained failure waiting to happen. Same for one I pulled out of my 69Z and that car with it's 302 saw 8K plus all the time, but also had a scattershield, the 68 did not. It only had the 621 aluminum bellhousing. Just stay safe!

One word of advice if you plan on running a manual trans, I assume with the short stroke you are, be very picky on your flywheel selection. This is no place to save $$ you'll need a very good quality flywheel to spin it high without worrying about it failing.

X2 I was in the back seat of my uncles 66 Chevelle with my Dad driving 283 4 speed when the clutch disc came apart and came through the floor, dash and hit the windshield.That will scare a 10 year old.

I was going to leave it up to my machinist to help me decide on what pistons to run, I was thinking 10.3-10.5, with a set of 64cc chamber heads. Currently I have 461s that I'm thinking about using but I'm still searching for some cheap 186/401 cores. I don't think that flat tops will give me that with the heads that I want to run. What pistons should I use in that case? I'm also looking into the 140 cam. From what I read GM offered it in a package with the cross ram intake and headers, so I was under the impression that it would be a good cam to use for this engine but I've also read on these forums that its not such a great cam to use with lower than 12:1 CR. I'm not looking for a huge lopey cam, just something mild.

One word of advice if you plan on running a manual trans, I assume with the short stroke you are, be very picky on your flywheel selection. This is no place to save $$ you'll need a very good quality flywheel to spin it high without worrying about it failing. I'd also run a scattershield. I've seen what happens when the flywheels fail and come through the floor with GM aluminum bellhousings. The flywheel I pulled out of my 68 scared me pretty bad when I saw all the stress cracks propogating in it. It was an uncontained failure waiting to happen. Same for one I pulled out of my 69Z and that car with it's 302 saw 8K plus all the time, but also had a scattershield, the 68 did not. It only had the 621 aluminum bellhousing. Just stay safe!

Thanks for the advice! I'll run the scatter sheild :thumbsup:

You can have the 461s angle milled .125 to bring the CCs down to the 55cc range.The 140 cam needs the comp. to keep it from being a dog on the bottom end.8500 rpms and mild cam don't go together.

The 140 is such a big cam that you shouldn't have any problems running the stock 11:1 DZ pistons with pump gas.

You can use 10.5:1 dome pistons here, this is the lowest compression you can get with shelf pistons on 5.7 rods and 64cc heads. I did this, but I also used a cam that built considerably more cylinder pressure(but was not much smaller) than the old school grinds. Way higher lift and comparable .050 duration to the 30-30, but less advertised duration and a tighter LSA. What this did for my engine is gave it a broader power band (2k-7200) when compared to the original DZ motor(~3500-~7000). That engine runs on 93 octane with aluminum heads.

With all that said, I'd definately run the 12:1 pistons if I was going to go with one of the offroad cams. I have a disassembled 301 short block in my garage with those pistons and also a set of ported 461's; I'm going to build that motor with the offroad cam some day and I look forward to doing it. I don't think it will run as nicely on pump gas as the 306 I have now, but it should have a completely different feel and be just as fun.

The other option you have is to run some new RHS or Dart heads that have 50cc/49cc chambers plus 350 flattops on powder 5.94" rods. That should get you around 11:1 and would be well suited to a 30-30 if you want a slightly cheaper short block and an authentic sound. It should run stronger and be less likely to detonate than a DZ: quicker flame travel with the flattops, heart shaped chambers, and the improved airflow through the modern heads all help in a performance build. The powder rods are supposed to be stronger than the old pink rods, and forged 350 flattops will run about half the price of 302 pistons. The rotating assembly will be lighter with this combo as well.

whats "Medium Journal"? I thought SBC used small 2.30 or large 2.45 journals.

There were actually 3 main journal sizes and finally people are beginning to use the correct terminology, SJ, MJ, LJ. I believe this is in part due to the 400 beginning to become popular finally as a performance engine. The SJ was 2.30, the MJ (what many refer incorrectly to as large journal) is 2.45 and the 400 is 2.65.

Vinnie for what it's worth TRW thick spacer main bearings are MS3110P for SJ crank in MJ block and MS3063 for MJ crank in a 400 block. There are others who make these bearings, but they are all around $200 a set.

Vinnie for what it's worth TRW thick spacer main bearings are MS3110P for SJ crank in MJ block and MS3063 for MJ crank in a 400 block. There are others who make these bearings, but they are all around $200 a set.

Ok, thanks but I think I'm going to just buy the eagle crank to avoid any of the problems mentioned earlier. It will end up costing me another 200-250 to go with the steel forged MJ crank brand new over a 40 year old turned SJ crank.