V8 (283,327) questions..

Doug Crooms · 07-12-2004, 11:46 AM

I want to do a conversion and would like to have either 283 or 327 SBC. Are these engines too hard to come by - doesn't seem to be many around. I really want a destroked 327 w/ 283 crank to create a 302. I know I'd need a 4"bore and 3"stroke - what is the standard 350 bore size and can a 350 be destroked in a similar way? Also, aside from cam and spring choices what goes into "moving" the torque to the higher RPM area in the curve? Do any of the 283 or 327s come with 4 bolt mains - is it necessary for a car mainly used on the street? TIA.

Doug C

Doug Crooms · 07-12-2004, 11:49 AM

Oh I forgot to ask for recommendations on pistons and rods, etc...

Doug C

914GT · 07-12-2004, 12:16 PM

Doug, there are still 327s around - in fact I know of one for sale in Tucson. The 350 has the same size bore as a 327 and 302, so you'd need a large journal 327 or 307 crank to build a 327 using that block. Either a 2 or 4 bolt main block would work. I don't remember if there's a large-journal 283 crank to make a 302 out of a 350. Somebody here should know. Besides cam and springs, other things to help would be choice of lifters and rocker arms, and higher flowing heads. It's pretty amazing how much improvement can be made to stock 350 heads by careful porting.

propricer · 07-12-2004, 12:20 PM

302 via 327 w/283 crank is a good way to go for a 914 since it can be a hi-reving engine which will match the 901 best. I've only ever seen 1 ad for a 327 4-bolt so it must be very rare ( if at all ) and would probably only be necessary if the engine was going to be blown. I see 327's on Craigslist all the time - generally $200-$300.
Are you sure you want the hi-end pump vs the low-end pump ???
Suggest you will use the low-end much more often which is why you also might consider a smaller carb - 650 or less, down to as low as 500cfm.
I'm just learning this V8 stuff myself so I will be watching the other posts and learning myself.
Good luck ...

Doug Crooms · 07-12-2004, 12:33 PM

Ed, you lost me on the high-end/ low-end pump?? Please 'splain.

Doug C

914GT · 07-12-2004, 12:39 PM

IMO you don't need a 4-bolt main for a 914 application. My guess Ed is referring to pump gas octane, stay away from high compression ratios you don't need it, stay with regular gas. Believe me, a well built 350 will be more than enough power for a 914.

914GT · 07-12-2004, 12:48 PM

Here - get out your credit card!
http://350chevymotors.twoffice.com/375%20hp%20327%20chevy.html

jhs914 · 07-12-2004, 01:50 PM

All 283's and (I think) all 327's have small main journals. The early Z28's were 302's made by combing the 4" bore 327 block with a 3' stroke 283 crank.

The later "DZ" 302 Z28's were large journal, 4 bolt main,, 4" bore blocks (same as a 350). If you can find a Z28 crank (casting #DZ1178) you can drop it in a 4 bolt 350 block and have a large journal, 4 bolt main 302. You should use the correct "pink" connecting rods and pistons for the '69 Z28 302. Bolt on a set of aftermarket or GM Performance Parts aluminum heads, use a cam with around 290-300 degrees of duration, about .500" lift and lots of overlap and you'll make your horsepower between 4000-7000 r.p.m.'s. Use a single plane intake manifold like the Edelbrock Torker II or Victor Jr. (Victor Jr. may be too tall) and this will insure you make your power at higher r.p.m.'s.

I have seen well built and balanced 302's turn 8000 r.p.m.'s at the drag strip, so you should be able to make one live at 6500-7000 on the street.

Doug Crooms · 07-12-2004, 02:03 PM

JHS (and all you other guys) Thanks for the great info, very helpfull. What about a block, 327/283 or otherwise that has previously been taken to 30over - still streetable? What's too much?

Doug C

skline · skline's Garage

My 283 block is 30 over so yes, it will work fine. The 283 was only a small journal but the 327's came in small and large journal. However, the only 4 bolt main 327 block was the DZ Z28 block. 69 was the only year they made it. It is worth a lot of money if you can find one. I know of guys selling them for 10k for the engines. To me, it just isnt worth it unless you are restoring an original car. You wont need a 4 bolt main to run in a 914.

1bad914 · 07-13-2004, 07:33 AM

I just purchased a stock original 327 from a 1967 Impala that had 84K original miles. I paid $325.00 for it. It is a 300hp model, the hi-rev low-torque characterisitics of this 327 is perfect for a 914. If you can find one like this, just re-build and it will definitly put a smile on your face and will not eat transaxles, upgrades increase hp thus eat transaxles. If you want more ponies than 300 or so, be prepaired to buy transaxles, and other drive train parts or spend the bucks for a builts trans!

It may be dirty looking, but is tight and will be a great core for the build!

AJS · 07-13-2004, 07:40 AM

Small journal 327's are still pretty well available. 283 cranks are harder to find, especially 10/10 or better. Good news is that most 283 cranks are forged. Large journal 327 cranks are mostly cast (you'll have to pay attention to the numbers). Scat can supply a 3.00" large journal crank at a resonable cost, which will allow you to go with the later block.

Andy

Doug Crooms · 07-13-2004, 08:09 AM

When buying a used crank, say a 302 what are the stock specs for the main and rod journals? What are safe spec if they've been turned (.010-??) ? Do those numbers change with regards to different cranks? TIA.

Doug C

jhs914 · 07-13-2004, 08:38 AM

Doug,

Skline is correct about large journal 327 cranks. I checked my Chevy parts interchange manual, any 327 made after 1967 will have the large journal crank. The 327 crank has a 3.25" stroke.

914GT · 08:55 AM

Small journal main diameter 2.30", rod diameter 2.00", stroke 3.00". Large journal main diameter 2.45". You just use oversize bearings with a turned crank, nothing else changes.

Another 302 option is to use a late model LT4 4-bolt main block with a 265 crank as used in the 97 Camaro Z28. Don't know if this presents other problems for a 914 conversion.

Doug Crooms · 07-13-2004, 12:34 PM

Guys, sorry for asking all the infantile questions but I'm getting a little confused about something... are all 4 bolt blocks necessarily "large journal" blocks or does that just refer to the crank? Could you use a 283 crank in a 4 bolt 350 block to create a 302 (which is what I want)? Is there an reason one block would be a better choice than another assuming standard 4" bore (327 or 350)?

Doug C

914GT · 07-13-2004, 12:44 PM

All 350 block castings, 2 or 4 bolt mains, are large journal and need the corresponding size crank. All 283 cranks are small journal. So you can't use a 283 crank in a 350 block. You'd have to get the large journal 302 crank or SCAT crank. A 327 block with small journals would only be an advantage if you wanted to build it to a 302 using a 283 crank.

Doug Crooms · 07-13-2004, 12:54 PM

Ahh...OK, that clears things up a bit for me. Thanks.

Doug C

AJS · 07-14-2004, 10:06 AM

Doug,

I just came across this 327 rotating assembly from Speed-O-Motive; long rod forged 327 kit, large journal. This means you can use any 350 block (except, I presume, the one-piece rear seal type).
http://www.speedomotive.com/327_cid_all_forged_pump_gas_long.htm

Andy

Doug Crooms · 07-14-2004, 10:37 AM

OK, I think the most attractive senario in my mind for building a 302 is to do as JHS914 has suggested and locate a "DZ" crank from a '69 Z28 which is large journal and put it in a 4 bolt 350 block. But are there specific year 350 blocks I should use or avoid (Andy just mentioned something about a one-piece rear seal?)? If I go this route I assume pistons and rods from the same year Z28 whould work just fine but are there better alternatives for those (i.e. cheaper, readily available)? Thnx.

Doug C