No!At least not for regular production.
This has come up before on several forums I'm on and so far no one has shown any proof.
Not saying it didn't happen-Just that I've not seen anything real.
Mike.:bowtieb:
:gba:

 

No they didn't, not for production cars.

I do think that a 327 large journal block casting could have worn the same casting number as a 350 4 bolt block.

I also think I've seen something where a 327 marine engine may have been 4 bolt. Don't worry about it, chances of you finding one are zero, even if it's true.

Now, there's no reason you couldn't build one, and that's been done lots of times.

 

WOW what a rare beast if you did find one. I have not heard of a 4 bolt main 327 but not to say some one off factory proto type is not out there. :flag6:

 

I know it never was a factory option but can't you build a 4 bolt 327 with a 350 block and 307 crank?
If so, they offered the parts, but never combined them.

 

Why say 307 crank? You use a large journal 327 crank (same as 307) with 4 bolt 350 block
Were 67 350 blocks (used in Camaro only in 67) same casting as 327 block? Or 68 and 69 also as both 327 and 350 were available those years.

 

Mortec shows 3-010 blocks as 302,327 and 350.
Just different guts!
Mike.:bowtieb:
:gba:

 

never. period.

 

EXACTLY......:shakehands:
:gba:
bowtie-trifive

 

307 Crank?

I think you'd have to add a ton of weight to a 307 crank to balance it to 327 spec's with the bore difference. BTW I have a fresh ground (10 YEARS AGO NEVER INSTALLED) 10-10 327 forged Large Journal in the garage somewhere.

 

I think you'd have to add a ton of weight to a 307 crank to balance it to 327 spec's with the bore difference. BTW I have a fresh ground (10 YEARS AGO NEVER INSTALLED) 10-10 327 forged Large Journal in the garage somewhere.

Same as 305 vs 350 crank, the 4 bolt factory 327 is urban lengend.

 

The large journal 327 cranks were only made in 1968, and were used on 275 hp engines. The rest of the 68-69 large journal 327 cranks were the same casting as 307 cranks.

There would a small bit of difference in the balance weight if using factory 327 pistons with a 307 crank. It's the difference in the weight of a piston for a 4" bore vs. the weight of a piston for a 3-7/8" bore. I just did a quick calculation and it's only 5 grams or so.

 

I have a 68 327 large journal that block #'s say is as follows:
From http://www.nastyz28.com/sbchevy/sblock.php#general
Block ID# 3914660 = 1968 327 HP:Low 210 Hi 300 2 main brg caps used in car

And, From Motors 1969 manual
1968 327 4 barrel:
HP TORQUE COMP OIL PRES LIFE INT LIFT EX
250 325 8.75 30-45 .390 .410

And, from a PDF of a GM very detailed specs for the 1968 full sized car the 307 was standard and the 327 an option with a 250 and 275 hp option, and shows a common crankshaft for 307 and both 327's, all dimensions exactly the same and they make no mention of different balance weights nor a difference in cranks for the 250 and 275 hp 327's. They do show the compression and oil ring groove depths are a bit more on the 327 than the 307. Could they have fixed the piston weight difference this way so they didn't have to mess with the weighting of the crank???

 

Speaking of urban legend , the need for a 4-bolt main block is as much an urban legend as the "black widow" . The amount of flex in the girdle of a 2-bolt SBC that's been line-bored and balanced , is negligible , according to all my Chevy heroes , Hayden Profitt , Bill Jenkins , Smoky Yunick et al . Even the 4-bolt main assemblies will fly apart if not built correctly , not maintained , or unnecessarily abused . I CAN , however , see the need for a racing marine engine that's subjected to a whole different set of stresses from a street engine . Be safe....Bob.

 

"and shows a common crankshaft for 307 and both 327's."

Simply said, your source is wrong, they made both forged and cast cranks in 1968 for 327s. I have 4 of the forged cranks in my shop.

I can also say from experience that a 4 bolt block is needed if you have enough power and/or rpm. It has nothing to do with the rest of the parts and how well they are machined or assembled.

 

My comment was only about a possible need for a weighting difference between the 307 and 327 crankshaft and that in my source, a 94 page pdf of a GM very detailed spec sheet for the 1968 full sized car, didn't appear to show any difference at all between the cranks for the two engines. I hope a genuine factory GM spec sheet is not wrong!
I am certainly no expert on 327's so I am not disputing that there were both forged and cast for the 327. I know there were for the hipro versions, but my PDF is for the 68 full sized car. The 327 in that application was a 250hp (L73) and 275 hp (L30) version, and for both 327 and 307 list one crank. They say, on page 45, they were both a cast nodular iron crank and as far as I can see don't make any differentiation on cranks between the two. Pistons, etc, yes, because the 307 was a smaller bore, but not cranks.
Did they make a hipro 327 still in 1968 and use it in other cars? I don't know. I thought they were relying on the 302 as a hipro engine at that time. But, again, I certainly am no expert.
Tried to attach it but it's too big. I will, when I have time, try to find the URL again and send it.

 

That's what I thought. Which tells me the same block was used for both displacements but they didn't tap the 327 for four bolt mains. Which does open up the possibility for a screw up and a 4 bolt 327 could have gotten through, theoretically. Not as feasible in 67 due to the journal size difference but easier to do in 68/69 since all were large journal.

 

There were no 4 bolt main blocks in 1967. 4 bolt mains weren’t available until 1969. Chevrolet redesigned the bottom end that year with thicker main webs for all sbc engines. This was a big improvement for all sbc engines including the two bolt main versions. The high performance and HD truck engines got the four bolt mains.

 

Are you sure there were no 67 Camaro 350's with 4 bolt mains?

 

Very sure.

 

Back in the day, I owned a 1965 Malibu SS, it ran a 350 4 bolt main, 4 speed ...wish I kept that sweet ride...:tu

 

The 275 hp 327 was the highest power option in 1968. Remember that 1968 was the first year for the 350 other than the Camaro, plus they had the 302 Z28 Camaros and big blocks too. The 327 was not marketed as a performance engine.

 

RickL. Are your 327 forged cranks large or small journal???

 

1968 CORVETTE HT coded L79 327 had 350 horsepower, HP, HO, HE, coded Base 327 had 300 HP, Corvette did NOT get the 350 'till '69.
327 large journal motors were used in calender year '68 in '69 Camaro's, Jan '69 went to the 307 as the base engine.

and even in the Vette, 327 DID NOT have 4 bolt blocks, though, the casting number of the block was also used for 350 and 302 sized engines.
and casting number and even horsepower, is no way to tell if it's a 4 bolt or 2 bolt, you gotta pull the pan to make sure.
I've never seen a 350+ hp 2 bolt but I have seen 275 hp 4 bolts.

And as to crankshaft lore, 396 and 427 cranks are interchangable, IF you use a lightweight forged 427 racing piston with the 396 crank. The counterweights are different thicknesses, the 396 being smaller/thinner.

 

1968 CORVETTE HT coded L79 327 had 350 horsepower, HP, HO, HE, coded Base 327 had 300 HP, Corvette did NOT get the 350 'till '69.
327 large journal motors were used in calender year '68 in '69 Camaro's, Jan '69 went to the 307 as the base engine.

And as to crankshaft lore, 396 and 427 cranks are interchangable, IF you use a lightweight forged 427 racing piston with the 396 crank. The counterweights are different thicknesses, the 396 being smaller/thinner.

Which would mean there was a large journal 327 steel crank? Or, did the 68 corvette use the small journal blocks still and the "run of the mill" 327 used the large journal because of the transition to 350???

 

307 crank and 327 crank had the same part number. I had a 67 engine I wanted to rebuild into a 4 bolt block, until I found out the 4 bolt block was large journal, and the parts weren't interchangeable. I had a 307 crank that would have worked, had it not been so severely scored. Of course then I would have needed new rods.
After I got all the info from the parts guy, the machininst there horned in on our conversation and said I'd have to have the block 'deck cut' an eighth of an inch. He must have been high, because the stroke difference is a quarter to start with, not to mention the difference is in the crank, not the block.

 

My 1968 model 327 forged cranks are large journal. That is what I posted.

We used in them in drag race engines either destroked to 3.18" stroke, or with the rod journal cut down to small journal size.

 

RickL
Your opinion, then, on the following, if I may. Would these be the equivalent?

http://www.scatcrankshafts.com/

Go to "chevy" "crankshaft" "4340 forged". Last I checked they were right at 500 for a 3.25 stroke (327).

THANKS!!!

 

Farm Boy, no 4-bolts till `69? `68, 302?

 

The 1968 302 was a 2-bolt main block.

There were major changes in the bottom end of the SBC between 1967 and 1969. The original 265's and 283's both had a short 3 inch stroke. This provided abundant overlap between the rod and main journals. The longer the stroke, the less journal overlap a crankshaft has, which makes it weaker. A small journal 327 crank has a 3.25 inch stroke and less journal overlap than a 3 inch stroke crankshaft.

When they developed the 350 for the 1967 Camaro they increased the stroke to 3.48 inches, further reducing the journal overlap. To compensate for this loss the engineers increased the size of the crankshaft main journals from 2.30” to 2.45” and the rod journals from 2” to 2.1”. This increased the journal overlap which made the crankshaft stronger.

Because the main journals were larger they had to machine the block more to accept this beefier crank. This “extra” machining made the main caps and the webs in the block weaker. The 1967 Camaro 350 and all 1968 blocks are basically small journal blocks line bored out to accept a large journal crankshaft.

Chevrolet solved this by redesigning their blocks in 1969 with beefier main webs and caps. 1969 was also the first year 4-bolt main caps became available.

 

My opinion on a $500 Chinese made 327 crankshaft? Get a stock one, even a small journal. You can use spacer bearings to put a small journal crank in a big journal block.

Or just get a 350.

 

Rick I am putting a 327 large journal motor together this week and would like to ask a question. Will flat top 350 pistons work in this engine? The pistons have reliefs in them for the valves. What heads would you reccomend, this is a basic street motor, no racing. A mild street engine with reliability is what I want. What about alluminum heads? Thanks.

 

You need 327 pistons if you are going to run stock length rods.

I'll pass on the head recommendation until you provide more info. Budget? Power level you seek? Do you have anything on hand? There are so many choices.

 

Rick, I mesed up on the crank it's a steel small journal, that's why I was asking about the 350 pistons. For power I would like to have about 300 hp. Budget wise I'm thinking 400/500 bucks for heads. The heads that were on this 327 motor are on the 56 you see pictured on my profile, it's a 327 also, so I do not have any heads for this motor right now.

 

Did I open a can of worms? I was just trying to win a bet that GM never had a production 4 bolt 327 but interesting to see the responces,I have learned something ,or did I ?

 

Based on the above, might be best to NOT use my 68 large journal block. Not gonna race, but just for a bit more lower end strength maybe get a 69 or 70 350 block to use instead???? Are there decking differences between the 350 and 327? any clearance problems in the bottom end of a 350 block using a 327 rotating assembly? (Let the reader understand, I have GOT this 327 THING! Had it since the 1960's when I had my 55 with a 525 hp 327! 350 is "generic". 327 is "cool" :sign0020

 

Your 1968 327 rotating assembly will drop right in a beefier 1969-1985 4 inch bore block. The deck height is the same.

Engine builders avoid using 1968 blocks for anything other than a stock rebuild.