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A Poncho Legend!

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4 Bolt Main 327 Blocks


There is another thread about 327's that has slightly derailed so rather than take it further off course, I'll post separately.

The discussion came up that there has been rumours for years (I first heard them in the 70's when I was a teenager) that GM made some 4 bolt main 327's. The Massey Ferguson combines of that era had 327's in them for a number of years, and supposedly they were 4 bolt main.

I never say never, but....

I have worked in the auto parts industry as well as being quite involved in the farm machinery business as well because my job has been doing GM parts as well as farm parts since 1976. In that time, of all the 327 Massey Combines I have knowledge of, not one of those engines has ever turned out to be a 4 bolt main. I have never seen any documentation substantiating the claim of 4 bolt main 327's for agricultural/commercial/industrial use either.

One of my current co workers at the dealership where I work is 65 years old and still lives on the family farm. He has been a GM tech all his life since he quit school in grade 10. He does some small scale farming and does mechanical work at home for many farmers. He and I have discussed this a number of times and he also says "no" to 4 bolt main 327's.

I think I am safe in saying that there never existed a 327 4 bolt main, as far as one coming out the doors at a GM manufacturing plant. The possibility of building one is 100%, because all you need to do is take a 350 4 bolt block and put in a 327 large journal crankshaft (same crank as a 307). However, there seems to be no small journal blocks at all, not even an L79.

As always, I'm open to proof that I'm wrong! But not speculation, there's been lots of that over the years but it's never been proven.

This is no slight against anyone who says they've heard of them, it's simply stating my own experience based on what I've seen. I have never seen one physically, or documentation to back up the proof of it existing.

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Summers Brothers used to either make main bearing girdles or 4-bolt caps for small journal small block Chevies many decades ago. As for a factory 4-bolt main on a small journal SBC it is like the Indian rope trick. People have heard of it but nobody has observed it. I heard of a '62 327 truck block that supposedly had 4-bolt mains, but unless that engine had never been rebuilt or had the pan off then how would anyone know the source of 16 bearing bolts staring at them?

Large journals were introduced to the rest of the small blocks for 1968 after having been introduced with the Camaro 350  for 1967. 4-bolt mains didn't make it on the large journals until 1969 models; by then the 327 was only offered as an entry-level V8 for the 1969 big Chevrolets & Camaros. All high performance & truck applications had switched to the 350 for '69.



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im pretty sure its safe to say no 4 bolt main 327s ever,and all small journal 327s have steel cranks, all large journal have forged cranks my fave is the early 327

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I think you are right, there were no actual production 4 bolt 327's in passenger applications, but remember there were no production 4 bolt blocks until 1969 model year, and by that time the only 327's left in production didn't need a 4 bolt block. These were of course the 210hp 327 used in early 1968 Camaro (and maybe some Canadian Pontiacs) before it was replaced in Camaro by the 307 around October 1968, and the 235hp 327 in Chevy full size (same engine as the 210hp engine except it used the later L65 350's bigger 2BBL carb and intake, whereas the 210hp engine used the 283/307 2BBL carb and intake). 4 bolt blocks weren't used in 1969 engines until the 300hp L48 and above which means only the L48, Z28, L46 and LT1 (I think that is all of them).

There was a sort of 4 bolt engine used in 1963 but not as a 327 - they were 377ci. These were the special Grand Sport Corvette with a stroked 327 (using what would later become the 3.75" 400 stroke and people wrongly now call a 383). From memory I'm sure I read these had a special 4-bolt 1963 327 block.

As for trucks or commercial applications I'm not sure. The original GM archives have just about every spec for the High Torque 327 truck engines for 1968, but they do not list how many mains bolts they have. Same with the high torque 350ci engines for 1969. They mention forged crankshafts, valve rotators etc but not the mains caps. They are all over the 1969 big block truck engines being 4 bolt but nothing about the small block, same with 1968.

Also not sure what GM offered as spare part engines or short motors or block and piston kits for say 1967-8 L79. You'd think they'd build these using a 4-bolt block, if policy dictated anything 300hp and up needed it.



-- Edited by HK1837 on Sunday 25th of November 2018 10:02:22 PM

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timbuk wrote:

im pretty sure its safe to say no 4 bolt main 327s ever,and all small journal 327s have steel cranks, all large journal have forged cranks my fave is the early 327


Not quite, most large journal are cast but some (mainly truck) are forged.  



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3955618 block may have a steel crank and yes the large trucks may also have these will be rare good point

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Slight hijack;

Is a 67 327/275 a good base to build on? It's a Camel hump engine, but is there anything else of note in it?



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cdnpont wrote:

Slight hijack;

Is a 67 327/275 a good base to build on? It's a Camel hump engine, but is there anything else of note in it?


A good engine. Of course it has a small journal crank & 2-bolt mains, but then again so did 327 fuellies, L-79s & those 365-horse Corvette 327s. Grumpy Bill Jenkins loved those small journal 327s and would use them to build his 331 cube race motors in his Pro Stock Vegas & Monzas. We all know how successful he was. Summers Brothers straps across the bearings. His thoughts were that the small journals had less friction, and where tenth's count in a race it was possibly an advantage. It just had to make the runs for the day and any tear-downs were just part of the business.

Chevrolet released the 350 in the Camaro SS for '67. They had larger journals from day one because the engineers found the 350's longer 3.48" stroke seemed to cause spun bearing inserts. Essentially the 327/275 & the 350/295 are the same engines except for the 350's longer stroke & larger bearing diameter. Same cam, heads, engine dress (except the 350 had chrome valve covers & air cleaner lid).

A 327/275 has 10:1 compression, cast pistons, 1.94" intake & 1.50" exhaust valves. A set of 2.02" intake & 1.60" exhaust would help if you seek performance, the revving kind. Still no need to overdo it though because the 275-horse 327 produced a relaxed 355 lbs/ft of torque. 327s like to and possibly need to rev more than a 350. I really like the idea of an old-school L-79 flat tappet hydraulic cam & larger valves on a 327/275, but at that point you will want pistons that can stand up to abuse. GM was still selling L-79 parts in the late 80s like forged pistons  & the nice rods. An L-79 cam really needs decent compression because of the overlap. It came with an 11:1 compression which was great when you could buy leaded 110 octane at the pump, but those days ended in 1974.

Passenger car small block V8s still came with the canister type oil filters through 1967. Probably any found running today would have the adapter to run a normal spin-on paper element filter.



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As above, nothing wrong with a 1967 327/275 but unless you want it to look or be totally original it is hard not to use more modern stuff as later or aftermarket stuff generally produces more bang for buck. SBC bits are so cheap these days it is often not even worth rebuilding old stuff, best leaving it for those that want originality. Vortec heads for example are far better performers than the 462's you have, and if you need pistons just buy whatever gives you the desired compression with the Vortecs, same with manifold, buy to suit the Vortecs. Even the alloy LT1 heads with 1.94/1.5 valves flow pretty close to the best GM Fuelies and they are cheap too. Both these and the Vortecs will happily run on ULP as well.

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cdnpont wrote:

Slight hijack;

Is a 67 327/275 a good base to build on? It's a Camel hump engine, but is there anything else of note in it?





Drop it in that 65 stone stock with a Muncie behind it. You'll love driving it and your wallet will be really happy with your decision.

You have that monster big block in the other car if you feel the need to peel some rubber off your tires!

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Carl Stevenson wrote:

There is another thread about 327's that has slightly derailed so rather than take it further off course, I'll post separately.

The discussion came up that there has been rumours for years (I first heard them in the 70's when I was a teenager) that GM made some 4 bolt main 327's. The Massey Ferguson combines of that era had 327's in them for a number of years, and supposedly they were 4 bolt main.

I never say never, but....

I have worked in the auto parts industry as well as being quite involved in the farm machinery business as well because my job has been doing GM parts as well as farm parts since 1976. In that time, of all the 327 Massey Combines I have knowledge of, not one of those engines has ever turned out to be a 4 bolt main. I have never seen any documentation substantiating the claim of 4 bolt main 327's for agricultural/commercial/industrial use either.

One of my current co workers at the dealership where I work is 65 years old and still lives on the family farm. He has been a GM tech all his life since he quit school in grade 10. He does some small scale farming and does mechanical work at home for many farmers. He and I have discussed this a number of times and he also says "no" to 4 bolt main 327's.

I think I am safe in saying that there never existed a 327 4 bolt main, as far as one coming out the doors at a GM manufacturing plant. The possibility of building one is 100%, because all you need to do is take a 350 4 bolt block and put in a 327 large journal crankshaft (same crank as a 307). However, there seems to be no small journal blocks at all, not even an L79.

As always, I'm open to proof that I'm wrong! But not speculation, there's been lots of that over the years but it's never been proven.

This is no slight against anyone who says they've heard of them, it's simply stating my own experience based on what I've seen. I have never seen one physically, or documentation to back up the proof of it existing.


 

I think you are correct on no 4 bolt 327 Engines that were ever factory built.

 

I would have bet there were no 4 bolt 305 blocks until I saw one.

 

454's never came in Grain Trucks either.

 

1968 Camaro TH 350

 

Typing practice over, good night!!

 

Thanks

Randy



-- Edited by GLHS60 on Monday 26th of November 2018 02:18:13 AM

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GLHS60 wrote:

Carl Stevenson wrote:

There is another thread about 327's that has slightly derailed so rather than take it further off course, I'll post separately.

The discussion came up that there has been rumours for years (I first heard them in the 70's when I was a teenager) that GM made some 4 bolt main 327's. The Massey Ferguson combines of that era had 327's in them for a number of years, and supposedly they were 4 bolt main.

I never say never, but....

I have worked in the auto parts industry as well as being quite involved in the farm machinery business as well because my job has been doing GM parts as well as farm parts since 1976. In that time, of all the 327 Massey Combines I have knowledge of, not one of those engines has ever turned out to be a 4 bolt main. I have never seen any documentation substantiating the claim of 4 bolt main 327's for agricultural/commercial/industrial use either.

One of my current co workers at the dealership where I work is 65 years old and still lives on the family farm. He has been a GM tech all his life since he quit school in grade 10. He does some small scale farming and does mechanical work at home for many farmers. He and I have discussed this a number of times and he also says "no" to 4 bolt main 327's.

I think I am safe in saying that there never existed a 327 4 bolt main, as far as one coming out the doors at a GM manufacturing plant. The possibility of building one is 100%, because all you need to do is take a 350 4 bolt block and put in a 327 large journal crankshaft (same crank as a 307). However, there seems to be no small journal blocks at all, not even an L79.

As always, I'm open to proof that I'm wrong! But not speculation, there's been lots of that over the years but it's never been proven.

This is no slight against anyone who says they've heard of them, it's simply stating my own experience based on what I've seen. I have never seen one physically, or documentation to back up the proof of it existing.


 

I think you are correct on no 4 bolt 327 Engines that were ever factory built.

 

I would have bet there were no 4 bolt 305 blocks until I saw one.

 

454's never came in Grain Trucks either.

 

1968 Camaro TH 350

 

Typing practice over, good night!!

 

Thanks

Randy



-- Edited by GLHS60 on Monday 26th of November 2018 02:18:13 AM



Randy, it would be rare that I don't agree with you 100% but this time I have to.

There was a tall deck 454 in the grain trucks for a few years. I am thinking roughly 80-84 but I can verify it when I get a chance.

And by the way, it was awful, had a bad reputation for being down on power vs. the 366-427 and didn't last long in production.

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I've seen 454's in 3tons and school buses in the later '90s. Not sure if tall deck or 4 bolt main though.

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And. The 327 in my 2+2 is out of a '68 3ton. And it does have the large journal steel crank.

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I just confirmed in the books that it was 79-80 for the tall deck 454's. At least that's the only two years I could find with a parts listing.

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Carl Stevenson wrote:
GLHS60 wrote:

 

Carl Stevenson wrote:



This is no slight against anyone who says they've heard of them, it's simply stating my own experience based on what I've seen. I have never seen one physically, or documentation to back up the proof of it existing.


 

I think you are correct on no 4 bolt 327 Engines that were ever factory built.

 

I would have bet there were no 4 bolt 305 blocks until I saw one.

 

454's never came in Grain Trucks either.

 

1968 Camaro TH 350

 

Typing practice over, good night!!

 

Thanks

Randy



-- Edited by GLHS60 on Monday 26th of November 2018 02:18:13 AM

 



Randy, it would be rare that I don't agree with you 100% but this time I have to.

There was a tall deck 454 in the grain trucks for a few years. I am thinking roughly 80-84 but I can verify it when I get a chance.

And by the way, it was awful, had a bad reputation for being down on power vs. the 366-427 and didn't last long in production.


 Sorry Carl, I mentioned the other oddities things that are commonly disputed but true.

 

Thanks

Randy



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I know this is a total derail but you're saying a TH350 came in 68 Camaro?

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JC2+2 wrote:

And. The 327 in my 2+2 is out of a '68 3ton. And it does have the large journal steel crank.


 

 

Do you know what heads were on it? There were four of these high torque 327's in 1968. Three 240hp 4BBL versions with 8.5:1 compression (flat tops with I believe 75cc heads), the difference being AIR on manual engines (180hp net), CCS (controlled combustion system) on auto engines (187hp net) or no emissions on 20-30 trucks (also 187hp net). The fourth engine was a 185hp 2BBL 8:1 327 (158hp net), used mainly in 50-60 trucks. Yours is most likely the 3rd one, ie no emissions 8:1 4BBL 240hp (187hp net).

 

Also which engine plant cast it (Saginaw, Tonawanda or McKinnon) and which built it (Flint V8, Tonawanda or McKinnon)? It may well be a mixture, I have seen 1967 passenger 327 4BBL engines with Saginaw block, McKinnon assembly with Tonawanda heads and intake.



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I only got the short block so not sure on original heads and intake. But definitely has the 8.1 pistons. And using the '68 double hump 291 heads with factory cast iron 4BBL intake.

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JC2+2 wrote:

I only got the short block so not sure on original heads and intake. But definitely has the 8.1 pistons. And using the '68 double hump 291 heads with factory cast iron 4BBL intake.


So it has the dished pistons? Cool, they drop 1/2 point of compression over flat tops with 75cc heads so you with the 291 64cc heads you will be sitting around 9.3:1 or thereabouts (the L30 (275hp 327) claimed 10:1 with flat tops and 291 heads but they are about 9.8:1 (GM rounded up almost always with compression)).

 

What engine pad suffix is it? ie V0420HI for example.



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Carl Stevenson wrote:

I know this is a total derail but you're saying a TH350 came in 68 Camaro?


Yes some were made. Not many though, maybe 70 or so and only behind L30 (327/275hp) engines. They were an evaluation car, used internally and probably sold off into the used car market in 1969 when the TH350 became the norm. The engine had an EN suffix code rather than the normal EE found on the Powerglide engines.



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On a further 327 note.....

Has anyone come across a 1968 SBC suffix code of H1, H2, H3 or H4?

I have seen H3 in the GM archives, can't find it again though, been looking again to see where it was. It was on a loose sheet of paper attached to the Engineering technical stuff. Edit - just found it, it was actually on a COPO 1968 307! It appears that the letter actually normally means a variation in distributor from normal.

We got H5 in Australia, which is a 1968 L73 (327/250hp) with Saginaw 4spd 2.54:1 1st gear in Holden HK GTS327. For H5 to exist there must have been H1-H4 at least. The very first of the H5 engines were assembled on 19th March 1968 at Tonawanda and being that late in the 1968 model year must have been close to the last H code. We believe that the 1969 year model codes must have been issued already and they'd used all of them up along with re-using some (like HH and HZ), the last being HY and HZ for the 1966-7 COPO 4BBL lower compression 327, hence the use of H1-H5 at least. This is probably why the change to 3 digit suffixes soon after, maybe?

 

The H5 cannot mean a variation in distributor on the GTS327 engine though, as it got the standard L73 distributor (1111150), the variation on this engine is the sump/pickup and the LH side Ramshorn exhaust manifold (angled backwards rather than straight down) 



-- Edited by HK1837 on Monday 26th of November 2018 05:09:42 PM

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