4 bolt main small journal block with 2 bolt caps
 

While helping this good friend of mine with rebuilding the engine in his 1970 GTO, I ran across something I had never seen on a small journal block before. It has the outer holes for 4 bolt main caps drilled and tapped, but only has 2 bolt main caps. I have seen this dozens of times on the 3.25 inch main blocks (my own '73 455 engine in my '66 is like this), but I don't recall ever seeing it on a 3 inch journal block. The engine is a 1970 400, with number 48 heads on it. Block casting 979914. Running across a lot of interesting Pontiac stuff lately. A few weeks ago it was a '73 455 that had 4 bolt mains installed on it out of a Grandville, now this.:)

I have seen both ways on the 400 blocks starting around late 1968-1969 time frame.

Personally my favorite 400 block is the 'lowly' 67 2 bolt main (non drilled for 4 bolt mains) block as you can add splayed caps fairly easily but $$$.
The other benefit is that the 2 bolt mains will be fine for many levels of street cars and the main webs are a lot stronger without the extra holes drilled in the block webs.

You have run across some interesting stuff like the '73 455 that had 4 bolt mains installed on it out of a Grandville. When the cars were going down the line and the 2-bolt main 455 block engine was not right there at the moment, the 4 bolt main block engine got installed.

Tom V.

Same on my numbers matching RAIII 400 block in my '70 Trans Am (automatic car). Outer holes for 4 bolt main caps but only had 2 bolt main caps.


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I have heard that the '67 2 bolt block is the best out there in terms of overall strength for an engine that bolts into the newer cars with Turbo hydramatics without issue. :)Just curious your opinion on this. Would installing short bolts with loctite in those open holes help the durability of the block? Never had an issue with my 2 bolt larger main 455 in my own car, but it is only at about 450 hp level. This person plans on adding a stroker kit to make a 461 out of it. He has a two bolt '69 grand Prix 400. I told him that would be a little bit better choice for a stroker kit. (The GPs engine did not have the outer bolt holes). He is also considering line boring it and adding Milodon main caps. The car has a 4 speed and drives it pretty hard. Thanks Tom for any input you may have.

Use ARP main stud kit. Pro-Gram Engineering main bearing caps are also popular.

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Good advice.

my '70 YD 2bbl engine with 16 heads is drilled and taped for 4 bolts, but only 2 bolt caps.

funny you mention the '73. my buddy got a 455 out of a '73 Grandville with 4 bolt caps on it.

All 400 blocks from 68-73 or 74[somewhere around there] that I have seen have 4 bolts drilled and tapped but only use 2 bolt caps. Very common, nothing special.

My 70 Trans Am Ram Air III was also this way. It was a WS block. Back in the day, I questioned whether someone had changed the caps for some reason. Later found out this was quite common. Saved Pontiac the cost of 6 bolts, and a tiny bit of iron to make the larger caps. Possibly $1.00-2.00 per car. That was a big savings at the time. Kinda makes you sick doesn't it?

Ford did a similar thing using four bolts on the wheels instead of five.


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very very common in 1970 blocks, I have not seen a 1970 400 block that did not have the extra holes.

Guess I haven't seen it before because most of the 400s I have messed with were either 1967-68 models or later mid to late '70s 400s. As well as 326s, 389s, a 421 and 455s.

My '72 YS block(GP) is drilled and tapped for 4 bolt mains, but my '72 YX block(Catalina) isn't. Has anyone ever heard an explanation as to why PMD did this?

I have info that states that all 1970 ra3 motors with a 4 speed in back should have been 4 bolt main.

This. I've disassembled a number of 400s from the late '60s and early '70s and all but one have been drilled for 4-bolt caps.

The one I have that is not drilled is a '74 block and it also appears to have the thickest main webbing I've seen. Should make an excellent foundation for my next 4" stroke build.

I read that same information. That's why I was so surprised when my WS stick Ram Air III had 2 bolt caps. My friends 69 Judge Ram Air III stick had 4 bolt caps. Go figure.
Almost feel they threw whatever caps they had lying around in the bins when the block came down the line. Seems to be very random. Years ago I disassembled a 400 2 bbl. and was stunned to find 4 bolt caps on it. Just weird.

I have a spare 400 (XH code) engine out of a 1970 Grand Prix that only has 5 of the 6 extra drilled and tapped holes. The 6th hole is only partially drilled. Drill bit must have broke during the drilling operation and because it was to have 2-bolt caps it wasn't worth reprocessing the block to complete the drilling and tapping of that 6th hole.

We (Marty, Bill Klausing, and I) located a 67 2 bolt main block in the late 1994 time frame.
Marty added splayed 4 bolt main caps from ProGram. (Think Marty had it 'vibra-shaken' to remove stresses in the block before the main caps and machining (caps installed).

The engine with a 250 cfm head (closer to 240) ran 6.96 et at 206 mph and lived for 3 years under high boost. It did have my old RA-IV SD forged crankshaft (prepared by Moldex). Old design Diesel Turbos and no head gaskets. Special sealing rings were installed.

At the time Donavan was the fastest pontiac out there and on the first full pass at Norwalk (with the trans skipping 1st gear and running 2nd and third gears) the car went 7.40s at 194-196 mph. With a JUNKY 2 bolt main production factory pontiac block casting.

I have a lot of respect for those 67 2-bolt main blocks as that was a real durability test on that thing.

So that is why I say it is the best common block out there.

Tom V.

We brought the Grocery Getter out in 1996 with three 1972-1974 455 stock blocks. Using Program Engineering caps. The crankshafts were stock Pontiac N cranks, carefully prepared by me with no surface treatments, just nice oil holes and large radius. Lots of tuning errors with the nitrous. Lots of time spent learning the ignition timing the engine really wanted. Even a quarter mile run starting in 2nd. gear with all that nitrous when a shift linkage part failed. Never made the kind of power Marty made, but I would argue, we may have been just as abusive to the block. We were right at 1000 HP which was allot in those days. All three blocks did eventually fail and they all failed in the same area. Right up the oil passage at the #2 oil feed drilling from the main saddle to the cam bearing. At least for us, that was the weak spot in the 455's. Overall, the Pontiac block is very tough. By the way, no lifter brace in any of the blocks. Roller cam though with .850 lift and 260 lbs. on the seat back in those old days. We also ran our blocks unfilled. Didn't want the weight, didn't want the bore distortion, did want the cooling.

70 RA III and RAIV blocks were 4 bolt mains.Tom

Who knows, Pontiac in the late 60s may have been getting stingy with the 4 bolt caps, as they where Armasteel, not the plane cast of the 2 bolt caps!

Marty had a NA block 455 HO I believe, that was run at Norwalk, 740 HP range, just prior to the Turbo project. He decided to stop racing the engine 'one pass before the engine failed' (He drove the car on the trailer and we saw the failures when the engine was torn down).

All three center 4 bolt main caps were cracked. #3 was starting to crack up the inside bolt hole in the main cap. #4 was cracked about 1/3-1/2 of the way up the inside bolt hole, and the #2 main cap was cracked all the way up the hole on one side.
The outer bolt and the center stud and nut/washer were the only things keeping the cap in place. It was now a 2 piece cap.

So my visual inspection of the block/main cap failure said: that the #2 main failed first, then the #4 main, then the #3 main was soon to follow.

That fits exactly with your failures in the "#2 oil feed drilling from the main saddle" with your 455 engine blocks, Mike.

Tom V.

Mike, would you have any block info on the WS?
(the engine unit number, cast date code, etc?)

Never heard or seen a WS with 2 bolt caps.
:eek:

Steve's YZ maybe, but I would think that would be an anomaly also?

Steve any block info on it?

Were these late year TA's?

1970 generally was the only years I have seen the 4 bolt drilled blocks, with 2 bolt caps.
(but doesn't mean much either :D)

:)

According to old records from 1982 my '70 Trans Am is vin 228870N115457, motor number 0518873, 9799914 YZ block. On cowl tag 22387NOR729068 BDY

And now looking at these records I think I was incorrect about the main caps in my previous post. These old notes say 4-bolt main. It came with a TH400 trans.


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On paper, at least. As mentioned, my 70 TA Ram Air III was drilled for 4 bolt caps but had 2 bolt caps on it. I was the second owner, it was a low mileage, numbers matching car. Who knows. It was a 4-speed car.

I owned that TA from Feb. 1977 to spring of 1988. I do have a photo album and possibly some block pictures. I will give it an honest look later today. I am certain I do not have the VIN, Production date, or block numbers. We just didn't care in those days or I was too stupid to care. Also, at least for me, I didn't take anything apart unless it was broken.

Tom, Marty was so very lucky he put that car on the trailer when he did. Some kind of divine intervention. One more run would have been total engine destruction. No doubt the flexibility of the Program Engineering steel caps helped keep our lower end together along with the aluminum rods and light pistons.

I was truly amazed when he showed me the engine.

A perfect example of where the failures started and the sequence of the failures.
One in a Million for sure.

Tom V.

By the way, this is a WT block.

I looked at my small album of pics I still have of that car. I need to scan them to make them easier to share. I have no pictures of the engine out of the car. Just a few pics of the underhood with engine installed. I don't think PHS was around in those days, the car cost me $1500.00 and it was a decent running car. I do remember the 2 bolt caps and being surprised. If no one else has seen this, then I would guess either the caps were changed, I would have no idea why, or it was a WS block from another year or model swapped-in before I bought the car. As I recall, the car only had 65K or so miles on it and it really looked like the engine had never been touched. Wish I would have been smart enough to have really investigated it. At least around here, nobody really cared about all this stuff in the late 70's, early 80's. We were just puzzled for a few minutes and went on to the next project.

Steve,

Where did you find this info?

" I don't think PHS was around in those days"

I bought my 72 Formula 455HO around 1981 and I called Pontiac back then and was able to get production numbers on the car. I still have the notes and the phone number I called to get the info. I think the department I reached is what PHS is today or where all that info came from or basically somehow connected.

1800PMCARES was the pre PHS way to contact for production numbers. Late '68 up into mid '70's Pontiacs. No earlier info tip PHS got going, also no invoice copies on late '70's. When PHS started, was $35 a pop.

Have owned several original '70 YZ blocks & engines & upon disassembly all had factory 4 bolt caps. First one I bought was as a decent running engine. Original RA carb to pan for $400, that was '84, I believe. Ended up tearing it down, still had original freeze plugs & original Morraine 400 bearings. Have to dig out records, seem to remember it having an E220 dated block.

Happy Thanksgiving OPH! Talk about bringing back memories.

I also called the 1800PMCARES number 1-800 762-2737 many, many years ago.

I talked to a very nice Lady there and told her my uncle owned a Pontiac Store.
I said I was trying to get information on my 64 GTO. She asked where the car was built, KC, and I gave her the VIN Number.

I said that my uncle was a friend of the National Sales Manager and I had received the car thru him. It was previously a Zone Car for the St Louis zone.

A few weeks later I received a Pontiac Motors Envelope with my GTO info in side.
All of the info was hand-written (one option at a time) and described each option in detail:
(The codes and what the codes meant for my GTO based on the info in HER records.)

Some years later I paid the money for the PHS stuff after talking with Jim M at a Pontiac event. As many now know the info did not line up correctly for a 1964 KC built GTO.

The Lady from Pontiac Motor's info was spot on. So again, if you have a KC built 1964 GTO there might be info that does not match with the PHS info.

I believe that the PHS info after 1964 is much more accurate for the KC built vehicles.

Tom V.

I really wish I had asked Mr McKeller a lot more questions (when he was alive and at the local car shows) about the engine stuff.
He could probably recite it "Chapter and Verse". PY is great for the posts and info. I hope someone is saving all of the info somewhere.

Rocky, you mean about the Armasteel main caps?

Yes

It's from a 1970 Pontiac A body drivetrain spec sheet.
I will post it up here tomorrow for you.

Thanks, Steve. I think we may have the same source, but I would be interested in seeing yours regardless.

This may shed some light:

Yes Ken, that's a part of the info that I have.
Mine is 3 pages from a 1973 Motion performance catalog.
They where located in Baldwin LI.

So if you have a Block with a Manual Trans block code and it was installed in a RA-III or RA-IV car with a Manual Trans, you probably got the better "armasteel" grade cast iron caps vs the normal iron block grade cast iron main caps.

That "armasteel" grade cast iron has fooled a bunch of people over the years.

"Much of this results from GM's marketing efforts to apply a certain mystique to standard engineering materials. First, Armasteel is not steel but a GM trade name for a grade of pearlitic malleable cast iron. As a 1982 GM brochure explains, it is a ferrous alloy with temper carbon in a matrix of tempered pearlite or tempered martensite. It was produced at the GM Central Foundry Saginaw Malleable Iron plant (SMI), which was closed in mid-2007."

So still a cast iron main cap block deal.

Tom V.

Excellent point, Mr. Vaught.

According to the 1970 Performance brochure all 1970 GTO/GP V8´s exc. non-R.A. 400 w/A.T. got the "armasteel" 4-bolt caps.

I wonder if that scheme carried through to the F-cars in 1970? Using different cap materials did carry over at least to Chevrolet. Not sure about Buick and Olds. HP SBC's had what they referred to as nodular iron caps. They would often lose their register when overheated or if they spun a bearing. You could put them in a press and gently squeeze them back out so the registers would fit tight again, then line hone them. The regular iron caps would usually crack when much pressure was applied.

In regards to Pontiacs I think it was across all the body types!

Here is the factory 1970 motor / drivetrain info I dug out.
Take note how the factory calls out a near 10cc chamber volume difference as only making a 1/4 point change in the motors compression!

interesting thread here...

This has actually intrigued me some;
I have previously understood that most 1970 400 blocks were drilled and tapped for four bolt caps;
But generally speaking only the "YZ"-L74/at, "WS"-L74/mt, & "WT"-L78-mt blocks received the four bolt caps - and even then, not all received the four bolt caps;
I have read that the likeliness of a WS blocks getting the four bolt caps was pretty much guaranteed;
I have read that the YZ blocks getting the four bolt caps was almost all the time;
I have read that the WT blocks getting the four bolt caps was more common than not...

I have never previously read of post-1970 400 blocks being drilled and tapped for four bolt caps.

I have never read of non-SD post 1972 455 block being drilled and tapped for four bolt mains;
And have understood that some 1971 non-455HO blocks were drilled and tapped...

I have a 1972 "WS" 400 block (complete & running) as well as another 1972(? maybe 1971) 400 short block that I am now curious to check for main caps...

I have a 70 YZ RAIII auto that has 4 bolt mains and my 70 WT 4 speed had 2 bolt, so there may not be any rhyme or reason with PMD

This is a 1970 WT block drilled for 4 bolt caps but had 2 bolt caps installed. My 1973 455 in my '66 Tempest Custom wagon came out of a Grand Safari. It has 2 bolt caps on a block that is drilled and tapped for 4 bolt mains. I recently helped another buddy of mine with a '73 455 out a a Grandville convertible that had 4 bolt caps installed.

All car 409 blocks came with 2 bolt Armasteel main caps. I think I even saw Armasteel on a posi carrier also.

Skip, are you sure these 2 bolt caps test out as not being plain gray cast iron?