If it is a 4 bolt and has its original number on it someone stuffed up at the Dandenong assembly plant and stamped A instead of M.

Although having said that it could simply be an error at the Tonawanda assembly plant where they used a 4 bolt block by accident for a 2 bolt application.

I wouldn't be too concerned putting a 350 in your HT. I have a HK GTS V8 auto, it is currently the oldest known V8 HK GTS recorded. I'm putting a 350 or a 427 in it, pulling the 307 Powerglide and banjo out over Xmas and storing it.

Edited by user Wednesday, 11 July 2018 4:46:47 PM(UTC)  | Reason: Not specified

Ben at HHS for the contact about the car. It is a car that will interest Ben as he is a HT fan, he has one of the rarest of all Monaros, an early HT 5litre manual which also has air and steer. Agree it is a good car to have, but I'd save your $ on restoring a 307 driveline, and use any SBC in it. But that is just me, once the original engine is gone can't see the point in fitting the wrong 307 back in. I would have had a perfect 307 for it too if it was a Pagewood car, and all my 307's bar one are from Pagewood vehicles so no good for you anyway.

Just looked at your block on Gumtree. It has been restamped, and that number is not original to that block. It is not from a GTS350 as it is a McKinnon cast block. Scratch at the cast number too to make sure it is original, reason I say that is I have NEVER come across a Canadian cast 618 block! Or for that matter a 4-bolt Canadian block from 1969! As far as I was aware McKinnon only made 2 bolt engines at this time, but there is still stuff to learn on these. Does it have 618 under the timing case cover too? You can see the McKinnon mark in the 4th picture between the cast number and the 3, plus the date code is on the side of the block and in the Canadian format.

A wave of an oxy flame across the engine number pad should reveal the original engine number too.

Because it is a Canadian block, but other stuff also like the font and the fact it is 350A on a 4 bolt block.

Plus the elephant in the room is the cast date is later than the completion date.

Edited by user Thursday, 12 July 2018 10:26:49 AM(UTC)  | Reason: Not specified

I suspect your engine number is real, but someone has stamped it into an imported block, probably after a failure. If you chase AOMC up and do a search on the engine number you will probably get back the chassis number of the car it was first registered in. So chase them up with both 350A47xxx and 350A47xxxT0612 and see what you get.

Not sure what you mean by Fuelie humps on the block? That is a head thing. In a passenger car this block would have had Fuelies on it, either 186 or 041 depending on which assembly plant assembled the engine. In passenger cars 4 bolts were only used on 290hp upwards for 1969 model engines, which means only L48, Z28 or L46. My guess is it was cast for the Flint V8 plant to assemble, as I have seen 186 cast heads cast at Tonawanda but machined and assembled at Flint V8 too. Flint V8 never cast its own stuff, it mostly came from the Saginaw casting plant, but this time in 1969 was a turbulent period with strikes across various GM plants which caused GM to cancel 1970 models which would normally see start of manufacture in August 1969, and delay 1970 model introduction until January 1970. This is why 1970 Camaros are called 70 1/2 models. So it is possible that Tonawanda and McKinnon were asked to cast stuff for Flint.

But as it has the clutch Z-bar setup on it, it probably was a truck block, these are 4 bolt but can be 2BBL. So in that case it may well have been McKinnon assembly too. But I'd put money on it being either Flint or Tonawanda assembly. We regularly see Tonawanda assembled L48 engines that use Saginaw blocks, so this could be another source for the 618 blocks not yet seen, or it only happened for a short while due to strikes etc as already mentioned.

Hi all, an extra 2 photos have been added to my Gumtree Add. I got caught out by the 4Gb. limit for photos, so they did not go on. Thanks.

All 4 inch bore blocks were the same at that time depending upon what engine plant foundry they were cast. They machined them for both 2 and 4 bolt applications. A 1969 Z28 290hp 302 uses the same block as a 1969 350hp 350 in a Corvette or the base 4 barrel 300hp engine (what we got here as manual in HT). Even the 2 barrel L65 350 used the same blocks, just as a 2 bolt.

There were no large journal 283 crankshafts, those 1968-1969 3" stroke large journal cranks are unique to 302. Only the 1967 302 used a 283 crankshaft but in a 1967 327/350 block.

All 1969 model year L48 (300hp 350) were 4 bolt regardless of whether they were cast in Tonawanda or Saginaw foundries, as far as I'm aware all the 4 bolt caps are the same. Only the 1967 and 1968 (295hp 350) were 2 bolt (there were no 4 bolt blocks until 1969 engines). Other than those few months of 1968 (Aug-Dec) where LM1 engines were produced all 1969-1970 4BBL 350 engines were 4 bolt, as were all commercial/truck applications for any hp. The 1968 dated 386 4 bolt block I have for my HK was from a C20 or K20 - it is a Saginaw cast, Flint machined 4 bolt block.

The main source of 2bolt 4" bore blocks (386, 388 or 618) you'll find from 1969-1970 vehicles is passenger L65 engines (2BBL 350) or those few months of LM1 production late in 1968 (L65 with L48's intake and carby - our auto GTS350 engine). There were also some 327 210hp engines used in Camaro in early 1969 year model Camaro and these are 2 bolt 386/388/616 but this engine was gone by October 1968 and replaced with the 307. There was also a 327 235hp in full size 1969 Chevy that used 2 bolt 386 or 618 or 388 blocks. Other than that the 2nd type GTS327 is a 2 bolt 386 and I know of no others.

The fact yours is Canadian cast is a mystery, but so is the Canadian cast late GTS327 block that is a 386 cast - both of these should be Saginaw only castings. We do know that around April 1970 the 010 blocks started to appear, so it is possible McKinnon got Flint's old patterns and were using them for a while.