20 replies to this topic

[Screamin]

Hi folks.

Took a risk today and bought a 308 for my LX. It has a QT number 786728 with 308 cast on the block. The heads say 3H6 which from googling seem to be HG HK.

Are these heads the same as the HQ as it seems the extractors are different fitting to later heads from my google searching.
I do have a running QR 253 I could swap heads from if I need to although the 308 has extractors with it. Pro comp distributor which I believe are pretty crap. I was thinking the VL electronic might fit.

I’t has an ‘Action ‘ branded intake manifold and Ross pulley set up. Excuse my ignorance but I’m keen for some info. WS told it was rebuilt and crank rods and pistons look pretty clean. I will post some photos.
Cost me $1900 so with the risk I think. Was in a modded commodore.
Thanks Richard

[Screamin]

Photos

[Screamin]

Sorry folks no idea why photos won’t upload. Reduced size but can’t select. Richard

[mick_in_oz]

Need pics...

 

Roughly speaking there are two head styles, Carburetted and EFI, carb heads have siamesed exhaused ports in the middle of the head, EFI heads have evenly spaced ports, any carb exhaust will bolt to a carb head, one pattern only.

[S pack]

3H6 is most likely the 3rd day of August 1976. Which means the heads are HX Holden & LX Torana ADR 27A type.

I'm guessing engine number QT786728 will have a cast date that is from around the same period as the heads.

[Bigfella237]

QT786728 is probably out of a HX Holden, around August '76 but would need the cast date off the front of the block (between the timing cover and the inlet manifold) to confirm.

 

Could be an Aussie or Chev bolt pattern, depends on whether it came from a manual or auto Holden (but not a Statesman).

 

Would also need the cast part numbers off the heads to confirm but a '76 cast date on them indicates that they may be the original heads from that motor?

 

If they are the original HX items then they would be ADR27A heads, so not exactly interchangeable with HQ heads because of the EGR ports. But the extractors should be the same.

 

EDIT: Doh, I must type too slow

Edited by Bigfella237, 09 April 2019 - 08:10 PM.

[S pack]

QT786728 is probably out of a HX Holden, around August '76 but would need the cast date off the front of the block (between the timing cover and the inlet manifold) to confirm.

 

Could be an Aussie or Chev bolt pattern, depends on whether it came from a manual or auto Holden (but not a Statesman).

 

Would also need the cast part numbers off the heads to confirm but a '76 cast date on them indicates that they may be the original heads from that motor?

 

If they are the original HX items then they would be ADR27A heads, so not exactly interchangeable with HQ heads because of the EGR ports. But the extractors should be the same.

 

EDIT: Doh, I must type too slow

I probably started typing before you Andrew however your post expands on mine so valuable info for the OP.

[Screamin]

 20190409_204032.jpg   125.53K   7 downloads

[Screamin]

 20190409_204401.jpg   111.42K   5 downloads

 20190409_204226.jpg   134K   5 downloads

[Screamin]

 20190409_205435.jpg   143.72K   4 downloads

 20190409_204135.jpg   115.26K   5 downloads

[Screamin]

Apologies had to take photo secondhand off phone.

Do the lathe type marks in the crank mean it was machined for some reason- balance etc?

[Screamin]

 20190409_204135.jpg   115.26K   5 downloads

 20190409_204135.jpg   115.26K   5 downloads

Attached Files

•  20190409_210206.jpg   89.88K   8 downloads

[S pack]

OK, so the block cast date is 3H6 and the heads are HQ/HJ pre ADR 27A type.

[S pack]

OK, so the block cast date is 3H6 and the heads are HQ/HJ pre ADR 27A type.

Correction. The OP is correct, the heads are the rarer HT/HG units. HQ/HJ, LH (exc L34) & early LX have a 281**** cast number.

[Bigfella237]

 

I can't quite make out that part number, is that 7449034?

 

Are both heads the same part number? And what are the date codes cast into each of the heads?

 

P.S. I note it has ARP head bolts so that's gotta be a good sign!

[Screamin]

It appears one head is 281217 and the other 744903.
Early and late I assume. Guessing this is not an issue?

[Screamin]

The bolt patter is as shown. I am assuming turbo pattern.

The roller rockers don’t say yells terra but look same as there street version?

Attached Files

•  638CEA00-BF0F-45E2-8F1F-976B59DF26C8.jpeg   159.15K   5 downloads

[Screamin]

The rolled look similar to yella terra street terra minus the yella terra writing. Did yells cast minus the logo?

[Bigfella237]

There should be a seventh digit on each of those part number castings (something like "7449033" and "2812174")?

 

Yeah, looks like one very early non-pollution head and one early EGR port head... bit of a mish-mash but the only trouble that might give is with exhaust gases coming out one of the bolt holes on the inlet manifold if it's one of those cheaper 'universal fit' jobs with the three centre bolt holes?

 

There should be date codes on each head as well similar to the engine block code, the 744 head may have the old format code (a letter followed by two or three numbers), but the 281 head should be the newer format code (one or two numbers, then a letter, then a number).

 

And yep, definitely the Turbo-Hydromatic bolt pattern block, it must have come from an automatic HX Holden then, but not a Statesman as they had the "11" prefix (ie "11QTxxxxxx").

 

Not sure about the rockers, but I would've thought all YT stuff would've had their brand on it?

[S pack]

281**** cast heads are HQ/HJ, LH & early LX heads, they are pre ADR 27A and do not have EGR ports.

I don't know what the exact differences are between the HT/HG 744 &  HQ/HJ 281 cast heads are but it cant be all that much.

[Bigfella237]

Ah thanks Dave, my bad. I had 2812174 listed twice on my list for some reason

 

EDIT: Just thinking about the difference between HT-HG 253/308 - 7449033 and HQ-HJ 253/308 - 2812174

 

When did they drop the two extra head bolt bosses in the valley?

Edited by Bigfella237, 11 April 2019 - 09:46 AM.