27 replies to this topic

[Kockum]

Some on here say  - no .

 

I say - yes.

 

There are two versions of this head .

 

Version -1

 

Standard LJ XU1 inlet valve 27F3 heads. 

 

This is what I have .

 

Why ? there were no more C233 heads left when my engine was factory assembled.

 

 

Version - 2

 

large inlet valve 27F3 heads fitted to some of the listed type cars.

 

Remaining listed type cars had large inlet valve 20F3 heads .

 

Were there standard LJ XU1 20F3 inlet valve heads made ? - I don't know .

 

These 27F3 heads were factory fitted to a number of good honest cars with known documented history so no tainted 'RESEARCH'  is required.

 

If you have a 7/8/9 month car with a SINGLE OR DUAL DATE CODED ENGINE BLOCK THAT HAS AN UNTAMPERED WITH ENGINE NUMBER PAD AND THEREFORE GENUINE HOLDEN ENGINE NUMBER STAMPING TNEN CONGRATULATIONS. Ditto for all earlier LC/J XU1 cars.

 

However if you have a restamped engine number and try to pass it off as a GENUINE ENGINE NUMBER STAMPING THEN YOU ARE LOWER THAN A SNAKES BELLY SO SLITHER BACK UNDER THE ROCK YOU CAME FROM.

 

One more point - if any forum members that are currently on a well deserved  holiday from the forum want to get down into the gutter upon returning I will not join you in the gutter.

[S pack]

Hi Graham, I'm surprised your engine reconditioner didn't suggest installing hardened steel seat inserts to remedy the valve shrouding problem.

 

[S pack]

Sounds like an expensive lesson learned.

 

Cheers

Dave.

[FLY_AGAIN_XU-1]

Over a 35 year period I have owned 14 second hand 27F3 heads with all having the larger inlet valves fitted. I have also owned 6 second hand 20F3 heads with all having the smaller inlet valves fitted. I have also owned 3 NOS bare 27F3 heads. I have never heard or seen of a NOS 20F3 head. Over this period I have seen around 6 NOS C233 heads with the last being for sale on ebay. A forum member " Fat Tony " had it. Of the last 30 1973 homologation specials I have viewed being genuine cars with their original dual cast blocks they have all had 20F3 heads fitted. I have been lucky enough to have been able to remove 2 heads off these cars. One being a non listed 8/73 and the other being a listed 8/73 car. Both were found to have the smaller inlet valve with no fly cuts. Speaking to Dave Bennett from Yellow Terror who was assigned with the machine work for these heads, he told me that he never started work on these heads until September 1973. Which makes it all but impossible for any production XU-1 to have one of his heads fitted while these cars were being produced. Dave Bennett also told me he was still doing these XU-1 heads when he was assigned with doing the L34 heads. He handed around 75 bare 27F3 heads back to GMH. Over a 35 year period I have owned 3 NOS bare 27F3 heads but have seen close to 40. I only know of 1 complete NOS 27F3 with the larger inlet valves which is owned by a former racing identity in Sydney. These were the heads he used on his Group C race car through out 1973, 1974 and 1975. The 27F3 also has a higher deck height compared to the production 20F3 and was available as a spare part in 2 forms, a complete head with larger inlet valves or a bare head. Please refere to homologation 9/2E. Your call to what you want to believe, this is just where my research has lead me.........

[FLY_AGAIN_XU-1]

The 27F3 is the perfect head if you want to run the larger inlet valves ( More Meat ) and combined with a duel cast block ( More Meat ) forms a great basis for a very strong high performance Group C engine............

[Kockum]

hommie1973,

 

thanks for confirming you had a 20F3 with standard LJ XU1 inlet valves .

Edited by Kockum, 20 December 2015 - 05:11 PM.

[Kockum]

FLY_AGAIN_XU-1

 

I have a 27F3 2815843 head with standard inlet valves.

 

These may be hard to find - there must be more out there.

 

Comparing the bolt boss width of my head to photos of other 2815843 heads up to and including C233 this head has a thinner bolt boss.

 

No grinding of inlet port area evident at all.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FLY_AGAIN_XU-1

 

ALL I can tell you is that I have a 27F3 2815843 head with  standard inlet valves .

 

They may be hard to find and there would have to be more out there.

 

Mine has the reduced cylinder head bolt boss when comparing it to photos I have of 2815843 heads up to and including C233 .

 

No grinding of the inlet port area at all .

 

 

 

 

 

 

 

 

 

 

 

-

Edited by Kockum, 20 December 2015 - 06:01 PM.

[Kockum]

Buggered this post up - the first part or the second part should be there .

 

NOT BOTH.

[FLY_AGAIN_XU-1]

Of the second hand 27F3 heads I have owned over the years, all had been modified in some way. Some had mild port work, some had wild port work. Some had there posts die grinded for better air flow, some had even had there cast posts totally removed and a very thin type pipe inserted. Most had also been heavily decked.

 

Quote 9/2E

 

revised o,all height - as per dimension supplied herewith 3.15+.020 (was 3.18+.010).

 

End Quote 9/2E

 

Even though the 27F3 had more meat in standard form, with this homologation the race teams were then able to deck there heads even further than before, thus adding extra compression and horsepower.

 

Of the 20F3 heads I have documented, they have had 2 different numbers next to the H at the back of the head, 8H and 9H.

Of the 27F3 heads I have documented, they have had 4 different numbers next to the H at the back of the head, 9H, 10H, 11H and 12H.

[S pack]

Of the second hand 27F3 heads I have owned over the years, all had been modified in some way. Some had mild port work, some had wild port work. Some had there posts die grinded for better air flow, some had even had there cast posts totally removed and a very thin type pipe inserted. Most had also been heavily decked.

 

Quote 9/2E

 

revised o,all height - as per dimension supplied herewith 3.15+.020 (was 3.18+.010).

 

End Quote 9/2E

 

Even though the 27F3 had more meat in standard form, with this homologation the race teams were then able to deck there heads even further than before, thus adding extra compression and horsepower.

 

Of the 20F3 heads I have documented, they have had 2 different numbers next to the H at the back of the head, 8H and 9H.

Of the 27F3 heads I have documented, they have had 4 different numbers next to the H at the back of the head, 9H, 10H, 11H and 12H

There is a good reason why the larger inlet valve heads had their overall height reduced straight out of the box.

Also, where does it say in the CAMS regs that the race teams could run a compression ratio higher than that specified on the Cert of Description?

[jd lj]

In reference to the above post I know of two 27f3 LJ GTR heads one is 10L and the other has 11L at the rear. Moulds 10 and 11 (or whatever this signifies) must have been popular on that day.

[FLY_AGAIN_XU-1]

 

 

 

 

I am sure you all can make up your own minds........

 

 

In reguards to the LJ GTR heads jd lj, were these off late 1973 GTR,s ?

[S pack]

In reference to the above post I know of two 27f3 LJ GTR heads one is 10L and the other has 11L at the rear. Moulds 10 and 11 (or whatever this signifies) must have been popular on that day.

 

James

 

LJ GTR cyl heads are different to XU1 cyl heads so having the same pattern numbers is more coincidence than anything.

 

Cheers

Dave.

Edited by S pack, 21 December 2015 - 01:50 PM.

[RallyRed]

Hi Fly,

Sorry mate, but I did hope to read the part you refer to....but cant see it?

Can you detail the part where the comp. ratio modification is mentioned.

Thanks

[yel327]

It is there from what I can see. The words say: "The engine shall be unmodified except for...". Meaning you couldn't touch compression, not legally anyway.

[yel327]

More misinformation?

[S pack]

There's no mention on the 9/2e amendment form about an increase in the compression ratio for the 150 list engines.

The  Cert of Description (Recognition form) dated 3rd February 1972 states the XU1 202 compression ratio is 10.3:1  + .5:1 = max allowed comp ratio is 10.8:1 for all LJ XU1 202 engines.

Edited by S pack, 22 December 2015 - 08:15 AM.

[FLY_AGAIN_XU-1]

That's why GMH homologated a completely new engine............