6 replies to this topic

[grumpy xu1]

Hi all, a friend is getting a head done atm & needs to get valve springs to suit a early 73 xu1 cam, engine shop wants to know the original xu1 cam specs please.

[yel327]

According to the GMH Engineering Technical Specs the production cam is the same as the early one. All that seems to change from the August 1971 release specs is the cam was initially stood upright but by the December 1971 revision it was fitted with a 6deg timing change in the front gear, looks 6deg retarded to me but its early morning! All the other camshafts are possibly just homologation trickery? Here are all the revisions of the relevant page.

 

 D-19 August 1971.jpg   87.05K   10 downloads

 D-19 December 1971.jpg   79.71K   6 downloads

 D-19 October 1972.jpg   78.31K   4 downloads

 D-19 August 1973.jpg   101.5K   5 downloads

 

[S pack]

According to the GMH Engineering Technical Specs the production cam is the same as the early one. All that seems to change from the August 1971 release specs is the cam was initially stood upright but by the December 1971 revision it was fitted with a 6deg timing change in the front gear, looks 6deg retarded to me but its early morning! All the other camshafts are possibly just homologation trickery? Here are all the revisions of the relevant page.

 

D-19 August 1971.jpg

D-19 December 1971.jpg

D-19 October 1972.jpg

D-19 August 1973.jpg

The exact opposite actually. The camshaft was retarded 6 deg in the LC XU1 and stood up straight in the LJ XU1.

[yel327]

I did say it was early morning! I believe you are correct.

[Bruiser]

 IMG_0790.jpeg   75.28K   10 downloads

The 373 is the HX, and the 391 is the XJ

[yel327]

It's interesting that Wade say the first cam was only a small production run? Isn't that the cam fitted to all LC XU1 until the final lot with the HQ engine coding on them (ie CK rather than 3100X)? That would mean GMH started making them themselves, which in turn might explain why they used that same cam in the ADR27A auto engines?

 

They probably state that the middle one was known as the "186 Bathurst" as it was used in those final LC XU1 and onwards.

 

I wonder what happened to all the "thousands" of XJ camshafts? GMH must have had a lot in GMP&A spares. Unless Wade made a mistake and meant that the 391 camshaft was a limited production run?

[S pack]

Yes all 3100x LC XU1 had the same camshaft so I believe Chris got a little mixed up about the production quantities. The shortest production run would have been the 5/5V homologation XJ camshaft.

Edited by S pack, 28 May 2024 - 11:55 AM.