39 replies to this topic

[S pack]

Are any of these factory/Repco L34 X rods forged? There are there so many examples of people stating they are forged? If they are all just cast are the L34 small X a beefier rod or basically a standard rod with the 3/8 bolts?

They are all forged steel. Even the Holden 6cyl conrods are all forged steel. 
 

[yel327]

Another interesting tidbit is that some 350 Chev rods had the X as well. These were mainly fitted into 1970's truck engines and the X was cast into the cap.

 

X rod Chev. Small x stamped on cap. Usually found on Blazers and C20's 3.png

 

When you go looking for info in the USA, and you find people that know what they are talking about. The rods with the X later O cast into the cap were normally used for high torque or high power engines, just like 4 bolt mains or forged crankshafts. The rods themselves appear to have started out the same as other rods but were machined and given extra shot peen treatment, plus it sounds like they had most of the balancing pad removed. This is one quote from an old dude that worked in the Van Slyke Road V8 plant (this is the plant built in Flint, Michigan for the new 1955 SBC V8, separate to the Flint engine plant that was a 6cyl plant, this is partially why Flint engines had an F and the V8 plant engines had a V in the assembly stamping):

 

X rods and "0" rods were used for the "pink" rod cores. Different production processes than regular rods.. They were always in separate baskets when on the assembly line floor. I used to be in the Chevrolet V-8 Van Slyke engine facility back in the day.

[Shiney005]

Are any of these factory/Repco L34 X rods forged? There are there so many examples of people stating they are forged? If they are all just cast are the L34 small X a beefier rod or basically a standard rod with the 3/8 bolts?

Definitely more meat around the bolts and at the little end.  

This is from GMH showing the difference between VL Group A A9L and VN Group A.

 

 Screenshot 2025-10-23 081254.png   333.08K   2 downloads

[Shiney005]

After talking to someone who is very much used to working on GMH V8's, the same X rod as the L34's (1st pic) were used in the higher performance variants of the 308 up until the 304 was released. The cap then changed to have the larger balance pad to counteract the slightly smaller stroke. (2nd pic) 

 

 X rods L34 have smaller balance pad on cap. Two types here..png   1.19MB   1 downloads

 

 

 Screenshot 2025-10-23 150331.png   933.16K   1 downloads

[yel327]

After talking to someone who is very much used to working on GMH V8's, the same X rod as the L34's (1st pic) were used in the higher performance variants of the 308 up until the 304 was released. The cap then changed to have the larger balance pad to counteract the slightly smaller stroke. (2nd pic)

X rods L34 have smaller balance pad on cap. Two types here..png




Screenshot 2025-10-23 150331.png

That explains the caps but what about the wider X? So the two sets of rods I have here are from a VK-VL 304. And the wide X rod has the correct cap for L34 or V5H 5.0L.

[Shiney005]

The fella with the bucket full of L34 rods (pictured above) had never seen a wide one until I showed him.  I am still leaning towards the early X block motors.

[yel327]

The fella with the bucket full of L34 rods (pictured above) had never seen a wide one until I showed him. I am still leaning towards the early X block motors.

Which were F5000 blocks?

[Shiney005]

I don't think so. The F5000 blocks were online in 1970 and featured revised water cooling passages as well as a different oiling system to the valve gear and smaller bore size. (302 ci) The heads were quite different as well, with smaller pushrod holes to allow for larger and higher inlet ports. In 1974, if you ordered the F5000 motor with all ancillary's, it cost as much as a complete L34!

The X blocks were all cast in May 1973, and I believe they were for the XU2 program. I have never seen the rear of one of these blocks, but I very much doubt that they have the extra webbing around the crank. some people say they all ended up in L34's, but I have only ever come across two, and in any case, I wouldn't want one in my car as they are inferior to the '74 blocks.  I am wondering now if they had a QT engine number.

[yel327]

I don't think so. The F5000 blocks were online in 1970 and featured revised water cooling passages as well as a different oiling system to the valve gear and smaller bore size. (302 ci) The heads were quite different as well, with smaller pushrod holes to allow for larger and higher inlet ports. In 1974, if you ordered the F5000 motor with all ancillary's, it cost as much as a complete L34!

The X blocks were all cast in May 1973, and I believe they were for the XU2 program. I have never seen the rear of one of these blocks, but I very much doubt that they have the extra webbing around the crank. some people say they all ended up in L34's, but I have only ever come across two, and in any case, I wouldn't want one in my car as they are inferior to the '74 blocks.  I am wondering now if they had a QT engine number.

 

The XU2 program was the L34. They dropped the RPO code for fear of the Supercar Scare and just referred to the car by its engine RPO code.

 

I haven't seen the rear of one either, only the sides.

 

Here is where XU-2 was cancelled and they cobbled together the SLR5000 package to replace it

 

 XU-2 postponed.jpg   63.56K   1 downloads

 

Here is the NSW Press Fleet car originally specced. This was changed to an L31 car and is the Saffron Press Fleet car that was road tested by magazines. They forgot to also change the rear axle to 2.78.

 

 XU-2 NSW Press Fleet car.jpg   62.76K   1 downloads

[Shiney005]

I meant the V8 XU1's, not the LH, although May 1973 would have been too late for LJ unless they were thinking about something special for Bathurst that year.  It is interesting that GMH had canned the XU2 nomenclature in August '73, and yet it still appeared in the parts book the following year.

Do you think that the L34 in the Press Test Fleet was actually LUK 356? It had the 308 with the GU4 rear end. The closest thing to an L34 press car was the Chrome Yellow one they brought out to Calder and that car is GU7.

 Press car at Calder.jpg   75.77K   0 downloads

 

[yel327]

I meant the V8 XU1's, not the LH, although May 1973 would have been too late for LJ unless they were thinking about something special for Bathurst that year.  It is interesting that GMH had canned the XU2 nomenclature in August '73, and yet it still appeared in the parts book the following year.

Do you think that the L34 in the Press Test Fleet was actually LUK 356? It had the 308 with the GU4 rear end. The closest thing to an L34 press car was the Chrome Yellow one they brought out to Calder and that car is GU7.

Press car at Calder.jpg

 

V8 XU1 was done before Bathurst 1972. So those 1973 X blocks IF they are special blocks can only be for L34 or F5000. The F5000 simply had pattern adjustment as far as I know so that the bore could be 3.960" finished. Its only 40 thou short of 4". It is possible they are something else, like a mark for a trial of a rope seal or something like that.

 

LUK 356 was a Saffron SLR5000, PSN J416792. Off-line on 18th Feb 1974. It was the only LH Press Fleet 5.0L car, assigned to NSW Press Fleet. It was supposed to be an XU2 with L34 engine as per the prior Press Fleet list page I posted up, but its scheduled build was changed to L31 as XU2 wasn't to be released with LH. Here is its sunvisor slip, these were attached to the Press Fleet cars for journos to get info off.

 

 LUK-356 sunvisor slip.jpg   85.54K   1 downloads

[Shiney005]

Back to the con rods.

I have a NASCO "GT" General Purpose Engine Catalogue with a part number of M396971.  It doesn't have a publishing date. It does feature the 186S, but there is no 202. Also the 308 has the oil filler in the timing cover so I will hazard a guess that it was printed in 1970.

The con rod assembly for both 253 and 308 in that book is p/n 7435450.

In the Feb 1974 LH Parts Catalogue it is 7435460.

The August 1974 L34 Parts Catalogue has the L34 rod which is 9935142.

The September 1975 LH Parts Catalogue shows both the standard 7435450 and the L34 9935142.

In the March 1976 LX Parts Catalogue the same two rods are listed.

The July 1978 Parts History Catalogue says that the part number 7435460 has been removed and 7435450 is to be used. (Both of these are the same standard rod) The L34 rod is no longer listed.

All A9X's came from the factory with the standard rods and single row timing chain from September 1977.

I need someone to look in the VB / VC / VH / VK parts books to see if the L34 9935142 part number shows up in those models.

Edited by Shiney005, 26 October 2025 - 12:58 PM.

[yel327]

Back to the con rods.

I have a NASCO "GT" General Purpose Engine Catalogue with a part number of M396971.  It doesn't have a publishing date. It does feature the 186S, but there is no 202. Also the 308 has the oil filler in the timing cover so I will hazard a guess that it was printed in 1970.

The con rod assembly for both 253 and 308 in that book is p/n 7435450.

In the Feb 1974 LH Parts Catalogue it is 7435460.

The August 1974 L34 Parts Catalogue has the L34 rod which is 9935142.

The September 1975 LH Parts Catalogue shows both the standard 7435450 and the L34 9935142.

In the March 1976 LX Parts Catalogue the same two rods are listed.

The July 1978 Parts History Catalogue says that the part number 7435460 has been removed and 7435450 is to be used. (Both of these are the same standard rod) The L34 rod is no longer listed.

All A9X's came from the factory with the standard rods and single row timing chain from September 1977.

I need someone to look in the VB / VC / VH / VK parts books to see if the L34 9935142 part number shows up in those models.

 

That M396971 catalogue is probably 1969. 7435450 is the rod shown in VB-VH parts book published March 1983. The June 1981 Bedford catalogue lists the same rod for 1979-80 Bedford 4.2 and 5.0. The HT parts book shows the same part number. The VK book is the first to list 9935142 as VK with 3/8" bolts, it also has other rod 7435450 listed as "with 11/32" bolts". All VL are 9935142 except for the GroupA cars.

 

As to why the LH book shows 7435460 I have no idea - it could even be an error. It not in any of the HQ parts books and its been fixed back to 7435450 before the end of LH. That fix in the parts history is probably just dealing with that.

[Shiney005]

That all makes sense to me.

 

This letter was sent to Fred James from Repco showing that the F5000 rod and "Improved" Holden rod are 2 different things.  Note that this is March '73, and therefore the X blocks may have been a part of this.

You may find that the wide X rod you have could be one of 106 original sets.

 

 Submission to GMH 001.jpg   138.19K   2 downloads

Edited by Shiney005, 26 October 2025 - 01:29 PM.

[yel327]

That all makes sense to me.

 

This letter was sent to Fred James from Repco showing that the F5000 rod and "Improved" Holden rod are 2 different things.  Note that this is March '73, and therefore the X blocks may have been a part of this.

You may find that the wide X rod you have could be one of 106 original sets.

 

Submission to GMH 001.jpg

 

 

If you look in Torana Tough on page 187. There is a March 1973 Repco Dyno chart reproduced there, shows: Standad, L34, L34+HO kit and F5000 engines plotted against each other. This all goes together.