Rover V8 - Gudgeon Pin Fitment, a Novice's Tale

[Ian C]

A salutary tale and an experience shared.

Having equalised the weight of my pistons & little ends (all equal +/- ½ gm) and confirmed the orientation of the pistons & connecting rods I decided to grasp the nettle and fit the gudgeon pins.

Those familiar with the Rover V8 will know that the pins are an interference fit in the little end and can only be fitted with a press or by heating the little end. After some research and viewing a number of videos on YouTube I decided that the “heating” method was within my capabilities.

In an attempt to confirm that my confidence was not misplaced I rigged up a threaded rod held in a vice and holding one of the old gudgeon pins. I then heated up the little end of one connecting rod, using a Propane blowtorch that I have used for plumbing work. I made a few tentative attempts before the little end became hot enough – the change in colour of the machined bearing surface to a blue tint was marked. With the little end at the right temperature I was able to slide the little end over the gudgeon pin and back off easily.

Confidence was now soaring but I decided that holding the connecting rod and pressing the gudgeon pin into position required more hands than I possessed. I enlisted the help of my son, who is both very practical & has steady hands. Our first attempt ended in a fumble as we were both feeling the tension. Fortunately the pin had only just entered the little end and we were able to withdraw it using the threaded bar and spacing tube I had made in a naive attempt to remove the old pins from the original pistons. In a way the failure made the next attempt easier and this time the gudgeon pin shot home – easy!!

You will have guessed that the next attempt, following our success & blossoming confidence, was doomed. The pin was pushed fully home but when oiling & waggling the connecting rod I managed to pull the little end back along the gudgeon pin so that when the pin is central in the piston the connecting rod is against one face of the piston boss (piston No. 4 in picture). Doom & gloom followed, there was not even an attempt to pull the pin back through the connecting rod to centralise it as I knew the force involved. As nothing could be done, at the time, we had to decide whether to press on or abandon the attempt and seek professional help (from either (or both) a garage or psychiatrist). The next one went like clockwork and once more confidence was restored. On the next one I attempted to switch the gas off on the torch while still holding the connecting rod which moved back slightly along the gudgeon pin before I had realised (Piston No. 8 in picture). Once again we were angst ridden and despondent – a 50% success rate was not a good basis on which to proceed. After a team talk we swapped roles, Daniel now did the heating and positioning of the rod while I pushed the pin home. The next four went like the video and by the last of the eight we had definitely got the hang of it (see Piston No. 7 in picture).

So if anyone wants to take advice from someone who has a 75% success rate (but 100% if you just count the last four!!!) this is what I have learnt:

1. Lay out all the rods, pins & pistons in the order that they will be fitted, doing all the odds & then all the evens (or vice versa) – this allows the same orientation of the piston to be used for four fittings rather than swapping after each insertion which can be confusing (see diagram).

2. The side of the little end marked, by the boss on the connecting rod (used to confirm the correct orientation when assembling), is chamfered and the pin should be pushed in from this side. This means that the orientation of the piston is different for the odd & even pistons.

3. Do not overheat the little end, the colour change is fairly clear. If the little end is too hot then too much heat is transferred to the pin (see 6).

4. Have the pin inserted in the piston leaving just enough room for the little end to slide into position between the end of the pin and the opposite side of the piston.

5. When the little end is up to temperature position it in the piston and slide it over the exposed end of the pin then IMMEDIATELY push the pin through the connecting rod and piston (I made a jig to stop the pin in a position that would leave the connecting rod central when the pin is pushed back to its central position).

6. We found that the biggest danger is not the pin jamming in a cooling connecting rod but in the heat transfer from the little end to the gudgeon pin causing the pin to lock in the piston. Even some seconds after the pin has been pushed into position the connecting rod can still be moved easily on the pin but the pin is held firmly by the piston.

So, it was very nearly a really good day – no rain, sun out and another step towards completion. I will be off back to my favourite engine workshop tomorrow to beg a favour and centralise the two failed pistons with a press. The pin is actually well within the piston skirt, when the rod is central in the piston, but I would rather have it right than “near enough”.

Hope this is of some help to other novice builders foolhardy brave enough to tackle this job. It can be done but takes some nerve, by the time we had done eight we both felt confident to do more. I will have to build a second kit to put all this hard earned experience to good use!!


Ian (Novice Engine Builder)


How it should be done

(Also worth viewing his other video (where he sets fire to his girlfriend) for a chuckle)

[jonny m]

Nice to see you didn't resort to the big feckin hammer approach

Tip 2 would have been nice to know a few weeks ago though !

[Ian C]

. . . . Tip 2 would have been nice to know a few weeks ago though !

Jonny,

Not sure which engine you are currently rebuilding so remember that the quoted orientation is ONLY valid for the earlier engines, according to the Rover Manual the later (4.0, 4.2 & 4.6) engines use a different system.

The good news is that my favourite engine shop (Northern Rebore in Newcastle) came up trumps and managed to rectify my errors. The first piston & rod are now safely fitted and the crankshaft still turns – only 7 to go. Starting to look like a real engine again!!!

Ian

[tonym]

Ian, have you got no head locating pins in your block?? What's the dark ring at the top of the bore on no1 cylinder?

[Ian C]

Tony,

The locating pins were taken out when the block was re-bored, have not got round to refitting them yet. The dark ring is the top of the liner, combination of the chamfer at the top, the darker metal & the camera flash have made it appear wider & a lot more obvious on the picture than in reality.

Ian

[Ian C]

I had started another thread as I thought I had a big end bearing problem (see RV8 - Big End Bearing Cap Fixing; Post #6). The bearing cap on the connecting rod of No. 1 piston was tight on the crankshaft journal and when tightened to the required torque the crankshaft was locked solid. All the other big end bearings fitted perfectly and the crankshaft rotated freely when they were all at the prescribed torque.

In an attempt to eliminate possible causes I swapped pistons 1 & 2 (putting them in back to front so that the connecting rods were facing the correct way on the journal). No.2 (on the journal for No.1) was fine but the No.1 big end locked up on the journal for No.2. This pointed the finger at the big end bearing and / or the bearing cap on No.1 connecting rod. On close inspection the connecting rod is bent like the proverbial banana (well it is out of true anyway).

This is the connecting rod that I practiced on to see if I could get the little end over the old gudgeon pin before trying for real on the new pins & pistons. The deformation of the rod is where the colour change lines are, either the temperature was way too hot or the repeated heating as I practiced the technique then did it for real the next day was too much for the rod’s constitution.

So learn from my stupidity; only try the insertion of the gudgeon pins by heating the little end if you are experienced or if you have been able to practice on a spare connecting rod. To repeat what we found during the exercise it is not the little end cooling down which gives the problems it is the transfer of heat into the gudgeon pin and the subsequent jamming of the pin in the piston. Excessive heating of the little end can only exacerbate this problem – Be Warned!!

So now I need to know if it is possible to buy a single connecting rod for a 3.9L RV8 – any offers?

Ian (was a Novice Builder, demoted to Apprentice)

[jrv8]

Ian,
If you want to give me a call , or PM me , I'll sell you a good condition HRC rod with its matching cap.
Regards
Jim

[Paul B]

Jim to the rescue again

When I built my engine, things like fitting the pistons to the rods, I left to the local engine workshop who have the experience and equipment with resorting to "Bodging".

I use the term "Bodging" with great respect as I am an expert in this method of engineering and have no wish to denigrate the level of expertise needed to attain this esteemed qualification

Seriously though, some things are best left to the experts.

Paul

[Ian C]

. . . . Jim to the rescue again . . .

Seriously though, some things are best left to the experts.

Paul,

If we all left it to “the experts” then we would all be driving Euro Boxes.

I am building a kit car, and rebuilding the engine, for enjoyment, personal satisfaction and as a challenge – you may have other reasons.

Whilst Jim has supplied a replacement connecting rod (- I have spoken to Jim on previous occasions and purchased other parts from him in the past and would recommend him without reservation) I object to the term “rescue”.

Ian

[Paul B]

Hi Ian

If you try to do everything, did you try reboring the block as well using an old Black and Decker drill and some sand paper ??

I fully stripped my engine, spec'ed it (with Jim's help), had the machining and piston fitting undertaken by those with the necessary expertise and machinery, then built it back again myself. I have run it for 12,000 miles producing 200 bhp with no problems, so something must have gone right.

All I was saying is that some things can be seriously damaged by not having the correct equipment and that others who read this thread and are contemplating their own engine build, should not be put off by the difficulties/challenges you have faced.

For example, the localised heating of a conrod “could”, and I use this term because I am no expert, soften the alloy and create problems later when running the engine. I do not know that this would happen but these are risks that I felt were better avoided after spending so much time, money and effort in building my engine.

And don't be so touchy about the term "rescue". All I meant was that Jim quickly offered a solution to your situation.

Paul