Hole in nearside con-rod

[berger]

Bagonails i hope the link kwi gf put on has helped, i did weigh them all but can't remember and had the lot weighed and crank dynamic balanced hence the 2 on the rod

[RichardL]

R and R dont make Thunder rods. Thunder Engineering is based in Leicester, England.

First photo show BSA rod on the left anf R and R rod right.

Second photo shows the Thunder rods which went into my A10.

Great pictures, Julian. The distinction at the small end is obvious. I was able to compare a picture of mine to your pictures. Now I can confirm mine are Thunder. So, no validation or detraction for plus 1/32” being OK in my engine, except, the Thunder rods (with my custom-drilled hole) are working great.

Richard L.

[Jules]

1.surely an extra mm in conrod length would make a significnt difference in compression volume, hence up the compression ratio quite a bit, unless you did Muskie's trick of adding a 1mm plate under the barrels??
2. wrt the oil hole, in my experience "squirt holes" were always aimed under the piston to help cool the skirt and crown, I've never heard of them being used to squirt onto the cylinder wall, until now! It may be that this was a "containment action" introduced while the real "root cause" of the problem was being established - this was the process we always used in a manufacturing environment to protect the customer from failures when it was taking time to find what the real issue was ie we introduced a containment action quickly which may have cost money to implement but protected the customer from the failure going forward, to buy time to find the real issue....

[limeyrob]

The pistons should stop at the barrel top so if the rods are 1/32 over then we are looking at protruding into the head gasket thickness. My thought would be that an easy fix would be a slightly thicker solid copper head gasket - laser cut?  Has anyone measured the difference between a solid and a composite head gasket once pulled up?

[CheeserBeezer]

Hi Folks, I started this thread about the hole in the left hand can rod. The answers given were very helpful and it would appear BSA introduced th'ole to reduce the potential of seizure on the left hand bore. We're now talking about alternative con rods and their merits (or otherwise). The contributions have been very interesting and useful and worthy of a separate thread in my opinion. If nobody else starts one, I will !!.

[RichardL]

Andrew,

You're right. the point of "no holes in Thunder rods" trailed off into something completely different. Guilty, as charged.

Richard L.

P.S. Well, there are holes, just big ones for the crank journal,  gudgeon pin and bolts.

[Swarfcut]

 To answer the question posed by RichardL, the critical factor is that a non standard rod will position the crank in a slightly different position to normal when checking the timing  with a stick down the hole. But providing the engine is timed up from scratch the piston height remains the same in relation to the point of firing. Timing with a degree disc will position the piston in a different place in the bore.

 But as for the timing, all this may be academic because these workshop settings were done with the backyard fix in mind, few owners would have had a degree disc, and also the change in octane rating of current fuels means the best results are obtained by trial rather than sticking rigidly to something published a long time ago.

 Swarfy.