Welcome to our Site for MG, Triumph and Austin-Healey Car Information.
MG TD TF 1500 - reconditioning conn rods
|I've been thinking about having the big end of several sets of rods done. Anyone have suggestions/recommendations about this. Any company here in the states you would suggest I talk to? Cheers Sam|
What do you mean by having some rods "done". Apart from fitting new shells and perhaps crack checking there is nothing that is needed.
|It's common to have the big ends sized--they tend to become elongated. You take a mil or two off the mating surfaces and hone them round again. Also, they can be lightened and/or balanced.|
|S.Maas You are right that's the only right way to go if you overhaul a engine. instead of just replace the bearings and hope for the best.|
|There is plenty to do to a connecting rod. Mag check, Shot peening, truing, resizing, polishing, fitting ARP hardware, balancing. Any competent performance machine shop can perform these operations. |
|W. A. Chasser|
|Some of you may find this weird or crazy or against your better judgement but here goes.|
I am currently rebuilding a TD engine and had the rods sized and checked for cracks. They were in good shape. While I was there at the shop, he showed me some rods he was restoring for some kind of car. Really interesting process.
After reading some of your comments discussing balancing in the past, I asked him to do that to my rods. He said no problem but I was wasting my money with this engine since I was not going to race it. The RPMs I would be using just did not warrant it. This guy builds everything from really old engines to high performance engines. Just a different prospective.
We also discussed setting expansion plugs with JB weld. Over the years he has changed his methods. He now uses it especially on older engines. He has not had a problem since this conversion to JB weld. So I followed his advice.
Saved some money by not doing the balancing, I could spend somewhere else.
|Given the inherent vibration issues and lack of a harmonic balancer on XPAG/xpeg engines that do lead to frequent crankshaft failures, I will race balance all my assemblies for greater durability and peace of mind. But that just me... |
|W. A. Chasser|
|I fitted forged rods with one-piece small ends. I've still got a crack checked set of the later, Wolseley XPAW rods if anyone (in NZ) needs them.|
|While we are discussing this, I URGE you to replace the standard pinch bolts (gudgeon pin bolts) with Allen-head cap screws. Due to the rod configuration it is practically impossible to tighten the stock bolt with any sort of accuracy, and the Allen-head makes the job a breeze. I have seen more than one engine where a stock pinch bolt came loose, with disastrous results.|
Also, magnafluxing the rods is an absolute necessity; I just had two rods rejected, with invisible-to-the-naked-eye cracks that would have grenaded the engine, had they been left in place. I was skeptical and ground down the marked area, and the cracks became clearly visible.
Your connecting rod bolts should be very carefully checked for stretch, and if any is found, replace them with the best you can find. Bad rod bolts is a very common flaw with these engines.
I also strongly believe in balancing; the last set of rods I had balanced had more than 25 grams difference between the lightest to the heaviest. Anything that can be done to even things out is guaranteed to give a smoother engine, one that will last longer, and an engine with less rotating stresses. These XPAG engines are high-rev engines, and every fraction of a gram that can be balanced out is a good thing. The cost is less than $200, which I see as very reasonable for the peace of mind the process provides.
|When you think about the distance the pistons travel in one revolution, with their long stroke, and you realize the piston speed necessary to cover that much distance, and the fact that the piston reverses direction every revolution, you soon realize balancing is worthwhile. It is not uncommon for the XPAG to be asked to go along at speeds over 4,000 rpm. |
I realized this when I was rebuilding an XPAG at the same time as an air cooled Volkswagen Beetle engine. The beetle stroke is so short, the XPAG pistons travel about twice as fast.
This thread was discussed between 23/10/2016 and 24/10/2016
MG TD TF 1500 index
This thread is from the archives. Join the live MG TD TF 1500 BBS now