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MG MGA - conn rod caps ID help
|Hello group - I bought a set of four caps last weekend that were marked MGA 1622 #'s 1G2372*N. I think 1500/1600 & 1622's are all different. Does anyone have a motor apart or can anyone confirm what these fit exactly. thanks Harvey|
| Hi There,|
I do beleive that the con rods for the 1500-1600-1622, are all the same
The 1622 valves are the difference in the engines apart from the bore.
|Don't forget that the 1622 engine has a different crankshaft as the main bearings are narrower.|
Are you fitting conrod caps to other (non-matched) conrods? I would suggest that have metal planed off the cap and it's rod at both the mating surfaces and then have them line bored to standard.
|M F Anderson|
|Con-rods for 1500/1600 are identical. Con-rods for 1622 have small end bushing for larger diameter floating wrist pin, but the big end bearings are the same.|
If you have loose bearing caps and do not have the exact original matching rods, then the caps will have to be machined to work on other rods. Take a light cut (0.010") off the mating surface of the cap, bolt it to a rod, and rebore the big end to original diameter. For bore dimensions see here: http://mgaguru.com/mgtech/engine/cs106.htm
Gents - Thanks to all that replied. The question still remains however, are these the correct numbers for the caps? Just because they were marked 'MGA' does mean the guy who sold them to me was correct or knew what he was talking about? Or maybe there are different numbers. These are all four the same but I would feel more comfortable knowing they were correct to start with. Yes, we are building a scratch 1622 for a TD to vintage race. thanks again for all the help. Harvey
|"Con-rods for 1500/1600 are identical. Con-rods for 1622 have small end bushing for larger diameter floating wrist pin, but the big end bearings are the same."|
Negatory on that, Barney (must have answered before you had your coffee). All con rods from 1500 through 3 main bearing MGB are clamped wrist pin.
All of themn also take the same rod bearings.
The only MGA that ever had a full floating pin was the Twin Cam, and it was in a larger diameter than the MGB, which first went to full floating in 1965 with the 5 main bearing engine.
In fact the Twin Cam rods were specified as a competition upgrade for pushrod MGA and MGB.
|Okay, correction here. The only rods having bushing small end were Twin Cam. However, the 1622 engine did use larger gudgeon pin, so the 1622 rods are still different from the 1500/1600 parts.|
As to the first question, Harvey does have the correct bearing caps for MGA 1500/1600 con-rods. I have some spare con-rods for 1500/1600 engine with the following casting numbers:
1H702 for #2 & #4 cylinder
1H704 for #1 & #3 cylinder
1G2372 for bearing caps
What follows the casting number on the cap appears to be a triangle with some small number inside, probably a cavity number in the sand casting mold (irrelevant).
Even though the rods are left and right handed parts, the caps are same casting (reversible for RH or LH) with similar machining, even having the locking tab depression machined in the same location. This makes it is easy to swap any cap to any rod, which creates a mismatch of the split lines and screws up the finish machined diameter.
To repeat, if you do not have matched pairs of original rods and caps, the parts will have to be machined to achieve the correct bore size for the bearing nests. It is a VERY good idea to put matching marks on the rods and caps to avoid mix up in the future.
|Yes, that's correct, Barney - 1622 and 1798 are identical with .750" wrist pins (and even the same part number, I think, but it's been years since I last checked).|
The 1498/1588 used a slightly smaller diameter pin, at 11/16" but the small ends can be easily opened up to fit the 3/4" pin if you can't find a handy set of later rods.
Answering the original question, which dealt only with the big end, they are all identical. But of course you and Mick are quite correct, you MUST have the rods resized with the new caps to make sure they end up with round holes in line.
I have never heard of anyone selling just caps, and If I ever saw them I have no idea why anyone would buy them, unless they had somehow lost the caps from their own rods.
|Hey all. I am rebuilding my mga 1600 engine and need to replace #3 conn rod but no one has new. Moss, etc, only have #3 for 1622 engine. Does anyone have a spare to sell or know of a source?|
This thread was discussed between 14/09/2008 and 17/09/2008
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