13 replies to this topic

[087dave]

I have mixed up my conrod s as i brought a lightened set on ebay which turns out
one bearing cap was not matched to one of the conrods
so i am trying to put in the orginal one s back in but i never marked them
coming out (bad idea)

so how would you know which conrod goes were
i have new big end bearings,piston rings
please help
cherrs...

[Cooperman]

First of all, if one of the caps is not a matched one for the rod, then there are only 2 options. The first is to get a small amount machined off the mating face of the cap, then bolt the cap to the rod and have a precision engineering machine shop bore the combined rod and cap assembly to EXACTLY the right internal diameter to accept the big-end bearings. The other is to scrap that rod, which is probably the lowest cost option. Then you would need to either get a complete new set of 4 rods with caps to suit your engine or get one which has the same part number as the scrap one and have it lightened and balanced to exactly match the other three. You will need to sent the other rods, with the replascement one, to a specialist balancing company such as MED.
You now know the perils of buying off ebay and as what you have bought is not what you got; i.e. items unsuitable for the use for which you bought them, then go back to the seller for a refund and/or make a complaint to ebay.
However, the rods cannot be put in incorrectly so long, and I stress this, so long as the caps match the rods and were the original matched parts. You must be absolutely sure of this. If you are not, then get a correct and proper set of rods complete with caps.
I'm sorry if this is not what you want to hear, but unless you get it right your engine will never run properly, if at all. The rods/caps and their fitting to the crank with the big-end shells are just about the most precision engineered parts of the entire car.

[087dave]

Thanks for the reply cooperman but what i am going to do is
scrap the lightened ones and go back to the ones that orginally
came from the engine but
the problem is i never marked them coming out
so is there anyway of knowing which cylinder they came from like i know that when the conrods
are in the engine 2 and 4 are the shaped the same and 1 and 3 are shaped the same
And how would i know which big end cap goes with which conrod
cherrs

[Cooperman]

If you have mixed up the caps from the original rods the chances of getting them correct is not good. You will probably need to buy another set of rods. Maybe you could try a rod onto the crank, without putting it into the bore, complete with new bearing shells and see if it rotates easily. Try the other caps in turn until it does, and repeat until you have a working set, but this is a bit 'iffy' as a way of doing proper engine building. Personally I would just source a new matched set.

[mini-geek]

I have been told you can match them back up by lining up the cross hatching on the inside of the big end, worth a go

[Cooperman]

I've never heard of that and don't see how it could work. Take a real close look at the rods and caps and see if there is some sort of marking to identify which cap goes with each rod. A replacement set of rads won't cost a fortune and you will then be confident that they are correct. If it's a 998 I may have a set of rods. PM me if you want to.

[087dave]

Thanks cooperman let you know 2omo

[TopCatCustom]

Not meaning to criticise too much but was it really that much easier to not pop the caps back on the conrods as you took them out?!

[Cooperman]

OK. The set I have are definately a complete, matched and marked set ready to fit.

[087dave]

Ya i know that but i got lightened set from ebay i did nt think
that one of the caps would be wrong

[Guess-Works.com]

As long as you have 4 rods and 4 caps which are from the same set then it's not difficult to match the rod to cap..

All you need is your finger..

Rod caps are always mounted tang to tang, so there's 50% of the permutations removed already... try 1 cap on 1 rod, when together if you can feel the edge of the cap by running your finger over the join in the journal, then it's the wrong cap.. keep doing this until you find the one which fits ( there should be no edge ) or run out of caps... if you run out of caps before finding one which feels right, don't panic, just pick up another rod and do it all again... eventually through trial and error you will match cap to rod...

If you loose a cap then that's a whole different ballgame.... but needing to buy a new set of rods... tosh !

[087dave]

As long as you have 4 rods and 4 caps which are from the same set then it's not difficult to match the rod to cap..

All you need is your finger..

Rod caps are always mounted tang to tang, so there's 50% of the permutations removed already... try 1 cap on 1 rod, when together if you can feel the edge of the cap by running your finger over the join in the journal, then it's the wrong cap.. keep doing this until you find the one which fits ( there should be no edge ) or run out of caps... if you run out of caps before finding one which feels right, don't panic, just pick up another rod and do it all again... eventually through trial and error you will match cap to rod...

If you loose a cap then that's a whole different ballgame.... but needing to buy a new set of rods... tosh !

Thanks guess works do you mean to put the conrod and end cap together on the crankshaft
and feel the front
cherrs

[Southy]

No he mean's to fit the conrod together whilst off the crank with no shell inside and feel if there is a lip on the inside of the conrod. Keep changing them round till you have them all without a lip. If in doubt with one, give it a try on the crank with a set of shells fitted and torqued up.

[087dave]

Thanks for the replys