20 replies to this topic

[Shifty]

What has happend is that your cap has been machine wrong, it's a common problem with 998s.

If you machine a 1275 cap you just do it flat, to do a 998 properly you need to take the centre section out leaving the locating slots in place. I have had some very reputable engine builders make this mistake.

If you leave it how it is you wil likely knock the tabs of on the thrusts wrecking the block.

You have a few options:

1) buy a strap from Morspeed that is wider and has the slots machine in it.

2) dowl the cap permanently locating the thrusts.

Thanks Wil

That seems the most likely explanation now.

I'll look into the options, thanks for the info.

At least the block may not be scrap now.

Shifty

[Shifty]

What has happend is that your cap has been machine wrong, it's a common problem with 998s.

If you machine a 1275 cap you just do it flat, to do a 998 properly you need to take the centre section out leaving the locating slots in place. I have had some very reputable engine builders make this mistake.

If you leave it how it is you wil likely knock the tabs of on the thrusts wrecking the block.

You have a few options:

1) buy a strap from Morspeed that is wider and has the slots machine in it.

2) dowl the cap permanently locating the thrusts.

Thanks Wil

That seems the most likely explanation now.

I'll look into the options, thanks for the info.

At least the block may not be scrap now.

Shifty

[Dan]

4 bolt main caps are available from lots of dealers, not just Morspeed. Shop around.

[Wil_h]

4 bolt main caps are available from lots of dealers, not just Morspeed. Shop around.

No, not a 4 bolt cap. If you fit one of these you have to line bore the block, and this is not cheap.

Morspeed sell a strap that is wider than everyone else sells with the locating slots machined in it, he made it after the problems of my engine came to light. It's a simple replacement for the one you'll have. And you can flog the old one.

[Shifty]

I'll give morspeed a bell on Monday and find out costs.

I didn't pay that much for this block/crank/pistons so I may well just use the internals on a fresh block and start again.

If the cost of the cap is greater than a rebore then its a simple choice.

I think I may have lost a bit of confidence in the chaps who machined and put this one together and would rather just use it as a good source of parts.

Its supposed to have been inspected and given a clean bill of health, however the cam brgs are shot??

Its got new crank brgs and pistons so is not a dead loss(far from it)

Thanks for all your help and advice, much appreciated

[Dan]

Morspeed sell a strap that is wider than everyone else sells with the locating slots machined in it

Oh you mean the strap with the locating grooves? I thought you were talking about replacing the whole thing to correct the problem. It's likely that the main cap will need line boring, or line honing at least in any case because of the amount of metal that's been removed from it. Once Simon's very heavy duty strap is fitted it's almost cetrain to crush the cap a little and close up the bore. If there really is reason for some concern about the competance of the engineer who did this then it's something I'd at least be getting measured if it were my engine.

Edited by Dan, 15 February 2009 - 01:19 PM.