exhaust port timings

[hendy]

who ported the barrel?

A man who makes mistakes ....

Aye, I'd rather just leave it at that for now. I don't want to spoil someone's reputation for one mistake.

If however he doesn't put it right then I will certainly have a change of heart.

[shocky]

In all fairness the cylinder might have been like it from new my piston sticks up a little from the bottom of the port and the previous mahle one did as well and that had a few thousand miles on it

[hendy]

Ok, kinda what I expected.

Now check this. When the piston is at BDC, do the bottom of the transfers and the bottom of the exhaust port all line-up? If the bottom of the exhaust port lies lower than the bottom of the transfers, then this is not a good thing.

Have a look and get back to the forum

The bottom of the transfers are about 0.5 to 1mm above the edge of the piston crown at bdc. Both transfers are nicely at the same level.

[eden]

bottom of the transfers should be lowered so they are level with the piston at bdc!

sounds like who ever did this porting is pretty stupid tbh..... if the bottoms of the transfers had been as low as the bottom of the exhaust I would have said that maybe the tne was done for a very long stroke but as the transfers are higher than the piston by 1mm with a 60mm stroke that means they have not been worked on at all because if you put a 58mm stroke in the bottoms would be level with the piston.

[Adam_Winstone]

I know of a longer than standard barrel that was intended to be run with a long stroke crank but went off for some porting first, only to find that the tuner simply applied the measurements that he had for tuning a standard length barrel... and in doing so completely f***** up a special barrel.

[hendy]

I know of a longer than standard barrel that was intended to be run with a long stroke crank but went off for some porting first, only to find that the tuner simply applied the measurements that he had for tuning a standard length barrel... and in doing so completely f***** up a special barrel.

I know what you're saying but I doubt that's the issue here otherwise I reckon the transfers would be much lower.

I am pretty baffled by how they could be this far out though.

Why would an experienced tuner cut the exhaust bottom 5mm lower than the bottom of the exhaust?

[hendy]

bottom of the transfers should be lowered so they are level with the piston at bdc!

sounds like who ever did this porting is pretty stupid tbh..... if the bottoms of the transfers had been as low as the bottom of the exhaust I would have said that maybe the tne was done for a very long stroke but as the transfers are higher than the piston by 1mm with a 60mm stroke that means they have not been worked on at all because if you put a 58mm stroke in the bottoms would be level with the piston.

You've misunderstood me I have a 58 crank, so with a 60 it would be worse still.

Anyone know where I can get a 54 stroke crank with a 111mm rod?

[Adam_Winstone]

"Why would an experienced tuner cut the exhaust bottom 5mm lower than the bottom of the exhaust?", maybe so the rings get less support for longer?

[rosscla]

Maybe it was that way to start with?

Surely most tuning raises the roof of the port or widens it?

[tea5ive]

tv crank ?