Porting

[JasonsBanshee]

I am planning on sending my cylinders to HJR to get the dune / hillshooter port. In the spring I am planning on building it into a 4 mil. I've been told that the port job will not work with the 4mil because a port job for a 4 mil is different. Something to do with the port timing?? I've also told that it will work just fine and that I'll have to get different pistons to work with the longer stroke and not modify the head or domes.

[johnny boy]

call kevin...

[yamaha11]

I am planning on sending my cylinders to HJR to get the dune / hillshooter port. In the spring I am planning on building it into a 4 mil. I've been told that the port job will not work with the 4mil because a port job for a 4 mil is different. Something to do with the port timing?? I've also told that it will work just fine and that I'll have to get different pistons to work with the longer stroke and not modify the head or domes.

 

 

iv been told its different for both 4mm and stock, your best bet is to ask hjr and tell him what your plans are your builder is best person for question. everyone else just gives you opinions.

[JasonsBanshee]

Yea, I sent him an email. I'll post the reply here so we all know. It's crazy how many opinions you'll get. LOL

[trex banshee]

it all depends on how far he ports your cylinders for the stock stroke. On some cylinders if they are very lightly ported for a stock stroke then they may be able to be ran with a 4mm. The problem you run into is your durations will be huge once you go to the 4mm.

[jbooker82]

You dont use different pistons and not moddify the the head or run standard domes.

 

The pistons they are talking about are Wiseco 795 series. They are made for a Long rod crank. You have to run these pistons with BOTH a stock stroke long rod crank or a 4 mill long rod stroker crank. It is because the conecting rod on a long rod crank is 5mm longer. So you need a piston that has the wrist pin moved up 5mm farther other wise the pistons would pop out of the cylinder and hit the head.

 

A regular rod 4 mill stroker wont require 795 pistons. All you would need to do is have the head machined, run stroker domes, or a 2mm spacer plate under the cylinders. Your adding 4mm stroke to the engine. So the piston is going to fall 2mm farther down in to the cylinder and it is going to pop up out of the cylinder 2 mm.

 

A Long Rod 4 mill storker will require both 795 series pistons and a cut head, stroker domes or a spacer plate.

[Wildcardracing]

The problem area on converting previously ported motors to 4mil specs is the transfer port timing. The exhuast port heights are very close to the same between 4mil long rods and stock stroke 110 rods as measured from the deck, not tdc. The transfer ports on the other hand don't get raised as much with the 4mil to achieve the same durations. Many of your trail ports can be redone to 4mil specs, more aggressive ports such as dune ports usually cannot. This all being figured on a -2mm deckheight running stroker domes and no plate.

[vulvafan537240]

i would wait until i could do it all at one time. otherwise youll be porting twice. that is, if the dune port isnt too aggresseive. then you may not be able to port for the 4mill.