ESR trx-9 portwork with +4mm stroke ???

[kiesta00]

Hey guys I'm thinking of buying a used ESR 310 cylinder thats ported for a 72mm crank with the trx-9 porting. I'm not sure about the port timings on "trx 9" level porting, but do you think that I can have it reported for the +4mm crank? I'll be drag porting it too.

What do you think?

[Aceman]

Why don't you ask your motor builder? After all, he'll be the one doing the work.

[kiesta00]

I just wanted to get a quick idea if it can be reported. I'm sure this cylinder will sell fast, and I don't want to pass up a good deal.

[Aceman]

I gotcha.:)

Maybe try a different builder this time too. Looks like the last one can't relieve exhaust bridges properly!

[C-LEIGH RACING]

With the cylinder ported TRX9, if you add in the + 4 stroker, yes it can be ported for drag.
Neil

[kiesta00]

yeah the other guy sucked, he can't get head gaskets or mechanical seals to work properly either!!

I'm happy with the power from the stock cylinder, I'm only upgrading to the pro-x for better reliability. I'm tired of fighting these blown head gaskets and sitting on the sidelines all day!

[wilkin250r]

Originally posted by C-LEIGH RACING
With the cylinder ported TRX9, if you add in the + 4 stroker, yes it can be ported for drag.
Neil

Correct me if I'm wrong, Neil, but isn't drag racing about the ONLY thing it can be ported for?

The transfers are already cut, the stroker crank will alter the port timing to want to rev higher. That's all well and fine if that is your goal, you simply adjust the ports to continue that tendency and make it a high-rev engine.

But you can never bring it BACK to a mid-range engine. For that, you would need to start with an unported cylinder.

Correct?

[kiesta00]

Wouldn't adding a stroked crank lower the port timings? The crankshaft has to rotate a few more degrees in order to let the longer radius arm (2 additional mm) open the exhaust port...correct?

[86 Quad R]

imo a trx-9 porting is about as far as i'd be comfortable using on a 4mm stroker if i were using it for anything other than dragging. especially if someone(another porter) has gone in afterwards and done some cleaning. if nothing else. you could possibly have a fresh LA sleeve pressed in and then port the openings to the desired timings

btw...... you running your current setup with a 2mm spacer?

[kiesta00]

I ordered the .250" spacer, and the engine builder cut it down to what he wanted. The deck height on the stock cyl and 86 style piston is about +.032" (popout).

I'm not sure how that'll effect the trx9 port timing, I guess it'll lower them a little.


Can someone answer my question about the stroked crank and port timing? Seems to me the stroker crank would decrease port timing because of the longer time required for the crank to rotate to a point that uncovers the exh port.

[wilkin250r]

Originally posted by kiesta00
Can someone answer my question about the stroked crank and port timing? Seems to me the stroker crank would decrease port timing because of the longer time required for the crank to rotate to a point that uncovers the exh port.


It changes both ways.

Anything that opens before 90 degrees will open later, which is usually only the exhaust port. So total exhaust duration will decrease.

However, the exhaust port isn't the only port in the engine. And anything that opens after 90 degrees will open earlier, which will be your transfer ports. They open earlier (and close later), which gives you an increase in total transfer duration.


So now you have a mis-match, because the transfers are open longer, but the exhaust is duration is shorter. You cannot ADD metal, so you can't bring the transfers back. The only thing you can do is cut the exhaust to correspond to the changes in transfer, giving you more exhaust duration and shifting the RPM range higher overall.

You can always cut more metal and get higher revs. This is why a mid-range porting can be made into a high-rev porting with a stroker, but you can never bring it BACK to a mid-range again.

[kiesta00]

ah yes I didn't realize the 90-180 degree rotation would pull the piston down faster then the shorter crank.


So you think I can get away measuring the transfer duration and then calculate the blowdown I'm looking for and adjust the exhaust port timing to make it run correctly?

[86 Quad R]

yeh as long as the ports havent been drastically changed as mentioned previously.

you have someone down your way that can port map, degree the engine and to come up with the required numbers(on all ports) to get it where you need it to be?

[kiesta00]

yeah I've got a friend who has setup numberous stroker 250r motors thats gonna help me setup my engine like his 310 4mill.


I just want a setup that is reliable, everytime I've ridden this stock cylinder setup I've had headgasket problems that put me on the sidelines all day long.

[86 Quad R]

YUPPERS............ the b/b stock cylinders are none to have that problem. especially when running the higher c/r. you ever try three bond?

[kiesta00]

nah I've never tried it. Hopefully this'll be the last of headgasket problems that I'll ever see.

You go to wiggins ms ever? I hear its a pretty good spot to drag race out there.

[C-LEIGH RACING]

Originally posted by wilkin250r
Correct me if I'm wrong, Neil, but isn't drag racing about the ONLY thing it can be ported for?

The transfers are already cut, the stroker crank will alter the port timing to want to rev higher. That's all well and fine if that is your goal, you simply adjust the ports to continue that tendency and make it a high-rev engine.

But you can never bring it BACK to a mid-range engine. For that, you would need to start with an unported cylinder.

Correct?

Yes & then no, he was wanting a drag engine reason I said it could be done.
Far as a drag cylinder never being able to go back to bottom end or mid range port, long as theres welding & machining tools, anything is possible.

You remember my mojo cylinder from Mac Dizzy few years back, it started out as a 330cc drag cylinder on top of a + 5 stroker crank, today, that cylinder is a 350cc STD stroke bottomend midrange cylinder.
Neil

[kiesta00]

Thanks for all the help guys. I should have it on by next weekend...I'll keep you posted on how it runs :)