372XP Rebuild and mod.

[dozerdan]

Back to it! Got the base machined tonight.

Got a short video uploading as well of machining the base.

Will
Give some thought to doing your lower transfer work before you machine the base. You don't have to worry about your tool slipping and hitting your nice machined surface. I have done it that way for years.
Your machine work looks good, no chatter marks in the chamber or the base.

Late
Dan

 

[dozerdan]

I can't believe what I just did. After spending an hour setting the cylinder up in the lathe, I ran the boring bar inside the cylinder moved it out to the outside of the squish, and without thinking ran the table back out and felt the bit hit the top of the cylinder FUKKKKKKKKKKKKKKKKKk, now there is a small score right up to the top of the plating about a 1/2" long. Can't freaking believe it after all this work on the cylinder. Actually thinking of running it this way and see what happens, what's the worst that can happen loose a few psi of compression? I buffed down the score so there is nothing raised. Dam I just feel sick about it. I guess you aint learning unless you mess up some parts. I guess I could also have it bored and replated, but not really worth it.

It could be worse. I was cutting a chamber a few years ago and had a customer walk in when I was almost finished. I should have stopped but didn't. I was talking and working at the same time, I did the same thing that you did only I had the cylinder spinning. It wasn't pretty. It went in the scrap aluminum pile.

Later
Dan

 

[parrisw]

Will
Give some thought to doing your lower transfer work before you machine the base. You don't have to worry about your tool slipping and hitting your nice machined surface. I have done it that way for years.
Your machine work looks good, no chatter marks in the chamber or the base.

Late
Dan

Ya, I've done it that way before, don't know why I didn't do it this time. Thanks for the heads up, and thanks for the compliments!

 

[parrisw]

[video=youtube;XNj_pCw_eUI]http://www.youtube.com/watch?v=XNj_pCw_eUI[/video]

 

[Mastermind]

Dammit Will....

I've done worse.........if you do this stuff things are gonna happen.

I do 4 or 5 saws a week, normally without any issues, but the learning process was expensive.

:hmm3grin2orange:

 

[jropo]

Pretty cool!!
I want a lathe.

 

[parrisw]

Dammit Will....

I've done worse.........if you do this stuff things are gonna happen.

I do 4 or 5 saws a week, normally without any issues, but the learning process was expensive.

:hmm3grin2orange:

Yup, it's not the first time I've messed up.

Pretty cool!!
I want a lathe.

Ya they are nice, I wanted one for a while before I got this one.

I figured I'd show a vid of that, since most people don't. Lots of vids of the finished saws, but none of the process.

 

[jropo]

Some people might not care so much, but I like machine work and can appreciate a nice finish.
I don't know how smooth I'd want to go on a sealing surface (not saying that yours is too smooth).
I like to see some "haze" for the gasket material to fill/ hold. Yours looks perfect.

 

[parrisw]

Some people might not care so much, but I like machine work and can appreciate a nice finish.
I don't know how smooth I'd want to go on a sealing surface (not saying that yours is too smooth).
I like to see some "haze" for the gasket material to fill/ hold. Yours looks perfect.

I like it smooth.

 

[Trx250r180]

nice work ,do you have any problem with the out of round jugs shaking on the lathe when spinning ? looks like an egg going around and around

 

[parrisw]

nice work ,do you have any problem with the out of round jugs shaking on the lathe when spinning ? looks like an egg going around and around

No, I turn it on the slowest setting, if you speed it up it does.

 

[parrisw]

Got some port work done this morning. Intake and ex done, no chamfer yet, lowers opened and gasket matched as well.

Who here that does port work, flattens out the bottom of the intake more then this? I've often thought about going flatter, but never want to open the intake too much to loose velocity, and end up with too much area in the intake port.

 

[komatsuvarna]

That looks nice Will!

 

[parrisw]

That looks nice Will!

Thanks. Lets just hope it runs nice too! I'm going slightly higher on the numbers then the last one, so we'll see.

 

[komatsuvarna]

Thanks. Lets just hope it runs nice too! I'm going slightly higher on the numbers then the last one, so we'll see.

I hope to get to do my other one in the next few weeks. I got an idea, but not sure which way Im going for sure yet..... thinking about staying low and going for torque... who knows though .

 

[parrisw]

I hope to get to do my other one in the next few weeks. I got an idea, but not sure which way Im going for sure yet..... thinking about staying low and going for torque... who knows though .

All the 372's I've done so far, I stay at 100* ex, 160*dur, and same on intake, 120*trans. That makes a great running 372. I just want a little more this time. Actually last saw ended up at 161duration on the ex, and it runs really great, but the compression isn't the highest on that saw, hopefully with the chamber cut .050" on this will net me some more compression.

 

[komatsuvarna]

Thats good numbers Will. I've went a little higher on a couple to experiment some. One thing I know for sure I wont do again is get much over 160 on the intake. Seems like the throttle response starts to suffer when ya get much past that point on a 372, in my experience anyways. I think 160 to 164 on the exhaust with about 20 to 22 degrees of blowdown make an all around good runner.

 

[parrisw]

Thats good numbers Will. I've went a little higher on a couple to experiment some. One thing I know for sure I wont do again is get much over 160 on the intake. Seems like the throttle response starts to suffer when ya get much past that point on a 372, in my experience anyways. I think 160 to 164 on the exhaust with about 20 to 22 degrees of blowdown make an all around good runner.

Yep, I agree. I'm going for 80* atdc on the intake. and 98* on the ex and 120* trans, 22* blowdown. Intake and ex are set now, just need to do the transfers.

I don't like a pile of intake on any saw. I don't mind burning fuel, however I hate wallking out of the bush over logs and crap to go fuel the saw up all the time, I suppose I could carry fuel, however I don't want to.

 

[Mastermind]

If you are looking for more......on your next 372 cut the chamber and do a small popup. Shoot for 190psi.

 

[parrisw]

If you are looking for more......on your next 372 cut the chamber and do a small popup. Shoot for 190psi.

Thanks Randy. This is the first squish mod on a 372 for me, and I don't know how far I can take it, so I started with .050" out of the chamber. We'll see what that gets me, the 372 cylinder base's are awfully thin when you machine this much off. I have another 372 cylinder here, that'll will be going into my 371.

Another Idea I had, I'm not sure how well it will work or if at all. I thought about cutting the chamber at 4* and cutting the top of the piston at 2*, maybe that will make a bit of difference maybe not enough to notice, but thought will give better flow across the piston then a popup, but likely not net as much compression as a popup.