I have a new jug on the way to freshen up my 372XP XTorq. I do not want a louder saw so I'm leaving the muffler alone. But I'm reading about lowering the squish. Is a lower squish a useful modification all alone on a stock saw? What is the reason the factory doesn't set them lower in the first place? Thanks, David
Lowering the squish just increases compression. It doesn't hurt to have a bit more but, if you are putting a decent aftermarket with a set of caber rings or, OEM top end on it, you are going to be in the 160-165 PSI range. I'm no saw mechanic and have very little experience in running a known saw over that much compression so, take what I'm about to say with that knowledge. After running my saw rebuilt in that range, I can't see where a lot more is better. And researching it on the internet and hearing from some well known saw builders, it seems to be subject of give and take. Meaning there are trade offs. And it seems to me that range is generalized in the 180-200 range between these guys. I cannot nor am trying to speak for others. Just stating what I have read. I'm not saying who is right. I don't know and, have never even run a saw that high that I know of. I just know I own a 385 XP that is setting at 170 PSI and you can literally lay on it in the cut and it just keeps on cutting. Fast at that. My newly rebuilt 372 XP is at 165 PSI. It runs VERY strong too. With no muffler mod in the plans, I see no reason to adjust the squish in my very limited experience. And, that is what it is. Very limited and open for criticism. So, hopefully one of these saw builders will come along and, agree or teach us both something. God Bless
I've heard the like new compression is a bit low on this model. It's not a big deal I guess to run it for a while and increase it later, just pull the intake and cylinder again.
The xtorq has higher compression than the old version. It will net a torque increase for the extra compression.
It has some scoring. I changed bearings and seals this winter and it was iffy whether to re-use it. Now I'd like to sell it so I'm freshening it up.
Even if you want to put a new jug on it dont worry about squish just to sell it. Just use the base gasket and be done.
What I'm hearing is you'll have a 372 w/new jug & piston. And a scored cylinder for sale. I'm all ears
I didn't realize that a stock x-torq would blow 165? I've had a few OE 372s and they were typically in the 135-145 range. I replaced the piston in one, and removed the base gasket, and got it up to 160... with no muffler mod, that saw ran pretty damm good. I'm sure opening up the muffler would've helped even more.
Think I ought to bolt it together without base gasket and see if it's ok to go? The old parts with stock. 020 gasket measured .041 just now. I hear .020 is a good number so hopefully I can simply skip the gasket. We'll see if the replacement parts measure the same.
Well, I'm not sure what to tell you. However, I do know the 3 stock 372's I've seen tested, all were right there. They were even tested o the same compression meter. And, it isn't broken. I guess they were stock. They certainly looked new enough and were being advertised as stock by their owners. However, the only stock 372 I have had, that wasn't wore smack out I just got and, I will test as soon as I get it to my uncles, who has the tester. I'll post the results. I can tell you right now from pulling the cord though, it has just as much if not more than the newly rebuilt one I quoted in that post. I'll let you know. With no valves, a Muffler Modification makes compression less on a saw. Which, I think you know. Which is why I said what I said earlier. I think it isn't needed to to be 180 in my experience on working saws. Which isn't the gospel. But, after running the saws I own and, saws of others that I knew the compression on, It's going to be hard to convince me that it is worth the wear and tear to run them at the higher PSI. Especially on a saw I intend to run well for a long time. God Bless
Compression has to do with the piston squeezing air/fuel mix in an enclosed space. A stock muffler or even a muffler completely removed has no effect on that.
Not to argue anyone's point, But My take on squish is this.. Although a tighter squish Will raise compression, the real benefit is a better running engine. if you look at the cross section of the chainsaw engine. as the piston is coming up the hole the fuel charge is covering the whole top of the piston. when the piston gets up close to TDC the spark ignites the charge (it takes a small moment for this to light, that's why you have advance) once lit and getting near peak explosion the fuel charge that was covering the whole top of the piston is now All forced to the middle of the combustion Chamber because the edge's of the top of the piston are all covered closely by the squish ring in the head. By forcing everything to the center at the same time the fuel charge is going to explode at max psi is what makes every stroke more powerful.. Yes the by product is higher static compression, But its worth it
The muffler has nothing to do with compression. Like Red said you can not have a muffler and it not matter. Reason is that your max compression is at the top of the stroke. Neither exhaust or intake or transfers are open when the piston is at the top of the stroke! Look at a cylinder again when its off the saw.
I agree that a muffler mod will do nothing to change the compression. I just didn't realize that an x-torq had that much more compression than a pre-x-torq. A real healthy OE 372 will only blow 145 or so. Ive heard that stock vs. stock the x-torq has more torque than the pre-x-torq saws... maybe the compression bump gave the newer saws a bit more torque?
