Have you Decked the cylinder

[Ononewheel]

I am doing a 440ex for my buddy. We found that the wiseco piston that came in the kit was about .040" in the hole giving us a quench of .073" and a compression ratio of about 9.5:1. It is labeled as a 11:1 kit. We cut the deck of the cylinder down to give us 0" deck, which in turn yeilds .040 squish and a comp ratio of 10.35:1. Will cutting this .040" off cause a problem with the timing chain tensioner? Has any one else noticed the advertised comp ratios to be that far off? Let me know what you think, Thanks

Check out Mickey Dunlap's tech article. He says pretty much the same thing except I don't recall anyone talking about decking the cylinder. Can't see how 30-40 thou. would cause much problem with the tensioner though.

[Ononewheel]

I just read what Dunlap had to say. He was right on, the piston was exactly .043" in the hole, same as stock. He did not mention anything about the timing chain so I am guessing that there will not be a problem.

[Matt Fisher]

Decking the cylinder, thinner gaskets, etc. will all cause the cam's timing to be retarded. Not stupid , retarded. Thicker gaskets will advance the cam. The cam tensioners position makes it all happen.

Get a degree wheel and check it. You can slot the holes in the cam gear to advance or retard the cam.

Good info about the Wiseco piston. When I do the Ross one in my bike I'll post the results. They say 11.2:1 using XR gaskets, and that the piston is .025 down in the hole.

[MIKE400EX]

Yes, the Wiseco 440 11:1 piston has the same pin height as the stock piston, hence the same deck height. It took .003-.005" to deck the cylinder after the sleeve installation. Deck height is now .040". Pretty close to what OnOneWheel measured. Cometic makes a .025" thk. coated stainless gasket. With that gasket the comp. is 9.8:1. Take another .030" off the deck and you get 10.8:1 >>>much better! Wiseco must have calculated the 11:1 number assuming a "0" deck height. Guess I'll go back and deck it another .030" or so and check the cam timing - should be retarded about 1.5 deg. I'll post all the actual numbers later. As a side note, Honda is right on with their 9.1:1 stock figure!

Matt Fisher: Does that Ross piston have a dome, or is it a flat top?
The Wiseco 440 11:1 piston, pin, rings & clips weigh 402 grams total, stock was 383.

[Ononewheel]

Good info guys, thanks I actually didn't even think about the cam timing. I have a degree wheel so I will check it out before we run it.

[Matt Fisher]

Mike, it'll be a couple more weeks before it gets here. I ordered 4 custom 89mm ones. Light milling around the pin boss area, special lightweight wrist pin. It'll weigh the same as a stocker, give or take a gram or two. I could have had it even lighter, but am unwilling to sacrifice strength, and by keeping it close to the stock weight, there's no balance issues. I'll also be polishing the entire piston before dropping it in.

Honda Jim (who designed JE's 440 piston) says it'll be an 11.2:1 using XR gaskets. I'll spec everything out when it arrives.

Why not use the thin Cometec head gasket, and no base gasket; just some sealant? Skip another trip to the machine shop. Plus, it's he11 adding metal later

Ononewheel: When you degree everything, check the valve clearances with the cam advanced and retarded, that way you can fool with the timing without worry. There's more power hiding in these motors, we just need to keep looking.

This is the kind of tech that's woefully missing from most boards, excepting some automotive ones I've followed. Good stuff!

[DISHO1]

how do you degree in the xr400 cam?

[Ononewheel]

Disho1, that is a good question. All automotive cam manufacturers give you a spec sheet that will tell you when everything is supposed to happen. Trouble is for some unkown reason the folks that are selling these quad cams are greedy with the specs, you can get lift and duration but after that you are pulling teeth. Web is the only one I saw that would give lobe centers but that is it. I am sorry I do not have a good answer for you. But try this, go to a performance shop for cars and get a book about building motors and it should tell you all about degreeing.
Oh, and Matt you rule dude. Are you into racecars? You are right about more of this stuff needing to be posted, there is so much free horspower in engine building it's shocking. The only reason we decked it instead of using thin gaskets is because we have access to a head broach and gaskets cost us more money and time. We are going to clay it up and see what we got. I am concerned that if we have to oblong the holes to advance the cam, it will be in the direction that it will slip back and fall off. Do you have any ideas? I will let you guys know what we find out we are waing on the cam to come so we are on hold right now.

[Matt Fisher]

DISH01 here's a simplified version- a disk (degree wheel) is attached to the cranks end, and it's marked for 360 degrees. You find piston Top Dead Center (TDC), and position a pointer so that it points to 0 while the piston is at TDC. Next you use a dial indicator on the camshaft, finding the center of the lobe. Look were the pointer is on the degree wheel. If you have a Megacycle 196-x2 cam, it should be at 107 degrees, since that's where Megacycle claims it should be. If it's not, or if you wanted to advance or retard it, slot the cam sprocket and set it where you want. The problem is that many of the cams out there don't have the specs available. Somewhat uncharted territory.

Ononewheel, I've done some work in the Mustang field. Mostly, I pay close attention to what knowledgeable folks have to say.

I remember that some aftermarket cam sprokckets for Honda's/Acura's don't have anything besides the tension of the bolts to hold it still. You could always make some bushings to take up the space in the slot if that doesn't leave you feeling warm and fuzzy. On automotive applications, if advancing or retarding the cam more than 6 degrees results in the best performance, you're not running the right cam.