No cylinder base gasket.

[400exdad]

I read one of Mickey D's replies the other day that got me to wondering... Has anyone removed the base gasket, used sealant and replaced the stock 400EX headgasket with a XR400 headgasket? (skip to end if you don't want to read my "blah,blah,blah" :D ) If the piston is low in the cylinder, I could see that the compression would be less than advertised. But, I think Honda knows what they are doing... One thing that concerns me is changing the cam timing. I haven't done the "math" yet as to if the cam was being advanced or retarded, but by closing the valves a little earlier may help the cylinder build more pressure. What do you guys think?

Yup,,,like if you buy a 10.8:1 piston and use a 400ex gasket your actually only gonna get like 10.5:1. If you use the xr400 then you'll get the correct compression,,,since the bore kits we all use for our 400ex are actually bore kits for the xr400. I used the ex gasket just so there wasn't any slop in the timing chain which might lead to premature wear,,I'm sure gabe would have some good insight on this question,,,people also peel off a layer or 2 from the 400ex gasket to get the same effect..

[MIKE400EX]

I believe that if you "lowered" the cylinder, you would as a result retard the cam timing slightly given the position of the tensioner.
I can't recall the cyl. gasket thickness, but removing a .020" gaskt. would only retard the timing about .75 Deg.(or 45 minutes). I don't think that's enough to worry about.

[oynot400]

I was wondering what to do with a 440? I would like to get to that 11:1 compresson. Will the xr400 head gasket work or not? I was guessing not. I am not for sure because of the larger sleeve. :confused:

[MIKE400EX]

A stock XR400 head gasket from Honda will NOT work on a 440! The aftermarket suppliers (cometic etc....) sell "big bore" gaskets kits for XR400's and 400EX's seperately - I believe the difference is in the head gasket thickness - but don't know why they would be different. I do know (not much but) there are thin & thick big bore head gaskets. I'll call cometic and post their reply.

[oynot400]

Thanks MIKE400EX, I would be curious to know. I didn't think that it would work. I would like to know how to check what my compression ratio really is. If it is really 9.75:1 I need to do something different. :eek:

[oynot400]

Hey I just reread this post. It sounds to me that you are worried about timing advance or retardence from the thickness of the gaskets. Now we are only talking about what 0.003"? Don't you think that the cam chain tensioner would take care of that. ;)

[400exdad]

Thanks for all the input guys. Bottom line is: I just need to get off my wallet, get on the phone with Marcums and order up the cam and don't worry about the base gasket deal. If I pull the cylinder off, I might as well put the right piston in it! Geez, I'll do anything not to spend money! Hey Rico, remember, what I said in my cam post and being my birthday and all.... I need to just do and use her credit card!:D

[400exdad]

Hey Rico, just noticed your new title... it was "flying a-hole", then "booger picker" and now its "ceo of exriders". Shouldn't it have been "brown noser extrodinaire" before CEO... :p

I'll use that one next...:D ;)

[MIKE400EX]

OYNOT400
I'm putting the Wiseco 11:1 440 piston in this weekend. I'll measure everything and post what the compression really turns out to be.
BTW, the base gasket is only .015" thk., or equiv. to about .6 deg. >> even less to worry about!

[Matt Fisher]

Whether the head gets milled, you run thin gaskets, or the timing chain streaches, all of the above cause the cam timing to be retarded. This results in the power being shifted to a slightly higher rpm. Just like advancing a cam causes the power to come in at a lower rpm. Depending on your motor, this may be good, bad, or irrelevant. Testing's the only way to know for sure.

Although the tensioner takes up the slack, the cam timing itself is still affected. Ignition timing is not.

On a OHC motor like a Chevy or whatever else, it has no real effect on cam timing.

You can't run a regular head gasket because the 85 mm cylinder hole is 4 mm too small for a 440. The edge of the gasket would be hanging off in the combustion chamber.

Cometic has 3pc stainless steel gaskets in thicknesses from .25 up to .40 (both base and head), so you can adjust your compression ratio and chamber volume. If you needed a smidge less compression, you'd be better off using a thin head gasket, and a thicker base. This would lower the compression ratio, while keeping the chamber volume down.

I spoke with Chad (I think that was his name) at ext125 the other day. Very helpful, he said they would custom make different thicknesses at no extra charge.

Mike, are you going to CC the head? Did you ever get a chance to check the cam's hardness?

[Wingnut]

If what y'all are saying is true, then even if the timing is retarded, and bottom end power is hurt, wouldn't you gain that power back, or maybe more, with the added compression?

[MIKE400EX]

MATT
Yes I will CC the head, check the deck height and post . The cam hasn't shown up yet - hopefully today.

[oynot400]

I wonder if Mr. Dunlap would jump in and give his views on this subject. :)

[Matt Fisher]

Wingnut- you are correct. Advancing or retarding the cam only changes the timing of when the valves open in relation to the piston. The old small block Chevy "advance it 4 degrees" meant that the valves started moving 4 degrees sooner than if the cam were installed "straight up". The same goes for any motor. This will more the powerband down in RPM's, retarding it moves the powerband up. The increased compression and displacement more than makes up for any minor lost bottom end.

The advantage to degreeing a cam is that you can optimize the valves opening and closing for the rest of your engine's combination. With some motors, retarding the cam a few degrees will have a very minor, almost unnoticeable effect on the bottom end, yet will certainly improve the useable rpm's on the top. I suspect that a 440 with an XR or stock cam would perform better this way, given the mild nature of these cams.

Other motor combinations will respond to advancing or retarding a cam differently. The only way to find out is to test it.

If you want to slot your cam gear and experiment, make sure that you won't have any valve to piston contact before running the motor.

Did that help? :huh


Mike- I'm more than a little curious as to what your results are. I'm assuming you'll be checking piston clearances, pin to deck height, etc?

[powerslider]

Thanks for the heads up info on this guys, I would appreciate your final findings as I have this project to conquer shortly. Are the JE and the Weisco pistons different resulting in a taller deck with the piston and less "in the hole" distance. I would like to get close as as I can to the actual 11:1 ratio. I plan to run the HRC or equivilent cam with the stock bore at 11:1.

Keep the good stuff coming!!!!

ok..can i get a strait answer before i put my motor together. no base gasket and sealent...worth it or not

[VegasEx'r]

I just want to add some info to this thread. I installed a 416 kit from Marcum's last week, & I asked Terry about using sealant. He indicated that that wasn't a good idea. He strongly recommended using the gaskets that came with the kit. I did measure the thickness of the old head gasket & the gasket that he sent to me, & they were the same. I did not measure the thickness of the base gaskets, but the new one was noticeably thinner than the stocker. This was a Cometic top end kit that he sent me. I haven't tested the compression yet to see if it is a true 10.8:1, but will shortly. I think it probably will be, because of the thinner base gasket (& domed piston). If anybody wants the test results, let me know & I'll post them in a day or two.

[Ononewheel]

I just finished up a 440 kit this weekend. Honda base gasket was used. The kit had a wiseco piston in it. The piston was advertised to be 11:1. which was not the case. It was .043" in the hole. My friend cc'd the valve reliefs and then the head. With a cometic head gasket that had .030" torqued down thickness it yeilded a comp ratio of about 9.5:1. It also had a quench area of .073". We cut the cylinder down on a head broach to give us .040" quench. You really shouldn't go tighter than that, I have heard of people going tighter but there is a point when you will have problems. With the cylinder cut down to .040" quench you get 10.8:1 comp. I do not know how wiseco got their figures. We used a Speed Pro chart to figure cylinder and head gasket volumes that is how we figured comp ratios. I did not degree it, I know, Iknow.... I even have a degree wheel hanging in the garage. We figured It would not be that far off, and we would not adjust it anyways so **** with it. It had no clearance problems. It makes mucho power right off idle and seems to want more when it hits the rev limiter. It has a TC GNCC cam in it. The timing chain tensioner had plenty of spring to be sprung.
I think it is a good idea to eliminate the base gasket and use a thinner head gasket on 400's. I would do that before I would buy another piston, The gasket thing is almost free. Be sure to check you clearances though, with clay or somthing at least. I see no reason why it is a bad idea... what's the worst that could happen? It could blow the base gasket, but if the case is vented, how could it? I hope this helps someone out. And LRD... do it. I do not want to come across as a know it all here but that is what I did and I think could help some out. I also agree with everything Matt Fischer had to say. Just my .02cents.

[Ononewheel]

Oh and by the way, EXCELLENT thread guys. It's things like this that make the big power. Taking the time to measure and adjust you set up will make a huge difference in power output, separating you from the other thousands of 440's and 400's. It is unfortunate that things are not always what the are advertised, but I guess that leaves the space we need to get ahead. All we need now is for the cam manufacturers to start giving out their cam specs so we can pick the best cam for the job.
Keep it coming guys.. I love it.

[Matt Fisher]

I have the specs for many of the cams out there. Right now, I have the LCA's for Megacycle cams, and stock. I'm going to see if Web will give me their LCA's.

I just pulled the valve cover (cam cover) off my bike last night. GT Thunder cam in there. It has 450/451 fight on the cam (Web makes the cam).

Has anyone put a 400EX head on a flowbench? I'd like to see what kind of numbers they achieve, and at what lift do they stall out.