Delete the base gasket?

Punkskalar

Punkskalar

Hugh's HandBuilt
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Been debating a few engine mods (as always) and I have my engine apart right now to replace the stainless valves and guides. I was diggin through Hoos's website a while back, and while looking at their 700CC Piston set, I noticed they say you can get a full point higher compression by not running a base gasket.

218358 JE 700 piston sets pistons, pins clips and rings $325.00 yes Shell liked these, make good power but don't need to re-sleeve 9.5-1 with base gasket 10.5 without.

I think I'll give it a shot. All my parts are gonna be bone dry and clean, so I should be able to use Hondabond and seal it up pretty good. Probably have to degree in the cam of course, but I do that anyhow. It would be the same as decking the head. I'll measure my base gasket (previously compressed) and see how much material I'll be "removing"
 
How'd do you think this would work on stock? I'm about to put my topend back together as well.
 
rwingsfan said:
Sounds cool Hugh, would'nt the two surfaces have to be perfectly planed to get a seal? Hell why not!
Click to expand...

Well,

They are flat enough to seal with a dry paper gasket, so some HondaBond might just be the trick... :thumbsup:

I'm gonna give it a shot, and let you guys know how it goes. A bump in compression is always nice.
 
Hugh, I tried lowering the deck by around .030" with a .016" copper gasket at the base and .020" at the head using 77.5 mm. Shell JE's (stock gaskets are .020" base, .048" head, uncompressed). The deck change produced contact (hard stop) between piston edges and head when I turned the motor--no squish clearance. Solder crushes were still too thin for comfort with the deck lowered only .010". That surprised me; I'd dropped the deck on stock displacement motors by .030" with no interference issues. If you're going to go that route you'll need to recut the squish bands--not an easy bit of machining.
 
I'll mock it up today, and see what it looks like. Im using the Wiseco CK194 707CC Pistons in this engine. If need be, I could machine the edge of the pistons slightly, but it if needs alot, then obviously it won't be worth it.. I'll take a look and get back to you guys...

Griz, Thanks for the input. It will all depend on the way these pistons are cut really.
 
Hell, why not? Because 10.5: 1 compression on a street engine is a grenade waiting to happen. I'd put the gasket in and call it good.
 
petesxs said:
Hell, why not? Because 10.5: 1 compression on a street engine is a grenade waiting to happen. I'd put the gasket in and call it good.
Click to expand...

10.5:1 isn't all that high. Its higher than stock yes, but I have a customer running an 840CC engine that is 11:1. He bends kickstarters, but it runs awesome :laugh:
 
Oops, sorry Hugh, didn't mean to sound so absolute--all I saw in your post was Shell JE, those Wisecos may work just fine with the deck lowered!
 
out of my own newb stupidity when i re-freshed my first XS 4 years ago, i didn't use a base gasket. Still running today in the new owners hands. No leaks, used a very light film of permatex. No dinged valves. i have learned alot since then.:laugh: I always ran shell v-power in it, never a ping or anything. seemed to run okay...but i'll compare it to the 74 i just refreshed.
 
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Go for it. I know some guys here are against raising compression ratio, (and sometimes lower it), never made sense to me, I say go for it. Gotta have a cam profile to match it , though. A lot of newer cars use just anerobic sealers like that now on case halves, cam boxes etc. Good stuff. Permatex makes a nice anerobic sealer if that helps.
 
I say go for it as well, just be sure no hard parts are going to bump. Shell himself used to leave out the base gasket when he need a little more umph, so you have great precedent on this. I'm running the JE pistons with stock base gasket and a thinner copper head gasket that I hope pushed me close to 11:1, so I'm interested in how this comes out!
 
So the stock base gasket from MikesXS is .018" thick, and the compressed gasket that I took of was .016" thick. I assembled the engine without the base gasket, and sure enough, the wiseco pistons were hitting the valves. :laugh: So I tore it all back apart, checked it over, and decided to run the bike with the base gasket as compared to spending to much time messing with flycutting deeper valve pockets into the pistons. These pistons are pretty healthy already, but I figured it was worth a shot.

I am running an XS1 Camshaft this time, as I have tried a 1981 camshaft (sucked), 1977 Cam (better) a shell #1 Cam (Awesome, but I broke it) and an XS1 cam (Nearly identical to the Shell Cam) in the past. I have a few XS1 cams I have been saving, as I really like them for the rephased engines.

I am building a 650 engine soon though, and it will be interesting to mess with this some more...
 
Question though, without the base gasket, isn't there a possibility that the o-rings at the base of the stock cylinders would fall into the sump?
 
You'll wanna do a dry fit. Sometimes you can keep the o-rings as they seat on the cases, and sometimes not. Either way, Hondabond will be the new gasket. I don't sweat removing the o-rings if needed
 
Thanks punkskalar! I already did a mock up with a 17 thousands copper head gasket and no base gasket. Put playdoh on top of the piston and in the valve pockets and the playdoh didn't get touched. If my calcs are right, no base gasket and the 0.017" copper headgasket will get 9.4:1 with stock pistons.
 
I know this is digging up an old thread, but I am thinking of deleteing the base gasket and I've heard the reference to indexing the cam.

I haven't had any luck finding exactly how to do this. Any help?
 

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