I'm curious how you are getting different numbers from different cyls... the stroke is the same, and the pistons should be a match... this leads me to believe who ever did the cleaning up* of your cyl bases didn't exactly cut them the same amount. and how are you arriving at your .035 squish number?? were the heads milled or not?? and how much...also how far out of the hole are you pistons coming out?? stock pistons?? weisco's 8.5:1?? or high compression pistons?? not ragging on what you are doing... im just curious how you have arrived with a .035 squish by only using .030 head and .020 base gaskets.

 

Possibly by the guy that cut them for me 20yrs ago but I don't think he was that concerned LOL.Like Omaha said it shouldn't make a difference

 

Being this is the first time I have paid attention to quench/squish/deck height during an engine rebuild, I will try to answer to the best of my ability.

From what I have read on forums, websites, etc. (and heard in conversations), there are certain manufacturing tolerances. Some components are at the upper end and some are at the lower end of those tolerances.

Knowing that no two components are exactly the same, and the manufacturers not wanting to spend the time or resources on matching components like cylinders, connecting rods, blocks, cylinders, etc, in a mass production environment, they have built in clearances or specs that will tolerate "worst case scenarios" like all the components being at the upper end or at the lower end of those tolerances, with the components/engine still functioning properly. I guess an example of these tolerances would be cam and pinion gear matching, look at all the different color codes they have.

Being a home builder or shop that can take the time to measure, compensate, adjust, and match up those tolerances and components helps remove some of the built in "slop or play factor" (for lack of a better term).

An example would be like the quench or squish.

What I did with mine is I installed the new pistons and pins on the rods without clips or base gaskets and installed the cylinders only. I used spacers and snugged up the head bolts. Then I ran each respective cylinder up to TDC and measured across the piston top (from left to right not front to back) over and inline with the piston pin to minimize piston rock variances.

I used a machinists ruler and feeler gauges, measuring multiple times from the left side and the right side and then comparing/averaging those numbers to determine deck height taking into consideration that I am using Cometic SLS base gasket that is .020 thick.

Yes, the pistons are wiseco 8.5:1 flat tops and my head gasket is Cometic MLS .030 btw. Heads have not been milled. I have read that there are other methods of doing this like using a sacrificial base gasket, and the method I used is similar to what some of the twin cam guys do. The twinkie does not use a base gasket, just an O-ring, and they measure it by temporarily omitting the O-ring, snugging down cylinder only, measuring and then doing the math like I did

I feel pretty confident of my numbers because I measured multiple times, and the SLS gasket has next to no compression since they a steel.

I cant speak for what my machinist did, I told him to true up the bases. How much he actually took off, I can't answer and don't really have a way to measure it anyways. Wish I knew.


EDIT: Forgot to include measurements, measuring without the base gasket my pistons after rearranging them protrude above the cylinder in a range of .014-.016, so take .020 base gasket into consideration then my pistons sits .004-.006 below cylinder deck. I am going with .005 number.

Hopefully that answers your question. YD

 

excellent....I was curious since you didn't give any measurements other than which gaskets you were using, and the differences** in cyl heights...front to rear and your initial question does it make a difference** on a side note..I haven't ever seen a weisco ( not that it isn't possible ) ever come up in the cyl which are the same lengths show more than maybe a 1 thou difference.. If you had , had your heads milled in the .050 range..it takes your weiscos in the lower 9.0- 9.25: range and really wakes the motor up without sacrificing any streetablility and of course changes the CC of the head.... there are and have been some really great motors come out of the garages**home shops...

 

Thanks for that tip regarding milling the heads. I am keeping things the way they are for now...I did put a Vthunder 3010 cam (and Johnson hylift lifters) in while the parts were at the machine shop (and new b-138 bearing), so I am looking forward to seeing the improvement in performance with that. Have been wanting to put a cam in for years. I used my stock cam gear.

I also understand the thinner head gasket will up the compression slightly, but probably won't notice much. I will strongly consider heads being milled at a later date, just gonna see how things run as it is now with the recent changes. The whole quench concept got my interest because of the comments I have read about a better burn, more efficiency, less chance of ping, running cooler, etc.

I am also looking forward to running an engine that is basically starting from scratch. The amount of carbon on the pistons and valves was startling. I vented the heads to atmosphere shortly after I got the bike about 5 years ago, and I corrected a really rich condition from the previous owner, so proof is in the pudding I guess with regards to these engines re-breathing the oil mist. I used a few additives here and there along with water mist, but looking at all that carbon tells me it did not do much.

I got the pistons and cylinders installed today after work so making some progress. We will see how much I accomplish this weekend. I try to keep myself from rushing but it's tough to do when you hear the bikes running down the road off in the distance...thanks again for the info and the double check on the deck height. YD