I mailed the seller of the $13 pistons (above) and he says they are marked JCC.

That'd make them the pistons Drag Specialties sell for about $68. They come with a good enough reputation.

 

My evo is bone stock Spanners,never been apart, so when Andrews and others say "bolt in " they should add, unless your evo is 84-86 then it may or will have NO valve relief pistons, so new pistons are required along with extensive measuring for proper valve clearance with chosen gaskets and any head skimming. Then I may have chosen a different route or planned accordingly from the start. I'm not really blaming anyone personally but I think a lot of people can be educated by this early evo rebuild. Money is not an issue and it's only December in Connecticut, so no biggie, it will all work out.

 

that's exactly right. there should be some kind of 84-86 disclaimer on all of their evo cams listed.

 

Thanks for having my back...

 

When will you have all of the parts back together to measure them up?

No need to worry until you do. Best not to do anything to the cylinders until you have.

In Andrews' defence, their instructions do state that it's necessary to check for other clearances, e.g. lobes hitting cases, but they do not mention checking piston clearances. I think would be a valid update for their instructions these days, especially given that many older bikes have been hacked around with. But I wonder if the responsibility for the "bolt in" myth really lies with all the catalogue printers and resellers who have repeated it as a shorthand 10,000s since?

With a loose squish and 60 thou head gasket, I'd bet it would still be safe. I'd bet the valves don't protrude below the face of the cylinder head, but performance would definitely be down. Setting the squish right (moving closer to 30 thou) should definitely be on your list of things to do which, yes, I would then agree probably does involve changing the pistons.

I've given a few good leads how to do so cheaply. I would not spend money on a like-stock build. It's just not necessary to do so but if you go for higher compression ones, you wont be disappointed.

 

if you were riding and or doing performance work in the mid 1980s you would have seen the info you are now confused about 30 YEARS later

 

that's not the point of this thread. the point is, the cam seller isn't telling prospective buyers facts they need to know. not everybody was doing "performance work" in the mid 80's. there's lots of people doing "performance work" today that know nothing about pistons in the early evo years.

 

I'd agree with you. There are plenty of techs who weren't even born when those bikes came out ... backwards according to your life and ask yourself if you would know about the idiosyncrasies of bikes built years before you were born.

However, pressumably Andrews assumed that anyone swopping a cam out would adhere to the most basic mechanical principles (check and measure everything first), which amateur end users might not. They really should not encourage people just to 'bolt in'.

But I think of 'bolt in' sort of shorthand meaning, "stock springs and rods with no case clearances", not that you actually can 'just bolt in'.

As a 'service to the community' I'd get on the case and call or write to Andrews suggesting they update their instructions ... or just 'bolt in' the cam according to the instruction, see what happens, and sue them afterwards if it breaks. However, it'd have to break and it may not ... Sadly, I'd be surprised if Andrews will bother without further provocation though, so just send them an invoice for your rebuild instead.

I'd be interested to see what you make the clearances to be when you measure it all up.

The bigger problem will unfortunately remain though ... of all the box shifters, catalog copy and Ebayers pasting erroneous information. That's a problem I see causing countless issues in numerous areas.

Ebay resellers are the worst, as most of them are just data inputers with zero mechanical ability beyond installing apps on their iPhones. It's a problem of the modern world where the end user is so detached from the individual causing their ails that no needs to care or bother who they **** up or how much as it will never come back to them, not like in the old bricks and mortar days of business.

But, please hassle Andrews over this. It might save someone pain.

 

its 30 years ago the info was out at that time and does not need to be now - and if he had asked a real harley mechanic instead of a twinkie boutique owner he would not be confused

maybe a hand full of those pistons are still being used today and it would cause more confusion to add a disclamer for a mistake harley made 30 plus YEARS AGO

i guess being confused is OK if your not prepared to move forward

 

Would you just "bolt in" any non-standard cam to any Evo head?

It would be good if Andrews could at least issue an edicts to all resellers not to sell them as simply "bolt in", and underline the need to check everything.

Again, I think it's an issue of definition of what bolt in means, and it's utterly misleading as even for the mild cams they warn buyers in the instructions that it might be necessary to machine cases for lobe clearances. They should say warn about piston clearnace too.

However, I just roughly measured up a set of heads I have around at present and the exhaust valve would not hit a piston without cut outs until about .270" valve lift, i.e flush with the squish or face of the head.

Faking up a 45 thou gasket, I make that a .360" TDC lift. Add to that the distance down the hole the piston tops out at, say 10 or 15 thou, and you have another another 30 thou.

Yet an EV27 has a TDC Intake Lift of 0.182" and a TDC Exhaust Lift of 0.166".

The book says "add an additional 50 or 60 thou clearance". OK, honest question, so where's the contact going to happen, or where is the methodology wrong?

That was roughly done, but measured with a dial gauge held at the same angle as the valve. These specific heads have been skimmed 50 thou but faking up a 45 thou gasket, I measured .310" before I'd hit a piston without cut outs on them.

I'd say those collision cases had to have had skimmed heads and/or hi-comp pistons, and the OP has been somewhat unnecessary spooked.