pistons
#11
12-20-2015, 05:45 PM
If doing the job on the cheap, is there enough material to cut reliefs in the old pistons?
Or is the cheapo way of doing it just looking for some OEM pistons from a later Evo?
What clearance are we talking about ... .060”?
Valve Head to Piston Valve Pocket
1. Paint the piston intake and exhaust valve pockets with machinist’s blue. This is a harmless coloring agent.
2. Secure both valves in one head, against their respective valve seats with an elastic band without valve springs.
3. Assemble the head to its cylinder without a head gasket and fix snugly with one head bolt.
4. Lower each valve individually and rotate it as the valve head touches the top of the piston to mark the machinist’s blue.
5. Remove the head and inspect the contact area of the valve heads to the piston valve pockets.
6. The valve should fit into its mating valve pocket cutout in the piston dome.
There should be minimum .060” clearance around the periphery of the valve head in the pocket. The thickness of the installed (compressed) head gasket will affect this tolerance.
7. If not, disassemble, grind or machine the valve pocket in the piston dome until there is sufficient clearance with the valve sitting flush in the pocket.
8. Repeat this with the other three valves and their mating valve pockets.
Valve to Piston Clearance at TDC
1. Put some mechanics putty (Plastocene) into all four-valve pockets with the pistons and wrist pins without rings in their cylinder bores to check the valve to piston clearance at TDC.
2. Install the assembled cylinder heads and head gaskets onto the cylinders with the rocker covers, roller rockers, and pushrods without pushrod tunnels.
3. Adjust the pushrods down collapsing the hydraulic lifters until they lightly bottom out.
4. Rotate the engine in its normal direction carefully. If meeting resistance, stop immediately and disassemble. Rotate two complete revolutions so that all four cycles or strokes move through their full rotation.
5. Disassemble and measure the putty in each valve pocket. Intake pockets should have minimum .060” clearance but some set the exhausts with .080” clearance between the valve face and the valve-pocket-recess face. I don’t increase my clearance in this case unless the manufacturer gives me reason to. Grind or machine pocket recesses if necessary to obtain minimum clearance.
[cue: comedic aside ...]
I thought I'd try and fit in more this time round!
(But, hey, don't give the game away too easy, will ya? I'm still H-D owner and support other H-D owners ... regardless of race, creed or color; or how the unpaid workers (moderators) of an $1.1 billion company feel about about people expressing alternative political views. I don't need someone else running off to snitch to the admin already!).
Or is the cheapo way of doing it just looking for some OEM pistons from a later Evo?
What clearance are we talking about ... .060”?
Valve Head to Piston Valve Pocket
1. Paint the piston intake and exhaust valve pockets with machinist’s blue. This is a harmless coloring agent.
2. Secure both valves in one head, against their respective valve seats with an elastic band without valve springs.
3. Assemble the head to its cylinder without a head gasket and fix snugly with one head bolt.
4. Lower each valve individually and rotate it as the valve head touches the top of the piston to mark the machinist’s blue.
5. Remove the head and inspect the contact area of the valve heads to the piston valve pockets.
6. The valve should fit into its mating valve pocket cutout in the piston dome.
There should be minimum .060” clearance around the periphery of the valve head in the pocket. The thickness of the installed (compressed) head gasket will affect this tolerance.
7. If not, disassemble, grind or machine the valve pocket in the piston dome until there is sufficient clearance with the valve sitting flush in the pocket.
8. Repeat this with the other three valves and their mating valve pockets.
Valve to Piston Clearance at TDC
1. Put some mechanics putty (Plastocene) into all four-valve pockets with the pistons and wrist pins without rings in their cylinder bores to check the valve to piston clearance at TDC.
2. Install the assembled cylinder heads and head gaskets onto the cylinders with the rocker covers, roller rockers, and pushrods without pushrod tunnels.
3. Adjust the pushrods down collapsing the hydraulic lifters until they lightly bottom out.
4. Rotate the engine in its normal direction carefully. If meeting resistance, stop immediately and disassemble. Rotate two complete revolutions so that all four cycles or strokes move through their full rotation.
5. Disassemble and measure the putty in each valve pocket. Intake pockets should have minimum .060” clearance but some set the exhausts with .080” clearance between the valve face and the valve-pocket-recess face. I don’t increase my clearance in this case unless the manufacturer gives me reason to. Grind or machine pocket recesses if necessary to obtain minimum clearance.
I thought I'd try and fit in more this time round!
(But, hey, don't give the game away too easy, will ya? I'm still H-D owner and support other H-D owners ... regardless of race, creed or color; or how the unpaid workers (moderators) of an $1.1 billion company feel about about people expressing alternative political views. I don't need someone else running off to snitch to the admin already!).
#12
12-20-2015, 05:53 PM
I will buy new pistons if need be but rather not bore over.
#14
12-20-2015, 06:36 PM
Don't be like that! I'm getting stressed out here, this was supposed to be a easy upgrade while I was only trying to replace my leaking gaskets! Now I need to buy pistons,people shouldn't be saying I can just pop in a 27 cam and go.
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
#15
12-20-2015, 06:46 PM
Join Date: Jan 2011
Location: Haslet Texas
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Don't be like that! I'm getting stressed out here, this was supposed to be a easy upgrade while I was only trying to replace my leaking gaskets! Now I need to buy pistons,people shouldn't be saying I can just pop in a 27 cam and go.
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
If you have read some of his other posts then you would notice wrong words used sometimes and when asked about it john said it was his phone.
Having talked to john I highly doubt that he meant to say he wouldn't help.
#16
12-20-2015, 06:47 PM
Join Date: Jan 2011
Location: Haslet Texas
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#17
12-20-2015, 06:49 PM
Join Date: Jan 2011
Location: Haslet Texas
Posts: 21,008
Likes: 0
Received 4,361 Likes
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1,953 Posts
Don't be like that! I'm getting stressed out here, this was supposed to be a easy upgrade while I was only trying to replace my leaking gaskets! Now I need to buy pistons,people shouldn't be saying I can just pop in a 27 cam and go.
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
What if I just get stock size cast pistons with relief and use the .045 in my kit ? That shouldn't be that close.?
I appreciate your input, you probably just saved me a grand..
I personally didn't know the early models didn't have reliefs in the pistons.
Can you just go back with the same cam you had?
#18
12-20-2015, 07:35 PM
You cannot assume anything whether from a manual or from an "expert" because
a) they/you don't know the full history of the bike, and
b) H-Ds manufacturing tolerances vary widely from bike to bike.
Yes, if I was doing the same on the cheap, I'd be looking for a low mileage takeoff pistons from a later Evo off Ebay (see comment re measuring above).b) H-Ds manufacturing tolerances vary widely from bike to bike.
Personally, I'd guess there is enough meat in the piston tops to machine a cutout. This is based on experience of machining other piston to vary compression, but it is purely an 'informed guess' as I have never measured them. It's the question I'd want answered from an expert like John.
However, as it's unlikely you have the equipment to do so, the next cheapest work around would be to pick up a pair of nearly new OEM pistons for next to nothing.
Unless John will machine them for you?
#19
12-20-2015, 07:47 PM
Well old cam has a bad lobe, pic was posted in the rebuild thread, so either way I need new one, stock .472 lift,ev27 .495 lift.
John said I need valve relief so why would he say if I bought new pistons with relief it wouldn't help ? So I thought he was insulted by my post. But he pm me,all good Tex
I'm going to mic my old cam at work tomorrow to see what lift.
California is ONLY .416 lift . Thought I seen a "CA" stamped on the engine case somewhere.
John said I need valve relief so why would he say if I bought new pistons with relief it wouldn't help ? So I thought he was insulted by my post. But he pm me,all good Tex
I'm going to mic my old cam at work tomorrow to see what lift.
California is ONLY .416 lift . Thought I seen a "CA" stamped on the engine case somewhere.
Last edited by glidein wide; 12-20-2015 at 08:25 PM.
#20
12-20-2015, 07:56 PM
No personal offence to John intended but the bottomline is ... you cannot trust anything that is just written. You have to measure, measure and measure again.
You cannot assume anything whether from a manual or from an "expert" because
Personally, I'd guess there is enough meat in the piston tops to machine a cutout. This is based on experience of machining other piston to vary compression, but it is purely an 'informed guess' as I have never measured them. It's the question I'd want answered from an expert like John.
However, as it's unlikely you have the equipment to do so, the next cheapest work around would be to pick up a pair of nearly new OEM pistons for next to nothing.
Unless John will machine them for you?
You cannot assume anything whether from a manual or from an "expert" because
a) they/you don't know the full history of the bike, and
b) H-Ds manufacturing tolerances vary widely from bike to bike.
Yes, if I was doing the same on the cheap, I'd be looking for a low mileage takeoff pistons from a later Evo off Ebay (see comment re measuring above).b) H-Ds manufacturing tolerances vary widely from bike to bike.
Personally, I'd guess there is enough meat in the piston tops to machine a cutout. This is based on experience of machining other piston to vary compression, but it is purely an 'informed guess' as I have never measured them. It's the question I'd want answered from an expert like John.
However, as it's unlikely you have the equipment to do so, the next cheapest work around would be to pick up a pair of nearly new OEM pistons for next to nothing.
Unless John will machine them for you?