Author Topic: 585" SOHC - Teardown, repair, rebuild, and re-dyno  (Read 31642 times)

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jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #15 on: November 28, 2011, 02:13:31 PM »
PV clearance was about .140" if I recall correctly, on both intake and exhaust.  I didn't recheck it on disassembly.  But since you mention it, it seems clear that the piston to valve clearance I measured had the valves touching the pistons in the middle of the pocket, rather than on the edge of the pocket where the contact is.  Obviously the valves hitting the pistons where they are is the result of dynamic engine operation, rather than the static PV clearance measurement.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

machoneman

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #16 on: November 28, 2011, 02:48:41 PM »
Yes, that .140 is far more than enough to eliminate in-operation clashing. Your analysis makes sense, pretty much eliminates the chain drive variable and given, say, tight .002 or so guides and a revised valve pocket location that problem should go away.

On those guides, I wonder out loud if the cammer's unique rocker arm, cams that push the rockers differently from one head's side to another, et al, have an effect on guide wear as opposed to mere lack of oiling (my comment on PC seals earlier).  Can't imagine though that the SOHC rocker arms, even with your high lift/duration cams, could cause that unwanted swiping action that can push a valve sideways more than up-down, the same effect as a too short/long pushrod in a non-OHC engine. Does this engine's sweep produce a narrow valve tip mark like a pushrod 427 or is it substantially wider?  Remember the worn, non-hardened tips you showed on some cammer valves awhile ago but didn't catch the sweep dimension. 

I also forget if these are B. Coon's heads or what. Not to knock them but if the guide material isn't wholly compatible with your SS valves, guide wear can be accelerated as you know. 'Course, if the valve's head perimeter was grazing the piston pocket at speed, that alone could cause rapid guide wear!

I wonder too if the engine has a few valves that did not touch the piston's valve pocket (if not all of them did) exhibit normal valve guide clearances (whatever you set them at initially)?      



« Last Edit: November 28, 2011, 03:27:55 PM by machoneman »
Bob Maag

jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #17 on: November 28, 2011, 03:56:03 PM »
There are indeed some pistons with no clearance issues.  Correlating the valve guide wear on the right head with the pistons that have marks is a good idea, and may shed some light on whether the valve guide wear played a part.  R&R has a valve guide measurement tool that goes down to a tenth, so maybe I'll haul the heads in there and have them checked.

The design of the SOHC rocker arm will put the arm into a twist when it is on the cam lobe.  I wonder if that is forcing the valve to one side or the other on the guide, and also contributing to the problem?  And it surely is a different force from side to side, because of the geometry of the heads (on the right bank the cam "pushes" the roller on the rocker arm, while on the left bank the cam "pulls" it).  Hmmmm....
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

Joe-jdc

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #18 on: November 28, 2011, 08:42:06 PM »
Jay, how much of the guide is supported by the head material?  That is a problem with the high arc intake ports on some SBF heads like the Yates, and the valve guides wear very quickly.  I would think you need at least 1.000 inch of head surface area around the guide for stability, and more is better.  If it is less, then you may consider welding a vane in front and behind the guide to support is from rocking, and blending it for flow. I know that is a lot of work, heat and warpage possible, but may solve the valve stability issue.     Joe-JDC.

jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #19 on: November 28, 2011, 09:14:42 PM »
The guide support is right about 1", Joe.  Maybe a little more, but not much.  Probably these valves are bigger than an SBF valve, so maybe its not enough to prevent wear...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

plovett

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #20 on: November 29, 2011, 11:30:29 AM »
I don't have anything to add other than I really hope you find your "smoking gun", Jay.

paulie

Cyclone03

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #21 on: November 29, 2011, 01:04:28 PM »
Could the power loss have come from the cumbustion pressure being lost down the sleaves to the crankcase? If so wouldn't/couldn't that "float" the sleaves in the bore?

Is it posible the valves were "lofting" over the nose?That would seem to mess up static P-V clearence.

With the carbon build up over the "relief's" it may have happened on the last run,weak springs?
Lance H

jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #22 on: November 29, 2011, 04:34:36 PM »
Thanks for the thoughts.  I would think that if the engine was losing any significant combustion pressure down the sleeves I would see significant blowby out of the breather, and the engine really didn't have much of that.  Certainly not 150 HP worth, anyway.  The springs were new, and checked fine on disassembly, and the cam/spring/rocker combination was checked on Bill Conley's spintron and found to be good up to 8000 RPM.  So, I don't think the issue is valvetrain related.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

country63sedan

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #23 on: November 29, 2011, 06:53:20 PM »
Sorry I missed the details in the original post. Guess I shouldn't try to read/comprehend when the kids and the dog keep tearing through the office. I did have an idea today, but it's a bit of a stretch. Is it possible that the engine kicked back or even tried to run backwards during the hard starting problems? Could this cause enough slack for the cam timing to get out of sync momentarily? I told you it was a stretch, but it's something I thought of today. Later, Travis.

P.S. At failure analysis training several years ago, they told us that over half of all failures (on big trucks)are caused by DRIVER ABUSE ;)

cdmbill2

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #24 on: December 09, 2011, 03:54:20 PM »
Jay, looking at this differently for a moment, what are the differences, parts, assembly, cam etc. between this version of the engine which shows that appearant piston to valve interference problem and the last version(s) that didn't form priro Drag Weeks etc.?

Given the way the valve intersects the bore and the piston face I'm wondering about those particular valves hanging up on the compression stroke bleeding power, and causing the piston to knock it closed otherwise its hard to understand how the witness mark can be so far from the scribed valve diameter.

You can obviously expand the radial size of the valve relief but you haven't actually discovered the source of the interference.

Also, what is that black curled up substance we see in the pictures? Carbon, or blackened valve material?

jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #25 on: December 09, 2011, 04:56:09 PM »
Bill, this is basically the same engine I ran in 2009.  The only difference is the switch to the ems-pro and coilpacks, and removal of the distributor.  Same heads, same valves, same pistons, same cams, same rockers, same springs - same same same.  Which is why this is so puzzling.

FYI I took one of the heads in to my shop to have the valve guides measured, and all the guide/valve combinations showed a clearance of .0020" to .0022".  According to my shop, that's not a problem.  I had held the valve an inch or so out of a guide and checked the movement with a dial indicator, and got .010" movement, but after getting the guides checked I tried to repeat that measurements, and only got about .004" of movement.  I have to assume that the dial indicator was moving on the first measurement, because I sure can't repeat it.

That curled up stuff is aluminum from the piston.  I assume that it is black because once it got out of the way of the contact, it carboned up like the rest of the chamber.  Seems like the valve was just shaving the piston eyebrows.

Still pretty confused about this...

Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

machoneman

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #26 on: December 09, 2011, 05:22:11 PM »
Jay, now that we know the guides, etc. are o.k. I'll ask you to go back to Country63Sedan's post above about the possibility that the engine, if even only once, ran backwards on a backfire or after a hot shutoff.

You could easily replicate the effect of the engine running backwards, even for one single revolution, and see if the chain tensioner backs off enough to allow a really loose chain and valve/piston clash. Hey it ain't your typical pushrod FE now is it?

Just a thought......otherwise the mystery continues!  Maybe we need Inspector Clouseau? LOL!
Bob Maag

Joe-jdc

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #27 on: December 09, 2011, 10:26:35 PM »
Jay,

I read your complete posting again, and I have a couple of questions and ideas.  How short is the piston skirt?  How far below the pin does it extend? What is the material the guides are made of? Is there enough room for a longer rod to help with piston rock?  This is one of those engines where I would try to squeeze the longest rod possible, and a slightly longer skirt on the piston for stability.  Your stroke and rod ratio is a curiousity in my mind to the piston rocking.  Piston bore size vs pin height vs rod length may be causing the problem.  The skirts may look good, but are they actually flexing under load and causing the problem?   Are they a full skirt  like a Mahle?  I still would suggest  welding a vane in front of the guide since you will probably be changing them, and trying to get the hardest material you can for the replacements.  Hope something I said triggers an idea.  Joe-JDC.

XR7

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #28 on: December 09, 2011, 11:34:47 PM »
Jay,
I have some questions and a few thoughts on this. I may be out in left field here... but there could be something to this. I keep thinking about the offset bores and how that effects things. If you went from a 4.63 bore center, to say a 4.70 (not sure of the dimensions you used) then if I am thinking correctly.... the center cylinders have another .070 between so now are .035 farther apart (each) from where they used to be, and the outer corner cylinders are .070 over from that.... which would be a total of .105 offset away from where those bores were originally. Is this correct? If this is, then do you have 4 pistons with .035 offset valve reliefs and 4 pistons with the reliefs offset over .105? The heads have the standard centers so now the chambers are offset to the bore. What about the crank rod pins? Were these offset or in a normal FE location?

I have read that the BBC connecting rods have an offset where a true Ford rod it is on center. I am assuming that that would be the pin or small end centers are different than the big end center, as far as fore and aft installed on the engine. What if this rod pin offset and your offset bore are stacking up together? Maybe the (heavy?) SOHC piston is (now not centered to the rod) rocking, and/or flexing the piston pin one direction only, to where they are leaning over at high RPM and kissing the valve? There is no piston skirt on the sides to support or locate the piston to the bore "square" this non thrust direction...

How thick are the piston pin walls, I would think you would want a thick tapered tool steel pin on this engine. Lightweight pins are not a good thing and will flex, hard on piston pin bosses and cause cracking or breaking right doewn the middle of the pin bore on the piston.

 I see where you made the center punch for the valve on the relief, and where it is hitting is way over or off center. Weird...

Like I said these things may be all wrong, but something I have been thinking about and trying to wrap my head around it. Doesn't really explain why some cylinders are problems and others aren't. If it were the 4 corner pistons hitting (which would be worse than the center 4 pistons) it would make sense... but that doesn't sound like what is happening either...

What are your thoughts and could you explain the offset bores and how you handled the piston valve reliefs and crank. I don't think it is the valves moving over that far myself, but I could be wrong. It has to be one or the other, or a combination of the two. Definitely a head scratcher as it just doesn't make much sense. Hopefully you will figure this out, this has to have had something to do with the power loss, the engine wasn't "happy".
68 Cougar XR7 GT street legal, 9.47@144.53, 3603# at the line, 487 HR center oiler, single carb, Jerico 4 speed, 10.5 tires, stock(er) suspension, all steel full interior

jayb

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Re: 585" SOHC - Teardown, repair, rebuild, and re-dyno
« Reply #29 on: December 09, 2011, 11:43:33 PM »
Jay, now that we know the guides, etc. are o.k. I'll ask you to go back to Country63Sedan's post above about the possibility that the engine, if even only once, ran backwards on a backfire or after a hot shutoff.

You could easily replicate the effect of the engine running backwards, even for one single revolution, and see if the chain tensioner backs off enough to allow a really loose chain and valve/piston clash. Hey it ain't your typical pushrod FE now is it?

Just a thought......otherwise the mystery continues!  Maybe we need Inspector Clouseau? LOL!

I think even if the engine ran backwards, which is certainly possible, it would not explain the piston contact.  The closest the valve ever comes to the edge of the relief is at TDC, and you can see how far away it is from the relief based on the center punch point and the scribed valve diameter.  No matter if the engine is running forward or backwards, this doesn't change.  If stretch or slack in the chain let the valve hang open, it should hit the flat part of the valve pocket in the piston, not the edge where it is hitting. 

Also FYI I run the chains on these engines pretty tight, so even if the engine ran backwards I doubt that there would be any significant variation in valve timing.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC