TOPIC: 1984 115 rebuild

I have torn down my 115 (140 @ crank) & it seems it was not before time. There is evidence of water (rust) around no 6 rod so the seals are shot & no 2 piston has suffered detonation at some time in the past, doesn't look recent to me. Someone has been in it at sometime as no 1 piston is a hi dome (wrong for a 115 I believe) 3 - 6 are all low dome's. No 2 I can't tell of course. No 2 is also very badly scored, I'm not sure yet if it will need boring. I was going to build the motor up with hi dome pistons & change the reed blocks to ones that don't have two ports on each one blocked off with the corresponding two reeds missing as this should boost the power a little - back up to 150 (crank) I hope.

The motor has never idled any sense & much has been said about the plastic restrictors in the transfer ports. What size is the hole in them? I have holes the are approx 3/32" - 1/8" with nothing in there, you look straight through the the bore of the next door cyl. I am guessing this isn't correct??

Also the b/e bolts have changed, instead of the familiar bolt with a locknut, this has small bolts screwed in from underneath. Anyone know what size it is so I know what to ask Snap on for??

What do you L6 boys think - Thom?

I tap the hole for the restrictor with 8-32 thread.

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Then install a stainless setscrew with a 0.035" hole in it.

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End of missing restrictor problems.

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And yes they do go to the cylinder below to help lubricate the skirt.

Those rod bolts are the type that stretch as they are torqued and once removed require new replacement bolts.
I like the professor's way of dealing with the bleed restrictors.
The original plastic things are going NLA anyway.
#2 certainly does look like it did a melt-down in the past, sent melted aluminum down the skirts and scored the cylinder walls.
Question will be what the cylinder walls look like once the aluminum transfer is removed.
High domes or low domes - always best to run all (6) the same - but not unheard of to find mix-n-match working fine in a subsequent teardown.
I run high domes in my personal Stacks and install low domes as per the factory specs when building someone a Stack.
I use the 850 4 cyl reed blocks in the hot-rod Stacks. They are 10/10 and have .170 stops. (biggest I've found)
Lower crank seals must be bad as you suggested so be sure and inspect the crankshaft to see how the surface is for the seals to run on.
I don't know if that crank has the factory speedi-sleeve installed or if that came a couple years later. Nice move on the engineers' part IMHO.
Thom

Thanks chaps, much appreciated. At least I know my restrictors are all missing (sorry to appear stupid, this is the 1st L6 I have pulled apart), that will account for the bad idle then - along with the bad piston of course. Professor, how do you stop the restrictors coming out again, locktite or do you peen the ali over? On checking the other pistons most have got at least one ring stuck so that won't help it either.

I was hoping to go that route with the 850 10/10 reed blocks as I have some here - although someone on Johns OM forum suggested it won't make any difference in performance but the 10/8's make the idle better??

How do you chaps feel about just boring one hole? I used to rebuild Perkins marine diesels in the late 70's & this seems to go against everything I have been taught & always done. You will end up with a bigger capacity on one cyl. plus (I assume) a heavier piston, I confess I don't like it.

Yes the crank does have the speedi sleeve on it Thom.

Geoff

ILL be damned! I thought my 1982 1400 crank had been repaired when I saw that speedi sleeve on it. Makes me feel better now that I know it is factory!! THe crank looks great and that was the only thing I was nervous about.

I think Thom has told me before it is ok to do just one hole. The new oversize pistons are weight matched to Standard ones I think. But I have found some variaty in piston weights from different years. All being High Dome Power port pistons.

I have never seen a slotted rod cap like that. I bet that aids in lubing the rod!

Conrad

I have a '78 500 that has the same speedi sleeve setup on it.

I did wonder if the pistons might be weight matched, so the extra capacity doesn't effect anything then?

Geoff

Geoff,
Besides installing the restrictors (yes - a small peen will keep them in place - or if threaded in tightly against the end of the threads you make that too will be enough) take a good look at the wear in the labrynths of the reed blocks at the crankshaft.
Too much wear will result in too much crankcase pressure slipping back-n-forth and fouling up the idle quality.
Thom

I wondered about the labrynth seals - especially on the btm reed block as the crank is a little rusty there. How do I check them the book doesn't mention the labrynth?? They all look much the same to me? Do we check by clearance on the crank?

To do it correctly you need to remove the reed blocks from the crankshaft.
Once removed you can carefully inspect the labrynths.
The raised portions will be mushroomed out - like a 'T' when they are worn out.
The original measurement across the opening for the crank with the two halves bolted together is 1.245".
When they get worn to over 1.249ish I look for replacements.
Usually the center reed block in an inline-6 is in pretty good shape and the top and bottom ones get subjected to more crankshaft wobble and consequently more wear.
Thom

great thread here

Thank you Thom, just the info I needed - as ever. I have found some of 10/10 L4 ones that will do the job I reckon, they are less worn that the ones I have taken out for sure. One needs a lube groove machining in it but that is simple enough to do.

I have been waiting all week for the Muriatic acid I ordered to arrive so I can clean the bore up prior to honing & measuring. Very frustrating not knowing where I am going with it at the moment. It also means I can't order my parts either, once I do that I will have 4 - 6 weeks for the bits to arrive (unless I stump up a shedload of £££'s (sorry $$$)) to get them here by UPS or similar. Of course if any of you guys are heading for the UK & fancy bringing some bits over . . . I also have a brand new block & c/case for a MK75 or similar to go your way at some time. No good to me here in the UK.

This forum along with Johns OM is an absolute mine of information, without which many motors would be pulled down time & time again to try & get them right. How many of us, for example, would have been aware of the transfer port restrictors & the effects of them not being there? Not many I would venture. I thank all of you for sharing your knowledge so freely.

There was a mention of rod bolts that " stretch " and need to be replaced.

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Well, materials follow something called " hooke's law "

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when stretched they are under tension ( doing what they should be doing )---when the nut is loosened off they go back to their original dimension.

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No reason why they can not be re-used.

interesting reading
I agree with the professor, I feel the only thing that breaks rod bolts is spun bearings and improperly torqued bolts. although I no longer have the tool to show you, I used a rod "bolt stretch gauge" when building my drag motors, used in conjunction with a torque wrench with a specific tightening process/sequence

torquing a bolt is really applying the stretch to obtain the correct amount of preload on the bolt, and there are MANY factors that affect the torquing, friction of materials, lubes used, material finish, the slightest damage to a thread, even dirt particulate

so the use of the rod bolt stretch gauge is the only real way you KNOW you have the correct stretch or "bolt preload"
this is not to say that a bolt cant be stretched beyond its physical molecular properties and needs replacing, however if Torqued/Stretched/pre loaded correctly they can be reused without issue
my 2 cents

I have run across these "stretch" bolts in automotive head bolt applications before, but didn't know they were also used in some marine motors. I'm no mechanical engineer, but the engine mfg. and the aftermarket parts folks claim that once they are "stretched" during initial installation, the tensile strength is compromised or something, they warn against re-using these type bolts. (My initial thoughts were "they just want to sell me new hardware"!) These type bolts do not return to original length and strength. There is a chance of bottoming out the bolt preventing proper torque values, or something. If you believe the people who designed and built the equipment, seems like good insurance to make sure it lasts as long as possible after rebuild. My motto is: when in doubt, read and follow the factory manual.

I am of a similar opinion MP - however I am not going to risk it & will be fitting new one's as insurance, as Conrad would say 'I am going to run the crap out of it' so belt & braces for me!

So sad when people do not " know or understand " terms in the field of materials.

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All bolts behave like a rubber band and return to their original length when they are loosened. That simply is how it works.

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For those who doubt it is time " google " terms like tensile strength, ultimate strength, modulus of elasticity, yield strength etc.

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I learned these things years ago in post secondary schooling.

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We work on motors that are 40 plus years old, few people would tear a good running motor down to replace the bolts, because they may have " stretched ".

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Bolts may be replaced to reduce the risk of a " fatigue failure "

With all due respect, gentlemen:

freeasestudyguides.com/a1_4.html

Torque to Yield Bolts



With a regular head bolt a technician could torque a bolt to its yield point and it would return to its original form and length. This is because of its elasticity it is able to stretch and return to its original form.

This is not so with a torque to yield bolt. There are two terms related to this phenomenon. The first is elastic deformation and the second is plastic deformation:

1. Elastic deformation: This is the amount of force or torque where you haven't changed the shape or length of the bolt. At this point you are able to reuse the bolt as it hasn't changed its shape.

2. Plastic deformation: This is the point past elastic deformation where the bolt has changed its shape and length. At this point the bolt can not be reused and needs to be replaced.

For example an aluminum cylinder head will be torqued in a sequence say one to ten. The first pass would be a torque of 36 foot pounds. This is the elastic deformation point. The second pass would be a 90 degree angle or a quarter turn. At this point the bolt is going into plastic deformation. The third pass would be another 90 degree angle. At this point the bolt has changed its form and if loosened or removed it must be replaced with a new torque to yield bolt.

So in summary you can use the old fashion head bolts over and over but when it comes to torque to yield they need to be replaced with new ones.

www.enginebuildermag.com/Article/2343/threaded_fasteners_torquetoyield_and_torquetoangle.aspx
(Another article stating the same thing, basically, for those who would like to educate themselves.)

My last post on this thread.......
Sad indeed.

My apologies to Geoff and Thom, once again I should have read and learned, left the commenting to others.

Well I cleaned the ali deposits from the no 2 bore with acid & buzzed a hone down all 6 & it isn't pretty. Unsurprisingly no 2 is still grooved badly & the other 5 are worn like a dogs back leg, so it's a .015" rebore on all 6 holes - when I can find someone who can rebore blind bores which isn't proving an easy task.

I am interested how bad the were out of round. I have torn down a few and they have all been with in a couple of thousands.

Check around some of the bike shops in your area I think some of the big hondas had cylinder head configuration
Charles

I am with g3jim, great thread.
I will soon be working with my first tower.
Tons of info here.
Thanks guys.
Neil

67sears wrote:

I am interested how bad the were out of round. I have torn down a few and they have all been with in a couple of thousands.

TBH I haven't measured the bore wear. I don't like the idea of fitting just one .015" O/S piston, I know Merc say its OK but it just goes against everything I have always done - & I was an engine builder for some years. If the other 5 had cleaned up OK I may have considered it, but as they didn't I was happy to bore all 6. I have to buy 6 new pistons anyway so the extra cost for the other 5 bores, in the scheme of things, is fairly insignificant. That way I know where I am & I know the motor will be better than new in that respect (fitting hi domes instead of the std low domes).