This thread has made me nervous
http://www.914world.com/bbs2/index.php?act=ST&f=2&t=33950
I have my engine ready to pull in the morning to do top end rebuild and after reading this thread about lapping the cyl to the heads I am getting worried.
I am having my heads re-built and buying new P&C's. What is the proper method when bolting the heads back on? Use seals or lap them. I have no idea how to lap somthing properly except my wife so what do I do? I watched Jake's type IV teardown and assembly and he made mention of not using the seals because of the buliten but didn't say anything about lapping either.
I am tempted to take my pulled engine down to my local VW shop and having them do all the work because I am scared LOL
Luke D
QUOTE (LukeD @ Jun 27 2005, 05:06 PM) |
I am tempted to take my pulled engine down to my local VW shop and having them do all the work because I am scared LOL |
QUOTE (Mueller @ Jun 27 2005, 07:17 PM) | ||
what method does the shop endorse??? Both methods obviously work otherwise Jake, nor Mark or the Cap'n would still be in business. Is someone helping you build the motor? Are you getting advice for it from the shop?? If so, use thier recommended procedure so if something does go wrong, you won't hear "I told you so" |
I am doing the work myself aside from sending my heads off.
Anything to watch out for when replacing the P&C's and using the same rods?
If I drop the engine off I am looking at about $800 in labor not including parts.
I would rather use that money for other things but if it has a better chance of being done right then it is money well spent. But after watching Jake's video I know I can do it but doing it perfectly right is another story.
LukeD
Luke,
Dont sweat it.
Use the seals or dont but dont lap your heads .
When are you dropping that puppy I'll give you a hand.
When I rebuilt my motor I tossed the head gaskets and lightly lapped the head and cylinder with some valve grinding compound. Seems nice and leak free so far...
Well, decisions have been made,
Heads are going to Rimco
Buying 96mm P&C's probably J and E's
Not using head seals
After Kelly "echocanyons" calming me down on the phone from uncontrolable hyperventalation I am confident, with his help, we can do the job properly.
Thanks buddy, after we're done we are going out for drinks on me so I can
Luke D
Pics to follow on my Top End rebuild thread
kelly lapping the heads to the cylinders is the best thing you can do even if you do use the seals. what the lapping does is it ensures the tightest possible fit. when i did the rings on my old 1.8 i lapped them in, and as you lap you can see the high and low spots, i was only getting about 80 % seal before i lapped, and 100 % after.
as for the original question jake and a few others including VW say no seals, but i did use the seals on mi 1.8 and they were fine for the 30 k mile i kept the engine for.
Scott,
Not much experience with the type fours only type ones(&356 T1's) but...
Why does the factory head not fit without machining? Warping?
If lapping the heads should be done with every build why would you use a seal between, if you use one does the seal seat and make up the difference?
How much should the heads be lapped and how do you know when your piston will have enough clearance...what are the tolerances?
If a thorough inspection show the heads to be straight why would you need to lap them? How thorough inspection is needed and what is entailed?
If they are torqued down properly they should seat, shouldn't they?
Instead of lapping why not use a copper seal or spray/brush on copper coating to make up the difference and hold the seal without cutting your heads down?
Is a lap job part of every head job? ( I know it sounds bad)
there is also another thread going on this too, if everything is brand new and has been machined perfect the the lapping would be un nessessary. but if the cylinders are not trued they can be off by a little ( dont know what a little really is ) basicly lapping them in is just perfectly mating the 2 surfaces. if the surfaces where a perfect match then they would not need it. as for the cutting of the head, if it removes .0001 material to true it up then its not a big deal. but if it takes .001 then that head cylinder combo has more problems.
as for the head gaskets that is a toss up, i used them because at the time thats what was done.
also the gaskets would not really fill any imperfections, and you would not want any sealant between the heads/cylinders/seals due to the fact as soon as it burns off you just lost head torque and maybe even the seal that it made
Are you talking about lapping the cylinder or the head?
I just think there has got to be a better way than removing material from the heads.
For this particular application he is having his heads professionally refurbished and Luke is using new P&C's. Would the truing of the face of the head be part of the process (prolly a questoin for the shop doin the work)
I am not sure about the other seals but the copper seals or copper paintable seal would not melt and is used by many on other types of applications to compensate for the potential gaps between the heads.
QUOTE |
Are you talking about lapping the cylinder or the head? |
QUOTE |
I just think there has got to be a better way than removing material from the heads |
QUOTE |
For this particular application he is having his heads professionally refurbished and Luke is using new P&C's. Would the truing of the face of the head be part of the process (prolly a questoin for the shop doin the work) |
QUOTE |
I am not sure about the other seals but the copper seals or copper paintable seal would not melt and is used by many on other types of applications to compensate for the potential gaps between the heads. |
QUOTE (Headrage @ Jun 27 2005, 05:07 PM) |
When I rebuilt my motor I tossed the head gaskets and lightly lapped the head and cylinder with some VALVE GRINDING COMPOUND. Seems nice and leak free so far... |
Please dont mistake what I wrote for using RTV or any silicone based sealant as a head gasket.
I did say that a paintable copper coat with or without the seal to make up for the imperfections would be better than removing material.
I do agree that if there are large obvious imperfections/damage that is should be addressed by machining, If the head wont seal anyother way machining is your only option right?
QUOTE |
well sort of both but i am sure most cutting happens on the heads, i would bet the actual lose of material in less than .0001. |
yup polishing is basicly like what you are doing, no real material removal
just make sure that your machine shop flycuts the heads well and insures that the tops of your cylinders are perfectly true. with that done, there should be no need to lap.
Are these things Rimco will ask if I want or are they implied?
Do i Just Send them my heads And they call me with what needs to be done?
thanks
Luke
Does anyone know how the "carbon seal" Jake uses functions? I thought it was some kind of groove or bevel where the head and cylinder meet.
QUOTE (nebreitling @ Jun 28 2005, 02:58 PM) |
just make sure that your machine shop flycuts the heads well and insures that the tops of your cylinders are perfectly true. with that done, there should be no need to lap. |
QUOTE (V6914 @ Jun 28 2005, 11:44 PM) | ||
Has anyone, besides me, done a close inspection (magnafied inspection) of heads after they have been flycut? |
QUOTE (Mark Henry @ Jun 29 2005, 02:48 AM) | ||||
Yep, doesn't matter how good a mill is, you are still cutting material that is harder in some areas that others. The tool will always try to ride over the hard spots. Still won't use a head gasket, the copper ones are a HAIR BETTER than the stock gaskets, but in my book that's just a pinch above SHIT. |
The issues with the gaskets is that they add ANOTHER expansion rate to the engine that already hass too many dis-similar expansion rates without them.
The stock gasjkets are 3 pieces of .007 thick aluminum and if you expose them to ANY heat, or ever overheat the engine they fall apart, blow and melt parts.
I am going over the process of omitting these gaskets in my new handbook on "Sealing the Type IV engine" and it should be done in 2 weeks and out to the printer...
The methods and practices I go over will keep your heads sealed off and will do so without the gaskets- The right way.
This thread brings back memories. It has been a long time since I have rebuilt the top end of an aircooled engine.
I vividly remember though lapping cylinders and heads on a few Type Is I rebuilt. You start off with fresh, new, used, whatever, heads and cylinders; spread a real thin smear of lapping compound (you do not need much) on the rim of a cylinder; seat it into the head and work it side to side about 30 degrees around 10 times; rotate 45 degrees from the starting position and do another set of 30 degree side to side reps; repeat all the way around a couple of times. The movement becomes smoother as you continue each set.
Check the contact area between the cylinder rim and the seat area in the head just after the first set and you will see spots where the lapping compound has not touched the head surface. Check it after a couple of sets and you will see a nice clean continuous lap ring where the cylinder rim completely contacts the head surface. Keep each cylinder matched to its lapped head position. Clean, clean, clean the lapping compound off of everything! I don't think you want that stuff hanging around the combustion chamber.
I can't imagine that you take off anything but a tiny fraction of material. I agree with Jake, adding a gasket would just add another element in the works to expand/contract. I vaguely recall that some Type Is called for the gaskets and others didn't (1200 vs. 1500 vs. 1600). I wouldn't be surprised if I got that wrong though.
Sorry for resurrecting this old thread, but the "carbon seal" may be a reference to the 3.2 Carrera spec for a .0015-.0035" taper across the sealing surface of the cylinder that causes a gradient in the clamp load when torquing everything down. We use this spec with Nickies on everything but the 930 and later cylinders (since 99% of guys prefer to flame-ring them, so we provide a precision ground surface to start with).
If the surfaces are perfectly machined it's true, you don't need to lap. So the catch is have you ever seen "perfectly machined" surfaces? Are you sure? If all machined surfaces were perfect then why would anyone use gaskets anywhere? And even if the surfaces look perfect your eyes aren't good enough to tell if they really are. In fact you won't know if they are or aren't unless you lap them. Absolutely no other way. And it's sensless to worry about or even think you're removing any significant, or even measurable, material by lapping. Think about it, if you have to remove a measurable amount of material to get the machined surfaces to match then they sure weren't "perfectly machined" to begin with, were they?
So it takes you twenty minutes to know that you have a good (they're never perfect) mating surface before it's all reassembled. Remember how bad that "oops" during startup feels? You might not have needed to lap them, but that bad feeling that the "oops" causes is exactly how much it's worth it to make sure it's right as you go along. I have an even better quesiton for you: why NOT?
QUOTE |
I have an even better quesiton for you: why NOT? |
Finally I got tierd of waiting for the weather to cool off. I pulled my pass head and here are some pics. The number 2 is on the left and it is the one giving me problems. There were no "head gaskets". I was also having a problem getting the ehaust valve on this cylinder to hold it's adjustment. 60PSI compression test.
Attached image(s)
Second
Attached image(s)
Recommendations? I know it is probably hard to tell what is wrong in a picture like this but I am completely lost as to what to do with this head.
Luke D
QUOTE |
I am completely lost as to what to do with this head. |
Just took the head down to a machine shop. Valve guide on number 2 exhaust is real loose. Needless to say that the valve wasn't seating properly in the seat and the guy doesn't know if he can grind it enough. He is going to call me monday and tell me if it needs a new seat or not. In which case I have to ship to Rimco.
Luke
would one use machinest's dye on both the head and the cly seating surfaces? when the dye is gone from both items you are assured the faces are dead on?
k
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