Rebuilding 20r head

[Up north mi]

Hi all I have a 1979 sunrader  I think the head gasket leaks, I read in a post about the same leak Montana chinooks MH. Under the exhaust manifold. I bought a head on creagslist milled .10"  no valves or cam should I use the cam bearings in the old cam or buy new? I paid 60 dollars for for the head it seems to be cleaned like sand blasting. How far should I take it new valves and springs I know new seals?from the pics it is hard to see the leak.it would be nice to buy a head from LC but way to much money.does any body have any info on a MLS head gasket they seem to have different thickness?

[fred heath]

20R head doesn't have cam bearings. The cam sits inside the machined surface of the head.

Hopefully your old cam will bolt onto the new head and maintain the factory specs. If not, you can't use the head.

If the only problem with the old head was a bad gasket, keep your original head. Send it out for a valve job if needed. It will be much cheaper in the long run.

[WME]

IF the head was warped and it was machined .10" its useless. If it was machined .010" then it maybe OK. The cam bearings should have been lined bored.

 

[zero]

On 4/16/2016 at 5:47 PM, Up north mi said:

Hi all I have a 1979 sunrader  I think the head gasket leaks, I read in a post about the same leak Montana chinooks MH. Under the exhaust manifold. I bought a head on creagslist milled .10"

 

Are you sure it wasn't milled .010" and not .10"?   .10 is a lot and would require using a head-gasket shim along with the head-gasket to avoid problems like detonation from too high a compression ratio.  It it really was milled .10" - I would not use it.  At the least - it needs to be bolted to a block - tight - and then have the cam mount line-bore checked.  If it was me - I'd rather use a known-to-be OK head from a running engine and re-do the valves, seats, guides, and stem-seals if wanted.

 

[payaso del mar]

I suspect he meant .010".

Upnorth, i'll try to answer your Qs in order.

1.  parts:  new valves are only "necessary" if old ones are too worn or are damaged.  check wear of valve head and stem, and check stem-to-guide clearance.  springs likewise can be reused if they check out OK as far as free height.  how long before you plan to do a complete rebuild of the engine?  this would determine whether I tried to re-use some of the head parts or re-do the head complete.  you MUSt use new valve seals; these should come with your head gasket set. 

2.  the different thicknesses of head gasket are to allow for milled heads and to slightly reduce compression ratio.

3.  have you removed your current head yet?  are you sure you need to do it?  I don't see any leakage stains in pic but I might be missing them.  how's your compression?  before you pull head, i'd have a radiator shop pressure test the cooling system to confirm the leak (or you can get the kit for about $65  http://www.rockauto.com/en/moreinfo.php?pk=225702&jsn=297  )

 

[zero]

59 minutes ago, payaso del mar said:

 

 new valves are only "necessary" if old ones are too worn or are damaged. 

I'd agree if this was the 1960s.  Not so much anymore.  Yes, if the valves are perfect with no step worn into them and the seat still as narrow as it should be - OK to re-use.  That would be a rare event on an engine with any kind of miles on it.   I've refaced a lot of valves over the years, as well as reground many a valve seat.  Now though -to protect valves from wear with the use of unleaded fuel - many are Nitride coated and that coating is less then .001" thick.  It is lost if the valves are refaced.  New valves are so cheap - I cannot imagine reusing on a four-cylinder Toyota.   $5 each for new  coated valves and $1.50 each for new valve-guides is a cheap investment, compared to the labor involved. Just one person's opinion.  I hate buying new parts but when it comes to valves on an engine burning unleaded fuel and wanted to last a long time - the new parts are a no-brainer to me. At least with the Toyota - the seats have deep hardness and can be re-cut or re-ground with few issues if needed.  Unlike some car and truck engines from the 80s (especially GM) that have induction-hardened seats that get soft as soon as they get reground or recut.

[payaso del mar]

so we're clear, i was just talking a stopgap fix; that's why i asked how long before he did a full rebuild.  i still wonder if we're sure that a head is in fact needed.

I just checked prices on valves and springs and have to admit you're right as far as a 20 or 22R.....some pretty cheap valves and springs there, and only 8 of em to buy.  on our 02 Subie and 02 Taco, the valves are more like $25 each x16 of em to buy.  altho I personally replace everything if I have it apart; my time to do the job is worth more than the cost of the parts. 

[zero]

1 hour ago, payaso del mar said:

so we're clear, i was just talking a stopgap fix; that's why i asked how long before he did a full rebuild.  i still wonder if we're sure that a head is in fact needed.

I just checked prices on valves and springs and have to admit you're right as far as a 20 or 22R.....some pretty cheap valves and springs there, and only 8 of em to buy.  on our 02 Subie and 02 Taco, the valves are more like $25 each x16 of em to buy.  altho I personally replace everything if I have it apart; my time to do the job is worth more than the cost of the parts. 

I've worked on some diesels that had valves that were $30 each and we often needed special thickness valve-heads to get the installed valve-head-depth correct (critical on some diesels).  Compared to them - these Toyota parts seem dirt cheap.

[Maineah]

One thing people do not think about on a badly warped OHC head is cam bearings. Flatting the head does not take the twist out of it it only makes the bottom flat.

[Up north mi]

Hay thanks for the info the head was milled .010 I miss typed it wrong. I want to buy a head gasket for it there's a lot of choices out there LC has a gasket  for a stock engine they have different thicknesses would that be for a milled head? The cost for the valves  is not to expensive I think I will just buy new . I should do a compression test the motor it has around 87,000 miles on the MH. The head started to leak around the time I put a new exhaust gasket it seems it was coming for one of the studs! So the head has no cam bearings?

[Maineah]

13 hours ago, Up north mi said:

Hay thanks for the info the head was milled .010 I miss typed it wrong. I want to buy a head gasket for it there's a lot of choices out there LC has a gasket  for a stock engine they have different thicknesses would that be for a milled head? The cost for the valves  is not to expensive I think I will just buy new . I should do a compression test the motor it has around 87,000 miles on the MH. The head started to leak around the time I put a new exhaust gasket it seems it was coming for one of the studs! So the head has no cam bearings?

The head is the cam bearings it was line bored when it was made very common practice on over head cam cylinder heads.

[zero]

I milled .010" from the head on my 1988 with a 22RE.  When done - one the first trip -the engine pinged pretty bad if I used regular gas but was fine with mid-range or high-test.
After the first trip - I retarded the timing a few degrees just by rotating the distributor and now it is fine with regular gas.  No special over-thick head-gasket needed.  I think when a head gets milled .020" or more is when the need for over-thick head gasket is needed.  Problem is with a used head - how do you know how many times it has been milled?