head observations and questions

[DanHoug]

today i removed the head on my '91 1.6 NA hydraulic due to pressurization of the cooling system. i've some observations and a bunch of questions... feel free to answer any part you wish!

total miles: 320K, last 70K on WVO
new STD rings at 250K miles
today's compression 290, 350, 342, 345 which is nearly identical to just after the re-ring job (disappointed in re-ring compression). at my current compression readings, with new injectors, i could only start down to about 10F without plugging it in.

so after running WVO for 70K miles, the injector tips, pre chamber, and combustion chamber look great with just a very light soot coating, way less than the carbon i removed at the re-ring job at 250K. i was very pleased with this.

so here's my bunch of questions:

- i did NOT see an obvious compression leak looking at the gasket. there is a pretty good head crack between 1 & 2, with no other cracks. i am a bit concerned to not find the "smoking gun" with respect to the coolant pressurization. thoughts?

- the piston ht is .026 which = a 1 notch gasket. at 250K i replaced the 3 notch with another 3 notch, not measuring the piston ht. how much will going from a 3 notch to a 1 notch raise my compression? i run in arctic conditions and am looking for all the compression i can get.

- the German head is possibly original, now with 320K miles. i can wobble the extended valves almost a 32nd of an inch so i'd like to replace the head. is it better to go with a brand new Topline or get a rebuilt? who does the best rebuilds.. Jack? (cometitor's name removed by moderator)?

- regarding gaskets, should i stick in a Felpro or go with a German one.

- does a headbolt with a notch cut in it clean the block threads good enough or should i get a bottoming tap? i've got a 12 X 1.50 but it is a taper tap.

thanks alot for your responses!

-dan

[bscutt]

If you use the wrong gasket you run a high risk of valves hitting pistons. Recheck the measurement on all 4 pistons and buy the right gasket. I like the felpro gaskets but others have had good luck with the german brands. I used a standard tap to clean the threads on mine and have had no problems in over 20K miles. I used it by hand with no tap handle just to make sure I wasn't putting enough torque on it to take out any appreciable metal.

[Vincent Waldon]

For optimum cold starting the best bet is to use the exact right headgasket... in your case, 1-notch. This raises the compression slightly over a 3-notch but more importantly maximizes the "squish" the piston provides as it forces air into the pre-chamber... giving you the best winter start.

Many folks advise against using a tap to chase threads in case it removes metal... a true thread-chaser or an old headbolt with a grove cut in it are safe alternatives.

If the only problem with your head appears to be wobbling valves the valve guides are easily replaced by a machine shop for a small fraction of the cost of a new head. If you opt for a new head most folks seem to do fine with the 3rd party Topline variety.

[82vdub]

I'd suggest getting the head to a local machine shop and have them take a look at it. If they can't find any area where combustion gasses are getting into the cooling system, then maybe have someone magnaflux the top of your block, or look really, really close for any cracks. If the cooling system was getting presurized from combustion gasses, it's getting in there somewhere.

I love Fel Pro products, but I'd go German or OEM quality replacement if I had a choice. With your valves wobbling, you may have found the source of your low compression. But, once again, a good machine shop should be able to tell you what's up with the head and if you can use it.

I would not use a thread cutting tap, only a chasing tap or old headbolt with a groove in it. A thread cutting tap is meant to do just that in a raw hole.

[Quantum-man]

today i removed the head on my '91 1.6 NA hydraulic due to pressurization of the cooling system. i've some observations and a bunch of questions... feel free to answer any part you wish!

total miles: 320K, last 70K on WVO
new STD rings at 250K miles
today's compression 290, 350, 342, 345 which is nearly identical to just after the re-ring job (disappointed in re-ring compression). at my current compression readings, with new injectors, i could only start down to about 10F without plugging it in.

so after running WVO for 70K miles, the injector tips, pre chamber, and combustion chamber look great with just a very light soot coating, way less than the carbon i removed at the re-ring job at 250K. i was very pleased with this.

so here's my bunch of questions:

- i did NOT see an obvious compression leak looking at the gasket. there is a pretty good head crack between 1 & 2, with no other cracks. i am a bit concerned to not find the "smoking gun" with respect to the coolant pressurization. thoughts?

- the piston ht is .026 which = a 1 notch gasket. at 250K i replaced the 3 notch with another 3 notch, not measuring the piston ht. how much will going from a 3 notch to a 1 notch raise my compression? i run in arctic conditions and am looking for all the compression i can get.

- the German head is possibly original, now with 320K miles. i can wobble the extended valves almost a 32nd of an inch so i'd like to replace the head. is it better to go with a brand new Topline or get a rebuilt? who does the best rebuilds.. Jack? (cometitor's name removed by moderator)?

- regarding gaskets, should i stick in a Felpro or go with a German one.

- does a headbolt with a notch cut in it clean the block threads good enough or should i get a bottoming tap? i've got a 12 X 1.50 but it is a taper tap.

thanks alot for your responses!

-dan

To clean your threads, just use a head bolt.
Clean it, then screw it in by hand, remove, clean, reinsert, remove clean, lube reinsert, remove, inspect for crud, and,continue if neccessary.
Cross sawing a groove or two in an old bolt can help.

Exactly how much gas is escaping to the coolant?
If it takes hours to charge up, then a compression check will reveal nothing other than burnt/nonseating valves, or poor rings.
A failed gasket can allow coolant pressurisation even with cranking when it's bad.
In my humble oppinion a worn valve stems do not affect compression, simply because the valve and seat are tapered, and self centering. Bent valves can.
Loose inlet valve results in burnt sump oil, and loose exhaust results in slightly pressurised cam cover region.
With young valve stem seals you may see nothing, but as they harden symptoms get worse...

[Quantum-man]

How do you know that your compression gauge is not reading low?

If the adaptor significantly adds to the prechamber... .

[DanHoug]

i ordered a new Topline head today... since i run WVO and drive year round, some in arctic temps, i figured the car could use all the help i can give it. it'll be nice to eliminate the worry of a warped head after my coolant system pressurized.

the WVO experience has been great.... 70K miles in 2 years on old fryer grease. my cost savings on diesel have more than paid for a head and the failure wasn't related to WVO anyway. always a kick to drive by a macho but stalled Cummins at -30F that had jelled up and i'm crusing by on fuel that would be like Crisco at those temps. heated tank, heated lines, heated filter, heated injector lines, even put in a heater for the diesel line and i ran #2 all winter but it never got much below -25F this year.

-dan

[Dallas]

Hey Dan, I am just up the road from you in Grand Forks. Are there any good salvage yards/VW places in your area?? I am looking for some parts for my 81 Rabbit.

[Homer T. Coyote]

A related question to the head: I was planning on buying new cam followers but that has changed. Can you mix them up on the valves or do i have to buy new ones? It is a 1.6 TD solid lifter head.

[Quantum-man]

A related question to the head: I was planning on buying new cam followers but that has changed. Can you mix them up on the valves or do i have to buy new ones? It is a 1.6 TD solid lifter head.

I assume you mean can you play "where's the pea?" with the solid shims?
Yes swap the discs around to get most valves in spec, and just buy the remaining 1 or 2 that remain out of spec, unless grinding helps.
Grinding valve stem end can do the trick too...

[anto]

Im having similar problems in my peugeot.
Pressurising of the coolant and some coolant loss.
I whipped the head off to find that the gasket had no breaks in it so the head is away to get pressure tested to check for cracks. No visible cracks in the head from what i could tell.

What else could cause pressurisation of the coolant like that?

[82vdub]

Im having similar problems in my peugeot.
Pressurising of the coolant and some coolant loss.
I whipped the head off to find that the gasket had no breaks in it so the head is away to get pressure tested to check for cracks. No visible cracks in the head from what i could tell.

What else could cause pressurisation of the coolant like that?

You may not have had a break in the head gasket, but only a minor lifting allowing combustion pressure to sneak over or under the head gasket.

Other things that could cause coolant pressurization are:

cracked head
cracked block (incl damaged head bolt area)
warped head or block deck
damaged oil (oil to water) cooler

[Fatmobile]

A related question to the head: I was planning on buying new cam followers but that has changed. Can you mix them up on the valves or do i have to buy new ones? It is a 1.6 TD solid lifter head

I don't think you'll have a problem if the buckets get switched around.

I had a gasser with a bad tick/knock,.. due to a bad cam follower,
I went to the junkyard and grabbed a set from a car with a broken timing belt (non-interferance engine so no damage) quieted it right down.

[anto]

Im having similar problems in my peugeot.
Pressurising of the coolant and some coolant loss.
I whipped the head off to find that the gasket had no breaks in it so the head is away to get pressure tested to check for cracks. No visible cracks in the head from what i could tell.

What else could cause pressurisation of the coolant like that?

You may not have had a break in the head gasket, but only a minor lifting allowing combustion pressure to sneak over or under the head gasket.

Other things that could cause coolant pressurization are:

cracked head
cracked block (incl damaged head bolt area)
warped head or block deck
damaged oil (oil to water) cooler

82vdub cheers mate, ive ruled out cracked head as ive had it pressure tested and it is fine.
cracked block - possibly
warped head - checked and is fine and also had a skim
warped block deck - not sure
damaged oil cooler - no oil in water so i assume this is fine.

I think due to some corrosion aroind the head gasket water ways (causing minor lifting as you say), it has allowed some pressure to escape from the cylinder into the coolant that way. Hopefully my new head gasket will cure it.

thanks,

Anton

[Quantum-man]

Im having similar problems in my peugeot.
Pressurising of the coolant and some coolant loss.
I whipped the head off to find that the gasket had no breaks in it so the head is away to get pressure tested to check for cracks. No visible cracks in the head from what i could tell.

What else could cause pressurisation of the coolant like that?

Does this engine have wet liners, Ie each cylinder bore is a push fit, with a seal down at the bottom...