replacing head gasket

[Drone Dog]

i am doing a leak-down test today but i am pretty sure i need a new head gasket.

little background: car runs fine and holds great oil pressure. i am not trying to build a hot rod or anything just put it back together as a nice driver.

ok, so past that it always seems i do work and then get better suggestions or find out there is a better way to do something. So i thought i would ask for some input before i get started. Since everything is running fine i do not plan to pull the engine. but while i have the head off, i figure i may as well put in new valves, seats, springs, guides, etc.

i also have a small oil leak at the front so figure i may as well pull the timing cover and replace the oil seal. then while in there, check the chain, etc.

i have been starting some research on parts, costs, etc and here are a few questions to begin with:

1) Moss lists a solid copper head gasket. pretty expensive. is the Payen one most places carry ok to use? or better to spend the money here? don't want to pull twice.
2) i plan to replace valves and seats. suggestions on who to go to? Good Parts has a couple different ones maybe?
3) valve springs. i see single and dual set ups. which to use on a street engine? (do not plan to change the cam)
4) plan to put in new valve guides. will buy the better ones here.
5) valve seals: i think i saw Good parts shows a seal. have not seen other places. worth it?
6) since the head will likely be decked, should i get the shortened push rods or depends on how much they take off?

what else am I missing?
things i should have the machine shop do while they have the head?

Thanks for any suggestions.

[tr250]

I think Payen should be adequate for your purposes

The machine shop I used had the seal or could source them. When I spoke with Richard Good about his cam, he suggested dual because of the cam I was going to. You’re not changing your cam so either should be fine. Tho if you have a late engine it probably has dual springs already

as far as skimming the head, if you’re just skimming for flatness, you should NOT need shorter push rods.

[YankeeTR5]

TR factory guides are cast iron...the "better" ones are bronze mixture. The advantage of the cast iron is that they expand with heat at the same rate as everything else, so no valve seals are needed. They are also very hard, so wear is pretty limited. The other type typically need valve seals (which harden over time, not necessarily use) because they don't expand at the same rate and so can burn oil until everything is all warmed up.

So if I were sticking to a stock build, I'd stick with stock "stuff". Valve seats, stock guides, stock springs (do you need new ones? measure yours)

That said, given you have a later (75/76) TR6, with the head off and going to the machine shop, I'd recommend two things. Bump up the compression a bit to 8.6 to 1 of the early North American cars and use the earlier, slightly larger, exhaust valve from the earlier cars (since you're replacing the seats, might as well go w/the bigger valve). Both of these will complement the stock cam in your car and you can still use your existing push rods and not really stress your engine (it was a factory set up after all).

BPNW has a sale on the Lucas top end gasket set for $17 right now. Guess the Payen gasket is better but the Lucas set has a metal gasket and works well. Most all of the failed head gasket issues (which really isn't that common) are the result of bad prep of the surfaces vs bad gasket. The copper one is so expensive because it can be re-used.

[poolboy]

When the head is off, remove all the cylinder head studs from the block if you planned on replacing them or not.
Stuff the cylinders with dry wiping cloths.Get the biggest (longest & widest) flat file you have and place it on the top of the engine block.
Using light pressure with your finger tips upon the file, make circular passes with the file across the top of the block..
After a few passes, areas that are high or protrusions around the threaded holes for the studs will appear bright and shinny.
Continue the procedure and sooner or later you'll see by the surface appearance that the entire surface is even and flat....uniform in appearance.

[Drone Dog]

This is why i asked. great info.

bumping the comression to 8.6, i assume, means shaving the head a little more than just flatten it. how much should be cut?

i assume the exhaust valves and seats i would order would be from a 71 or earlier?

i like the idea of increasing the compression. i also plan to send the diz out to be recurved with a vac advance. another reason i want to check the timing chain. one question here: can i get the damper pulley off with the engine in? Do i need to pull the steering unit?

looked today while doing the leak down test. my car does have dual springs now.

by the way my leak down looked like this
#1 10%
#2 12%
#3 11%
#4 23%
#5 25%
#6 10%

i did not get any bubbles in my radiator neck which surprised me a little. i am losing coolant as i drive and i do get the white smoke. i did get air out my #5 cylinder when checking my #4 cylinder. So i don't think my head gasket is blown but is just getting weak/worn. i was encouraged by the test though in that it looks like my rings are in pretty good shape. will have to see once i get the head off and can look at the walls.

[SapphireBlue72]

Possible that there is a crack in the cylinder head. Have shop Magnaflux to check it.
Sometimes between the cylinder walls- for example between 4 & 5.

[YankeeTR5]

Poolboy and Walt offer great advice for the top of the block and cylinder head.

There's two ways of figuring how much to shave. One would involve burret tubes and carefully CC'ing the combustion chamber and doing the math to come up with how much to shave. The other (much simpler) method is to use a target deck height for the cylinder head. Given you're not planning on going high compression the deck height method is ok. The factory PI head is 3.4' tall which equals 9.5 to 1 (per factory) but use a shorter pushrod. Richard good has a published chart of deck heights and corresponding compression ratios so maybe use that. Chris Witor has a published list of the various 6 cylinder head and lists several with a deck height of 3.475" that still use the same length push rod as your car.

Not sure when the changeover happened on the exhaust valve, but BPNW shows the larger valve appropriate for 73' and older.

It is a PITA to pull the timing chain cover with the engine in the car. Yes, it is possible and I've done it, but now prefer to at least lift the engine up when doing so (ok, ok, I was given an engine lift a few years back and it has changed my perspective). You will need to at least loosen the steering rack to access the nuts/screws for the cover and get the damper off. The bigger issue is going to be getting the timing cover back on correctly. Its awkward due to the timing chain tensioner and not wanting to damage the timing cover gasket while installing. And, you want to do this right since a leak from the front oil seal is bad (although a great sealer for both the driveway and underside of the car).

You don't mention how many miles are on your car. If above 100K (or near) with the head off, it might be a good time to replace the rings and redo the rod and main bearings (and thrust washers). The bottom end bearing job is surprisingly easy to do. At a minimum, it'd be a good idea to pull and look at the bottom of the mains and the top of the rod bearings (that's where the wear shows up) to see if copper is showing. You might be surprised at what you find at the bottom of the oil pan if you have never dropped it.

[Drone Dog]

i have not pulled the pan since i have had the car and pretty sure it was not touched before me. car has about 79000 miles. i have had it about 4 years and i don't put a 1000 miles a year on it either.

i figured once i got the head off i would look at the cylinder walls and then see about pulling the pistons. if they are scored much then i will pull the engine.

thanks for all the suggestions. i am making notes.

[SapphireBlue72]

If that is original actual mileage, the bottom end should be fine. The head is nearly ready for a valve job. Typically they were good until 100K miles, but yours indicates a problem developing.

[Drone Dog]

it is original miles. 3 previous owners, all local. most of the miles by the first owner who sold it back in the 80's. the last owner never really drove the car and when he did it was only a few miles. the worst situation. it sat a lot. i drive it a lot more than he did but still not that much. but when i do, i run it enough to get all the moisture out of it.

[SapphireBlue72]

If the car is still drivable, I would first pour a large container of SeaFoam or Chevron Techron into the fuel tank and put 50-100 miles on it, then check if situation is better.
It could just be a problem of engine parts needing to be cleaned internally.

[ima68tr]

Concerning bronze valve guides: the head on my driver so equipped has 90,000 miles on it so far. No valve guide seals present, and oil consumption is between 3000-4000 miles per quart, best it's ever been and far better than original. No smoke ever. To aggravate matters, it also has the auxiliary oil feed line for the rocker shaft and those dreaded Weber DCOEs which everyone knows flood the engine with excess fuel .

What I was told is the rocker geometry governs guide life. Successive valve jobs recess the seats and adversely affect this. Since the source of this info was the source of the head, I assume they got it right, along with equal stem heights, etc.

Seems a pity to leave the emissions cam in the engine if the head's coming off - this is the worst part of the job, and with such mileage the timing gear is due for renewal as well. Similarly, a 9.5:1 c/r can be effected ( why bother with anything less? ) which translates to a head thickness of 3.400" for an otherwise unmodified head.

Tom

[YankeeTR5]

I believe Drone Dog has a later (75/76) model based on the turn signal location of his car in his profile pic. This would mean he's got the 125 bhp PI cam, that provides a good tradeoff of power and smooth idle. Bumping compression a bit and putting in a larger exhaust valve will really open things up power wise - not maximized, but much much better than the setup he has today (I know as I daily drove a 75 1/2 for 6 years).
You must be one of the lucky ones relative to the bronze guides. Many reports on burning oil upon installation and why folks like Goodparts offer them turned for oil seal these days.
If you pull the oil pan and find a grey plasticky sludge in the bottom it will give a good indication of bearing wear as that will represent the first layer above the copper wearing off and settling in the bottom of the pan (it doesn't necessarily drain out when changing oil.....I agree that at 79K miles your bottom end should just be getting broken in.

[Drone Dog]

I do have a 76. Still reading this info but am away for a couple weeks.

[Craigfairfield]

Payen gasket is the way to go. I don’t think you can use the solid copper head gasket on the later models due to the recessed fire ring on the block.