[supersport#69]

Questions For stock 1968 #16 heads::

1. Do I need to order special valves or are they just regular valves?

2. Do I need a certain thickness of head gaskets to keep compression as stock original?

3. What type of shop price range can I expect for a stock rebuild with no 3 angle?

Anything else I should know? I’m taking them in in 2 weeks.

[steve25]

You should go to Butler for the valves.

You there FER-F5143-8 set of Intake valves and there FER-F5144-8 set of Exh valves are the size and lenght you need.

The head gasket you should run is the Fel Pro 1016 set.

These compress to .039" which is only .016" greater then the stock .023" gasket and really does not change the compression ratio any to fret over.

[Schurkey]

Originally Posted by supersport#69

Questions For stock 1968 #16 heads::

1. Do I need to order special valves or are they just regular valves?

There was nothing special about the OEM valves. Materials are probably better today; but depending on where they're made, the actual machining may not be as good. Steve25 seems more aware of good parts than I am.

Originally Posted by supersport#69

2. Do I need a certain thickness of head gaskets to keep compression as stock original?

Are you having the heads shaved? That would tend to increase compression.

Are you having hardened exhaust seats installed? That might maintain the same compression. Having the existing metal ground down would tend to lower compression. I think you'd be nuts to NOT have hardened seats installed on the exhausts, but others will disagree.

What is the existing compression ratio?

What is the existing quench distance? Getting adequate quench/squish is probably more important than the actual compression ratio.

I'd want to have answers to all of that before I selected a head gasket.

Originally Posted by supersport#69

3. What type of shop price range can I expect for a stock rebuild with no 3 angle?

Of course you're getting a "3-angle" valve job. It's the minimum needed for proper positioning and width of the valve seat. The idea that a "3-angle" valve job is something special or fancy is magazine bullshiit.

With the head "upside down" on the work bench for access to the valve seats:
You need the seat angle. No getting around that.
You need the steeper angle under the seat, leading into the port--to set the lower edge of the seat at the right height. Again, mandatory.
You need the shallower angle above the seat, leading into the combustion chamber--to achieve a suitable seat width. Mandatory.

Cutting multiple angles on the valve itself--back-cuts and such--is optional. No getting around three angles on the seat, though.

Originally Posted by supersport#69

Anything else I should know? I’m taking them in in 2 weeks.

Seat grinding, and valve grinding is the easiest part of a "valve job". Getting the valve guides reconditioned takes specialized equipment; as does installing hardened exhaust seats. The guides need to be done before the hardened inserts can be installed; and the hardened inserts have to be done before the seat grinding.

Ideally, the new valves shouldn't need to be ground at all. In practice, I've seen brand-new "OEM-quality," "famous name" valves that were less-concentric than the originals with a hundred-and-fifty thousand miles on them, and new valves that were less-concentric than the used valves after they've been ground on my antique Sioux valve-grinder. Which means your machine shop may be re-facing brand-new valves if the ones you select aren't appropriately high-quality.

While the heads are off, find out how far in the hole your pistons sit. At least verify 1, 2, 7, snd 8. Select a head gasket that gets you to .035--.045 quench distance.

Look close at your rocker arms. They're probably scored where they touch the valve tips; not uncommon to have to scrap all 16. Might want to test the valve springs for tension, too.

When the heads come back from the machine shop, make sure the valve tip heights are all the same.

IF (big IF) your heads need guides, hardened seats, new valves, maybe new springs/retainers/keepers...consider just getting some new Edelbrock aluminum heads. They'll cost a bit more, but they'll provide benefits the old castings don't. The price difference may not be too bad.

[mgarblik]

Good info in this thread. Another perfect example of where a set of REPLACEMENT IRON HEADS would be a more cost effective solution to the OP's question about a valve job, Unless there was a need to keep the OE heads for a concours restoration, the cost of new valves, springs, reatainers, keepers, new valve guides, hard exhaust seats, labor for cleaning and machining would FAR exceed the cost of a pair of new heads. Just a shame for over 50 years, Pontiac fans have not had that option.

[supersport#69]

1. Compression: I don’t know other than it has never been rebuilt and the phs shows 10.75:1
2. It’s a numbers matching drivetrain ws 400 ho motor so I’d like to just keep it as it was.
3. I talked to the machine shop today about the heads. He said hardened seats will depend on the condition of the metal. He said he’d reuse the guides if good. Reuse valves too if good. No mention of springs.
4. As for hardened seats he just said if it’s not a ride being driven a lot I don’t really need them but up to me. For $160 to put them on exhaust seats I’m leaning on doing them.
5. As for shaving the heads I’d rather not unless that’s needed.

[STEELCITYFIREBIRD]

Your going to have 1000+ in those heads.
Make sure they’re not going to knurl any guides!!!
When you get your quote with options post it up.

What is the reason you have them off??

[supersport#69]

I’m hoping for less but prepared for that amount if so.

What knurl mean for the guides? I’m learning as I go.

[Schurkey]

Originally Posted by supersport#69

What knurl mean for the guides? I’m learning as I go.

Knurling is a prehistoric method of "repairing" wear in valve guides (internal knurl) and on piston skirts (external knurl).

It works...for awhile...IF (big IF) it's done to "best practices". Overall, it's a poor method of reconditioning parts. But if you're living in 1940, it may be the only way you get your engine back together.

The process involves creating "indented" gouges in the metal surface, which creates raised ridges next to the gouges--the metal is distorted. Then the raised ridges are reamed or smoothed to size, so that the valve stem fits through the "reconditioned" guide, or the pistons fit the cylinders.

You see the same sort of process on older ratchet handles or surfaces intended to be gripped by hand--typically a diamond-shaped knurl that has a bazillion "points" that make for a non-slip surface. When knurling handles and knobs, there's no reason to jpartially-smooth the surface, as you would on automotive parts. Here's a photo of a knob with external knurling, shamelessly stolen from Amazon.


Another take on piston knurling:
https://www.enginebuildermag.com/201...es-skill-guts/

Company I worked for (not for very long, though) decided it was a great idea to bore the block .020, but re-use the standard pistons after knurling the skirts to take up the clearance. Then they put .020 rings on the standard pistons. That thing knocked like a diesel, but ran for thousands of miles and was still in use when I got the hell out of there.

[racegto65]

Originally Posted by STEELCITYFIREBIRD

Your going to have 1000+ in those heads.
Make sure they’re not going to knurl any guides!!!
When you get your quote with options post it up.

What is the reason you have them off??

Wow prices on the east coast are high.
I do iron heads all day for about 600.00
clean, mag, mill, new stock valves, springs, retainers, locks,
bronze liners, 3 angle valve job.

[supersport#69]

I’m hoping for a number closer to $600. I live in central California.
I don’t have the heads off yet. Long story short my engine was smoking badly on passenger side exhaust and missing. A compression test found one cylinder at 35 lbs. removed valve cover and a screw in stud somehow backed out and a rocker nut was loose. They were tightened. Then instantly smoke completely disappeared, wasn’t missing and idled fine.
Problem is the compression is still only at about 105 in that cylinder. The mechanic thinks it’s a burnt exhaust valve.
So I am in a spot where I can drive it with no smoke but something isn’t right or chance a valve job to fix it.

[65sport]

Having a rocker stud back out should not cause low compression after re-installation. However, if a valve is too tight then that will burn it if it's ran very long. Try loosening the adjusting nut a little to see if it smooths out or increases compression. If that works, you will need to get a Chevy rocker nut (crimped) and an appropriate washer to convert that one to adjustable. If that don't work, do a de-carbon before you take it apart, you can use just water keep the RPM's up and pour it in carefully not to kill the engine and not "hydraulic" it. Then take it out and blow the cobbs out of it (brisk drive). Then do another compression test you may be surprised.

[Steve C.]

supersport#69
Curious, are you trying to run on 91 octane gas ?

.

[supersport#69]

I should have mentioned too that the rocker was not actually compressing the valves at all.

When the spark plug was removed for compression test the first time it was clean as a whistle. It looked like brand new.

As for octane I’ve just been running 91 but there not very many drives to speak of. After this happened I bought octane supreme and added it to the 91. I put half the can to 10 gallons so I think that bumped it to 96?

[Steve C.]

What is the 'octane supreme' to make 96 ?


.

[supersport#69]

Stuff I bought online.. my engine didn’t ping on 91 that I heard but this stuff also has lead.

[Steve C.]

https://forums.maxperformanceinc.com...hlight=booster

.

[Schurkey]

Originally Posted by supersport#69

Problem is the compression is still only at about 105 in that cylinder. The mechanic thinks it’s a burnt exhaust valve.

Find out for sure. A cylinder leakdown test will positively identify a leaking valve.

Your mechanic should have already done this.

[PontiacJim1959]

Disregard everything you just read except racegto65 as none of this is helping you and only confusing you.

First, what are your intentions? Are you just trying to save a few dollars & get the car back on the road and later invest in better head work later or a better head when you re-build your engine?

In reading your post, it sounds to me like you are just trying to get by with a basic & inexpensive (if there is such a thing) rebuild? So let's answer some questions.

1968 HO shows to be 10.75 compression and is most likely closer to 10.5.

The word "quench" came up. Quench is the small space between the top of the piston and any flat areas found on the bottom of the head. A smaller space is better as it can help to prevent detonation. But, most Pontiac pistons are down in the bore .015 - .020" from the deck surface. You won't know until you actually measure from the top of the deck/block surface to the top of the flat on the piston. The preferred quench, or space between the piston and head is generally .040", but can be slightly tighter or larger, .035" - .045".

So for example if your engine's pistons measured .020" down into the bore at top dead center, to get the ideal quench would mean a head gasket thickness of .020" which when added to the piston distance equals .040". However, you are not going to find a .020" head gasket unless it was something custom. Pontiac offered a head gasket that was .023" which would make the quench .043". Still within the "good" range of quench. But, the Felpro gasket that most buy is thicker and lists to be .039" compressed, so that plus your .020" down in the bore piston equals .059". Is this concerning? Not really, just not optimal.

Thinner head gaskets will also mean additional compression which you really do not want and why when rebuilding the engine compression can be dropped by larger combustion chamber heads or larger valve relief's or dished pistons. Unfortunately, you are not looking to rebuild your engine so you are somewhat stuck with the high compression as it is and will have to do what you are now doing which is premium gas with an octane additive.

Next is what do your replace or save to keep costs down? This can only be determined when you machinist gets your heads. He will tear the heads down, hot tank, magnaflux, and inspect your parts. He may or may not feel the heads will need to be surfaced, and he will only take off enough material to clean the surfaces up, so it will not be enough to change compression. When he hot tanks the heads, he will knock out all the freeze plugs on the heads and you will want to replace these and get a new heater hose nipple and replace it while being cleaned.

He will examine the valves, check the valve guides, and can test your present spring pressures to see if they are useable or not - ie too weak. You will want to give him the cam information that is in your engine so he will know if the spring pressures are acceptable or not. If stock HO cam, I recall it will be .414" lift. If the machinist says they are good, use them and save money, if bad, invest in a new set that matches stock and nothing more.

He will inspect your valves and tell you of their condition. If they are worn out and cannot be re-ground to save them, he will tell you. If he can save a couple and you only have to buy a couple, he will tell you. If you need a complete set, he will tell you.

If the head's valve seats can be safely ground to match the above valves, he will tell you. Sometimes a previous valve job has already been done and this makes the opening where the valves close, the seat, larger and this can cause the valves to sit deeper into that seat (called sunken valves) which is a bad thing. New fresh valves can often remedy this, so using your old valves will be out. But, he will tell you the condition of the seats and if your old valves can be used, new ones needed, or even if you need new valve seats installed to save the heads. You don't want to skimp if he tells you its your call, then get new valves.

With regards to valve guides, he will measure these for correct clearances. If they are worn, some will knurl them but as pointed out, DO NOT do this as this is simply a quick fix and something you can do if your were to sell the car and let the next owner worry about the poor oil control. Next option is iron replacement valve guides which are essentially the same as the head. It is said these are good for a stock rebuild. Then there is bronze valve guides which are more often than not used in performance/race builds.

When doing a performance build, generally you will opt for stainless steel valves, bronze valve guides, and Viton valve seals which means another extra machining process to cut down the valve guides so the Viton seals can be used. Stock oil control is done using the O-ring seals at the valve retainer, umbrellas seals on the valve guides ( which I don't recommend) and your valve springs may or may not have what are called "oil shields" that look like hats over the tops of the valve springs. Pontiac designed their heads to use a little oil and had a little extra clearances in the valve guides. If using bronze valve guides for example, the clearances are a little tighter.

Do you need the hardened exhaust seats? Listen to your machinist. For street driving, I don't see the need. If you pull a heavy camper and get the exhaust valves/ports really hot for extended periods, then yes. If you don't drive the car much, use this additive which helps to lubricate the seats/valves and adds a little more octane, but don't use it as a substitute to the octane additive you are already using.

https://www.drivenracingoil.com/defe...-additive.html

That all said, the costs will depend on what you machinist sees you need and recommends. He will work up a list of parts and prices for the parts and his services. It could be as low as $400-$600 depending on what he can save, and on up. I rebuilt my heads with all new and it ran me $1200 for the SS valves, 3-angle valve job, bronze guides, Viton seals, springs, retainers, etc. plus machine shop work.

Hopefully that gives you a better and clearer understanding of what you are getting into.

[65sport]

When intake airflow drops, compression drops down to where it will not sustain combustion, and it will make a white smoke that smells very gassy. That is unburned hydrocarbons up the ying yang. This will wash down the cylinders to some extent and that will cause compression leakage. Drive it a couple days and re-check the low cylinder. The rings need a chance to get oiled for the compression to even out with the other cylinders.

[supersport#69]

The smoke was definitely oil burning. Oil was even spitting out the passenger tailpipe on start up. It completely stopped after rocker was retightened.

For the heads I want to have them rebuilt as good as original. I don’t want to skimp just not looking to go beyond stock. However I don’t mind going with better materials for the parts if not too much more costly. I’m prepared to buy new springs and valves too if needed.

As for the cam I think it was called a 068 model but not certain at all..

My hope is I have the heads done without issues and remount them with no bottom end surprises. Having not compression tested the drivers side cylinders I am a bit nervous.