Bad valve guides so pulled head - Couple questions about what to have done by machine shop.

R

reweb67

Well-known member
Car is a 1967 Mustang 200 - I have a couple other posts here first asking about the valve seals then another when I realized my guides were worn and the valve stems would wiggle around. I pulled the head yesterday and dropped it off at a local machine shop that was recommended by a friend.

Was happy to see the guy doing the work was an older dude who said he has been in that shop for 45 years! Guessing he knows what he is doing. He is going to tear it apart today and call me Friday to let me know the condition and I need to tell him what I would like to have done.

The head has hardened valve seats already and has been ported / polished. I had that done about 30,000 miles ago as part of a full rebuild. Don't know why the guides are toast already?

I have told him I will want all new guides machined for viton valve seals. Someone has suggested a 30 degree cut on the intake valves? Should i do this?

The car has all stock ignition. I do have a clifford header with the port divider. When the engine was rebuilt they put in an RV cam. Not sure exactly what size tho. I'm running the stock autolite 1100 with matched distributor. Not trying to hot rod the car and would rather do things to help it be reliable more than anything else. Car is a weekend fun cruiser.

Any suggestions appreciated. Also he did briefly mention something about maybe being able to use 250 valves in it? Not sure on that one. Thanks!
 
if U just want it "reliable" I wouldn't do anything beyond what you've mentioned. Machining will not degrade that.

If you want 'modernized', better MPGs, some pep, cleaner, etc follow the Handbook or Tech Archive suggestions. The latter is above, at the crossed screwdriver / wrench symbol (Level II or III w/o the bottom end/piston work).
 
Howdy Reweb:

IIWIYS, I'd specify a performance three angle valve job and the back cut on the intakes.

Was the head milled to maintain or increase the compression ratio? IF so, How much?

Also, If not already done I'd have him disassemble the rocker shaft and clean the inside of the shaft.

Keep us posted on your plan and your progress.

Adios, David
 
X2 a good three angle valve job (or a radius type Serdi) is worth some extra power at very little extra cost over a standard valve job, plus it's durable and long lasting. Since you have head porting do you have stock or oversized valves now? Good bowl blending and tapering of the valve guides is good for head flow too. Many go with a bigger 1 3/4 inch intake valves and also a bigger 1 1/2 inch exhaust valves. So if you need to replace your valves that might be worth doing for some extra power potential too. Good luck (y) :nod:
 
Thanks for the replies.

Sounds like I should ask for a 3 angle performance valve job and have intake valves cut back - Will do. Will also have the new guides milled and fitted with viton positive seals. If I do need valves I will ask the machinist about getting the bigger ones.

The rocker shaft really looks to be in good shape. Very clean with no issues so I'm thinking it must have been taken apart during the full rebuild 30K ago. Will probably not mess with that. I took it off before bringing the head in.

I have a few more questions.

1) It is ok to spin the motor by hand with the head off right? Want to look at cylinder walls etc. Pretty sure this ok just want to confirm I won't be miss aligning something.

2) "Was the head milled to maintain or increase the compression ratio? IF so, How much?"

This is don't know. I'm sure the head was checked for being flat and ground down a bit if needed. The machinist with the head now will do the same. Not sure about this?? Do I need to check the head height or something?

3) The head had a fel -pro metal head gasket when I took it apart. Can I get another one of those? If so, is that what I should use?

Thanks again! Excited to get the car back on the road. Hopefully my plugs won't foul out anymore after all this! (y)
 
You should try to optimize your static compression ratio.
> have the machinist measure the combustion chamber
> measure the cylinder bore
> measure the piston shortfall below the deck
> choose a gasket and get the compression thickness

Use these numbers in an online formula or post them here. Unless you know for sure, the pistons are most likely replacements and have a 1.5" compression height. Once you have a estimate of your SCR, play with the numbers for combustion chamber volume to get yourself in the 9.0-9.5 range.
 
Howdy Back Reweb:

Yes, you should verify how much, if any, your head has been milled. You will want to maintain, at least, a 9:1 compression ratio. You will need to compensate for the difference in thickness of the factory stock steel shim head gasket at .025" thick and the FelPro head gasket at .050". You will need to measure the volume of a chamber or two in cubic centimeters.

I can't believe I didn't already ask you for the date code on your head. It is cast onto the intake log just behind the carb hole. Early sixties casting have a chamber volume of 52 ccs. From mid-seventies and on have a chamber volume of 62 ccs. You will need to start by determining what chamber volume you now have and figure from there to determine how much you should have the head milled to maintain your goal compression ratio.

IF you havent already bought a valve job gasket kit you should do so. It will include a head gasket as well as all of the other gaskets needed to reassemble and reinstall your head. FelPro is a good one. It is cheaper and handier to buy the kit than to buy the bits and pieces separately.

So, keep it coming. We are here to help you.

Adios, David
 
reweb67":13ytmemu said:
Thanks for the replies.

Sounds like I should ask for a 3 angle performance valve job and have intake valves cut back - Will do. Will also have the new guides milled and fitted with viton positive seals. If I do need valves I will ask the machinist about getting the bigger ones.

The rocker shaft really looks to be in good shape. Very clean with no issues so I'm thinking it must have been taken apart during the full rebuild 30K ago. Will probably not mess with that. I took it off before bringing the head in.

I have a few more questions.

1) It is ok to spin the motor by hand with the head off right? Want to look at cylinder walls etc. Pretty sure this ok just want to confirm I won't be miss aligning something.

"1. Yes it's ok to turn the engine, the only time this would matter is if your Distributor is also out of the block. Even then it's just a simple matter to again find TDC on the compression stroke before reinstalling the Distributor."

2) "Was the head milled to maintain or increase the compression ratio? IF so, How much?"

This is don't know. I'm sure the head was checked for being flat and ground down a bit if needed. The machinist with the head now will do the same. Not sure about this?? Do I need to check the head height or something?

"2. X3 have the combustion chambers measured so you can calculate the compression ratio."

3) The head had a fel -pro metal head gasket when I took it apart. Can I get another one of those? If so, is that what I should use?

"3. Yes the metal head gasket would be nice and would keep your compression ratio close to stock. However they are quite hard to find now days in many ways the newer composition head gaskets like FelPro and Victor seal better then the old metal head gaskets. You will need to mill the head an adistional amount because of this. Ie the approximate .025 thicker new gasket versus your metal head gasket."

Thanks again! Excited to get the car back on the road. Hopefully my plugs won't foul out anymore after all this! (y)
Click to expand...

Good luck on the repairs. (y) :nod:
 
Hi, it is OK to turn the crankshaft. Clockwise is the direction the engine runs. You will want to be at TDC on the compression stroke when you install the distributor. You can see if the mark on the balancer lines up with the tab. If you turn the engine upside down the lifters will fall out. You should keep the lifters in order if you remove them. Each one is matched to a camshaft lobe. You should see cross hatching on the cylinder walls. There should not be any ridge at the top of the bores. Good luck
 
One other thing you also should do is to open up the carb throttle bore hole in the log to at least a 1 3/4 inch opening (some go as much as 2 inches) radius the bottom of the hole into the log too. This will give better flow and also give you the option of allowing you to install other carburetors in the future if you wanted. Good luck (y) :nod:
 
Thanks for the advice to open up the carb throttle bore hole in the log but I'm happy with autolite 1100 on there and don't plan to swap out carbs. I managed to find an NOS 1100 that works just fine. Regarding the head. I can't read the numbers now but have confirmed before that my car has the original motor (stamped / dated properly anyhow) for a 1967 200 Mustang.

Talked to the machinist today. For $500 (including parts and labor) he is going to do the following:

1) Install all new guides milled to accept new viton positive valve seals. He said I was right and the guides are toast.

2) I need all new intake valves. He said the exhaust valves are good. He is going to do a 3 angle job on the intakes and back cut the intake valves. He does plan to install bigger intake valves. If I understood him correctly 1751 thousands? Verses the standard valves that are 1651 thousands. He also said the exhaust valves I have now sit out farther than the intakes when seated. By adding bigger intake valves they will sit out the same distance when seated. Guess this makes sense?

3) I asked him about milling the head and measuring the height so I can figure out what gasket to use. He is going to mill the head to make it flat. It has been milled once before. He asked me to find out where to measure on this type of head.

Where do you measure the head to see how much has been milled off?

Appreciate all the help!
 
Just have him measure the size of the combustion chambers. Somewhere I have it written down, but I think 0.010" mill reduces the chamber volume by 2cc. So just back into the correct chamber size using the static compression ratio calculator.
 
I looked How To Calculate Combustion Chamber Volume on the web and it seems to involve pouring some type of liquid into the head?

Is that the only way to figure it out? Not sure the machinist is going to have the set up to do that. He asked me where to measure so pretty sure pouring liquid in there is not on the radar.

Thanks
 
"...He asked me where to measure..."
duz he do engines often?

"...not on the radar..."
too bad U can't (didn't?) get the volumn down, do the math, & tell him the cut.
You'd B alot more in control of where this is going.
 
The machinist has been doing the work for 45 years. He is an older guy in a large well known old school shop.

Maybe he does have the equipment to measure the Combustion Chamber Volume? I did not ask because I did not realize it was required. The head has not been milled yet.

Although when I said I needed to figure out how much the head has been milled to decide what gasket to use he asked me to find out where to measure from on the head?

It does require the set up to pour liquid in the chamber and measure the volume right? Sorry but I have never heard of this before.

Can someone explain the process? So I can figure out what I need to do. I could buy the equipment and do it myself at the machinist shop. Again this is all new to me. Did not even know this was a thing! Ha Ha

Thanks appreciate it.
 
Thanks for the link. I get it now.

Just out of curiosity, what if I do not figure this out? My car had the Fel-Pro 7916 PT-1 gasket on it when I pulled the head.

https://www.amazon.com/Fel-Pro-7916-PT- ... B000C2E6UQ

The head has been rebuilt one other time (maybe twice). Assuming the head has been milled two or three times to flatten it out and I used the above head gasket what can I expect? Slightly lower compression?
 
Actual volume measurement is best but can be tedious, my machinist simply subtracts how much has been milled from the OEM specs on the head which is OK IF head is uncut yet... Typically, milling the head .010" will result in an approximate reduction in volume of 2cc's.
from CI pages:
actual chamber volumes may vary considerably, which means they must be re-measured (cc'd). The key is to measure carefully and record the results, then mill the head accordingly to obtain the desired compression ratio. Typically, milling the head .010" will result in an approximate reduction in volume of 2cc's. For example: if your cylinder head currently has 62cc chambers, and you want 52cc's, you would need to mill .050" off the head to reduce the chamber volume by 10cc's.
FYI: All small six cylinder heads can be safely milled .090".

DODE _70 Mav' 170 'closed chamber ' head @ 54cc's measured





haev fun
 
reweb67":20bv88cf said:
Thanks for the link. I get it now.

Just out of curiosity, what if I do not figure this out? My car had the Fel-Pro 7916 PT-1 gasket on it when I pulled the head.

https://www.amazon.com/Fel-Pro-7916-PT- ... B000C2E6UQ

The head has been rebuilt one other time (maybe twice). Assuming the head has been milled two or three times to flatten it out and I used the above head gasket what can I expect? Slightly lower compression?
Click to expand...

The add dose not state what the thickness of the head gasket is, can you measure the thickness of your old head gasket? Orginal Ford steel shim head gaskets were about .025 thickness new FelPro composition head gaskets measure about .050 thick. Besides what you mill the head to get the combustion chambers to the desired Compression Ratio your after then you need an adistional .025 milled to make up for the extra thickness of the new style head gaskets.

Also your machinist is correct about using the larger intake valves so they are standing up higher to match the exhaust valves this gives better flow than a valve that's been cut down so much it's been recessed into the combustion chamber. Good luck (y) :nod:
 
ur comments: “The head has not been milled yet.”
“needed to figure out how much the head has been milled” indicate need
for more info to continue ur build...

gotta start with a known (carb, cam, etc, etc & here:
"Just how much has been milled offa this head in 50 yrs, if anything?"
"Does it need a truing cut to the face or is it completely level and will seal to the gasket/block w/o any pass?"
Also 2 guide the machinest:
"What CR do I want for MY purpose?" therefore the need to CC the head).
 
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