Head Work and some valve spring stuff ??? (long and Picts)

[Greg]

Well I've recieved my new cam, springs (with dampers), teflon seals, etc... I have been working on the head removing carbon build up caused by my previous carb running rich (now fixed by new 32/36 carb) and smoothing out the combustion chambers to help prevent any further buildup.

I have a bunch of qustions I was hoping to get some help with.

1) Has anyone had the machining done to the head to install the teflon seals? The teflon seals have an inner diameter of 0.460" (~15/32") where they should go over the head's post which has a diameter of 0.635" (~5/8"). If so with what process did the shop remove the excess material and how much should I expect them to charge? Grinding the posts with a dremel would take forever.

2) The combustion chambers measure ~ 60cc, the block was bored 0.030" over, and I was using the 0.055" thick Felpro gasket. The compression calculator yeilds a compression ratio of 7.7:1 for this combination. If I have the head milled 0.050" (assuming 0.010" for 2cc reduction in combustion chamber volume. Any one have experience with this rule? Is it accurate?) the compression calculator yeilds 8.6:1 with the felpro gasket and 8.8:1 with the Victor Gasket. Since I am going for a good cruising engine and if possible would like to continue running 87 octane would milling the head 0.050" be recommended or could I mill more for a slightly higher compression ration and more power?

3) The intake valve has a ton of black build up on the intake side. I assume its from the engine running cold, too rich carb, or bad valve guides, but the head was remanufactured about 40,000 miles ago. The intake valve measured 1.750" in diameter and the exhaust 1.390 (D7, 1977 head). Can I just order the FSPP stainless steel stock replacement valves and install them with no further machining? The valve seat were supposed to have been cut when he head was remanufactured with a 3-angle valve job.

4) Any idea on how much to pay for valve guide replacement? Althought there is just the tiniest bit of movement possible. Any advice as to if I need them?

5) What do burnt valves look like? Are my valves burnt? and what do you do for burt valves if they are burnt?

Pictures are bellow. Thank you for the help,
Greg


Head before cleaning (head gasket still on):
http://members.aol.com/gfeing4935/cylinderheadbefore.jpg

Combustion chamber before cleaning:
http://members.aol.com/gfeing4935/chamberbefore.jpg

Head after cleaning and smoothing combustion chambers. It's not perfect, but much cleaner and smoother than it was:
http://members.aol.com/gfeing4935/headafter.jpg

Single chamber closeup:
http://members.aol.com/gfeing4935/chamber.jpg

New Valve Stem sitting on head post that needs to be machined to a smaller diameter:
http://members.aol.com/gfeing4935/seal.jpg

Valves. I was very surprised by the amount of buildup on the intake vale. What causes that?
http://members.aol.com/gfeing4935/valves.jpg

 

[48fordnut]

Any good machine shop can machine the head for the teflon seals, the valves being coked up like they are is a indication of valve guide wear. letting oil be sucked into the valve pocket from the head. i would try for at least 9.5 comp to best get a return on your money for the work. you don't need stainless valves because this is not a high perf eng. I am sure others will post about the comp, but in my opinion, get as much as you can , and burn the gas you want too. What i do on v/g is put liners in them, if the guides are not worn out. jim

 

[Guest]

Thats just oil soot from burnt oil on your valves, no not burnt. Its mainly from your seals or guides, like you had said. I thought I had guide problems, but the old umbrella seals are not reliable past 15 years. If they crumbled upon taking the head apart, that might be the problem.

You really should invest in sandblasting them, measuring both the top, middle and bottom of the valves with a micrometer. If theres over a .002 or .003 difference in the three (top,middle, bottom (bottom is just below the retainer slot) measurements on a valve, your valves are too worn. Also, look up or get information on the specs of the valve stem new, stock. If youre off in that category, you need new valves. Usually you can tell by a shiny wear somewhere in the middle of the valve stem, but a micrometer will definitely tell the story.

I bet a good sandblasting ($20 a set where Im at), youd find your valves arent "burnt", but just coated with carbon, a complication when oil runs down the valve into the combustion chamber and gets hot and burns. A re-grind is cheap also.

Before you reassemble the head, put the clean valve 3/4 the way into the guide and push it lightly side to side, without scuffing the inner guide. If theres not a considerable amout of play, where its noticeable, you might not need guides. Try one at a time though, because oil distribution problems can make certain guides wear more thoroughly than others. Make sure you have numbered each valve with a numbering punch, unless you never plan to use them again.

Sure, dump the umbrella seals, they turn to hard plastic or bakelite and just crumble.

 

[CZLN6]

Howdy back Greg:

This head has been suffering from leaking valve stem seals and/or worn valve guides for some time. The valves should be able to be cleaned up to a shiney clean surface. If burned they will show signs of pitting, cracking and discoloration. If they show these signs they should be replaced. If you use standard size valves they will be a direct swap. If you use Mike's oversized exhaust valves at 1.5" your exhaust seats will need to be enlarged and recut.

You didn't say what engine you're working with. What is the D7 head casting replacing? What is your elevations/ location?

The ratio of .010" mill cut is APROXIMATELY equal to 2 cc. You must measure the volume on each chamber to be accurate. The variable is the casting. Not all chambers are created equal. And as you smooth them, and you should, you are slightly enlarging the chambers. Find the largest and make all chambers equal to that one. Go slowly. The deeper you mill the greater the volume reduction effect gets. If your chambers are already at .060" it is likely that this head has already had a mill cut at some point in the past.

Due to the narrow bore on these engines, the wedge chambers, dished pistons and your cleaning up the surface you should be able to run a 9:1 CR on 87 no-lead with very little problems. If you're above 2,000 ft elevation you will have an added safety margin. The unhelpful parts are the thicker head gasket that ruins the marginal quench height. That with a deck height of (Typically) .025" gives a deck clearance (deck height +gasket thickness) in the range of .070" to .080" depending on actual dimensions. An ideal deck cearance for best quench effect is more like .030" to .040".

Those aftermarket composite head gaskets do seal better, but they sure do play havoc on quench effect on these engines.

Your machine shop will have just the right tools to machine the valve guides for the teflon seals. Ask them about valve guides- Do they need to be replaced or will the seals take care of it? Have them advise you on the burnt valve question too.

Consider having them add a 30 degree cut on the port side of the intake valves. It is called a back-cut. It will add a little more flow and lighten the valve slightly.

Enjoy the journey

Adios, David

 

[Greg]

Thank you every one for your replies. Assuming the costs of the machine work on the head doesn't get too far out of hand I think I'll go with FSPPs stainless steel stock replacements. At only $65 I figure I'd rather have new valves than try to clean the current valves. Well time to get back to removing the remaining valves and grinding the exhaust ports...

So how long until those aluminum heads come out??? If the machining costs are too high I may wait a little..

Greg