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StitchB

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Machining heads, pros and cons and other
Dec 25^th, 2015 at 7:50am

Hey guys, I work in maintenance so don't do a lot of heads but the subject keeps coming up and would like some feed back. I have my own opinions but being I don't do a lot of RR not the best on the subject. My first experience with milled heads was 25 years ago when after doing the heads and surfacing I could barely get the manifold back on in a 400 CU chevy. You can talk about it but seeing is believing as now the valley is narrower than the part. The new stuff has to affect the cam position, and all the rest of it.

My point is there are machine shops and repair shops milling heads and I know this has to throw the timing on the cam off. They say they run great, I wonder? As we all know the compilation of stretched chains, belts and misc part make for an ongoing problem. The car in question that I am thinking of is Subaru, major gasket failures for what ever reason. Not picking on Subaru just when I see 6 heads on the floor of the local Auto retailer/machine shop, I always ask the question, do they use a thicker head gasket to offset the loss. They say not a problem, they also have no idea what an airlift tool is either as a little air in the coolant, Lips Sealed

not a problem.

Would like to see a Compression wave for before and after using MCCT as an example

Larry AKA stitchB Tongue

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top4 Senior Member Picogroup Offline Posts: 222 Ellwood city pa Tennessee USA Gender:	Re: Machining heads, pros and cons and other Reply #1 - Dec 25^th, 2015 at 8:16am Hi you tube has a channel south main auto he has a 4 part id on this well worth the time Also if overheated badly watch out!
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StitchB

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Re: Machining heads, pros and cons and other
Reply #2 - Dec 25^th, 2015 at 10:08am

top4, thanks for the info. Did watch most of it and the last is over and hour. But seems it is more a tutorial on doing the job, might have missed it as did not do it all but he mentioned the obvious getting the cranks TDC and the like, but not sure my question is address of the head now being lower.

As stated might not have seen all of it, feel free to correct me if I am wrong. If you lower the center of the cam it is going to shift the tooth to what ever degree. could actually trig it out if I knew the Dia of the cam gear and specify the actual change in degree.

Again maybe picking the fly poop out of the pepper, but maybe not.

Stitch

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Spence

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Re: Machining heads, pros and cons and other
Reply #3 - Dec 25^th, 2015 at 10:43am

StitchB wrote on Dec 25^th, 2015 at 10:08am:

top4, thanks for the info. Did watch most of it and the last is over and hour. But seems it is more a tutorial on doing the job, might have missed it as did not do it all but he mentioned the obvious getting the cranks TDC and the like, but not sure my question is address of the head now being lower.

As stated might not have seen all of it, feel free to correct me if I am wrong. If you lower the center of the cam it is going to shift the tooth to what ever degree. could actually trig it out if I knew the Dia of the cam gear and specify the actual change in degree.

Again maybe picking the fly poop out of the pepper, but maybe not.

Stitch

You are correct that on an overhead cam decking the block and/or milling the head will retard the cams if something is not done to correct the relationship. This is more in the extreme then just cleaning up a surface. Adjustable cam sprockets are what we use. The newer setups from the OE's address this issue with a key less camshaft/sprocket setup.

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Ward Zintel

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Re: Machining heads, pros and cons and other
Reply #4 - Dec 25^th, 2015 at 4:27pm

Hello stitchB
Right out of high school I worked in an automotive machine shop. On the north american V8s of the day when it cam to shaving heads if you took .030" of the cylinder head you would take .010" off the intake face of the head so the intake manifold would still line up.
This was back when a 1980 was new production with a warrantee, they were cast iron push rod engines, unless some one was trying to bump up the compression ratio by shaving the heads we rarely ever shaved them .030". Pushrod engines valve timing was not affected providing the lifters still had enough travel.
-Ward-

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StitchB

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Re: Machining heads, pros and cons and other
Reply #5 - Dec 26^th, 2015 at 5:51am

Spence wrote on Dec 25^th, 2015 at 10:43am:

You are correct that on an overhead cam decking the block and/or milling the head will retard the cams if something is not done to correct the relationship. This is more in the extreme then just cleaning up a surface. Adjustable cam sprockets are what we use. The newer setups from the OE's address this issue with a key less camshaft/sprocket setup.
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Spence, thanks, as my point when talking to these people is that from what I can glean they are doing nothing to take this into account to my knowledge. You have made a point which would answer my question adjusting the cam as it would be off, thanks for the input.

I know my instructor does play some games with keys and the like and other games can be played if the cam is merely tapered. It is a sad state but when I keep asking the folks supposed to be in the know, they are doing nothing to adjust this. Sure it might run okay!, but okay and right are different. My son has a Subi Forester and thinks its the hot stuff. We did struggle on it with Cat inefficiency codes and seems to be predominate on this car, the fix was a strange one but my point is how many of these ongoing problems are the accumulation of a lot of small errors and leave the next guy chasing his tail.

Ward Zintel wrote on Dec 25^th, 2015 at 4:27pm:

Re: Machining heads, pros and cons and other
Reply #4 - Yesterday at 4:27pm Hello stitchB
Right out of high school I worked in an automotive machine shop. On the north american V8s of the day when it cam to shaving heads if you took .030" of the cylinder head you would take .010" off the intake face of the head so the intake manifold would still line up.
This was back when a 1980 was new production with a warrantee, they were cast iron push rod engines, unless some one was trying to bump up the compression ratio by shaving the heads we rarely ever shaved them .030". Pushrod engines valve timing was not affected providing the lifters still had enough travel.
-Ward-

Ward thanks, as I am aware that a push rod engine would not suffer from this, but I know it was a struggle to get the manifold bolts in, pretty funny now, was not then. Cry

Most the heads I have been involved with did not need to be done more than .010.

I ask these questions as there is a lot of stuff done out there that is not right, even from the dealer. I did the timing belt on the secretary TDI @ work. This car as been serviced from the dealer for 85,000 and I said I would do the timing belt. It had a historic ECT code on and off for several years and several new sensors, not to mention the timing when viewed on the Vag was off. When I did the coolant using an uplift tool, amazing enough the code left for good and the fuel mileage improved by about 5 miles to the gallon. I ask numerous shops about this practice and they have no idea what I am talking about. Many of these are ASME certified with 30 years, again this is how I bought a Pico and started down this trail, I just got tired of it.

By the way I have the source of many high level Techs, but like a broad base as they do not all agree, as really that would be kind of boring. I do value your input, thanks again.

Have a great new year. Grin

Larry, AKA Stitch B

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daveyK Super Nerd Picogroup Offline (Retired) - Elevation: 525 feet Posts: 2,357 Hellertown, PA, USA Pennsylvania USA Gender:	Re: Machining heads, pros and cons and other Reply #6 - Dec 26^th, 2015 at 7:55am Spence wrote on Dec 25^th, 2015 at 10:43am: The newer setups from the OE's address this issue with a key less camshaft/sprocket setup. Spence, I thought the "bean counters" were just trying to save a few $$$ by not cutting keyways and the cost of a key. It is an excellent point tho - - - Thanks
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Spence

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Re: Machining heads, pros and cons and other
Reply #7 - Dec 26^th, 2015 at 2:17pm

StitchB wrote on Dec 26^th, 2015 at 5:51am:

Spence wrote on Dec 25^th, 2015 at 10:43am:

You are correct that on an overhead cam decking the block and/or milling the head will retard the cams if something is not done to correct the relationship. This is more in the extreme then just cleaning up a surface. Adjustable cam sprockets are what we use. The newer setups from the OE's address this issue with a key less camshaft/sprocket setup.
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Spence, thanks, as my point when talking to these people is that from what I can glean they are doing nothing to take this into account to my knowledge. You have made a point which would answer my question adjusting the cam as it would be off, thanks for the input.

I know my instructor does play some games with keys and the like and other games can be played if the cam is merely tapered. It is a sad state but when I keep asking the folks supposed to be in the know, they are doing nothing to adjust this. Sure it might run okay!, but okay and right are different. My son has a Subi Forester and thinks its the hot stuff. We did struggle on it with Cat inefficiency codes and seems to be predominate on this car, the fix was a strange one but my point is how many of these ongoing problems are the accumulation of a lot of small errors and leave the next guy chasing his tail.

You have a good thought! We have a saying at our shop. An idea (in this case a thought) is all it is until you go and prove or disprove it. What would 0.010" of resurfacing a cylinder head do to the cam timing? How about 0.030"? Compare that to more then one engine that has not been touched yet. The reason for more then one is you might find there are a bigger difference between untouched ones then there is a change in milling the head(s).

You then may or may not agree with them but you would then have an answer and an opinion.

StitchB wrote on Dec 26^th, 2015 at 5:51am:

Ward Zintel wrote on Dec 25^th, 2015 at 4:27pm:

Re: Machining heads, pros and cons and other
Reply #4 - Yesterday at 4:27pm Hello stitchB
Right out of high school I worked in an automotive machine shop. On the north american V8s of the day when it cam to shaving heads if you took .030" of the cylinder head you would take .010" off the intake face of the head so the intake manifold would still line up.
This was back when a 1980 was new production with a warrantee, they were cast iron push rod engines, unless some one was trying to bump up the compression ratio by shaving the heads we rarely ever shaved them .030". Pushrod engines valve timing was not affected providing the lifters still had enough travel.
-Ward-

Ward thanks, as I am aware that a push rod engine would not suffer from this, but I know it was a struggle to get the manifold bolts in, pretty funny now, was not then. Cry

Most the heads I have been involved with did not need to be done more than .010.

I ask these questions as there is a lot of stuff done out there that is not right, even from the dealer. I did the timing belt on the secretary TDI @ work. This car as been serviced from the dealer for 85,000 and I said I would do the timing belt. It had a historic ECT code on and off for several years and several new sensors, not to mention the timing when viewed on the Vag was off. When I did the coolant using an uplift tool, amazing enough the code left for good and the fuel mileage improved by about 5 miles to the gallon. I ask numerous shops about this practice and they have no idea what I am talking about. Many of these are ASME certified with 30 years, again this is how I bought a Pico and started down this trail, I just got tired of it.

By the way I have the source of many high level Techs, but like a broad base as they do not all agree, as really that would be kind of boring. I do value your input, thanks again.

Have a great new year. Grin

Larry, AKA Stitch B

Even a push rod engine can be effected with milling and even more so when you mill the heads and deck the block. You say you can just adjust the valves so no biggie... What will happen if the push rods are not corrected is the arc of the rocker arm with the valve stem has changed. Valves may open at a slower rate then if the push rod was shorter. This will cost you power and other running issues as well.

Just some more thought for you to chew over.

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sneaky pete Super Nerd Picogroup Offline Posts: 730 Regina Saskatchewan Canada	Re: Machining heads, pros and cons and other Reply #8 - Dec 27^th, 2015 at 5:49pm also have to take into account the manufactures spec for cylinder heads. most newer engines, they don't even want machining done. throw out the heads and get new ones. very little margin for error.
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fisher Super Nerd Picogroup Offline Deceased Posts: 2,734 Concord California USA Gender:	Re: Machining heads, pros and cons and other Reply #9 - Dec 27^th, 2015 at 7:12pm Reliable automotive machine shops are not unaware of these issues and the machining of heads is something that is done commonly, as is the install of new valve guides and valve seats.
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Matt H

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Re: Machining heads, pros and cons and other
Reply #10 - Dec 28^th, 2015 at 5:53pm

Very rarely do it anymore. If the factory service data doesn't give specs, it's a safe bet that they don't want it being done. Many even specify not to do it.

If the head is warped, there's a lot more to take into consideration than how flat the deck is. Most of the time, it's new head or if it overheated, a used engine.

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fisher

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Re: Machining heads, pros and cons and other
Reply #11 - Dec 28^th, 2015 at 9:18pm

I have been working on older engines. What is in my shop right now is a 2008 6.0 Powerstroke Ford.
It's head cannot be machined.
My 1992 Aerostar has a head that cannot be machined but there are aftermarket alternatives for it that can be. I bought one for it.
If you had a machinable head that would benefit from it then do it.

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StitchB

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Re: Machining heads, pros and cons and other
Reply #12 - Dec 29^th, 2015 at 6:39am

StitchB wrote on Dec 25^th, 2015 at 7:50am:

Hey guys, I work in maintenance so don't do a lot of heads but the subject keeps coming up and would like some feed back. I have my own opinions but being I don't do a lot of RR not the best on the subject. My first experience with milled heads was 25 years ago when after doing the heads and surfacing I could barely get the manifold back on in a 400 CU chevy. You can talk about it but seeing is believing as now the valley is narrower than the part. The new stuff has to affect the cam position, and all the rest of it.

Thanks again for all the feed back. As noted in this previous paragraph above, I stated that I have my own opinions, but never committed to it. I am of the opinion to put a new head on it, not saying there are ways around it but most the folks I am around are of this opinion. Doing a head is a lot of work and to do it and find out you have major issues it is @ that point a regret.

Thanks again for all the input.

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