Quote:
Originally Posted by Seriousracer
Lapping is easy
What about setting the margins ?
What about guide replacement ?
What about topping or throating the seats to set the proper contact ?
What about checking installed height on the valve ?
Spring seat pressure?
Spring installed height ??
What if the valve has started to recess in the seat ?
And holding gas is not the same as being properly vacuumed check for seal.
Need more??
Been doing this a while
Spend the money have the head done right.
Edit by the way the seats and valves are so much harder now a day’s than when lapping first came out it takes a lot longer to “lap”.
At least by a quick way or neway cutter and save yourself a ton of time and headache
https://www.cylinderheadsupply.com/nestdicubo.html
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I would replace all the valves and springs with new ones, if the motor is that beat. No need to check for valve margin, if they are quality new valves. No need to check spring pressure if new quality springs. Valve height ain't hard to check, either.
Installed height ain't hard to check either....but
If the valve seat has recessed (or pitted or burned), I would think about a new head. If the seats need need topping or throating, then take it and spend the $250-$300 or more per head at an affordable shop.
valve guides may come out with a solid set of taps with a hammer, or may need to be pro-pressed out in a shop. The last time I asked my machine-shop guy to replace my guides, he told me not to bother, the play I though was "too much" was fine, and that he has replaced guides with new ones that had more play than mine. The time before that he told me the guides were so shot and locked into place, that they needed to be drilled out.
The old-schooler who was my boss taught me about using gasoline. If water can get by, you can blow through it with your mouth! If gas can not, it will be about as air-tight as you are going to get it! Show me the machine shop setup with a vacuum gauge setup for heads, and I'll show you a $800-$1000 head job! Are we competing in an Indy 500 race, or rebuilding a skoolie to get another 200K miles?
The first time I took a head to a machine shop was at a NAPA. A 1977 Honda Accord 1.8L CVCC engine. They re-assembled assembled it wrong! I knew next to nothing then (30 years ago) but I could see the mistakes, and took it back. They still did a poor job. I do all my own work on my own vehicles now, because most "shops" are just kids outta school.
Just because a "pro" does the work, does not mean it will be right! If you know a quality machinist with an excellent reputation who will help you at a reasonable price, then great! My experience has been NO ONE touches the mechanics of my truck except me, or the results are poor.
Last time I got a head from a "cylinder head supply shop" it was a damaged core that they had tried to push along (mass re-production) and I had to exchange it.
Last time I took a vehicle to a shop was my 1993 Mercury Villager that I traded for $300 to get the bus (can't drive 2 at once!). I put struts on it myself, and found minor end-play in the front (drive) wheel, rocking it from top-to-bottom. My van was in Atlanta, my tools in Hawai'i. I took ti to Sears and they said they would not replace the pressed in bearing because the bearing was not yet making noise! Fools! I took it to Tires Plus and they again told me the bearing was fine. Fools! I told them to rock it top-to-bottom, I was taking the van cross-country, and did not want to replace it on the road. They did it for a reasonable price (less than I charge
).
How about the one time I took my vehicle for an oil change? They guy was trying to remove the filter for several minutes. I made an excuse to get into the pit with him, and saw he was tightening it. I said "let me try" and had it off in 10 seconds.
Or the time I was on the road and bad gas at a hole-in-the-wall station had my truck barely running. It was 40°F, raining, and my tools were buried under stuff, so I asked a shop to replace the filter on the side of the frame rail next to the tank - super simple, $20. They installed it backwards.
And I could go on with stories about "professionals" in the field.
The machinist I worked with in Hilo was great, though. Saved me headaches, since I was a mobile mechanic with no benchtop. Saved me time, all cost passed on to the client, while I focused on keeping happy the backlog of other clients. But I really doubt that for $250 for a duel-overhead cam head with 3 valves per cylinder that he spent the time perfecting the valve-seating or checking the spring pressure, when he was already re-surfacing the head, etc. And one setup he got back to me still had pitting in the valve edge. Seated fine, though the pits would affect air-flow and therefore air-fuel mixture into the cylinder, and therefore a (unnoticeable) loss in performance. But the car was not meant to be "racing".
When I started this whole game (repairing vehicles), yea, I agreed with you, seriousracer, but now I have learned better!
I trust myself more than a shop (most shops, anyway), even when I have to feel my way along in the dark and know nothing! But that's me and my experiences.
But if you want to sub-out your work to a "pro" machine shop, you're choice.