Question Regarding Machine Shops Etc.

Hey all,

We have a decent machine shop in town, however I have never used one before. I am currently rebuilding the top end of my dauntless. I am installing a cam kit that comes with new valve springs. I am thinking I want the heads gone through and have hardened valve seat/new valves and seals etc. Can I just take the heads and the new springs in and ask them to do the rest? I am assuming they can source the valves and seals etc.?

Again this may seem like a dumb question but this is the first time I've done this on my own.

Thanks!

 

With heads, you pretty much have to trust the shop to recommend what's needed. You can take the springs to them and they will assemble with your springs, after the work is done.

Don't be shocked at what they quote though. The "Basic valve job" usually only includes disassembly, cleaning, the physical grinding of the seats ("three angle" or "four angle" grind), magnaflux (crack check), and reassembly. In addition, they will likely recommend surfacing the heads, recondition guides, and maybe some new valves. The seals are usually included (factory style seals are cheap), unless you want the teflon "Perfect Circle" seals, which require some additional machining. It is not uncommon to need some or all new exhaust valves. To recondition guides, they can knurl (raise the existing material and ream), or machine for replacement guides. Knurling is ok, especially for a hobby car that won't see a lot of miles. The shop likely has a favorite replacement guide and installation method - there are a few types and they are all more or less equivalent.

Regarding valve replacement, there is a spec for how thin the edge of the valve can be and still be usable. The exhaust valves see a lot more heat and erosion than the intakes, and the thinner the edge of the valve, the hotter it will get from combustion. So typically it's exhaust valves that need replacing. Grinding makes the edge thinner.

I would not go for hardened seats, but others here may have a different opinion. I think you would benefit from new exhaust valves more ... not an expert though. The shop will do whatever you tell them to do, but they will also offer advice. They are in the business of selling the work, so they have a conflict. And there is an element of CYA in this too.

 

Tim has a point regarding the shop having a conflict, and hopefully they won't recommend more than is needed. You really won't know what is needed until everything is disassembled and inspected.
Valve seats may or may not need to be replaced. If the seats are heavily pitted, usually exhaust side, then install new hardened seats. Grinding the original seat too much just pockets the valve, killing performance.
The guides need to be evaluated as well as the valve stems. My preferred method for refreshing guides is reaming the iron guide and installing a bronze sleeve, broaching to expand, then reaming it to size. These last nearly forever. Count on replacing valves, usually due to stem wear. Maybe you'll be lucky.
The heads may need to be skimmed if they are not flat, but the 225 heads usually don't need this unless they have been run hot.
Installing your new springs is just part of re-assembly.
Another part to look at, and maybe take in for evaluation, are the rocker assemblies. Carefully look at the pushrod end of the rockers to make sure the pushrod hasn't deformed the socket. Carefully look at the pushrod ends (keep them in order as they come out!) to see if any have abnormal wear. These are a problem area on the 225. Also look at the hardened tip that pushes on the valve stem. They should be arched with no stem impression.
Project creep can rear its ugly head!
-Donny

 

Comment on surfacing - when I was working parts counter, customers would drop off heads and we would send them out. The shop had a fixed price for the basic job, something like $39 per V8 head (this was a while ago). This shop would always recommend surface, apparently regardless of the condition of the head. You can determine if surfacing is needed using a straight edge and feeler gauges. There is a spec in the TSM. Iron V6 heads are short and rigid, and unlikely to need surfacing.