This is related to the AA/HAM head GB but I didn't want to hijack. But that offer means I need to make some decisions sooner than anticipated on my resto.
The main question is whether to rework these heads or buy new? My very strong preference is to rework what I have, assuming the castings are good. They have not been cleaned so I was thinking about walnut blasting them myself so I can inspect for cracks before deciding whether to move forward on reworking. Is there any reason I should not blast them myself? Any spots that should be masked or blocked before blasting?
Basically, I just want to get to a decision point on whether to rework or buy new. After reading so much about how hard it is getting to find good original castings has me a bit spooked, and if I hit a dead end on reworking, I'd like to do it while the HAM GB is still an option. I also don't know what a basic head rebuild will cost. Anyone have a ballpark estimate? I used to be able to send them out to Cali for a couple hundred bucks, but those days are gone.
Here's a short version of the history my engine. It's GA 2.0L engine that I rebuilt the bottom end on in the late 80s, but the project stalled before I got to the heads. My best guess is that the engine had about 110K-120K miles on it when it was split. That's a guess because the odometer quit at about 92K shortly after I bought the car. The engine ran strong when the FI cooperated when it was pulled, so no reason to suspect any major issues. Other than a busted exhaust stud, the heads look good with no broken fins and very little carbon in the combustion chamber. So, overall, I feel these heads are a good candidate for rebuilding but would appreciate any advice or opinions.
Even if someone could weigh in on DIY walnut blasting the heads. Would like to clean them up enough to inspect for obvious cracks before shipping them off to a builder. I might work on them this evening unless someone talks me off the ledge. It seems safe enough but...
A few years ago this option was nonexistant.
Only option was the AMC bus head reworked into the 2.0 combustion chamber and plug angle, mucho buckos.
So the option of redoing a cracked 2.0 head might have been cost effective.
Time to repair is the factor. Rebuilt heads from a quality shop will have all of the parts replaced as will happen with the "new" AA casting.
So if the repairs are more expensive than a new AA head, the balance tips to the new.
Some heads are in good shape and only need a valve job, but the stress and strain of 40+ years will take its toll.
Hey a whole bunch of 914er's are jumping into the 123 dizzy, and rightly so.
Performance per dollar...
No reason not to walnut blast them. Go ahead and see what you've got.
I was using mostly rebuild old heads for most of my engines until the AAPistons heads came out. So reworking your old heads is still just as viable as it always was. Nothing has changed in that respect.
The HAM GB is a great opportunity, and new castings are an improvement over old. BUT, if this is a budget/money situation, reworking your old heads will be cheaper and will work well, unless they are cracked.
So for my opinion, blast them, check for cracks and that will make your decision for you.
Thanks guys! I very much appreciate this. When I read that some of our best rebuilders were no longer working on used heads, it got me rattled. These heads only ran for 13 years before they got mothballed. Budget is definitely important, but mostly, I hate to replace expensive parts unnecessarily. I'll clean them up and give them my amateur inspection before sending them to a pro.
Another question, I have a set of NOS genuine Porsche valve guides I bought back when the engine was torn down. Any reason not to have those installed with the rebuild?
Simple way to check for cracks is a propane torch.
Just heat up the suspect places, crack will open and spew oil and smoke.
No reason not to use NOS, except if you expect to go bigger.
Guides can be used if they fit the specs of what's needed. Some old head rebuilds need oversize guides.
But there's nothing wrong with the NOS guides/springs.
The lifters and cam make me nervous. There was a period of time where cams were causing some problems. Not to mention the hardness of the cam and the lifters must be matched so one doesn't eat the other. If I were building that motor I would be getting a new WebCam and lifters, instead of risking that combo. It's not a guaranteed failure, so if you're stuck with what you've got then keep moving forward.
Are there any numbers stamped on the cam? Usually they're stamped where the cam gear bolts on.
If you're that on the fence, I'd recommend:
Stock fuel injection
Stock heads (back to the crack question)
Pretty easy build, great torque, reliable fuel injection.
Carbs take some 'babysitting' to keep running right and have no cold-start aid.
Ah, that makes total sense.
Get those heads blasted.
Didn't get the heads blasted last night but will work on them tonight.
I was reading through the Web Cam catalog last night and saw that OEM lifters are to be used even with their reground cams, but Web Cam lifters must be used with their new cams. So I'm feeling pretty good about the cam/lifter combo I have... if the Automotion regrinds were good. Thanks again for your help.
Finally got my heads walnut blasted. They still need a good soak and boil, or whatever they do to make these things look new again, but I think they look good. A total of 3 engine tin screws that need to be extracted, a broken exhaust stud on one head, and one bent fin on the other. But I'm not seeing any cracks and I didn't find any smoke genies when heating with a torch. I think they look pretty good. Wondering if you experts can see anything I'm missing.
- Should that bent fin be straightened? My guess is no, but curious.
- New seats? I was planning to have them replaced, but was reading in Tom Wilson's book where he says that factory installed seats rarely drop. I'm guessing as long as the builder knows what they are doing; heats the heads and chills the seats before pressing, it would be the same. But wonder what the experts think. Again, best estimate is these heads have between 100K and 130K miles on them. Probably at the lower end of that estimate.
- What is the best way to remove head and exhaust gaskets without damaging the sealing surfaces? All of them are stuck on pretty tight and I was worried about messing something up gettig them off.
Dental type picks are a good way to get the gaskets out. The exhaust ones can be pretty challenging and a pick may not be able to apply enough force to grab it.
Don't straighten fins. They may break off instead. And it's not going to affect the cooling.
Full rebuild would be new seats, new guides, new springs, new valves, new retainers, new keepers, and flycut the sealing surface to ensure it's flat. If the sealing surface is flycut, then a matching amount of material need to be removed from the face of the heads so they don't hit the cylinder fins.
I see something that looks like a crack in the spark plug hole (which is a super common crack site). Use some machinists die and that will tell you quick if there is a crack there or not. Post 14, Second picture, left hand cylinder, 3 o'clock on the spark plug hole. Could be a casting flaw, but it looks like a crack.
You should replace them all. The sodium valve can snap off (probably what happened to nditz1's engine). Dropping a valve or a seat makes a big mess and is one of the more catastrophic failures.
Mark is correct my valve snapped in half.
I've never had to use dye to see cracks on a T4 head, they're always quite obvious. Also check the exhaust guide boss area inside the port.
Did a little more blasting around those exhaust guide bosses and inspected for cracks. None found. Also got those little bastard exhaust gaskets out. Like you said, couldn't get enough force with the pick, but was able to carefully catch an edge with a small screw driver inserted from the combustion chamber side and pop them out with a light tap of a hammer.
Last question.... for now. What are the best valves to buy for a stock 2.0L? I'd like to get them before sending the heads in so I have better control over what parts get installed. As I mentioned, the last two pairs of heads I had rebuilt did not end well. I want this one done right.
Manly Stainless are commonly used.
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