BlueTwoToneCorvette

I am rebuilding my 1985 C4 L98 143k miles. No prior valve work done on it and it ran great before disassembly. I need some advice on Valve seat / Valve work.

The intake valves appear to be in good shape. Very minor imperfections on the valve contact area that are only apparent under a magnifying glass, no visible wear. They have a ~30 deg backcut that I am guessing is stock.

The intake and exhaust seats have very slight pitting only visible under a magnifying glass. The condition seems good for the mileage. Stock angles should be 46deg/45deg seat/valve.

The exhaust valves show a little more wear. Minor pitting of the contact area. Some show barely visible wear of the contact area. Given the extra heat load on the exhaust, they also seem to be in pretty good shape for the mileage. I think it would be best if they could be recut as they show the most wear.


I'm not sure what my options are.

I read that valve lapping is a bad idea, but that would be the easiest for a minor refresh.

How much would it cost to have a machine shop clean up the valves and seats? I'm talking about a basic valve and seat cleanup to remove the imperfections back to stock specs, and add a 30deg backcut on the exhaust valves.

I don't want to put much money into head work as these are the original iron heads. They weren't leaking oil down the stems, but I'm sure they have some guide wear after 143k.

I live in the Jacksonville Florida area and don't know of any shops that have a reputation for reasonable, quality SBC work.

PatternDayTrader

I would be hesitant to reuse 100k plus valves no matter what the condition. They don't last forever.

cv67

Lapping isnt bad for them done every day

Would I invest in new seats valves etc in a stock head, no.

Prices vary on valve jobs depends on where you go.
Some little over 100 some as much as 2-300

Where do you stop though, guides springs seals surface etc etc it can add up quick

If it were me and just an occasional cruiser lap them in put a set of springs seals surface and motor on.

84Z51J

New valves would be cheap insurance, while you have it all torn down, unless you don't mind doing it again when (not if) a valve burns. At the very least I would do all new on the exhaust side. Any pitting in the seats demands a recut to me. If the heads are flat, with fresh seats and new guides/seals/springs, you would almost certainly be good to go for another 143k; just depends where you wanna spend for extra insurance & where you're willing to gamble.

I didn't want to invest in the smoggers for no performance gain, so ended up going to aftermarket aluminum castings. While I was still shopping around, the local shop quoted me $300 to fully refurb both iron heads, before hardware--not worth it in my book! They could get new valves for $5/ea, but probably cheap welded pieces, which I'd avoid like the plague. Revving the engine would feel a little too like spinning the barrel in a game of Russian Roulette...

Joe C

FWIW, on my iron head 85, no (professional) shop work. I checked for flatness, checked and inspected valve guides, and valve seats. as for flatness, I could not detect anything over .002" (standard 5-way check). I cleaned the heads and did some minor port clean-up. spent several hours, carefully inspecting for cracks, especially valve seats - nothing. on the valve guides, I had two guides out of spec - spec at .0028 max - I had one at .0033, an one at .0037. I did not have any issues before I tore the engine down, and performance seemed quite good for a 150K mile small block, so just threw in a new set of (fel-pro) valve stem seals. I did have one valve seat that seemed questionable, but it didn't appear to be too bad. the seat face on my exhaust valves were questionable, and I had one intake that need to be replaced. I opted to throw in a new set of elgin I/E valves w/ new springs. all the valves lapped in perfectly. long story short, after 1000+ miles, everything seems fine, performance as good, if not better than before. no oil issues, no cooling issues, nothing! best part, I didn't have to run these thing through a machine shop - i'm thinking it's around $200 for hot tank, magnaflux, and pressure test. because of the valve guides, the shop would want to replace all 16 valve guides, cut new seats, and replace valves and springs. I most likely would be looking at hundreds of dollars for a valve job. I didn't want to spend a bunch of money on heads at this point in time on an engine with 150K on the clock. I've done valve jobs like that in the past - back in my early years when I had no money for fancy shop work. back then, I was lucky I could put gas in my cars!

BTW, if anyone is interested, these are the valves/springs I used. I know they're cheap, but I took a chance. to be honest, I thought the quality was very good. comparing the valves to GM NOS valves I have, I thought they looked damn good, in fact, maybe better. elgin is a tier supplier for GM, so there's a chance these are the same as current OE and service replacement parts.

http://www.ebay.com/itm/New-Z28-Springs-1-94-Intake-1-5-Exhaust-Valve-Set-Chevy-400-350-327-283-/221595439283?hash=item33981e10b3

BlueTwoToneCorvette

Yes I think it's good advice to not put much money into this. I already have the other rebuild parts

I'm leaning towards getting the exhaust valves recut, and seeing if they will add a 30 deg backcut for the same price.

Then I can get some fine lapping compound to clean up the seats.

mtwoolford

just been through this with a set of 1986 iron heads.

new springs, retainers, locks and seals, bought as a kit from summit #SUM-174001, $67.97 ($156.88 if purchased separately)

stainless steel intake valves, set of eight, SUM-V8000-8, $65.97; and,

stainless steel exhaust valves, set of eight, SUM-V8010-8 $65.97.

At these prices it's hard to justify reusing / reconditioning the old stuff.

mtwoolford

that's quite a deal

BlueTwoToneCorvette

Unfortunately, there are few options for valves for stock 85 heads that don't require some machine work. Summit has 1 exhaust valve that's direct fit and they aren't as inexpensive as those above. I am going to take them in to a machine shop along with the heads and let them look at what I've got.