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Since Kev's thread has brought the 492's out of the woodwork...here's some pictures of mine. They haven't been on an engine in 20 years...getting them spruced up to use on my neverending 406 build.

I've been calling the shops around to check on prices for refreshing them. The cheap b****d on one shoulder says just scrub 'em up, hand-lap the valves, put new springs/seals/locks/retainers on and bolt 'em on. The good do-bee on the other shoulder says to drop the new parts off at the shop and have them redone. The jury is still out...

The S-A book says to check the guide clearance by measuring the wobble at the valve face at 1/4" off seat with a dial indicator. I get .015 on the intake...which is at the high side of OK according to the book. Is that reasonable?

Just out of curiosity, what measurement is quoted in valve size? Is it the overall OD of the valve, or the diameter of the largest edge of the valve seat, or...??? Anyone know what the "GM T" stampings mean?

These are the angle-plug variety...makes finding headers that fit a pain, so they're not really worth the trouble unless you're running domed pistons from what I have read. The 3rd picture shows the ridge between the seat machining and the bowl. I was thinking about smoothing that ridge out a bit with my trusty dremel.

Post 'em if ya got 'em...comments welcome.






 

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I run these heads with hooker super comp 1 3/4 and have no trouble with the plugs. I didn't have to use any shorty plugs either. Just need a really short box end wrench. I wish I could find my pictures to compare, they seem to be gone or buried somewhere. All I could find was a shot of my runners during a intake swap.
http://i53.photobucket.com/albums/g55/66chevyIISS/intakeoff.jpg
 

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66chevyIISS said:
. Just need a really short box end wrench.
That is what I use too.....it is the best tool I have found for installing/removing plugs....;) :)
 

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the Flyer said:
freshen those babys up !!! :cool: :cool: :cool:

you'll kick yerself later big time if ya don't :(

:D
I agree with Nightshade.:rolleyes: ..errr I mean Flyer on this.:D..freshen them up now then you can install them and furget about 'em ;) :)

Are you thinking about pocket porting, port matching, back cut valves, undercut valves, etc????

Now is the time to do this stuff if you were thinking about it.:)
 

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The valve size is the OD of the valve. A quick check on OEM heads is if a nickel fits between the intake and the exhaust it's 1.94 if a dime fits it's 2.02.

Those intake valves need to be replaced. The margins on the intake valves are too thin.
You probably need guide work but that wobble test isn't as accurate as measuring the stem to guide clearance. It takes special measuring tools to get that.

The seats don't look too bad but might be sunk a bit. Again without checking it's hard to say. Definitely the casting would benefit from the usual porting techniques.
It's interesting that the guide bosses on the '492 are smaller than on the S/R heads. The valve looks a little less shrouded. I'd be curious what these would do with similar porting.

If the guides are on the high side of clearance it's iffy how long they would last.
If you replace the guides then the valve seat has to be redone to be concentric to the new guide. If the seats are sunk (too many grinds) then new seats need to be installed. It's a slipperly slope. If you have $500 into just refurbishing them, then a set of modern $800 better flowing heads might be a better bargain.
 

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Discussion Starter #7
<sigh>

Thanks for the assessments... I think I'm going to take them over to the machine shop and have them give the heads the once-over and give me an estimate, see what I'm in for. I could see putting $300-ish into these...but beyond that, I don't think they're worth refurbing. I'd probably go with a vortec instead.

I had just stripped the threads out of a sparkplug hole and needed a set of heads, and these happened to be for sale. I know the guy who sold them to me (25 years ago) said they had 'just been redone', but I don't know (remember?) any more details about them than that. Famous last words, right? I don't remember exactly how long I had the heads on the car, but it wasn't for more than a couple of years, and I put maybe 4K miles on them.

The reason I asked about the valve size is that I measured the OD of the intake at 2.08 (!) with my dial calipers, which isn't one of the usual choices. Given the GM stamps...I figured I was just measuring the wrong thing. So I just went back and checked again...and got 2.08 again. Exhaust measures 1.61. Just as a sanity check, I used my micrometer, and got 2.08 also...and checked both tools with my 2" standard...and that checked out too!

Could someone really have put 2.08 valves in these? I thought 2.02 was the top of the line back then. Could that explain the thin margins?

I was hoping I could use these for a few years until I saved up for some aftermarket heads, but...maybe I gotta bite the bullet sooner.
 

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patman said:
<sigh>

Thanks for the assessments... I think I'm going to take them over to the machine shop and have them give the heads the once-over and give me an estimate, see what I'm in for. I could see putting $300-ish into these...but beyond that, I don't think they're worth refurbing. I'd probably go with a vortec instead.

I had just stripped the threads out of a sparkplug hole and needed a set of heads, and these happened to be for sale. I know the guy who sold them to me (25 years ago) said they had 'just been redone', but I don't know (remember?) any more details about them than that. Famous last words, right? I don't remember exactly how long I had the heads on the car, but it wasn't for more than a couple of years, and I put maybe 4K miles on them.

The reason I asked about the valve size is that I measured the OD of the intake at 2.08 (!) with my dial calipers, which isn't one of the usual choices. Given the GM stamps...I figured I was just measuring the wrong thing. So I just went back and checked again...and got 2.08 again. Exhaust measures 1.61. Just as a sanity check, I used my micrometer, and got 2.08 also...and checked both tools with my 2" standard...and that checked out too!

Could someone really have put 2.08 valves in these? I thought 2.02 was the top of the line back then. Could that explain the thin margins?

I was hoping I could use these for a few years until I saved up for some aftermarket heads, but...maybe I gotta bite the bullet sooner.
They do make larger valves aftermarket but those certainly look like stock valves. My guess is they've expanded from years of pounding the seats.
It's like hitting a penny with a hammer. It will flatten and expand. The razor thin margin is because it's been ground too many times. The stems may be worn also which hopefully might contibute to the looseness.

You might be able to get away with just having new valves fitted.

Make sure whomever you take it to is a cylinder head specialist.
You don't want a hamfisted grinding and knurling shop. IMO, 8 out of ten shops don't do good work. Get 3 estimates and opinions. If you get a bad vibe then walk away. Trust your instincts. If the shop is clean that's a good sign and if they have a Serdi machine that's a plus.
 

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Freshen those heads!!!!

If those were mine I would spend the money and refurbish them with hardened seats, valve guides and stainless steel valves. I know they are a little more pricey but definitely worth it, IMO.
As for the machine work, do the 3 to 5 angle valve job on the seats and put a back-cut on the valves themselves. I read that trick in a CHP awhile ago.

Just my 2 cents

Dan
 

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ovrdrive said:
.....and put a back-cut on the valves themselves. I read that trick in a CHP awhile ago.
Dan
Really?
Good thing someone's paying attention around here. :rolleyes:
 

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Paul Wright said:
They do make larger valves aftermarket but those certainly look like stock valves. My guess is they've expanded from years of pounding the seats.
It's like hitting a penny with a hammer. It will flatten and expand.
Hmm...good point, I hadn't thought of it that way. That would explain a lot. I know there are 2.08 valves...just not SBC ones from GM that are 20-something years old.

Paul Wright said:
The razor thin margin is because it's been ground too many times. The stems may be worn also which hopefully might contibute to the looseness.
The exhaust valve seems to be much tighter in the guide, and the margin is much bigger than the intake. Maybe just the intakes need doing?

Paul Wright said:
You might be able to get away with just having new valves fitted.
That would take up some of the guide slop, I measured a few spots and got from .339 to .341 on the intake stem, that's .002 wear right there. What's involved in installing new valves? I took a peek at the catalogs, and for $75 or so it looks like I can buy a decent set of new intake valves. Since the guide and seat aren't changing...and the valve would have a brand new grind on it...wouldn't it just be a matter of hand lapping things and checking the seal area with dykem? (I know, wishful thinking...)

Paul Wright said:
Make sure whomever you take it to is a cylinder head specialist.
You don't want a hamfisted grinding and knurling shop. IMO, 8 out of ten shops don't do good work. Get 3 estimates and opinions. If you get a bad vibe then walk away. Trust your instincts. If the shop is clean that's a good sign and if they have a Serdi machine that's a plus.
I have been making some calls, I have two shops on the list, I'm going to stop by with the heads and see if they'll give me an estimate. Would it be bad form to show up at their door with the heads, new springs/seals/locks/retainers, and new intake valves?
 

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Some shops might be OK with you bringing in your own supplies and others might not.
You shouldn't buy any parts until you check them over first. The seats may be sunk (ground too many times). Replacing them requires machining out the old cast in seats and installing new ones. Just bring the heads and get the two estimates.

I must be a a total sucker but if you want to send me the heads I can check them over and fit them with new Stainless valves...provided the seats & guides aren't too bad.. Just pay for parts and shipping both ways.
 

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I still don't know how some people on this board have called you "rude."

You're like the Santa Claus of hot rod parts!!! No one ever calls Santa rude!

Kev
 

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492 heads?

Hey Now Patman, Paul's offer is a Gift, and Never Look a Gift Horse in the Mouth.!!!! Now the pictures that I see indicate only one valve job has been done, the guides have been knurled; that's OK. Appears as if Old Style Three Angle valve job was done on both valves and Seats. Intake side combustion chamber, unshrouded with larger seat stone. Still No problem. Valves appear to be Truck Sodium filled. Most likely 2.02 intakes [Tuliped] spring pressures & thin top edge. Exhaust look good. A mild port job [Blend in the seats and just under on seat toward runners. Then port match intakes. Paul Knows how to do what you need.!!! Respectfully, "Bill's" II
 

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Bill's II said:
Hey Now Patman, Paul's offer is a Gift, and Never Look a Gift Horse in the Mouth.!!!!
Ditto...I would jump on that offer in a heart beat before Paul's medication wears off.:rolleyes: ...BUT seriously..Kudos to Paul for his generosity:)


hmmmmmm.....Now I wonder if I could get him to look at my old heads:rolleyes: ...that would let us see which head is better the 492 head or the 041 head...:rolleyes:....lol.:D ...JUST TOTALLY KIDDING Paul;)
 
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