Will oversize valves work?
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Will oversize valves work?
I have the stock 1976 L48 heads on the car. I was considering upping the valve sizes to 2.02 and 1.60. Will this give me any benefit if I don't have the heads ported?
Also, how much work does this entail to replace the valves, guides, and seals?
Thanks. :confused:
Also, how much work does this entail to replace the valves, guides, and seals?
Thanks. :confused:
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Will oversize valves work? (dgruenke)
2.02/1.6 with very mild pocket porting will flow allot more than what you have now. Bigger valves require bigger seats and you also need to take metal out of the throat area above the seat. It might cost $250-300 for a total refresh
The real question is: "Is it worth it?" There are so many aftermarket ready to bolt on heads for so cheap why beat on a dead horse. Other than bigger valves what you really need is more compression. So buy heads with less than 70 cc chambers.
The real question is: "Is it worth it?" There are so many aftermarket ready to bolt on heads for so cheap why beat on a dead horse. Other than bigger valves what you really need is more compression. So buy heads with less than 70 cc chambers.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Re: Will oversize valves work? (dgruenke)
Just replacing the valves will get you nothing to even a deficit. It takes a blended entry to the valve to realize a flow improvement when upping the valve size. So you're talking machining the valve seat for the larger valve and blending the port bowl for those larger valves. But, unless you've modified the engine to the point where you've exceeded the air flow of the current heads, you won't see a performance increase or at least not a large enough one to justify the cost involved in this modification. The 1.94/1.5 valve heads flow well enough to just leave them alone.
As to the work, you'd want to do the guides and seals and you'll also need to have a new exhaust seat installed since the machining will exceed the factory induction hardening. A whole lotta money for zilch gain.
As to the work, you'd want to do the guides and seals and you'll also need to have a new exhaust seat installed since the machining will exceed the factory induction hardening. A whole lotta money for zilch gain.
Le Mans Master
Joined: Jul 1999
Posts: 9,206
Likes: 17
From: Sewell NJ
Re: Will oversize valves work? (gkull)
I agree with Gkull. If you're talking about reworking the stock heads that much you could go with a set of SR Torquers with the 2.02 x 1.60 stainless valves installed. They come with a set of springs that are good for .550 inch lift and flow as good or better as any OEM head. You can get them in 67 or 76 cc chambers and just bolt them on.l I've been running a set for about 4 years now and have had no problems with them. The stock heads at their best were prone to cracking and not very good at oil control. In another thread someone posted that they could get a set of Torquers for $600 or so. I don't think you could refurbish your stock heads with the upgrades you're talking about for much less. Good luck.
Thread Starter
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
Re: Will oversize valves work? (vettfixr)
Thanks for all of the info. It is very helpful. The reason I was interested in doing it was because I believe that one of the valves is bent. A couple of months ago, unbeknownst to me, a tiny screw from the carb dropped in there and now it is knocking. I think that it bent one of the valves. I am just now getting ready to take it apart and, so long as there is no other damage, replace the bent valves. I just figured that while I had them off, maybe I'd just replace them all, but it sounds like too much work for nothing. I guess maybe I will just replace the bent valves until I am ready for a new set of heads.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
Re: Will oversize valves work? (vettfixr)
Agree w/ the others. Any where from - to about +12. The SR (Street) heads vettfixr mentioned are good for +20 over the 882 & +12 to 15 w/ larger valves done right.
:cool:
:cool:
Race Director
Joined: Apr 1999
Posts: 15,135
Likes: 477
From: NM
Re: Will oversize valves work? (Ganey)
The L48 and the L82 use the same head casting number. The L82 has the big valves. So when they machine the heads for the L82 big valves do they do other work on the heads? Seems to me if they were doing port work they would use a different casting with the ports already done, would be cheaper then doing machine work. Any insight??
tom...
tom...
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