Hey Guys,

Recently I had pulled my '73 L-48 heads off (casting 3998993) to get them redone. During their visit to the shop the machinist found a crack coming out of the seat of one of the exhaust valves. It had already left the seat area and was beginning to spread. He said he might be able to repair it, but recommended against it. The story is staged...

Machine shop suggested a "functional replacement head" would be the 333882's which were used on Corvette's 74-77 (Lo-Po and Hi-Po models) and according to one of those "interchange manuals" a lot of other Chevy V-8s.

Before deciding I did a side-by-side on the two heads. Valve sizes are identical, combustion chamber size is identical. Technically these should be good replacements. Looking more closely at the intake runners and exhaust ports there IS A DIFFERENCE. The intake runner openings are restricted in size as compared to the '993's. Also, there is a noticeable step in the exhaust valve port of the '882's where the corvette heads are essentially "smooth".

It is my opinion that the original '993 heads would probably flow much better. Will the difference be noticeable? I'll let you know. Right now I'm trying not to let these details kill my buzz about getting some new heads on my car.

Now on the flip side if these heads were used on Corvettes (Lo-Po and Hi-Po models) which have at least as much if not more HP than my '73 L-48, then it stands to reason that the "flow factor" may not be as much a factor as say valvetrain (valve lift, etc.). Perhaps the flow characteristics would only be noticeable if I was trying to pass Dale, Jr. at Daytona (not likely, haha).

For reference I did look on the internet for heads and found a number of places that sell remanufactured heads ready to go. "Cylinder Heads To Go" accepted used cores and their heads have valves, springs, etc. are ready to bolt on (no endorsement implied here). The best price I got on '993's was $130/ea. That might have been with core, but less shipping cost. In hindsight I probably should have gone with these, but I always prefer to see what I'm getting rather than get it in the mail.

So anyway, I've got the heads back and painting is in process. I'll give more feedback on these heads as they land on my block and my foot on the gas pedal (haha!)

Rod Hisle
Louisville, KY
:chevy

 

882's are pretty popular on chevy SB's. I like some of the 80's chevy heads off of 350 trocks & vans. Some have decent valve sizes and small chambers.

 

I replaced the non-stock 624 heads on my '73 L-48 with a set of casting#14102191 87-up centerbolt GM truck castings. They have 1.94/1.50 valves and 64cc chambers. With Fel-Pro .015 steel shim gaskets my compression ratio now works out to 9.46:1. These are sometimes called "swirl port" heads because they have a ramp cast into the intake ports to promote better combustion. This ramp can also limit higher rpm flow as I understand, in exchange for better low end response. I am really happy with them and glad to have bumped up my compression. Plus, they are fairly common castings, and I got a pair rebuilt from my machine shop for $200 with valve covers. I don't care much about the higher rpm restriction because I run a really mild cam (204/214). They are definately worth a look for a guy like me on a tight budget.



[Modified by ORVette, 8:08 PM 4/2/2002]

 

882's are popular because they have a lot of iron for porting and runner massaging. I used a set for several years with a crane 272 and a Performer and had great performance with them.

 

Check this out about the 882 heads.
http://www.angelfire.com/wv/fuzzychevy/gm882.html

I have the 993 heads and like them. See what you think about the link.

[Modified by Paul 75 L82, 7:39 AM 4/3/2002]


[Modified by Paul 75 L82, 7:40 AM 4/3/2002]

 

It's not uncommon for induction hardned heads to show cracks radiating from the exhaust seat. It's also commonly repaired. If you want to keep your original heads, look to having them repaired. I don't know why the shop recommened against it. If you're not concerned about originality, then replacement is fine and unless you're trying to add power over 5,000 rpm, the 882 head will do just fine. Just don't turn in your original heads for cores. They have value that will follow the car should the day ever come where you part with it (I plan on being burried in my '72).

 

Haha!

I agree. I DID keep my originals. Like I said, it was a hairline crack, but was leaving the valve seat at least a 0.5". What kind of repair would you recommend? The machinist said somthing about drilling, etc. around the crack, I forget. Is this typically welded? Curious...

Rod Hisle :flag

 

Hey Paul,

Good link. Are they talking about 0.400" valve lift when they talk about the heads flowing good up to "0.400""? Guessing. Anyway, that makes me feel better about not worrying about performance differences. My corvette doesn't see 4000 rpm that often!

Rod Hisle :flag