57 heads 3731539

[Mike T.]

I'm trying to build a correct engine for my 57 #2623. I bought a pair of 3731539 heads with the right dates. I've read Nolan's bible, John Amgwert's spec guide and Colvin's book, and I'm still confused.
Is the 3731539 head for the 220 HP and other lower HP engines, and is the 3740997 head for the fuelie?
Also, two of the head bolt hole bosses that are below the spark plug holes have damage. One has a small chunk broken off, and the other is cracked. It looks like they were over-tightened. Can a machine shop or good welder repair that kind of damage? Thanks.

[Jack H.]

Re: 57 heads 3731539

Kinda sorta backwards...

3740997: 220,245,250, and 270 HP
3731539: 283 HP

The '539 head is reasonably common as many were sold over the counter. The '997 head is a SOB part to dig up.

[Mike T.]

Re: 57 heads 3731539

10/4. Thanks.
Mine had a column mounted tach, and has the right emblem mounted in the tach hole in the dash. No other evidence of being a fuel car, so maybe I should just keep looking for the 3740997.

[Joseph T.]

Re: 57 heads 3731539

10/4. Thanks.
Mine had a column mounted tach, and has the right emblem mounted in the tach hole in the dash. No other evidence of being a fuel car, so maybe I should just keep looking for the 3740997.

#2682 is pretty early for a column mounted tach although possible. Does your dash show three holes around the tach hole opening where the emblem extensions would have been located?

Does your car have a flat or round throttle rod coming off the firewall?

Joe

[Tom P.]

Re: 57 heads 3731539

To some degree, the 539 head is moderately common. The reason is because it was also the same exact head used on passenger cars with the 4bl carb "Power pack" 283 engine.
The key here is to make sure that any 539 head you locate has a SINGLE number cast in the cast date code for the year (6 if it was cast in 1956 and 7 if cast in 1957). The reason is that Corvettes ONLY got engines from Flint whose date codes ended with a single number for the year. The Tonawanda engines had cast date codes ending with TWO numbers for the year.
Flint engines were used for BOTH Vettes and pass cars, but Tonawanda engines only went into pass cars.
Soooooooooo, if you find a pair of 539 heads on a 57 pass car 283, check to see if the cast date has one or two numbers for the year.

[John H.]

Re: 57 heads 3731539

Soooooooooo, if you find a pair of 539 heads on a 57 pass car 283, check to see if the cast date has one or two numbers for the year.

And, although the casting date is hidden and isn't judged, Tonawanda heads have an externally-visible discriminator - the surface of the casting symbol on the end of the head is rough "as-cast" on Tonawanda heads, and those surfaces are machined smooth (broached perpendicular to the deck surface) on Flint heads.

[Tom P.]

Re: 57 heads 3731539

And, although the casting date is hidden and isn't judged, Tonawanda heads have an externally-visible discriminator - the surface of the casting symbol on the end of the head is rough "as-cast" on Tonawanda heads, and those surfaces are machined smooth (broached perpendicular to the deck surface) on Flint heads.

And I have always understood this to be the case, BUUUUUUUUUUUUUT, since I have not seen every 57 head that was produced, I didn't feel totally comfortable adding this comment.

Also, as I understand, the same holds true for the later double hump symbols on the hi-perf heads.

Now, here is one for you John.
On some double hump symbols that I've seen, ocassionally there is a "notch" cut out of one of the humps (shown below). Why?

[John H.]

Re: 57 heads 3731539

Now, here is one for you John.
On some double hump symbols that I've seen, ocassionally there is a "notch" cut out of one of the humps (shown below). Why?

Tom -

I dunno - haven't seen one of those before - I've only dealt with Flint heads.

[Gary C.]

Re: 57 heads 3731539

John, a Judge can request the valve cover to be removed to confirm it's a Flint head if they suspect it might be a Tonawanda head. Gary....

[Joseph T.]

Re: 57 heads 3731539

And I have always understood this to be the case, BUUUUUUUUUUUUUT, since I have not seen every 57 head that was produced, I didn't feel totally comfortable adding this comment.

Also, as I understand, the same holds true for the later double hump symbols on the hi-perf heads.

Now, here is one for you John.
On some double hump symbols that I've seen, ocassionally there is a "notch" cut out of one of the humps (shown below). Why?

Someone recently talked about the notch you mention. Would it have been done to clear something on some engine application?

Joe

[Mike T.]

Re: 57 heads 3731539

Thanks Jack, Joe, Tom, John and Gary. I'm going to build a 220 HP. With your info, I know I have to find 997 heads. The question of repairing the 539 head becomes moot.
Thanks again for helping.

[Mike G.]

Re: 57 heads 3731539

539 heads are also a lot cheaper than the 997 heads because they are not that hard to find. the real late 539 heads also had an " x " cast on the exhaust side of the heads. the x is about 3/8" tall. alot of people will tell you that all the true corvette 539 fi heads had the x casting. this is not the case. all the late 57 539 heads had the x.