770 heads versus 550 heads

[Philip M.]

I have owned corvette J59 S100146 since March 1975 and I have the 739 block which was cast on June 17 1958 (F17 8 ) and the engine assembly date of Aug 14 1958 (F814 CU ) now I would like to acquire the the correct dated heads and I know the dates are not judged by NCRS but none the less I want to do this correctly.
QUESTION
as you are no doubt aware ther were 3748770 heads produced in June 1958 with X58 on the side but in order to keep the engine build dates in sequence would it be better to to have 550 heds cast inJuly 1958 without the X58 markings.?
as far as I can tell the car was built on sep 11 1958 that may explain the why there is nearly a one month gap from engine assembly date to the build date of the car since the plant mat have closed down while they changed to 59 from 58 production this as you can see is the 146 th 1959 none the less what would be best June 1958 770 heads or July 58 550 heads for an august 14 -58 engine assembly date on a june 17 block casting date
Thanks to anyone who would care to comment
Philip McLachlen Ottawa Canada member 54904

[Arthur T.]

Re: 770 heads versus 550 heads

I have owned corvette J59 S100146 since March 1975 and I have the 739 block which was cast on June 17 1958 (F17 8 ) and the engine assembly date of Aug 14 1958 (F814 CU ) now I would like to acquire the the correct dated heads and I know the dates are not judged by NCRS but none the less I want to do this correctly.
QUESTION
as you are no doubt aware ther were 3748770 heads produced in June 1958 with X58 on the side but in order to keep the engine build dates in sequence would it be better to to have 550 heds cast inJuly 1958 without the X58 markings.?
as far as I can tell the car was built on sep 11 1958 that may explain the why there is nearly a one month gap from engine assembly date to the build date of the car since the plant mat have closed down while they changed to 59 from 58 production this as you can see is the 146 th 1959 none the less what would be best June 1958 770 heads or July 58 550 heads for an august 14 -58 engine assembly date on a june 17 block casting date
Thanks to anyone who would care to comment
Philip McLachlen Ottawa Canada member 54904

Phil,

I just went through the business of matching heads to a block for my '58. I examined several intact period blocks assembled the week of June 2, 1958. All of them had heads cast between E-22-8 and E-29-8.

What I would do is look around for original Flint 283's assembled the same week to see when the heads were cast and whether they were 770 or 550 heads. Do not hesitate to include any Chevy Impala or Belair 283 / 220hp with power pack heads on them. These engines were assembled in Flint right along with the Corvette Engines but do make sure they are Flint Engines with Flint heads and not Tonawanda. I've seen BelAirs with Tonawanda castings.

My best guess is that correct heads for your car were likely cast around July 31 and they were probably 550's. I have heard that a few very late 1958's have some 'hybrid' head castings that had 770 characteristics on one half of the casting and 550 on the other. These are reputed not to have the x58. I have not seen any of these myself, so I would take this with a grain of salt, and investigate.

Art T.