I posted the following on C3 general and didn't receive any comforting answers. Will try again in tech.

I am the original owner of a 1969 Corvette with the L46 engine.

Date Produced: November 26, 1969
Block build date: November 17, 1969 (K 17 9)
Block cast #: 3970010
Engine Code: HW

That all fits in. Now I'm going to the heads.

Left Head: Cast # 3927186
Head built date: September 13, 1968 (I 13 8) Used on 69 Corvettes

Right Head: Cast # 3927186
Head built date: November 15, 1968 (K 15 8) uSED on 1969 Corvettes

I'm positive about the build dates.

My first question is: The build dates on the heads vary about one year from the block build date. From what I have read on this forum, the build dates for this engine should be within a month of each other.

Did someone steal my heads or is it an absolute possibility that the dates could vary that much?

The car has been serviced over the years.

Not looking for spectulations.

Thanks,

John

 

Hey brother John..our cars were built only a few weeks apart..I am Dec 6 of 69..pretty neat..so we have identical car codes..HW block also..build dates on the head? Well all I can see by looking in the valve cover oil fill is K79 above the casting number which is the same as yours..not sure if that helps..I am not all that good at decoding the numbers..but at least that is what I have..if there are any other numbers you need I have them written down..I just havent gotten to the heads yet..

 

this is contrary to what I have seen in previous posts regarding your question, but according to my book, Colvin's chevy by the numbers, the 3927186 was used for 69 corvette 300HP and 3927187 was for the L46..
the 300hp was 1.92/1.50 valve sizes, while the L46 had 2.02/1.60 valve sizes.
so the next question you need to find out is if you have 2.02/1.60 valves? it is my understanding that a L46 had big valves.

the corvette black book says that this head was used for 300 and 350 hp.. so if I am reading it right, and I may not be, there is a contradiction between colvin and the black book. or maybe I have old books..

 

Wow now you made me nervous..I had to go check the head number again..its the same..ok..I have no idea what size valves I have..one thing I do know is that these cars after the strike got all kinds of stuff chucked at them..the block is technically a 70..the vacuum is also a 70..who knows for real what these cars are supposed to have..being a 2 month build..hopefully its not wrong as then my heads are wrong too..

 

Well, first...there wouldn't be a 1969 model car produced in November of 1969. Model changeover is in late summer. 1970 cars started being produced in late July or August of 1969. So, that may be where your problem is. You need to determine the CORRECT build date for your car...and it isn't November of '69. [It could be November of '68, however; then the heads wouldn't be produced a year early.]

Lastly, if your data plate really converts to a November '69 build date...and the car is a 1969 car...the data plate has a "typo" on it--or it has been erroneously duplicated. Sorry.

 

Well you should check some books out on this one..since there
Was a strike Mr Deloreon extended the 69 production run thru December..its crazy..that's why there were so many 69 built..we got cars that are very difficult to identify..(not trying to be rude bro)..trust me I threw in the towel for at least a month trying to figure out the vacuum lines under the hood since I was using a 69 diagram..I needed a 70 diagram..ugh..its a basket case is what they did!..so anyhoo that's a fun GM deal that makes a early and a late 69 different.

 

yup, definately the 69 run lasted thru december 69, did not make any 1970's until early january 1970. the 70 registry, the c3 registry and the black book confirms all this. I think all the numbers for the OP line up except for the heads.

 

Ok so we are all good with everything but the heads..so what and how is this figured out as John and I have the same deal? Can you point me in the direction of the 69 vette registry if there is one..would like to get on that..
Thanks

 

69 model year production ran through the middle of December, 1969 due to the strike.

Blue: in your other post you said you had owned the car since new and it had never been out of your sight. If that's the case, your heads are original. No speculation.

Heads, intake, and block usually have closer casting dates, but that does not mean your heads are not original.

 

Well haven't removed my valve covers yet to check # but I have a December 18, 1969 coup, 350/350 vin# and engine, trans #s match. but the rear end is a 1970, not because it has been changed, in the corvette registry it said that late in the year they had to use 70 rear ends, I have also done some research on this, the rear end is CAN identification, I don't have the #s in front of me now, at work, but yes they used some 1970 parts on the 69s to finish up the year, Your head question, I think the cast #s are the same 68,69 300 hp and 350 hp just different size valves. It was also stated in the corvette registry that there was a conflict between GM and somebody abought the rear ends in late 69 were not true posies or something to that affect, don't quote me, have read a lot abought the strike and the way GM had to complete the 69 year cars, maybe that's why we cant find any stored sales docs or transport records for 69. Well just my 2 cents

 

Hi John,
Just to clarify... K 17 9 is the casting date for the block.
What's the engine build date?
The long period of time is certainly not typical of factory production, BUT I'd say POSSIBLE! Can you prove it? Probably not. If the other numbers are what they should be, it makes the odd dates less critical in my mind.
Since it is fairly close to the end of 69 production perhaps the engine build line was 'cleaning house'.
Regards,
Alan

 

I have the original “Corvette Order Sheet” for my vette. Date produced is clearly marked 11-26-69. I purchased it brand new on February 4, 1970 at Porter Chevrolet in Cambridge, MA. The car was on display right in front of their showroom window. I would drive by it almost every day while working. Yes, the strike did extend production. The engine is now again out of the car and the heads are off. I'm positive of the casting #s and have done as much research as I can to find out if they are original.

One website I found http://corvettec3.ca/casting.htm lists the 3927186 being used on early 69 vettes with the 350-300hp & 350-350hp as well as mid 69 vettes with the 350-300hp & 350-350hp. For the late 69 Vettes 350-350hp, the head casting # was 3927187.
Is that Correct?

I have read many times on this forum that the build dates of the block, manifold, heads and other components should be within a month or so of each other. That is certainly not my case. Was the vehicle ever out of my sight? Yes, at several times for a couple of fender benders and mechanical work.

Why am I going thru all this? The engine was redone by a recommended vette shop by the president of a local vette association about 1 1/2 years ago and when I picked it up, it ran crappy. So many problems. The hood would pop open while driving. The tires would howl when driving on curves, the coil wires were reversed letting it run but break down after 60 MPH. I posted that a year ago and fixed the wires myself. Stepping on the brake produced a rubbing sound. The clutch had no free play in it at all. Readjusted myself and there were more problems. I was getting water in one cylinder. I had another shop http://www.patsauto.com/ pull the engine a few weeks ago to find out what was going on. One valve is sunk into the seat and one slot for a push rod is egged shape and not oval. I paid for a valve job from the first shop. I'm trying to determine if my heads match my block and fits in with the block date which is K 17 9 and build date. I'm beginning to think that someone stole my heads. If so, I'm not going to put them back on. I'll put on something better and a cam change but want to maintain the original look to include original valve covers. Any suggestions?

But, I really need to determine if they are original or not. If they are, then I will have them redone. Besides measuring the valve size as someone mentioned, the 300hp was 1.92/1.50 valve sizes, while the L46 had 2.02/1.60 valve sizes. which I will have done after this storm passes, are there any other things to look for? This new shop told me that my studs are pressed in and believe they should have been screwed in for the L46. Is that correct? There are so many opinions and contradictions on this forum and even on the web. Does anyone reading this have an original late built manual 69 vette with the L46 and knows their head & block numbers? Or, does anyone positively know the answers to my questions? Sorry for the long post. I just need to find out.

Thanks for any help.

John

 

Hi John..I assume that you missed my post from yesterday..my car was built just two weeks after yours..also the original owner is from Barrington Ri..not sure what dealer yet..I have the same head numbers as you..block number also..

 

I read your post. You wrote: "Well all I can see by looking in the valve cover oil fill is K79 above the casting number which is the same as yours."

I originally wrote: "
Left Head: Cast # 3927186
Head built date: September 13, 1968 (I 13 8) Used on 69 Corvettes

Right Head: Cast # 3927186
Head built date: November 15, 1968 (K 15 8) uSED on 1969 Corvettes

Believe that is about a 1 year difference on our head dates so I am still searching for an answer.

Thanks for the reply,

John

 

Bummer John..I was hoping that finding another car similar to yours would help..I wish I had more to offer..if there are any numbers or anything else that may help your search give me a buzz..I really hope someone did not steal your heads..but you never know what chevy did on these cars during the late build.

 

Standing corrected on the end of 1969 production dates...and having worked for GM for 40 years...it is clear to me that the plant was using anything that was saleable near the end of the strike. They were probably searching the plant for parts when various supplier plants quit producing and found some old but useable stock. If some research were done on what vintage parts were in those late 69 vehicles, I would imagine the dates would be all over the place. Just a suspicion...

 

That is a possibility and will look into it.

 

Look at your valves if you have not got your answer yet. If they are almost touching (I mean close) they are the larger valves. The smaller valves will have around 3/16-1/4 of an inch between them. If they are close I would say they are the right heads, if not who knows what happened. The way people are talking maybe they installed the wrong ones at the factory. I am trying to do research on a car right now to see if it is a 350hp car. I don't know how to truly determine it if it has the same casting numbers on the heads as yours. My only chance is if it has the 187 heads. I don't want to pull the heads to see. Good luck

Tucker

 

Boy, this is getting interesting for me. The shop pulled the valves from one chamber and they measured 2.02 and 160. Yes Tucker, the valves are extremely close. Heads are positively stamped 186. The shop also showed me the exhaust valve on one head is sunken in and a tiny crack in the other head right by one of the valves which was why I was getting that plug wet all the time.

I am not a pro but they showed me the valve stems of the pulled valves and it had only one slot cut into the bottom of the stem but they said the valves designed for this engine had two slots. One was used for a seal of some sort. He then showed me something with a blue color in the head that was some kind of seal. Also they claim that the head had been modified by enlarging the hole in the 186 head where the valve stem passes through in order to accept the 2.02 & 160 valves. Being a late production engine, maybe GM fabricated heads to satisfy supply due to the strike.

Like I said, I'm no pro but all these guys do is build engines and they said my heads aren't worth saving with a sunken valve and crack. They want to install a new cam with aluminum heads, manifold and Holly carb as well as design headers to work with my factory side mounts. They also want to replace my domed pistons (3942545) and install flat tops. I get to keep anything they replace. They dynode the car before pulling it apart and believe it was about 260 to 280 hp at the wheels. They are telling me that it will be a lot better when done.

Any comments from anyone?

Thanks,

John

 

lots of 3927186 heads for sale on ebay and elsewhere, be careful though.
beware of the new heads and intake and holley fitting under your hood?