[Hitman]

I got these numbers off my engine. Can any of you gurus help decode these?

Passenger side rear of block 481988
Front of engine block YN 0478073
Rear near distributor (Best I could read) 80201

Head drivers side J088
Head Passenger side B049
Head casting numbers on both sides 62

If these numbers are nothing please point me in the right direction cause I would really like to know exactly where this engine came from. The previous owner bought the car like it was and cannot find the person he bought it from. Thanks in advance guys.

[johnsma22]

The block casting number of 481988 means that it is a 1971- early 1975 400 block. The numbers you gave from near the distributor are unusable as a date code, as it should have a letter, followed by 3 numbers. The letter = month, next 2 numbers=day of the month, and last number=last digit of the year. For example, A273 would be Jan 27th 1973 or 1963. From what I could find though, there is only one YN coded 400 block with the casting number of 481988.

It is a 1973 230 hp 400ci that originally came in an automatic B or G body with 8.0:1 CR, an 066 cam, 4 barrel with 4X(7H) heads.

Head drivers side J088: This date code could mean Oct 8th 1968 or 1978
Head Passenger side B049: This date code could mean Feb 4th 1969 or 1979

The head date codes don't really tell us much with out the casting numbers located on the center two exhaust ports on both heads. Suffice it to say that they are not originals to the block and by the difference in date codes are most likely not even a matched set, even if they are the same casting code.

So what we really need to continue is to try and get the date code near the distributor to confirm the year of the block, and the casting codes from the center two exhaust ports on the heads. If the 400 block you have is from 1973 and is in good condition ie.. not cracked, etc, it would be a good candidate for a rebuild.

I included this link to a site that has great info with photos to locate where to look for all the right numbers.


http://www.yearone.com/updatedsingle...pontengid1.asp

John

[johnsma22]

You must have edited your post with the head casting numbers as I was typing my last post.

The # 62 heads were used in 1968 on Pontiac Big cars and Grand Prixs with 400's and 428's with 10.5:1-10.75:1 CR respectively.

The #62 heads were used in 1969 in all cars with 400's and 428's, depending on the combo's. Other head castings were used in those years of course. The factory lists the combustion chamber size at 72-75 cc's for 1968 depending on whether in came on a 400 or a 428. In 1969 the factory lists the chamber size as 72cc's, which yielded a CR of 10.5:1-10.75:1. We all know how inaccurate these factory numbers can be so your best bet if you intend to use them is to have a reputable machine shop cc them for you. No telling what kind of work has been done to them over the years.

These heads are considered to be high performance heads with large valves (2.11" intake/1.77" exhaust) closed chambers and screw in rocker studs.

IMO, these heads may put you into the position of not being able to run this motor on pump gas, due to the risk of detonation with such a high CR. You must find out if the block has been bored, zero decked, heads milled and so forth. That is a debate for another day I suspect. Hope this helps

John

[Hitman]

It helps very much cause the motor was rebuilt and bored .30 over. And you are right with the detonation. I ran 93 in it and it pings like you would not believe. I am looking for a lead substitute or am going to get some gas from the local drag strip here. Thanks for the link and the help. And I figured something was up with this motor cause when I bought it the owner had about a half of tank of gas and it ran like a raped ape spinning those 215/75/15's with very little ease off the line and also spinning them when while the car is already rolling at about 15-20 mph.

[johnsma22]

I hate to tell you this but there no lead substitute that you can get "off the shelf" that is worth a damn. True TEL (tetra ethyl lead) for gas is illegal to use. All the so called "octane boosters" at the part stores are snake oil at best and are a fraud. Some guys here have had good luck using toluene to raise octane, you can get it at any hardware store. I'm not sure of the mixture ratio but I'm sure you could do a search here for "toluene" and get some more info. Mixing chemicals in my tank every time I fill up is not for me!

IMO you have only two realistic choices. (1) Run racing fuel either at full strength or in some ratio that you find by experimentation to eliminate the detonation. (2) Lower your compression ratio ie.. dishing pistons, changing to larger cc heads etc.

I guess you have a third choice. Do nothing and risk hammering your rod bearings into oblivion in very short order or worse, like I did.