[TnVTX]

After fighting high oil temperatures on my Hard Blok filled stroker 400, I have decided to start looking for another 400 block. I don't really know enough about the differences in the 400 blocks from year to year, or what casting #'s to look for. The machine shop I used filled my XX block since it had to be bored .065 over. So, here are some questions I have in my quest for a good 400 block:

1) Would any 1970-74 400 block be a "thick" walled block with correct motor mount holes for a '78 T/A? Is this what I should look for?

2) What casting #'s should I avoid, and/or look for?

3) Is there any advantage a 400 block from the sixties would have over the 70-74 vintage? (I did find a '67 block that has been out in the weather, but it may be too far gone).

3) Is trying to reuse my .065 pistons going to overbore any 400 block too thin when I'm not wanting to Hard Blok it?

[johnsma22]

Take a look at this link for Pontiac Engine ID Codes. You can see all the different casting numbers for each year block. The 400 block that you should be on the look out for has a casting number of 481988. In 1970, all blocks received three additional motor mount holes for possible mounting in the new Firebird chassis. In some cases, only three holes were tapped, but five pads were machined. The 1970 400 blocks will have a casting number of 9799914 and 9799915 for the standard 400 and the RA III and RA IV cars, respectively.

If you're wanting to avoid the "thinner" blocks then look for casting numbers 488986 and 500557. I'm not sure of the year, but if you find a block from a later 70's W72 car that will be a 481988 block as well.

I've heard that the pre-70 400 blocks have a higher nickle content, or some such thing, but they will not have the correct motor mount bosses for installing into the subframe of a 2nd gen f-body without the use of adapter brackets.

As far as reusing your .065" over pistons is concerned, I wouldn't bore a block just for the purpose of reusing pistons that you already have. Take it only as far as necessary to properly clean up the bores, and even then it's a good idea to have the block sonic tested. Due to core shift during casting, cylinder wall thickness can vary from block to block.

[Motor Daddy]

I have a standard bore 71 481988 400 block I'll sell ya if you pick it up in PA.

[TnVTX]

Thanks for the info!!
I had just about came to the conclusion I was going to abandon my .065 pistons to aviod future potential issues.
I'm hoping to find a block a little closer to East TN...Thanks for the offer though!

[440GP69]

Originally Posted by TnVTX

Thanks for the info!!
I had just about came to the conclusion I was going to abandon my .065 pistons to aviod future potential issues.
I'm hoping to find a block a little closer to East TN...Thanks for the offer though!

You should find a shop to Sonic Check your block and report back here with results, Nothing wrong with .065 over if the blocks thick enough, I have a 455 I'm building That could easily go to a 4.25+bore size It just depends on how thick an How much Core shift when thy Cast it IMO

[TnVTX]

Originally Posted by 440GP69

You should find a shop to Sonic Check your block and report back here with results, Nothing wrong with .065 over if the blocks thick enough, I have a 455 I'm building That could easily go to a 4.25+bore size It just depends on how thick an How much Core shift when thy Cast it IMO

I was going to have my current XX block sonic checked before Hard Blok filling it, but, after calling around several shops, there is not a shop close to me that can peform the test. I was going to have to haul the block to Kentucky (I live in TN, near Knoxville) to a shop up there to perform the test, and I was told the test would cost at least $500. Surely it doesn't really cost that much...

[440GP69]

IMHO Every Block you Plan On using needs to have it done Especially after 30-40+years of Water running through it Corrosion Catches up!, Ive seen people put Lots of money into blocks that were No good and Only way to tell how thick they Are is Sonic or X-ray, Sonic should cost 100-150$

[TnVTX]

Originally Posted by 440GP69

IMHO Every Block you Plan On using needs to have it done Especially after 30-40+years of Water running through it Corrosion Catches up!, Ive seen people put Lots of money into blocks that were No good and Only way to tell how thick they Are is Sonic or X-ray, Sonic should cost 100-150$

Now that's alot more affordable! I will continue to search for shop within a reasonable distance, that can do it near those prices!
Assuming I find a shop, what "specs" am I looking for to determine if i can go .065 or not?

[440GP69]

I wouldn't want any Major thrust sides under .180 and if it were close I'd Personally use a Little Pontiac Dude Block fill to the Middle freeze plug IMO

[BVR421]

I dont understand what the block has to do with high oil temps?

[CaptCrunch]

Originally Posted by TnVTX

I was going to have my current XX block sonic checked before Hard Blok filling it, but, after calling around several shops, there is not a shop close to me that can peform the test. I was going to have to haul the block to Kentucky (I live in TN, near Knoxville) to a shop up there to perform the test, and I was told the test would cost at least $500. Surely it doesn't really cost that much...

Butler's in TN and he can do it for you........

[TnVTX]

As far as it's been explained to me, with my block having the water jackets filled with Hard Blok (metallic concrete), the water can only cool the heads, and just the upper part of the combustion chamber. All the heat generated down in the cylinder liners is "heat sinked" away into that concrete. Some of that heat is then transferred to the oil.
When drag racing, this is not a problem as the block has time cool down between passes. But, out on the street, after ~20minutes of driving, the oil just gets too hot.
If the block wasn't filled with Hard Blok, then the water would carry away the heat from the cylinder liners.
At least, that's the way I understand it...

[BVR421]

how about an oil cooler? might be less expense than replacing block and pistons but you might be looking for an justification to upgrade a few things while you are at it? LOL

FWIW
oil temp 20degrees warmer than coolant temp is pretty much the norm for any motor

[TnVTX]

Originally Posted by BVR421

how about an oil cooler? might be less expense than replacing block and pistons but you might be looking for an justification to upgrade a few things while you are at it? LOL

FWIW
oil temp 20degrees warmer than coolant temp is pretty much the norm for any motor

Actually, I had already attempted a nice oil cooler with remote filter & thermostatic control. By the time all the parts came in with the braided hoses & ends, the tally was right at $1k. I just couldn't see invested yet another grand into this block, that probably can't even be bored one more time...
But like you said...this might give another excuse for a couple of more upgrades.

If I could keep my oil temps at ~220 for constant driving, I'd be happy with that!

[6tee4gto]

what year block is yours?67 to 70 are the best i have seen. if its one of them and its filled to bottom of water pump holes you should not have problems. i have a bunch of street miles on a half filled block and its 0.65 over

[TnVTX]

Originally Posted by 6tee4gto

what year block is yours?67 to 70 are the best i have seen. if its one of them and its filled to bottom of water pump holes you should not have problems. i have a bunch of street miles on a half filled block and its 0.65 over

It's a '78 W-72 "XX" block.

[steve25]

My 671 blown ,non hard blocked 455 produces 230 to 235 degres of oil temp with 180 of water temp on a long summertime 3000 rpm drive. The motor at first got the oil temp into the 250! range untill I got the jetting to where it should be.
My guess is that fatter jetting and more part throttle cruse timing( not just 32 to 38 degrees drag timing) something like 44 degrees will drop that oil temp nice!
By the way, the oil temp needs to get over the boiling point of water(220) to get rid of condisation and other combustion by products if you are not going to change the oil every 2 months.

[Kenth]

The '78 W-72 "XX" block should have the 481988 casting #, meaning it is the thick casting?

Only blocks to avoid for the highest performance builds would be the thin castings with 1975 and later casting #´s in the 5xxxxx-series.

[TnVTX]

Originally Posted by Kenth

The '78 W-72 "XX" block should have the 481988 casting #, meaning it is the thick casting?

Only blocks to avoid for the highest performance builds would be the thin castings with 1975 and later casting #´s in the 5xxxxx-series.

Yup, but, I didn't find out that information until a few months after the hard blok had been poured. (My typical luck).