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Old 06-12-2010, 05:54 PM
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Pontiac casting numbers help

ive looked on every pontiac site but no info on this pontiac 400 every site ive try'd wasnt even close. i figured some 1 here would know

the numbers on the front of the block are
845848

XH

23c127250

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Last edited by 87fubar; 06-12-2010 at 06:01 PM.
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Old 06-12-2010, 06:02 PM
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If you're sure it's a 400, it could be a '67-'70 400 or a '77 from a B-body (big car) w/AT and 4-bbl Q-jet. In '77 it would have had 6X heads originally.

There was also a XH in '78- it was the 301 cid engine and came w/the 01 head casting number.
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Old 06-12-2010, 06:03 PM
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its got 400 cast next to the motor mount an its got 4x heads on it

would this block be worth doin any thing with??
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Old 06-12-2010, 06:13 PM
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The 4X heads were used in '74, but by now, the original heads may well have been swapped out.

There were different size 4X heads- they were also used on the 455 engines and can be as large as 114cc nominal. Even if they are from a 400, the CR was low on these engines, about the best stock 400 head from the smog era was the 6X-4 head that was around 95cc.
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Old 06-12-2010, 06:15 PM
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The block is buildable, for sure. Check to see what the casting number (raised up, cast in, not stamped) from back by the distributor area.

From “Rick” of the tech staff on Hitman's Pontiac Trans Am Forum:
"The original casting number for the early 400 CID Pontiac blocks was the 481988 number John mentioned above. It is a very strong casting and it has been successfully used for many high-power and stroker builds without any block problems at all.

"The engineers in the drive train division looked at their engines, and decided that they could shave a few pounds out of the 400 block by redesigning it with thinner internal webs. The result of this was the 500557 block. It IS weaker than the 481988 block, but it's plenty strong for most street applications. In particular, it was WAY stronger than the factory needed for the 185 HP engine they were putting out in 75-76.

"So... during the 1975 model year, Pontiac switched to the 500557 casting. They stuck with it through the end of the 76 model year. But as car production moved into the 77 model year, the painful memories of the gas lines of early 1974 faded. Pontiac had a few production problems with assembly of the 500557 block engines, and they wanted to emphasize performance a bit more with introduction of the higher-HP option package. Rather than sink the cost of engineering yet another revision to the 500557 block, they decided to simply revert to the 481988 block.

"The use of the more robust block continued through the end of the Pontiac 400 CID engine production, during the 1978 model year. A set number of the 400 engines were stockpiled for the 79 model year, and then all the tooling was ditched because that was the end of the Pontiac 400, per corporate edict. The Olds 403 was use for the "big engine" production once the 400 engines were gone (all 400s were 4 speed, all 403s were autos), and for 1980 there were no more "big engines".

"A 500557 block is fine for almost any streetable 400 engine you'd want to build, right up to 450-500 HP, and with RPMs under 5,000. It's not the BEST candidate for a stroker engine or a drag engine that's going to see 6,000+ RPM -- the 481988 block is much better for that. But given a choice, most people opt for the 481988 block if they can find one for the same or approximately the same money.

"That's the entire ugly story... warts and all."

Last edited by cobalt327; 06-12-2010 at 06:21 PM.
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Old 06-12-2010, 06:21 PM
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i just went out to check those out 481988 is all i could find
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Old 06-12-2010, 06:30 PM
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Quote:
Originally Posted by 87fubar
i just went out to check those out 481988 is all i could find
You have the "good" late model block (see the addition to my last post above). This block is suitable for using as a "stroker" 455, this is where a 455-stroke crank w/the 400's smaller main bearing size (this is a good thing) is used in combination to make a better 455 than the original Pontiac 455, from the ability to rev higher w/o bearing speed issues.

Suffice to say, the block you have is a good foundation for a 400-up performance engine.
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Old 06-12-2010, 06:33 PM
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thank ya very much for all this info

is the 6s-7 heads any better just wonderin

Last edited by 87fubar; 06-12-2010 at 06:58 PM.
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Old 06-12-2010, 06:59 PM
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Quote:
Originally Posted by 87fubar
thank ya very much for all this info

is the 6s heads any better just wonderin
I believe the 6S was used on 350, 400 and 455 engines, so you'd need to measure the combustion chambers to be sure of what you had. I'm not familiar w/the 6S personally- I've used the 6X-4 heads on a 455 and they worked well. Other 6X heads had larger chambers, so you need to know what you are getting.

6S-7 2.11/1.66 99-101cc Mid-'75-'76 400ci w/A.I.R.
6S-9 2.11/1.66 92-94cc Mid-'75-'76 350ci w/A.I.R.
6S used on the 455 will be too large for use on a 400 engine. Or a 455, for that matter.

Unless the larger of the 6S chambers could be brought down small enough to get a decent CR, there wouldn't be an advantage in using them, IMHO.

6X CHAMBER SIZE ID
6X-4 93cc (mine measured 95cc), Mid-'75-'77 350ci; '77-'79 W72 (TA "6.2 Litre" option) 400ci
6X-6 124cc
6X-7 93cc
6X-8 101cc
6X-9 101cc

The 4, 6, 7, 8, and 9 identifiers can be found stamped on one of the vertical ribs on the side of the head. These heads have hardened exhaust seats, screw-in rocker studs and guideplates, 2.11" intake x 1.66" exhaust valves. They can be easily taken out to 1.77" exhausts. If nitrous still is in the cards, this mod should be considered.

There are also 1973-'74 cast #4X heads w/98 cc chambers and screw-in studs.

6X ID article- http://www.pontiacstreetperformance..../6XheadID.html

There is more in a thread HERE, as well as other info on this forum- hit up the search for 'Pontiac 400', etc.
The '75 5C heads are 101 cc, but they have smaller runners than the 6X. 5C are about 7cc smaller and the 4X are about 5cc smaller. Bigger is better, in this case.

Some sites and info, et cetera:

Butler- http://www.jbp-pontiac.com/

Kens- http://www.angelfire.com/fl4/pontiac...chineshop.html

Nunzi- http://www.nunzi-pontiac-expert.com/

Rock & Roll Engineering- http://pontiacpower.com/

SD Performance- http://www.sdperformance.com/

GENERAL INFO SITES FORUMS ETC

Jim Hand “BUILDING A STRONG STREET MACHINE”@ Classic Firebird
http://www.classicfirebird.com/hand/hand.html

Jim Hand’s 474 2002 updated specs http://www.pontiacstreetperformance....455jh2006.html

Pontiac Street Performance Featured Cars & Engines
http://www.pontiacstreetperformance....turedcars.html

Hand’s 455 w/#64 heads
http://www.pontiacstreetperformance....ld455jh99.html

Hand on Cams
http://www.dapa.org/jhpages/pontiac-cams.htm’

Hand on ROCKER RATIOS/MODS
http://www.pontiacstreetperformance....ockerArms.html

HP PONT. Smog Head Performance
A Technical Comparison of Pontiac's Most Common '70s Cylinder Heads
June 01, 2005
http://www.highperformancepontiac.co...nce/index.html

HP PONT Tech Articles, Various Pontiac
http://www.highperformancepontiac.co...les/index.html
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