# Need help with mysterious engine block casting code



## 1968gto421 (Mar 28, 2014)

After checking out shoeman68’s post on his 455 engine number and the great info, I thought I would post a separate post on my engine number rather than hijacking shoeman68’s thread. The folks I bought my GTO from were upfront about the original engine with factory A/C being replaced with another Pontiac engine. They were used to driving newer cars with 4’s and V-6’s and thought the Pontiac torque must be a 455 but still were unsure what it was. The engine needs some work so for me it could be anything from a 326/350 to an old 428/455 based on the way it currently drives.

To get specific, the engine came with the Q-jet in pieces in a box in the trunk and an Edelbrock 1406 that needs help (I have a Holly off another car I can use until I know more about my engine and then Mr. Ruggles may get the Q-jet), Edelbrock Performer intake, a Mallory Unilite distributor, 6X-4 heads, an “assembly lug” by the #8 cylinder, and a “rough idle”.

I can’t get a photo of the manufacturing date by the distributor because of after-market stuff on the firewall. I’ll get that off once I diagram it but for now I was able to get photos of the engine casting number on the back of the block behind the number 8 cylinder. I also got photos of the alpha code on the front of the block in front of number 2 cylinder. Hopefully these pics can help ID this engine.

To my eyes, the block casting engine number reads as 9792068 but I cannot find this number on any of the websites covering Pontiac engine numbers (Wallace Racing, teufert, etc.). The number could have been messed up when cast or later by a shop. In that case, I wondered if it was really 9792968 which is a 1968-69 428. According to Wallace, the XF would make it a 1969 428. But I still wonder, could I be lucky enough to have a 428 (instead of the 350 I fear I have). (I was told that the Q-jet in the trunk was original to this engine (not the OEM 400.) For what it’s worth, the number on the Q-jet is 7018268 WF.

My appreciation for all help….Thanks!


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## 05GTO (Oct 6, 2004)

To me it looks like a 9 and not a 0, in early 69 Pontiac changed from a 6 digit EUN to a 7 digit EUN, they also went from an 8 bolt water pump to an 11 bolt. I agree with you and believe you have a 69 428.


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## PontiacJim (Dec 29, 2012)

The big "lug" that looks like a tall triangle identifies the 421, 428, and 455 engines. Appears to me to be a 428CI by everything you have said.


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## 1968gto421 (Mar 28, 2014)

Thanks, guys, I appreciate your input and knowledge. The short block with its old looking seals, oil pan gaskets, and all make me think it's an untouched factory assembly. After looking at this post http://www.gtoforum.com/f12/issues-buyers-want-know-91802/ I am glad that its a worn original engine and that I don't have to re-do someone's shade-tree-overhaul. While I have 50 years behind me working on Mopars and Chevs, I am a newbie to Pontiac engines, this forum and the incredible knowledge and sharing of you all is a fantastic blessing. The more I learn here, the more I appreciate the GTO I've been blessed with and the friends here to help me with it. And when I can help someone, I certainly will. Thanks!!:thumbsup:


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## Pinion head (Jan 3, 2015)

the '69 XF is one of the really good 428's as it will have 4 bolt main caps. Originally they had the 62 casting heads, and ran really well in stock condition. Have pulled quite a few '69 XF engines out of GP's, I used to even catch grief from some of my Chevy friends for buying GrandPrixs, but I like 'em. Years ago had a '69 XF block built up with a 455 crank for local customer that was dead set on a 4 bolt 455 shortblock for his engine build, but had a Pontiac that could accept the early style engine mount...easiast way to take care of him.


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## 1968gto421 (Mar 28, 2014)

Pinion head said:


> the '69 XF is one of the really good 428's as it will have 4 bolt main caps. Originally they had the 62 casting heads, and ran really well in stock condition. Have pulled quite a few '69 XF engines out of GP's, I used to even catch grief from some of my Chevy friends for buying GrandPrixs, but I like 'em. Years ago had a '69 XF block built up with a 455 crank for local customer that was dead set on a 4 bolt 455 shortblock for his engine build, but had a Pontiac that could accept the early style engine mount...easiast way to take care of him.


Thanks, Pinion head, I appreciate the info. I'm feeling really fortunate with this car.

Since mine no longer has the 62 heads, any thoughts on the possible compression ratio with the 6X-4 heads? (Assuming it has the original pistons.)

I noticed last night in the garage that my 428 has the 8 bolt water pump which surprised me since I expected the 11 bolt pump. Interesting discoveries:jawDrop:


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## PontiacJim (Dec 29, 2012)

This is probably a slim to none shot, but Royal Pontiac in Michigan offered a 428 swap/upgrade on 1968 GTO's. 1968 Pontiac GTO 428 / Royal Bobcat Road Test – Review – Car and Driver I would get the PHS documents on your car and see what your car originally was equipped with and what dealership may have sold it. Its probably not a Royal GTO, but you might consider doing a Royal GTO clone seeing you have the 428 in the '68. https://www.mecum.com/lot-detail/CH0911-116174/0/1968-Pontiac-Royal-Bobcat/4-Speed/


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## Pinion head (Jan 3, 2015)

C/R is going to depend on numerous things.

-Cylinder bore, am assuming the 428 is an unknown core and the plan is to rebuild it...
If so, say, .030 overbore, lets say going to run AutoTecs forged pistons which have a small valve relief, only 3.8 cc's, not the large volume relief of a stock 428 piston or an old TRW. The AutoTec pistons take stock length Pontiac rods, so if there is another design/length aftermarket rod you are set on, will have to go with another line of pistons, say a set of Ross pistons, most likely the other lines of aftermarket pistons will have slightly larger valve relief.
-Deck height. Pistons are not going to be at zero deck, theyre going to be down in the hole a tiny amount. That needs to be measured. 

With slightly milled 6x-4's (92 cc chambers), zero deck block, the above AutoTec .030 428 pistons, felpro blue head gaskts, going to be very close to 9.5-1 C/R


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## 1968gto421 (Mar 28, 2014)

My thanks to Pinion head and Pontiac Jim for more information and some very good directions on which to take the 428. I appreciate the compression thoughts and the parts with which to do a really good rebuild.....hadn't thought about taking it down but it's looking like a really tempting project. Of course, one thing leads to another and then I need to consider the rear end and suspension and consider the TH400's possibilities. But what fun when finished!:smile2:


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## oldskool (Apr 26, 2015)

You can get the Auto-Tec shelf pistons with any pin height you want, for no extra charge. So, if you have accurate measurements, you can order 'em with a pin height which will raise the pistons to zero deck height, without cutting the deck down. 

Shanon claims that he'll beat anybody's price for the Auto-Tecs. He's the one who told me about the free pin height change. 

AUTO TEC SMALL BLOCK PONTIAC - 400/428/455 FLAT TOP PISTONS ? Shanon's Engineering Inc.

Here's some $350 H-beam rods to go with the pistons. A guy at CP told me they are RPM brand rods. At the time of this post they are listed on the RPM site for $400. Part # LG3-6625H

http://www.competitionproducts.com/...ontiac-V8-6625/productinfo/6625/#.Vca5mHFViko

http://www.racingpartsmaximum.com/sae4340steelhbeam-2.html


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## PontiacJim (Dec 29, 2012)

oldskool said:


> You can get the Auto-Tec shelf pistons with any pin height you want, for no extra charge. So, if you have accurate measurements, you can order 'em with a pin height which will raise the pistons to zero deck height, without cutting the deck down.
> 
> Shanon claims that he'll beat anybody's price for the Auto-Tecs. He's the one who told me about the free pin height change.
> 
> AUTO TEC SMALL BLOCK PONTIAC - 400/428/455 FLAT TOP PISTONS ? Shanon's Engineering Inc.



SMALL BLOCK PONTIAC?????? That scares me when they advertise something like that. Wonder if they have any BIG BLOCK PONTIAC stuff. I could use some of that.:confused


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## oldskool (Apr 26, 2015)

I suppose when you compare 'em to a BBC, they do seem more like small blocks. They are much smaller in size and weight.

Anyhow, I've read that a lot of engine builders say these are good pistons. 

http://www.speedtalk.com/forum/viewtopic.php?f=1&t=28878


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## Pinion head (Jan 3, 2015)

oldskool, do you know if the Pontiac Auto Tec pistons be ordered with a slight dome?


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## oldskool (Apr 26, 2015)

Pinion head said:


> oldskool, do you know if the Pontiac Auto Tec pistons be ordered with a slight dome?


No. The Auto-Tecs are flat top with 2 valve reliefs. You can get 'em with a different pin size and location, and either stock width or metric rings.

For a dome, you'll have to go thru the Race-Tec side, for a custom piston. Shanon can get a price on 'em for you.


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