Technical Strange 400 Pontiac engine

Hi, I know you guys discussed this in the past but I am stuck. I have a 67 Pontiac Grand Prix convertible that was bought as a 400. It has an original engine with XJ on the block. The previous owner had the engine rebuilt and tells me the engine is a 428. There is a bump behind the distributor and from what he says, it has a 4 bolt main and 268 cam. He also said it has a windage tray. He rebuilt the engine to 428 specs and it runs great. Could this be a 428 from the factory and still be stamped XJ on the block like a 400? I have attached a picture that he took when rebuilding it. I want to badge the car as a 428 but wont do it unless it is truly a 428. Thanks.

 

428 was cast on the side of the block between the freeze plugs and the #28 cast in the lifter valley on a true 428 block. Pontiac also cast the size numbers on the left side of the block by the fuel pump on their other motors for identification. Loved the 428 motor. Great tourque. Read guick.

 

Pontiac re-used that code over the years:

67 400
69 428
73 455
77 400
78 400

The "transfer lug" he is referring to means it is a 59 and newer non-389/400 block. The block will also have a casting date.

 

Badges? We don't need no stinkin badges!
http://www.phs-online.com/

 

Thanks for the feedback. I have some more pictures of the engine that I have to look at. Stay tuned...

 

Can't you install the 428 rotating assembly in a 400 block?

 

Not directly. 421 428 455 are 3.25 main journal diameter vs 3.00 for smaller engines

 

Yes. My friend Larry Climbie bought a GTO new in 68. 400 automatic. Eventually he decided it was a Bonneville car and I learned from him that a 455 crank could be ground to fit. He wanted to keep as much of the OEM parts as possible. #16 heads that came on it he kept. So it kind of looked original. The Kinsler injection gave it away a little bit. We tried the engine in my Vega and went 208.526 mph I think 187 or so in the GTO at El Mirage. He got it all cherried out and painted and parked it in his driveway. About 25 years ago. And there it sits to this day. WTF?

 

I don't know what it is but its a four bolt main and that's on the rare side with Pontiacs.. What are the head numbers on the center exhaust ports?

 

Someone may have installed the 4 bolt main caps. I had a set from a cracked '69 XP around here for decades, and now I can't find them.

 

The “bump” is a transfer lug used on 421, 428 and 455 engines. See my pic. Look at the date code near the distributor hole, to the left of my red circle in the pic. Should have 3 freeze plugs per side and yes a “428” should be cast as per 66gtopont member said above. Randy




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Thanks. It has the transfer lug bump behind the distributor. There is a 6443 on the side near the three freeze plugs. Can you tell from the attached picture if this is a 4 bolt main? I'm not sure how to tell. Also, the previous owner said it has a 268 cam.... does this help figure out what size engine it is?

 

Not sure what you are asking. Clearly the block has 4-bolt main caps on 2,3 and 4. The pic from below isn’t clear enough on the driver’s side to see any casting number. The date code would really help. Do you have the vehicle nearby? The 068 cam is common and used in many HP Pontiacs so it does not help in identification since it can be replaced at will. What heads are installed (large number between the center ports)? You will have to crawl around and inspect and record the numbers to help ID it. Randy


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Would a 400 ever have the transfer lug? Without pulling the engine, I'm trying to determine if this engine is a 428. I believe it is original to the car but the person who rebuilt it 10 years ago insists it's a 428. I'm now thinking that it doesn't have a transfer lug because i think my lug is flat on the top and the pictures I see comes to a point

 

No lug on small main journal blocks (389 and 400). Just get a flashlight and lean over the fender and look for the date code near the distributor. Might need a small brush if there is a lot of paint on the numbers. Looking for 3 or 4 digits. The engine year will prolly be nearby as my picture shows for my 1970 455. The block casting number will be close by on the rear passenger side top of block near the head.
If you don’t have the vehicle with you then I understand, but I’ve already asked that and you didn’t answer it. Head casting numbers too while you are there would help. Randy


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Even if it has a transfer lug, that doesn't prove it's a 421/428/455. The smaller engines have them too.

 

Well maybe this is one of those engines I don’t know. The OP has been given enough information for sure to settle the question that he has. Regards, Randy


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My wifes younger brother totaled out a 69 bonnieville. We installed the 428 in a 74 grand prix. sO theres one someplace with a 428?

 

Take out sparkplug and check stroke. 400 and 428 same bore .

 

Could someone explain what a "transfer lug" is? Does it have a use or purpose?

 

Good on ya. One of my favorite cars was my ‘68 Catalina convertible that had what turned out to be a ‘71 low compression 455. When got tired I rebuilt it, using an Edelbrock Performer, matchin E carb, and a really radical hydraulic cam that I can’t temper the specs on. Turned out to be a happy combo, it was a stump puller and was SUPER fun to drive.


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The " lug " on the back of the block identifies it family, 326/350/400 or 421/428/455.

It's the bigger engine, 428 or 455, the small crank engines 326/350/400 do not, will not, or ever had the tall lug on the back of the blocks. 99% sure it's the '69 428 with #46 heads. Most of the 428's were four bolt mains, and most all Pontiac's used a windage tray also. The cam would have been a #9779067, standard four barrel cam used in the big chassis cars. The HO motors would have gotten the #9779068 cam, yours is likely an aftermarket copy. Read the numbers on the side of the block by the motor mounts, and get the date code off the distributor pad, then you will know for sure. Again, the 400 did not have the lug on the back no matter what anyone tells you. Pontiac did this for a reason.

Look here, http://www.wallaceracing.com/engine1.htm You must have the date code!

 

Jack car up, lay on your back and slide under car, look between freeze plugs on side of block, do you see a "428" cast into the side of the block ? Yes ? Then it's a 428 !!! No? Then it's not a 428 !!

Yes it's really just that simple !!! No date codes needed, just need to get off butt, Jack up car and look.

If it's not and it's a 400 with a cut 428 crank then the only way to tell is basically pull engine, drop pan and start measuring stroke of crank, no other "special" ways needed.

 

Thanks. I'll be jacking it up tomorrow. I tried to take pictures but they all came out bad.

 

Hopefully he “jacked car up” and then put it on a jack stand before sliding under the car.......... he said he was doing it yesterday.

 

My glasses stink and I couldnt see any numbers. I tried using my camera and no luck. I am going to take it to a garage and get it on a lift. Then I can take good pictures but I didnt see any numbers.

 

Ok. I got the car up on ramps and I only see a GM8 or GM3 on the block. here's the picture

 

You have to look between the freeze plugs, around the motor mounts. They are also marked in the lifter galley, dead center, 00 - 400, 55 - 455, 28 - 428, 50 - 350, but this requires pulling intake and valley cover.