Hi all.
Yes, I think this is my 1st post. I have been using this site for a ton of useful information but have a question at this point that I can't find already answered.
Anyways, I have a '67 Firebird with original 326HO. Motor was running but on tear-down, noticed a few issues. Would need a total rebuild. With the money I am putting into it I figured a 400 would be the better choice. (With many recommendations from this board).
I have a source for a remanufactured 400, block number 988,577(?) and head number 4X, 6X or 5C. 2 3/4" cam centering ring. Specifies it is for a '73-'74 Pontiac XX.
or
400, I can request head casting number, 5 motor mounts on left, 4 on right. 2 1/2" cam centering ring. Specs for 75-79 Pontiac XX.
or
400, I take the heads they have at moment, specs for 67-69 Pontiac XX.
I would like to keep my existing '67 Timing housing, pulleys, A/C mounts and pulleys etc as all are either new or in very good condition.
My questions:
1. I am under the impression that the years are crossable as to the accessory equipment on the front of the motor, is this true and will I run into any issues using my existing equipment?
2. Which block era would be the best? (Wall thickness, etc.)
3. Heads - Would like to make sure I get the big valve stuff.
4. Motor mounts - Do the newer, multi mount blocks include the correct holes for the mount in the '67?
5. Transmission mounting - I believe all the above engines will have the correct mounting holes for the early Pontiac transmissions, just want to get this verified.

Thanks so much in advance for your valuable input. THis has been one hell of a project and am ready to drop the powerplant and trans in at this point.

Those heads listed are way too big for a 400 chamber wise.

All accessories will cross over.

The 6X, 5C and 4X are 2.11/1.66.

Personally, I feel you should look elsewhere for an engine rebuilder. Those core numbers you provided for heads and block are high production/availability and not that great for a 400 or for strength.

I would look for 67-71 400 block, even lower cost Y and X coded motors which are just as good. 67-71 400 rebuildable core with caps, crank and rods $100-400.

Would also look for #13 or #62 heads (cores $200-400) that have a verified chamber CC of 78-82. Or you could find a set of 1970 #64 heads for around $700-800.

A full service machine shop will be able to build you a motor for roughly $2000-3500 with your core. The price difference is due to many variables in quality of internal parts and options. I would also stick to a Pontiac only engine builder. These motors are quite different and you do not want a Chevy of Ford profile cam with a specific RPM in a Pontiac. As well, the motor should be built around the rear gearing, weight and exhaust..not the other way around.

My must haves for a stock motor

1. Have rotating assembly balanced
2. Can use stock rods, upgrade to ARP bolts.
3. Torque plate bore and hone.
4. oil galley plugs.
5. SERDI valve job
6. Comp Cams valvetrain.

There is a lot to answer here. The head/displacement you are looking at would be a dismal performance of 7.8-8.0 to 1..That is unless they (engine place) spent a lot of time and money milling those heads.

And you would be very disappointed at the dollars spent and result. Personally, spending another $500-1000 for excellent heads and a better block and corresponding machine work would make you happier.

P.S. See you are in Cali.. Steer way clear of Bruce Fulper and Rock and Roll Engineering.

Rock & Roll Eng. Hahaha, funny. When doing a search for Pontiac engine rebuilders, he came up, browsed his site and looked good. Then I backed up and checkWay to many bad BAD stories. Was going to steer clear of him from the 1st place, but thank you for the reinforcement of my opinion.

Pontiac only builders are very few if any here in Fresno. If anyone knows of anybody, I will definetly look into it. I can also easily get to the Bay Area.

The Engine supplier I have been talking to has the '67 era 400 available. He can supply me with head casting numbers available when I am ready to order. He says they usually have a decent selection. Also have a friend that has a set of #64 heads he will sell me cheap. No problem putting them on the 67' era block?

Thanks for all your help!
Jonathan

The 64's no. The only "problem" is the 87 cc stock chambers. I owned 3 sets and they all cam in at 84-85 likely due to milling the decks and time. The smaller the chambers, the higher the compression. The heads you referred to (6X/5C/4X) are typically 110-114 cc with some coming in at 94 cc. Stock 67-69 Firebird heads were 72 cc with variances up to 75-77 cc for the 62's. The heads you are looking at would perform MISERABLY on a 400. Yes you can run 87 octane, but you would be at 180-200 HP. By getting the 400 to at least 9 to 1, you can run 89 octane,with 9.5 92 octane and 10 to 1 can be done with a well tuned carb and distributor.

You can put any 67-79 400 head on any 400 engine. Before you decide on a set of heads, just ask.. Been at a machine shop for years as a side gig and work on only Pontiacs. I do not know everything, but can certainly point you in the correct direction.

If you want to go South instead of West, there is a superior shop in Santa Clarita that will build you a far better engine than you will get almost anywhere else.

Take Banshee's advice and don't ask your builder which heads he has. Find the right heads and bring them to the builder, regardless of which builder you choose. There are variations of each of the 4X, 6X and 5C heads that will make a huge difference in how well they could be modified (if need be) to work well on a 400. Bjorn has a set of 5C heads on his 400 which were worked over correctly. As far as I know, they have been a positive addition.

Advice is free ... so, you get what you pay for. Experience isn't free, so if you can benefit from someone else's take advantage of the opportunity.

When you start to put together an engine from parts scattered across different years, there will be a few more details to look for, such as timing covers, water pumps and accessory brackets and pulleys. Even though everything will bolt up from 1967 (and even as far back as 65) through 1979, there will be some combinations that simply won't line up until you match up other parts from the same era.

Well, obviously I have not yet made an engine "decision". Who is this in Santa Clarita? Heck, almost consider that local nowadays.

Thank you all for your And yes, I should add pictures of what has been done so far.......

I'd check in with Quenton and get the contact info for the builder he recommends, you won't be sorry! He and Banshee know these motors inside out and could build them in their sleep...

It would be well worth the time spent in travel.

Brett - 67 Drop Top 455!

not to completely change the subject, but what are the pros and cons to going with a 400 vs. 455 if you are going to change motors?

Pros of going with a 400: Most likely fewer rear tire changes.
Pros of going with a 455: Can build much milder to obtain same torque.

CON's what the heck!!! Ain't no cons's going bigger, "NO SUBSTITUTE FOR CUBIC INCHES," unless you force-air in an already big mota. As long as you don't spin the tires on every corner, and drive like a mature (not old-foggie) adult, why not play with more cubes?? It's just a plus to go 4-5-5.

thats what i kind of figured, but had to ask since i usually see people posting about keeping 400's or most of them seem to go .030 over.. whats that punch the 400 out to anyway? and are the 455's just bored out 400's, which is a bored out 326? or am i completely lost?

Completely.

455, originally was designed as a large journal stroked and bored 428. It's not a derivative of the 400.

The 326 is an orphan and spawned no children. Originally meant to be 336 CID, the GM brass told Pontiac to make it smaller than the Chevy 327. There's a few year's worth out there marked as 326 which actually measure 336.

The 400 is a bored out 389. The 350 is a 400 stroke but smaller-than-necessary bore compromise. You can not bore a 350 out far enough to make a 400 without sleeving the block, at which time you ask yourself: "Why didn't I just turn down the mains on that 455 crank in the first place?" Olds thrust bearings to the rescue.

good to know.. im trying to learn.. its too easy to find bs info on the www, and somewhere i read all these motors were the same, just punched out differently. thanks for the response, and sorry for hijacking the thread