400 Vs 455

[chris_Py]

Whats your email jim?

[MrPbody]

[email protected]

** unapproved link removed **

Go have a look at what we do!

Jim

[chris_Py]

Just visited your site!! WOW!!
I dont have a four hundred block so I would need to get one from you when I do this. So am I correct in assuming that there is no real good way to build the 326 I allready have? I dyno'ed my mopar and I had on my best pull 253 at the wheels. I was thinking if I could get 400-500 in my firebird that I would be happy,, any chance with the 326??

[MagicRat]

Originally Posted by chris_Py

Just visited your site!! WOW!!
I dont have a four hundred block so I would need to get one from you when I do this. So am I correct in assuming that there is no real good way to build the 326 I allready have? I dyno'ed my mopar and I had on my best pull 253 at the wheels. I was thinking if I could get 400-500 in my firebird that I would be happy,, any chance with the 326??

Well, this is what Wikipedia said about the 326

This engine was actually 336 cu in in 1963 only, corrected to a 326 in 1964 For 1963 Pontiac dropped the Olds/Buick sourced 215 aluminum V8 it had offered on the Pontiac Tempest and replaced it with a small-bore version of the standard 389 Pontiac V8. It shared the 389's 3.75 in (95.3 mm) stroke, but its bore was reduced to 3.72 in (94.5 mm), giving it a displacement of 326 cu in (5.4 L). It is interesting to note that the very first 1963 326 engines used a 3.78-inch (96 mm) bore size for an actual 336 cubic inch displacement. In 1964 Pontiac reduced the bore size to what was correct for 326 inches (8,300 mm) of displacement, a 3.72-inch (94 mm) bore. It was rated at 250 hp (193 kW) with 8.6:1 compression and 260 hp (194 kW) at 10.25:1 compression. Both used a single, two-barrel carburetor. The 326 subsequently became the optional V8 engine for Tempests, and later the Pontiac Firebird, through 1967.

A higher-output version was offered, called the 326 HO (High Output). It had a four-barrel carb, dual exhausts, and higher compression, and was good for 280 hp (209 kW) for 1963-1965, and 285 hp (213 kW) for 1966 and the final year, 1967.

IMO the relatively small bore limits the valve size and the ability for the engine to rev particularly high. Big hp numbers are not easily gained.
However, the 326 can be built for good torque to make a fun little driving machine.

IMO you have a pretty rare combination here, given that you have the first-year Firebird and the last year 326. Why not keep it like that?

Firebirds with the 400 are pretty common, but a nice performing Firebird with the original 326 would be a great nostalgia piece.

[chris_Py]

Thanks for all the great info so far! I seem to have run into an issue with Identification of my motor. While browsing ebay for a 400 block, I found a couple and the always included the production number with the motor. Some were YS, some were YR, and one was a YX. Well I looked at my motor, and it has YJ stamped on the front driver side part of the block, above that is the numbers 672659. I have one manual that only show a YJ motor, and that is a 1968 350. I have another firebird book that says it yj as a valid number, along with some motors the WX, WM maybe and some others. Any other ways to identify this motor?
Thanks

[MrPbody]

Chris,

On the rear of the block, next to the distributor, is the date code. It looks like a little tag attached (it's actually cast in). It will have a letter and three numbers. The letter is an indicator of the month of production. The first two numbers are the day of that month. The last number is the last digit of the year. EXAMPLE: D047 would break down to April (4th month) 4, 1967 (in your case, as there were no 326 engines in either '57 or '77).

At wallaceracing.com, there's a big database with all the codes. Yours (YJ), if truly a '67, is a 250 HP 326 w/2-bbl. carb., automatic transmission. Most of the "W" codes are for manual transmissions and "Y" for autos. There are some "X"s out there, and could go either way.

Building 326 for performance is "done", but it is a case of diminshing returns. As MR says, the small bore really inhibits head flow. You get a LOT more "bang for the buck" with 389 and larger Pontiacs. I've never seen a 326 Pontiac built to where it could stand up to a 327 Chevy at the same level of tune. A 400 Pontiac is MORE than a match for a 400 SBC.

Jim

[chris_Py]

Originally Posted by MrPbody

Chris,

On the rear of the block, next to the distributor, is the date code. It looks like a little tag attached (it's actually cast in). It will have a letter and three numbers. The letter is an indicator of the month of production. The first two numbers are the day of that month. The last number is the last digit of the year. EXAMPLE: D047 would break down to April (4th month) 4, 1967 (in your case, as there were no 326 engines in either '57 or '77).

At wallaceracing.com, there's a big database with all the codes. Yours (YJ), if truly a '67, is a 250 HP 326 w/2-bbl. carb., automatic transmission. Most of the "W" codes are for manual transmissions and "Y" for autos. There are some "X"s out there, and could go either way.

Building 326 for performance is "done", but it is a case of diminshing returns. As MR says, the small bore really inhibits head flow. You get a LOT more "bang for the buck" with 389 and larger Pontiacs. I've never seen a 326 Pontiac built to where it could stand up to a 327 Chevy at the same level of tune. A 400 Pontiac is MORE than a match for a 400 SBC.

Jim

F137, so it apears that my motor was built on June 13th 1967! So the good news is that it seems I still have the original motor and 2 speed tranny in tack! I was at the machine shop where I had the 326 rebuilt today to ask him if he remembered for sure if it was in fact a 326 kit that he put in and we got to talking 400 blocks. He mentioned that for one, all these motors use the same block, I didnt think at the time to ask then,, cant we just bore this 326 from the 3.72,, to a much larger 4.12 or so?

[e12Euro]

I highly recommend Jim Hand's "How to Build Max-performance Pontiac V8s", published by SA Designs in 2004. This is by far, the most current study of the ol' Injun. Jim's '71 LeMans wagon weighs over 4,000 lbs. and goes 11.50s all week on 93. 3.55 gears and a "tight" torque converter, this is a true street car.

Since that book stops with the last of the 400s, here's some interesting budget tips for the 301 Turbo.

4.9 Turbo mods

[MrPbody]

Chris,

Yes, that's the date it was CAST.

No. The blocks are not all "the same". The bore spacing, deck height, cam bore to main bore spacing, ARE the same. The bore sizes vary from 3.5 all the way up to 4.15. The castings are different in the bore area for this reason. There's not enough "meat" in a 326 or 350 block to bore them that far. 421, 428 and 455 have a larger main bearing "tunnel" down the middle to accomidate the larger main journals on the cranks. IMO, 400 is the best place to start for a performance build. For a heavier street car, stroking the 400 to 461 is an instant "success". We (CVMS) have many examples out there making 550-plus HP and 600-plus lb. ft. on 93 octane gas.

Jim

[oldgoat8369]

what is cvms is it a shop can you pm me your number or email address I have many questions I need answered

[maxwedge]

Welcome to AF, in the future start a new thread, this is a dead 1.5 year old thread. MrPbody will kick in here as his advice and Pontiac knowledge is number 1!

[MrPbody]

Thanks for the segway, MR,...

CVMS = Central Virginia Machine Service

You can reach me through our website. If your questions are more about building a powerful Pontiac and what's available, feel free to ask here. Many others can benefit if they have similar questions. If you're asking about parts and "work" pricing, etc., it would be better to discuss that "in private".

Jim

www.centralvirginiamachine.com

[e12Euro]

Originally Posted by maxwedge

Welcome to AF, in the future start a new thread, this is a dead 1.5 year old thread. MrPbody will kick in here as his advice and Pontiac knowledge is number 1!

This thead is like the GTO, dead, but the legend lives on!

Mini Goat 350