[chris everitt]

motor ID
ive looked thru the wallace database and all the numbers on my motors dont match up. engine code, engine date code, and block casting codes.
please see info below.

motor1. WS / F059 / 9790071 - block only has 2 motor mount holes
motor2. YD / K119 / 9799914
______________

ive got two sets of heads and i would like to know which would be better for a mild street engine build (375-400hp). i plan on port matching the heads to a performer intake, and i will get new pistons if needed.

heads1. 1975 400 185 HP 5C 2.11/1.66
heads2. 1970 400 290 HP YD 1.96/1.66 10.0cr /16 /sm valve /64 Block Casting 9799914

notes:
heads1 97cc
heads2 86cc
heads2 the rocker arms get oil thru the rocker arm pressed studs - not a good design
heads2 require hardened valve seats

[steve25]

Both motors are 400 cid, the first is a 1968, the other is a 1970.
I would build the 68 if it does not have the mains taped for four bolt caps as it will be stronger than the 70 block which most likly is taped.

I would run the 5C head, rebuilt with new guides and valves, with the exh stepping up to the 1.77" size and hardend exh seats going in the head.
You will need to mill the head both deck and intake face to get the motors comp to 9.2 to 9.4 and no more!
Since this block only has 2 motor mount bolts per side you can not bolt it in a 70 and latter firebird body with out adp plates.

[Mr. P-Body]

A couple of things here. The "F059" date code indicates June 5, 1969. That makes that YS a '69 350-horse 400, GTO w/auto trans.

The 16 heads are not as desirable as they COULD be, as the chamber size is good, but pressed studs and small valves is "bad". They don't oil through the studs, though. Even with the holes there, those studs are "leftovers" from the '64-back production. They oil through the pushrods from '64 (GTO) on.

With screw-in studs, large valves and some judicious port work, those 16s are "better" for a 400 than the 5Cs. The 5Cs would be better on a 455-plus CID engine with their larger chambers.

"Hard" seats are only required if the seats are "receded" or the engine will be subjected to high-load operations. Towing, "lugging", etc. A good valve grind will take care of the heat disapation (.100" wide seat, 45). It's a "myth" that ALL pre-EGR heads REQUIRE hardened seats.

Jim

["QUICK-SILVER"]

F059 WS Block code 9790071 is RAIII 400.
Use either block, both are good, just use the one you need with the motor mount bolt pattern for your application. Holes can be drilled and tapped in the 70 block if they're not already done.

Raising compression with the 7.6 CR 5C heads would require more work than 16's, and Since you don't mind buying pistons, a custom dish with the 16s could drop you into a good pump gas friendly power making range. As Jim said, the 16s could stand some work. But even as is, they were 290 HP with 2bbl, with 4bbl and duals they're closer to the 330 HP range. Work the 16's and pick the right cam, your HP wishes should come easy.

Run your numbers again, they're all good at Wallace Racing!

[steve25]

Al things being equal ( valve size flow and compression) the 5C heads make more power due to the smaller openings of the exh crossover passage on the center two exh ports!
Oil temps also run cooler due to the air gap hole above the crossover passage.
If you step up to the 1.77" valves in the 5C heads cutting the seats to fit the new valves will cut thru the factory induction hardening and and make the need for seat incerts a MUST!!!

[Mr. P-Body]

Sorry, I missed the "WS" thinking it was "YS". 366 HP is correct. Manual trans, as well.

Steve,

At the risk of causing "issues", first, cutting the .110" extra will NOT go through the induction hardening. One can clearly see the change in the metal color as you cut. Second, we have HUNDREDS of stockers and mild performance Pontiacs out there with the earlier heads (pre-EGR) without hardened seats, running thousands of miles without issue. Installing hard seats can be becessary, as said before, IF there is previous damage OR the engine is going to be "worked" or lugged. High performance engines don't require them "just because".

Jim

[chris everitt]

thanks for all info, please keep adding stuff. i especially like the part P-body mentioned about the rocker studs left over from 64, good info.

does the 5C heads (1975 egr) have hardened seats from factory?

[chris everitt]

thanks to all for the info.
please note i know very little about pontiac motors and this forum and members provide a good opportunity for me so i will be able to meet my project goals of ~400hp with my first pontiac 400 75 t/a build! please feel free to correct me if you see anything of interest.

here is my take on the build so far____

heads i need to buy new pistons anyway, so it seems more reasonable to increase the compression with pistons (9.5-10.1) and use the 5C heads instead of completely rebuilding the #16(small valve 2-bbl) heads. after all i believe all i need to do to the 5C heads is increase the exh valve to 1.77", do some port matching and they are ready to go. the #16(small valve 2bbl) heads require hardened seats (my opinion is non hardened seats under normal wear will go 30,000 miles), larger valves, and screw in rocker studs. alot of work for not much gain as it seems!

cam 5500 to 5800 rpm.
please feel free to suggest suitable cam. considering comp cams 268 series.
car will be weekend driver with a/c & pwr brakes, but i want to hear the cam.

car 1975 t/a, automatic, 4200lbs, stock quadrajet, performer intake, no cat, no egr, 1&5/8" headers, 2.5" exh, 2.5" flowmasters, 3.23 rear differential, 350thm with stock converter

[runningbwdog]

Hi,
I have a Comp Cam XE-268 hydraulic in my 462. Quite mild, no lope to the idle. Tons of low end torque. Dies off in excess of 5200 rpm.
You may want a XE-274 to get what you want.
9.2-9.4:1 compression is all you can stand with 93 Octane gas.
#16 heads can be the 68 GTO variant with large valves. I'd measure them just to be sure. Should be 2.11 intakes and 1.77 exhaust.
Mike

[chris everitt]

hi Mike, thanks for the quick reply and good info on the compression ratio tip. i believe cr and cam selection must be carefully matched. and unfortunately the #16's i got have 1.96"/1.66". ---- but they are perferctly good heads and they may be better for my application for all i know!

[runningbwdog]

Hi,
The 1970 455 with #15 heads was rated at 370 hp for what that is worth
I have a set of #15 on my 462 with the XE-268 cam. Had the exhaust valves replaced with 1.77 in. Engine has great low end torque. I just don't push it beyond 5200 rpm. . I'm running 9.34:1 compression and BP, Shell and Chevron 93 octane runs fine at 12 initial and 34 total advance.
Mike

[GTO JOHN]

Chris, I think either block is fine for your build and in fact you could sell that F059 WS code block for more than the YD code one, so using the YD for a non-stock buildup makes sense.

I- am interested in that F059 WS block for my '70 Judge if you decide to sell that block please PM or email me.

Sounds like you have a nice engine setup so far.

Thanks, John