71 T/A 455 HO build

[Will B]

Hi all, Great forum! thanks for having me!

My new engine is nearly ready for assembly. The builder is a knowledgeable Pontiac guy down here in Georgia. This is what we have so far-

71 WC 455HO, 197 heads, factory aluminum intake, stock stroke, 30 over Butler rotating assy, forged crank, Eagle rods, Ross pistons with slight dome to get 9.3 compression. Heads are port matched and bowls blended. Because of shortages on every other cam that I was looking at, we ordered a Melling SPC8 RA4 cam. I'm comfortable with the choice, and it will keep the build moving along. We plan on using 1.65 full roller rockers with regular lifters.

I have a new Tremec TKX with 2.87 first and .68 5th gear. Car has a 3.08 rear.

Plan to use Dougs or Hooker Super Comp headers with 2.5 in X-pipe exhaust.

I have two loose carbs.
69 RAIII  28270
70 RA 7040570
I also have access to a genuine 7041273.
Thoughts?

Rhoads lifters? I know some people love them. I talked my self out of them after reading a lot of opinions about the noise. I think it would bother me. I would reconsider if they make a big difference in performance and drivability.

I was happy with the old 455 that I had before. It had stock rods, forged TRW pistons, 96 D ports, Ultradyne 288/296 cam, Holley 3310 on a performer intake, Super Comp headers, 2.5 in exhaust, with a Doug Nash 5 speed. I drove it daily. It was trouble free and ran great for years. Sounded great too.

If you're still with me ...thanks for reading all this! Any input would be greatly appreciated. Will B.

[Cliff Ruggles]

Rhoads lifters are excellent parts and really help with that much camshaft (seat timing) in a 455 build with lower compression.  With over 80 degrees of overlap I really don't see them optional for what you are doing and I would use them.  Get the V-Max variety as they are limited travel and you can tight lash them with less plunger travel to have full and precise control over bleed-down and noise a the same time.  I would also degree the cam to 109-110ICL, most likely "dot to dot" it will come in closer to 112.

I've never found Rhoads lifters loud enough to pay them much mind and use them in every flat cam Pontiac engine build we've ever done here with perfect success.  I'd also avoid using really strong springs on the Melling RAIV cam.  It's has much slower opening/closing ramps than the currently available aftermarket whiz-bang stuff and very easy on the valve train so doesn't need a butt-ton of spring pressure to keep things in check.  I can't make an exact recommendation (not enough info) but my go-to springs for Pontiac builds here are the Crower 68404's (1.600" installed height) and 68405's (1.700" installed height.  Both have pretty "normal" spring loads and plenty of room for extra lift at the valves when you go to high ratio rockers on the RAIV cam.

Without question get the 7041273 if it is a genuine original 1971 455 HO 4 speed carb.  It is a better choice than the other two and perfect for hat you are doing.

The new build will make impressive power, have done a lot of them here.  Without much effort and a cam with at least 230 @ .050" on a 112-114LSA you'll be at least 1hp/CID and 525-540 torque........Cliff

[Will B]

I'm glad I came here so you could set me straight.
Hopefully I can find some Rhoads V-Max part 9518x.
Thank you for sharing all that. Your last paragraph got me pretty fired up!  -Will

[Cliff Ruggles]

Below is a dyno sheet and cam card for a 455 Super Duty I did here a few years ago. 

Flat top pistons, zero deck height, probably 8.5 to 8.8 to 1 compression.

The cam is a small HR, 230/236 @ .050".  It was very "mild" in that build, making plenty of vacuum and smooth idle clear down to 600rpm's with only 10 degrees initial timing.....

[Will B]

Impressive numbers! Low compression with a "mild" hr cam wow!

I've been into Pontiacs since High School. (1985) Lately it hit me that I've only been through this process a couple times. Fact is I'm just not as knowledgeable on engines as some other aspects of the hobby. This engine build might be my last, so I want to get it right.
I consider my engine builder a best friend. This 71 WC has a story unto itself, and it's somewhat sentimental to both of us. Once the short block was close to completion, he asked me to do some research / pick a cam. This is probably so I would feel like I had a part in the build. He specifically mentioned you Cliff when he told me to start reseaching. I am thankful for your help and reassurance. I plan to keep you updated and I'd appreciate any further input. - Will

[Will B]

  The 041 cam arrived last week. Still have not located any in stock vmax Rhoads lifters.. I received some pictures of the 7041273 today. My buddy decided he couldn't sell it, but he offered to "let me borrow it indefinitely."  !!!  Normally don't like to borrow,  but this time I'll be making an exception. Hopefully my pics will load. It's a real beauty. Will

[Cliff Ruggles]

Cool, looks like a "survivor", mostly all there aside the fuel filter housing.  Even some added parts from a mud dauber.

Rare and valuable carb for sure.  They didn't make any 4 speed units as Service Replacement carbs that I've seen, so the production numbers were limited to how many manual transmission 455 HO's they made that year.......

[Will B]

Wow I didn't know that there aren't any known SRs! Those dirt daubers were trashing it up on some prime real estate. I already knew the number of HO F body's with manual transmission. When I checked the production numbers on GTOs, I was surprised that there were so few. They say 476 hardtops in an article that I read on Hemmings. I know there are different opinions about which cars got 267 or 273 carbs as well.  Will

[Cliff Ruggles]

Rocky Rotella may know the production numbers and where each part number was used.

If you look at posted literature the 7041267 was used on the 455 HO engines with manual transmissions and "non Ram-Air".

The 7041273 was used on 455 HO engines manual transmissions for Firebirds and GTO's WITH Ram Air.

That makes for confusion and some controversy depending on what cars you could order that year with the 455 HO engine and manual transmission and whether or not they had a "Ram Air" option......

[Will B]

 

[Will B]