455 engine build for 71 Grand prix
 

I'm looking to build a 455 +30 for my 71 GP. I will be running 3.55 gears on the street/cruising with occasional drag strip trips . I have accumulated an array of parts and looking for some input as to the assembly of such.

71 455+30 stock crank and new 6.6 and 6.8 forged rods looking for thoughts on the rod choice. I have not selected the pistons as of yet but the heads are SD Performance worked over cast iron 6X flowing 265 cfm intake and 200 cfm exhaust with 90 cc, with the crossover filled and Harland Sharp 1.65 rocker arms.
Thinking 9.5-10:1 compression (everyone's go to compression numbers it seems) I have a stock 1971 intake and a Edelbrock RPM to choose from for the intake with for the Mixer I have been looking at the Holley Sniper fuel injection long term but will start with the Cliff built Q-jet that is on the car presently.
Now the Can of worms I have an old cam from Crane and looking for input from some of the more educated than me, on this ....and everyone has an opinion let's hear them! :-) I have attached the Cam card for review I am interested in hearing which way you are leaning. regarding the rods, compression, intake and cam. As far as the transmission I currently have 700r4 with a 10" tight Continental 3200 stall. Looking for input and reasoning for the decision please
Thanks

That 71 B body is over 4K pounds no?
I think a Cam with those duration numbers will kill off too much needed average torque even in light of your running 3.55 gears out back

'71 intake won't work with 6X heads, unless the passenger side blind hole is filled, tho some say that a piece of thin stainless, in the correct shape, will make it work.. '72 intake will work. and the RPM will work.

With the 1.65 rockers, an 041 clone cam with Rhoads lifters has been a very popular combo, for many years. Don't know how much lift you wanna run. But, if the cam has .500 or more lift with 1.5 rockers, that puts the lift well over .500, with 1.65 rockers. The stronger springs required for bigger lifts might cause more stress on the entire valve train, which many consider unnecessary with a mild to moderate street car.

If most of your driving will be under 5000rpm, a cam/rocker combo with around .500 total lift, might be plenty, and easier on the valve train. But then many here don't want any power left on the table. So, it mostly depends on what you want.

A Lunati 10510312 will have near .500 lift, with a little over 220° intake dur @ .050 lift, using 1.65 rockers. Should make great low end torque, vac, and plenty of power to at least 4500rpm. Max hp ? No.

If my math(using a calculator) is correct, the intake lobe of a Howards 410051-14 cam would have .528 lift with 1.65 rockers, the exhaust lobe of a Summit 2802 cam will have almost .537 lift, with 1.65 rockers. The ex lobe of a Crower 60243 will have aprox .543 lift. The ex lobe of a 268 Voodoo will have aprox .554 lift. The ex lobe of a 276 Voodoo will have aprox .580 lift.

Just curious as to how much total lift you want or would be OK with.

I believe a 700R4 has a ~3.06 first gear ratio. But second is a big spread @ ~1.63. Not ideal but it will get 2+
tons rolling out of the hole.

The 3200 stall will truncate the torque loss below that rpm.

I would use the shorter connecting rods. When octane is NOT a limiting factor, use a longer rod (more dwell). But if using pump gas and pushing the limits of CR, use a shorter rod.

Should be a fun combo. Well tuned and with ample traction, should be capable of breaking into the 11's.

That cam is very similar to the Wolverine Cam Jim Hand used to run. With a CR of 9.5+, and heads that flow that well I think it's a great choice. Run Rhoads lifters on it. The low first gear of the 700-r4 and the 3200 stall converter will get that car moving just fine.

A note on the lift & rockers though - the HS 1.65 ratio rockers are actually closer to a true 1.7 ratio. You're going to end up with right about .572 lift on the exhaust side. That's a lot. Give careful consideration to your valvesprings or use some different rocker arms. I like the high ratio rockers and would use them if I could, but not if finding springs that will work with the rest of your parts is a huge headache.

I would research the cam , don't pick one that makes the car miserable to drive.

What are you running on the exhaust side?

For 15 years, I ran the following combo in my '70 GP: 455 +0.030, KB pistons, stock crank and rods, Ultradyne 280/288 (223/231 .463/.485, 104 ICL, 110LSA), 98cc 4X heads with competition valve job, Edelbrock RPM intake, Holley 4150 750 cfm Street HP, short branch Ram Air exhaust manifolds, full 2.5 mandrel bent exhaust with x-crossover, TH400 w/13" Continental, 3.42 rear, 28" tires. Stock fuel system. No porting, no port matching, no balancing, no blueprinting.

That combo was good enough to propel me to 13.0 at 99 mph in triple digit heat. The car produced incredible torque, frankly too much torque, but was all done really by 4800 rpm. It was quick but also could easily nuke the tires.

Similarly, I ran the following combo in a '78 Catalina wagon (similar curb weight to the GP): 455 +0.030 TRWs, stock crank and rods, 041 cam (231/240, .470/.470), stock lifters, 90cc 6X heads with same competition valve job, Edelbrock RPM intake, short branch RA manifolds, full 2.5" mandrel exhaust with crossover, TH350, don't remember the converter, 3.08 rear, 27" tires. Stock fuel system, no portwork, etc.

Running head to head with the GP, that car was not as quick early on but did not take long to blow by it and keep going. Even with the bigger cam and less gearing, it had monstrous torque and really did some damage on the street! At freeway speeds, it was a real beast. Seeing the embarrassment of either getting smoked or not being able to run away from a maroon with red interior station wagon was fun to watch!

Both ran on premium pump fuel without problem. IIRC, the GP was about 9.25:1 and the SW about 9.5:1, and either could be +/- a bit.

I would think that the ported heads you have would solve the breathing issues that my GP had and provide upper end power without resorting to a larger cam the SW had. Add your larger cam and your heads, and it sounds like you have a winner.

Yes, agree will be great.

Excellent camshaft for a 455 build with ported factory iron heads. As mentioned it is similar to the old Wolverine 5059 cam, and will be a LOT happier with 10 to 1 compression vs 9.5. That little bit of difference really helps with idle quality and vacuum produced at idle, and improves it's street manners as well. I've seen that cam make great numbers on the dyno is relatively "mild" 455 engine builds, all of them were using heads with at least 240cfm intake flow and at least 10 to 1 compression......Cliff

That cam seems to be very nearly the same as the Wolverine 5059 (Wolverine was a Crane off shoot company, I believe...) AND the cam that Jim Hand last ran in his wagon, before he and the wagon retired...Jim?

‘69-‘77 GPs are “G” bodies. The “B” body GPs ended in 1968.

Hello and thanks for the input,
Steve25, ponyakr, steelcityfirebird,Will I already have and running a 041 clone cam in now from Ken Ace Brewer PPR with the Rhoades lifters and SD Peformance setup the heads with the 041 clone in mind (but I will need to go back and check to make sure they will handle lift or I may look into other options for the rockers thanks for the reminder), along with the stock 71 intake so neither of those are a issue in my opinion. I think with the low first gear 3.06 plus the converter aren’t perfect… but do work together and the butt load of torque help elevate many issues. ;-) The 1971 is a G body not the B model, mine has a chevy 12 bolt rear end and I have the 3.07 gears now and it’s fun to play with, so the 3.55 will be an upgrade for sure and should move that 4XXX lb car around quite nicely.
Lee I always appreciate your input I always enjoy your comments and I have read a lot about your cars over the years on here…it’s all about the little things for sure. The rod thing is interesting because everyone was going to the longer rod so now I know what to look out for thanks.
For exhaust I’m running the log manifolds and dual 2 ¼ out the back but, I have the Tri-y from Ron Watts and plan on running the 3” back to X or H pipe to 3” Dynomax 17959 I have or Dyno Ultraflow, Super Turbo to 2.5 tail pipes… I like to speak softly but carry a big stick
Cliff I’m the great state of confusion Calif. And this cam only has 70° overlap , the engine will be 0 decked but we have watered down E85 here…. I am not sure if I want to chance the death rattle but I hear ya! What’s your thoughts on the overlap?
Jim

With our crap gas and where you live I would not push CR past 9.5.Im sure your avg summer temps are over 100.JMO,Tom

I'd even lower that to 9.3:1 with the great state of california (lower case on purpose) garbage fuel they call gas. Lots of engines built around here for comparison, and anything higher than 9.5 gets the can of marbles going under the hood regardless of timing tweaks and carb jetting when the temps and fuel take a turn for the worse. Bart stuck to 9.1:1 with his 421 build and he won't be hurting for horsepower.