Pontiac 455 build

[1980Ttops]

I have a pontiac 455, would like to be in 400-450hp and 500tq range. For my 1963 Catalina 3.23 gears
Parts that I have,
#62-75cc, done with comp springs for xe284
#7k3-96cc, only 4 exhaust bolt holes
#46-96cc, screw in studs w small valves. All measured #7h1 4 bolt exhaust, pressed studs, big exhaust valve
#4X-H pressed studs, small valves
Cams, #041, xe 284, lunati bm 292, lunati sm 295
Intakes, pmd 4 barrels, performer, torker, torker2, hurricane (tomahawk knock off)
Carbs, quadrajets, 600 & 750 edelbrocks, holley 750
Distributors, HEI, points, dual points, cheap HEI
Trans, 350th, 400th, 200 4r
Which combo to make the most power and reliability for mostly street with some track runs. More concerned with usable tq than peak hp. Have built mostly 400's with 12,13 & 16 heads, 068 & bm 292 cams. Long post but wanted to include as much info as I could

[mag2555]

It will be very difficult to top 420 hp with either of those big valve heads in stock form that you listed , even with a 9.5 compression.

In terms of the other small valve heads you have, forget about making even 380 hp with there well less then 200 cfm of intake air flow!

They would need to get the 1.96” valve removed and a 2.11” valve installed and a minor bowl porting job done to get the throat up from 1.48” to the big valve size of 1.60”.

Also with the lift you will be running to top the 350 hp mark you will want any iron head you run to have screw in rocker studs!

[1980Ttops]

The 7k3 has the 2.11 & 1.66 valves and screw in studs, not enough material on end exhaust ports to drill & tap for header bolts. The 46 heads have all 6 bolt holes, I can have big valves installed in them. The 62 heads are real good heads, just to much compression with flat tops. My T/A runs great with 400 +.060, 15cc dish pistons, 13 heads gasket matched with felpro 1233, some porting work by Wasserbecks, bm 292 cam, rpm intake (gasket matched) and a quadrajet. 2300 converter, 3.23 gears. Was thinking kind of the same approach for the 455, 9.5 compression, some mild porting and gasket matching. It's +.030 & deck height is at .010 so if I blow it up it can be rebuilt again. Short block is done so I don't want to change to dish pistons to use the #62 heads

[mag2555]

The 7K3 heads do have enough meat in the head bolt boss to drill and tap for fine thread 5/16” grade 8 studs which is enough to seal up that side of the header tube .
Just make sure to drill and tap dead on the angle needed and then only tap deep enough to not allow the 5/16” stud to touch the shank of the head bolt.

If you or a friend can weld then it’s also helpful to tack weld the studs in two opposite spots, and then grind that back to not interfere with gasket sealing.

I think Paul Spots makes a kit that uses rap around bolt on brackets to do the same basic thing, but I think the grade 8 studs will seal better long term!

[1980Ttops]

Thank you for the info. Looking at them I thought 3/8's holes would leave it way thin, hadn't thought of using 5/16. Hate a leaking header. I'll bolt manifolds to them, grind a point on manifold bolt and use it as a punch to mark them. That should center them as close as possible before I put them in the drill press. So the 7k3 heads, which of my cams would work best? The ram air 4 041, the bracket master 292, the xe 284? The street master 295 may be higher in the rpm range than I want. If there's a better choice, I'm all ears, I'd rather have it right the 1st time. I'll buy another HFT, roller for pontiac is quite pricey

[tjs44]

Just me but I hate headers on a street car.I would run the Long Branch exhaust.I would run the a Performer RPM with a good QJ and more like a 722 cam.The 041 would not be a good choice with your rear gear and such a heavy car.Tom

[mag2555]

With 3.23 gears you do not want to run the RA4 cam without Rhoads lifters, and the 744 cam does not have the needed valve lift to get the job done in a 455 !

If you staying with those gears and want a drive it anywhere and long distance to boot, then you do not want a Cam of over 225 intake duration @.050” especially if your fighting to get just a compression of 9 to 1!

I will dig out a chart I have later and post it up for you that is dead on in terms of a true every day drive to work if need be street car.

If this is not your intent then please detail what your goals are more!?

[PRH]

A local build from a couple of years ago.......

455 with 4.25” stroker crank, bowl blended 64 heads, RPM intake, 850 carb, headers, XE274 cam.

Made 530-ish Tq, 430-ish HP.

[1980Ttops]

Want to mostly cruise the car, run at the track a few times. I'm ok with the Rhoads lifters the tick doesn't bother me. Or installing a vacuum canister. My original thoughts for it were the 7k3 heads, 041 cam, rpm intake, cliff ruggles qjet kit. It's a manual brake, non a/c car, will get power disc for front. Sources I've found say curb weight is 3685 lbs. It now has fiberglass hood and decklid. Always willing to learn from others and the advise is appreciated, unless some one tells me to put a chevy in it. Just can't do that

[1980Ttops]

PRH, those numbers are about what I'm shooting for

[mag2555]

Here’s the chart I spoke of.
Note that the Cam and gearing suggestions where with compression ratios above 9.5.

I would install any Cam 2 degrees advance just to comp for normal chain stretch at high rev’s and over time.

[1980Ttops]

Thank you mag2555. Gonna go with the 041 w rhoades, 7k3 heads, rpm intake. Gotta call cliff and get a qjet kit. Fabcraft has 3.64 gears for the 9.3 rear. If it runs 13's I'll be happy

[1980Ttops]

I have a set of Harland Sharp roller rockers 1.65 ratio. Also have some roller rockers that came on a 400 I bought. No idea what ratio, only markings are PSP on them. The only info I could find were chevy applications for PSP with no specs listed

[mag2555]

While the heads are out getting rebuilt be sure to have the machine shop run a 1/2” drill bit at least 3/4s the way down all 8 intake push rod holes for safe higher lift clearance.

This is much faster then grinding them out at home and is needed many times with the base circle of the RA4 Cam and with 1.65 rockers at times, and for sure with the stock 1.5 rockers.

Speaking of push rods if your topping 280 psi of open spring pressure then the factory push rods are likely to fold up on you at high cycling rates so aftermarket ones will be needed.

The factory used 318 psi of open pressure @ .520” lift with the RA4 Cam, and consider that the max for Cam and lifter lobe life that they could warranty.

With this Cam and a 455 I have found that a good safe starting point for timing with Rhoads lifters and the engine hot is 8 BTDC, 24 Centrifugal with a 12 to 14 degree vacuum advance unit with it all in by 12 inches Hg.

[1980Ttops]

Good info on where to start with on the timing, thank you. When I was 16 (30 years ago)I learned that stock push rods & stiff springs don't get along, after learning stock springs & a high lift cam are a no go on my first engine build. Taught me to spend the money and do it right the first time and to seek as much info as possible before spending that money.