[steve25]

It was proven way back in 1976 by HO racing ( I think it was 76) that the SD455 in the F body lost up to 90 hp thru the off the show room floor exhaust system.

If even back then you built a D ported headed 455 with the 744 cam and headers , along with a 2 1/4” exh system you where making more power the the show room floor SD.

[77 TRASHCAN]

If you have the skills to replicate Jim Hands 455 in his book, that's a brutally powerful engine, yet still streetable.

[PAUL K]

This a great budget build. It will work with a stock torque converter, out run a factory built SD-455 and responds well to Rhoades lifters when using a two series highway gear. It was a straightforward basic build with the most exotic part being the 1966 tri-power. A 73 455 two bolt main block with original cast crank and cast rods were used. Other than basic blueprinting we used Sealed Power forged pistons, ARP rod bolts, Moly rings and a Melling M54DS oil pump. The camshaft was a single pattern HFT from Lunati featuring 292 adv. duration, 230 @ .050, .490 lift and a 110 LSA. The compression ratio was 9.8 and the engine uses 93 octane. The heads are small valve 1970 casting 15 which were stock with the exception of a gasket match (std size gasket) and a good flowing valve job. The rocker arms are Comp 1.5 rollers. A factory points distributor with a Pertronix kit was used. We didn't do any tuning at all. Just wanted to break in the cam, make sure the engine made decent power and didn't have any oil leaks. We were happy with the almost 525 ft-lb of torque and nearly 425 horsepower all below 5000 rpm.

[android 211]

I recommend new forged rods from now on. Last year I had a mild 455 built and it grenaded after about 30 miles. After I took it out to examine it, it was clearly a stock rod failure. I took off the oil pan and the rotating assembly is jammed from a broken rod. The rods had new ARP bolts, it was balanced and the rods were resized on the big end.

[PAUL K]

Originally Posted by android 211

I recommend new forged rods from now on. Last year I had a mild 455 built and it grenaded after about 30 miles. After I took it out to examine it, it was clearly a stock rod failure. I took off the oil pan and the rotating assembly is jammed from a broken rod. The rods had new ARP bolts, it was balanced and the rods were resized on the big end.

Maybe they missed that rod when they were Mag'd

[Dragncar]

Originally Posted by android 211

I recommend new forged rods from now on. Last year I had a mild 455 built and it grenaded after about 30 miles. After I took it out to examine it, it was clearly a stock rod failure. I took off the oil pan and the rotating assembly is jammed from a broken rod. The rods had new ARP bolts, it was balanced and the rods were resized on the big end.

I just think these engines cost too much and we speed too much times and effort to use cast rods in performance builds. 500 $ on cheap forged rods is money well spent IMO.
I know people use cast rods and they do their job. But IMO the biggest problem PMD had was the cast rods. We would have many, many more blocks available if Pontiac just used decent forged rods.
In High School we were a bunch of Hot Rodders. I was the only Pontiac guy and we all talked $h!t about the other brands. Cast rods were the biggest come back from the Chevy, Ford and Mopar guys.
So I still hate them.

[tempest1964]

If you do go with aluminum round port heads, it is not difficult to stealth them. Here is an example of KRE d ports, stealthed to look like 0716 heads:

[67Lemons]

Originally Posted by android 211

I recommend new forged rods from now on. Last year I had a mild 455 built and it grenaded after about 30 miles. After I took it out to examine it, it was clearly a stock rod failure. I took off the oil pan and the rotating assembly is jammed from a broken rod. The rods had new ARP bolts, it was balanced and the rods were resized on the big end.

I’m going though this as we speak, I just dropped off my 455 to my local machine shop to replace the rods with forged units even though this was a perfectly running engine recently rebuilt prior to my purchase. I just didn’t want to think about it every time I dumped the clutch or did something stupid.

[SD455DJ]

Here's another 'budget' 455 build very similar to the one Paul K. listed earlier. This is a '70 YH 455 (rated at 360 hp/500 lb-ft torque) with the small valve #15 heads. The block is .040 over, stock stroke crank, Eagle H-beam forged rods, 9.94 to 1 compression (90 cc chambers with new Ferrea 1-pc valves with stock 45 degree seats/street valve job, pinned pressed-in rocker studs, and used the 1.50 factory stamped rocker arms. The cam is a Summit 2802 (224/234/114 @ .466"/.488" lift) and flowed through factory log exhaust manifolds. Used the factory iron 4-bbl intake and Q-jet carb. We didn't touch any of the ports on the heads, intake, or exhaust manifolds. It made 390 hp at 4600 rpm and 512 lb-ft torque at 3400 rpm. It just needs the SD455 valve cover decal, late '73 engine paint and RA manifolds to look more like the SD...can't mimic the center exhaust ports, but will fool most folks who don't know the physical difference.

Dennis

[steve25]

The KRE heads look good especially in the early powder blue, but the deleted air injection boss below the valve cover plane is tuff for a Pontiac guy not to miss.

[sdbob]

SD455 Dyno sheets showed that factory exhaust at least lost 75-90 hp. Significant gains in hp with cam lifts over .500 compression around 11-1.