I thought I’d share details about a few of my customer builds.

426" 651hp 91 pump gas 12.75:1 compression Small Block Street/strip Motor

340 X block with splayed billet main caps and ARP fasteners, bushed lifters, decked/squared to 9.585, align honed, stroker clearanced (machine work performed by DRAM Dan Costello (RIP) at Performance Only in Florida)

360-1 Indy heads ported by Dwayne Porter, with Harland Sharp rockers, PAC-1325 springs

K1 4.125 stroke crank with Chevy rod journals

Callies Compstar H-beam rods 6.200”

Diamond Custom forged pistons 4.060 bore, 1.308 comp height, Valve relief volume -6.7

Indy 360-1 Intake also ported by Dwayne Porter
Hughes Engines custom street/strip billet roller cam .656/.672 269/275 108 LSA installed at 105 and solid roller lifter designed specifically for this build with 12.75:1 by Dave Hughes (Dave actually spec’d the compression, I ordered pistons after we designed the cam for this motor)

ProSystems custom built 4150 carb

TTI headers for E body

Made 651 hp and 585 torque on the Dyno with 91 octane pump gas, will make 700+ with race fuel and more timing (Dyno’d with only 29 degree timing)

I was really nervous about the 12.75:1 compression but I decided to trust Dave and his years of knowledge and ended up very pleased. Our goal was 650hp with 91 pump gas and the use is 70% street and 30% strip.

Link to all the build pictures: 426 Build pictures

12.75:1 on 91 pump gas Hmmm!

Magic is in the cam

Now that is cool!

The 29 degrees total timing helps too but if the owner gets greedy or a bad load of gas all heck could break loose. If he’s the car show type like lots of guys are and just wants to talk horsepower numbers at the shows it could run forever.

Very cool small block, should run good.

congrats, nice looking engine and project. Lots of people get hung up on static compression numbers, the real factor is dynamic compression or cylinder pressure the engine sees while running. years ago I built a couple engines for pulling truck where the rules required pump gas, they had 13 to 1 pistons, but performed very well and never burnt a piston. Only advice I can give is make sure if you store the car, you realize that the 91 octane fuel might be only 85 octane when you fire it up after sitting. Pump gas tends to evaporate out the lighter components of the fuel and go bad a lot worse than it used to. I had a buddy that burnt a piston on his street blown motor because on a warn day after sitting all winter he ran the crap out of it with stale gas.

True on the gas sitting.

I wouldn’t recommend building a street strip motor with this much compression but to get 650hp out of the components we had, we had to push some limits. We started out thinking of a super charger but that would add $4k to the build so we settled on the 650hp goal on pump gas. If he wants to get 700+ hp at the track he can add in some Q116 (oxygenated), bump up the timing to 36 and let it eat.

As it turns out it’s still in my shop and for sale if anyone is interested but it’s not cheap.

Sent PM

What do you think you would have made if it was a non-roller cam?

Can you provide any flow numbers on the heads?

Thanks.

You would probably loose 20-30hp with a hydrolic roller.

I’ll look for the flow numbers on the heads, they aren’t fully ported, it was like a stage 2 port job

Nice performance numbers, not sure id be comfortable running it on pump gas any higher then your timing is set. But I know you know that as well. Did you do a cranking comp test? My calcs on your DCR is at 9.40 Typically with a 9.4 comp, cranking psi would be around 140/150.

A bump in case you missed my last post ? Wade.

No, I didn’t, but I know Dave used that (projections) in his calculations when designing the cam and told me what compression we needed as I ordered the pistons.

You gotta love those stealth small block killer motors!! Nice work on a nice piece!!

Very nice build!!!

Very nice!