426?

[chevy19]

what should i get the 426 kit with 10:1 compression or the 11:1 what octane gas should i run and what other mods should be done when boring out the engine also do i have to rejet? thanks

[GPracer2500]

10:1 or 11:1 is your choice.

10:1 is surely OK to run on pump gas. 11:1 is mostly likely OK on pump gas if 93 is available where you live (I can only get 91--arrrrrrhhh) but might be borderline in some cases. Elevation, cam specs, and ignition timing (CDI or timing key) can push you one way or the other on that. I'd think at the worst you might get a little detonation at 11:1 under high load, high temp circumstances. If you did, that could be rectified with a mild race/pump mix.

The 10:1 will yield less torque than an 11:1 but the 10:1 will put less stress on the engine (rod, crank, less heat, etc.). Punching your rod through your case gets expensive real fast.

I'd probably go with HD head studs either way. I'm guessing you could get away without them running 10:1 but it'd be good peace of mind. I ran a 10.5:1 406 for 5 years on the stock studs before my head gasket blew. My current 10.8:1 416 has HD studs and an O-ringed sleave. No way I'd run a 426 at 11:1 without at least having HD studs.

I would definitely get a cam. Stage 2 variety would be a good choice but even a stage 1 would be worth doing, I think.

Air scoops and perhaps other cooling aids would be a very good idea (plus air scoops look cool!) for keeping the heat under control.

You can bore the stock sleeve for a 426 or you can re-sleeve. With a re-sleeve you should wind up with a thicker sleeve than just boring the stocker (I think) and that aids reliability. If you just bore the stock sleeve than controlling engine temps becomes even more important.

If you're going from a stock piston to a 426 you'll absolutely need to rejet the carb.

If your current engine has lots of hours on it than a rebuild is a good time to check your valve springs, valve faces, and valve seats. When I rebuilt mine I had significant wear in some of those items. Intake valves seem to take a particular beating--I needed two new ones. And if your checking those items out than don't forget new valve stem seals.

That's what I can think of at the moment.