mesterious

iTrader: (1)

Well i have a question.. i have a 86 camaro and im going to do a swap on it and i see a 400 SBC block and its bored 40 over.. i see alot of people saying they wouldnt go over 30 but i see guys saying they have bored to 40 and they run pump gas.. and i just want to know some combos or things that i would have to do to keep it at a low enough compression ratio for pump gas..

Shadow Z

iTrader: (2)

All you'd really have to do is get some decent aluminum heads with bigger chambers. I wouldn't even go .30 over though. I've had aboslutely no luck with bored engines. I stick with stock bores now.

Atilla the Fun

For a 400 horse street driver, there's nothing wrong with a 40 over 400. Just be sure to choose dished pistons. If you'd like more advice, then you need to decide which heads. I suggest Dart Pro 1 Platinum 200s or AFR 195s, but if those aren't in the budget, how about some Dart Iron Eagle Platinum 200s?

AlkyIROC

The cylinder walls are very thin on a 400 SBC. Going .040" over is pushing the limits. Chances are, if it went to .060" over, it would hit water. Those thin walls allow flexing and distortion. In a race engine that's been pushed to .040, the block is usually filled with block cement to stabilize the cylinder walls.

My BBC Dart block has very thick walls. If my engine ever gets bored out .100", the walls will still be .250" thick.

Compression ratio builds torque. Too much compression ratio and fuel can start to self ignite (detonation). To decrease the chance of detonation, you increase the octane which slows down the burn speed of the fuel.

When you say pump gas, there's usually a couple of different options. Running on the lowest octane of 87, the compression ratio needs to be low. Probably not much higher than 8.5 to survive. Using the highest octane of around 92, a compression ratio around 10.0 can usually still survive without detonation. Others have pushed the ratio to 11 or 12 while using a high octane pump gas and made an engine survive.

If you don't get detonation with a low octane, you won't make any more power by using a higher octane fuel. You only need enough octane to eliminate detonation.

Atilla the Fun

Of the 400s I've sleeved, never once have I hit water at less than .160 over. They are thin, but not scary thin for just 400 horses. If you can't get a 406 to 400 hp by 4800 rpm then you're doing something wrong. You should be safe to 5500 rpm.

Atilla the Fun

about the RockBlok in the water jackets, adding an inch in the bottom of each side won't hurt anything, and isn't a bad idea, though you will need to have the cylinders re-honed afterwards.

mesterious

iTrader: (1)

well change of plans this sucks.. the guy im suppose to be buying the 400 block with 40 over is not anserwing his phone so it seems like im going to buy a 400 engine that hasnt been bored or anything.. but it needs rebuilding so im going to bore it 30 over and i am wondering will this work out as far as the crank connecting rod and piston goes?crank- http://store.summitracing.com/partde...0&autoview=sku connecting rod- http://store.summitracing.com/partde...8&autoview=sku piston (SRP 10.3:1 Forged SBC 400 Dished Pistons) http://www.gofaststuff.com/pistons.html

AlkyIROC

A 400 bored out .030 makes a 406 which is the most common overbore for a 400.

Starting with a bare virgin block will probably be better. You can then pick and chose all the components.

mesterious

iTrader: (1)

k so when i bore it 30 over will
that set up worktogether that i posted?

Atilla the Fun

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