treyZ28

That is more gear for for the 7000rpm 4.8. It is going to have a numerically higher (steeper) effective gear ratio.

02sierraz71_5.3

iTrader: (2)

This isnt true especially when considering FI setups, for example a turbo likes to be "loaded". Plus you have to take into account the ability to hook acceleration is based off distance over time and if you cant travel any distance because the tires are spinning you arent accelerating.

I would be looking to cross the traps in third at max power rpm, obviously too tall of a gear is going to put you into 4th and thats not a good thing.

vanillagorilla

iTrader: (1)

You can look in to coatings too. I've heard of cast iron head cars running on pump gas with 11.5:1 compression. They use flat tops and small cc heads as stated above, but they also use a ceramic coating. I'm not sure what exactly is in the coating, but any good piston manufacturer offers it and can tell you more. They'll coat the piston tops, combusiton chambers and sometimes the bottom of the valves all it an effort to reduce detonation. It seems to work really well for them.

I run 10.5:1 SCR on my car with cast iron heads in +100* heat here and I haven't had any problems. I run 36* total timing on 91 octane pee water. I keep the under hood temps down via a big *** fan and radiator and all the valve events are where they need to be. If I had to do it again, I'd go with the coating and bump it up to 12:1 at least with aluminum heads. I could probably still run a similar cam too. Hey, its only money.

treyZ28

well, you can definately launch harder with taller gears.

if you are trying to launch at 4000rpm, your tires would rather go 0-12mph instantly (close to) than 0-22mph instantly (taller gears).

with the taller gears, you'll either spin the tires or bogg the engine. This does however assume that your pedal isn't an on-off switch and you can actually drive. no need for this last sentence

Flyer

iTrader: (1)

Trey, drop it. This threads about compression, not gears. If you want a debate on that, start another thread.

Zippy, that's some very good information! I think I'm gonna stick with about 12:1 with a thin gasket. If I have problems, I'll just put thicker gasket on. That may be a good idea too in case a bottle finds its way on my truck.

Since it's brought up, you think that like I'm thinking would handle nitrous good?

66 or 65cc heads, .030 cometics, -2 flat tops

zippy

I think it could pretty easily handle nitrous, but it depends on how big of a shot you are looking into. A 100 shot would work excellent on just a direct hit, but any more than that and i'd say look into a progressive nitrous setup. This would alow you to come out with a small shot of say 75 or so and ramp it up to say a 150-200 shot by rpm, speed, or gear. With a healthy 408 as you're looking into and a progressive nitrous system you could probably run a low 10 without too much trouble. I'd say a direct 100 shot along with what you're planning to build should go a high 10 given the truck hooks.