Trying to stay on pump gas...

[Hazieview]

Okay so I'm building a sb400 with the works! Just wondering if anyone here is running 10:1 compression. If so are youmaking it on premium pump gas?

I'd like to be able to drive the truck almost every day but if I have to run premium then I'll cut it back to a tank a week.

Throw in your change on the matter. How do you budget your toy and still enjoy it?

[Dooley]

I've run a lot of 400's. Built a couple and found that 9.5 was about the limit for everday driver on pump gas.

[slugish]

have a 400 myself . HAVE NEVER run anything but premium . Around 10-1 comp. this probably dosen't help , sorry

[N2TRUX]

Carb or injected? If it's injected, you should be able to tune out any detonation problems and stay on pump gas.

If it's carbed, your going to need a case of octane booster.

[Hazieview]

It's going to be carbed for sure but I think my compression is going to end up being 10:1 I would like to run between 9.5 and 10 if I could. Just wondering if anyone was kind of running a similar setup.

Hey slugish can you give me a little info on your engine and what your running on it?

Anyone else running a 400 with 10:1 or 9.5:1 just wondering what I can expect. Never built an engine like I'm talking about so I'm curious to know what to expect.

sb400, buying new forged pistons, bigger cam, vortec heads, roller rockers, air gap, not sure what carb, possible MSD, flowmaster (duel 40s) exhaust etc.

350th trani, .308 gears but I'm looking hard for possi .373!!!

[N2TRUX]

You might look at the new generation of alcohol injection systems. They have come a long way from the old systems.

10:1 isn't extreme but it might be on the edge.

[f.monroe]

What cam are you going to run ? I think I remember your other post mentioned a 268 or so . I may know where a good deal on a Lunati Vodoo 268 is if interested .
Frank

[sdavid]

There are alot of things that determine if your are going to detonate or ping at 10 to 1 or higher compression. How well the engine is built is one. The quench needs to be exact for another. You need a good cooling system. Don't run too much timing to it. The rear gear has to do with it to keep the engine from lugging. Your cam overlap, etc.

My big block 402 is at 10.5 to 1 with iron closed chamber heads. It does not ping. I put too much timing in it, and it will. I am running a voodoo 262 cam. I am at the edge of having pinging problems.

Your cam needs to match your compression, along with the rest of your components.

[Pyrotechnic]

Modern quench style combustion chambers

Pick a cam that will give not more than 8.5:1 dynamic compression. This is really more important than your static compression ratio.

Make sure you have a quench distance of .040 or less

[swb85]

Originally Posted by Pyrotechnic

Modern quench style combustion chambers

Pick a cam that will give not more than 8.5:1 dynamic compression. This is really more important than your static compression ratio.

Make sure you have a quench distance of .040 or less

There's the right answer, forget everything else.

You're using vortec heads, that's good....they have a very efficient chamber that will deter detonation.

I'm running just under 10.5:1 static (8.3:1 dynamic) compression in my iron vortec headed 383. It runs on 91 octane with zero detonation, even in 100*F+ ambient temps with the a/c on high.
I'm running 12:1 static compression in my LSx camaro with 91 octane pump gas. It's all about the combo.
If you'd like any help with your build or parts recommendations I'd be happy to help.

[454HO]

Originally Posted by Pyrotechnic

Modern quench style combustion chambers

Pick a cam that will give not more than 8.5:1 dynamic compression. This is really more important than your static compression ratio.

Make sure you have a quench distance of .040 or less

Yes, a cam with more overlap will lower the dynamic compression. That is why cam manufactures state a minimum static compression ratio that you should have with their cam. So if you have 10:1, then look for a cam that requires a minimum of 10:1. If you use a wiennie cam that is meant for a 8:1 engine, then your dynamic will surely be too high. Always check to see what the dynamic ratio is. There are plenty calculators on the web to help do this.

And I must dissagree with the statement 'Make sure you have a quench distance of .040 or less'. The optimum quench is equal to the minimum piston to head clearance. This is determined by several factor, including but not limited to the max rpm of the engine, connecting rod design, piston design, etc, etc. You typically set the quench distance on parts that aren't moving. When the engine is spinning at 6000rpm, connecting rods stretch, crankshafts flex, pistons rock in the bore, etc. So you need to take that into consideration. On a tight engine, you may get away with .030". But to be on the safe side, about .040" is what most engine builders suggest for the minimum piston to head clearance. On the other hand, if the quench is much over .050" it becomes ineffective.

[Desert1957]

Back in the day I built a 400 with 10.5 compression , but what made the difference was running "Brodix" Aluminum Cylinder heads , My machine shop guy told me this trick and it worked. Running an Aluminum Head pulls Combustion temperatures down enough to help any detonation problems.

Desert

[85Bowtie]

If your truley running 10:1 there should be no problem running 93 octane.

The 440 in my Charger is 11.5:1 and I usually mix 5 gallons of 110 into 93 and add a little Marvel Mystery oil, but in reality it will run fine on 93, just can't get on it as hard.

[Jonboy]

a 268 cam is a little small in a 400, isn't it?

[sdavid]

You can call or email these guys to get some help and get a cam made to fit your application.

http://www.bulletcams.com/index.html

[Hazieview]

Check this out!!!

http://www.popularhotrodding.com/eng...ine/index.html

Only thing is I think I'd be happier with the vortec heads considering the price. However it looks like I would spend a lot on fuel too if I went with the more expensive heads.... Hmmmmm... What do you guys think?

I got a little money to do what I want right now but I just need to make sure I do it right the first time...

[Hazieview]

bump

[sdavid]

Use the vortec heads you have. They will work great for the rpm range a daily driver type truck will see. Spend the extra money on a good carb, the msd, shift kit for the trans, or gears.

With out getting crazy or super expensive you can get enough power out of the 406 w/ vortec heads to start breaking drive train parts and having to replace back tires often.

[swb85]

^^^Agreed. Run the vortecs and a split pattern cam and you'll be grinning ear to ear.