355 with 11.5:1 compression...

[stomis]

Huh... See this is all a bit of a shocker to me. :lol:

So we'll see... what you guys are telling me is making me feel a lot better about it. The car has a 100 shot of nitrous hooked up in it on top of the engine mods, hopefully he didn't use that too much... I know I never will. So I'm going back to look at the car a second time tomorrow with one of my buddies it's always good to have a second pair of eyes. But if all looks good no metal or coolant in the oil, clean radiator (no oil in it), or cruddy burned oil in the valve covers, and it runs as good as he says it does I'm probably going to buy it. I wanted to build one up for myself, but this one is already built and the sum of it's parts is worth more than he's asking for it complete.

If it doesn't turn out to be a streetable motor maybe I'll drop the compression down to like 8.5 or 9 to one and put a turbo on it. 8)

You are aware that turning down the compression a tad and adding a turbo will give you WAY more power right?

 

[kornball426]

Yes I realize that. Hence 8)

More power is always better isn't it? :lol:

My worries about street ability don't really have to do with the power, so much as idle, vacuum, and not being able to run on pump gas.

I would like to do a compression test... But I don't have the tool.

 

[Minion1186]

No, you're right, there are no gas stations that sell 110 octane or 112. I am lucky enough to live 3 miles away from a local speed shop, sells it right there and there's also the drag strip 12 miles away for it. It is more expensive at the speed shop than the strip i heard, because who else sells race gas for $42 for 5 gallons!? Oh well maybe thats why i havent touched it in a while.

Also 11-12.0:1 compression race motors arent the best around town, especially with a 3000 stall converter, no choke on the carb and a manual valve body

Idle wise, i have mine set to about 1100 in park, and in gear it barely (if any idles), and i dont really worry about gas mileage in this car.

 

[kornball426]

Yeah I know the gas mileage will suck so I'm not even taking that into consideration. I'm guessing 6-7 mpg, but maybe if I'm careful 9 to maybe 11. I had an F350 mud truck with a souped ford 460 stroker with heads, headers with no cats just glass packs that dumped under the cab, a big bump stick, an edlbrock intake and a 850 carb on it. Never knew how much power it really had, but quite a lot. I think it was 521 but it could have been 514, and that would get about 4 mpg in the throttle, but if you were very careful driving it you could squeek out 10 mpg. It had so much torque though, you really didn't need to give it much gas.

So my guess is a 355 will get better mileage but not too much especially without overdrive... And without as much torque it'll take more revs to get moving. But I bet the mileage will be comparable to my stock, crapped out, badly out of tune Olds 307 in my current regal. Only it'll take premium instead of 87 to run so there's another 15-20 cents a gallon.

 

[larryo454]

Hi 11.5 with a alum head is good no prob like others say.But i run a bbc 461 with a steel head now with 12.9 and can get way with it with the cam i use.You just need a more overlap cam at the .050 duration but bring down the compression like a high 260s up in the 270s and lay back the total timing a bit like 34 degs. With alum head is the way to go if you want a high compression engine and make it perform good with little or no pre detention.I run my bbc with 12.9 with steel head and the cam is 600 lift and duration at .050 is 268 the cam has alot to do with how much compression u can run and how experienced you are with high compression engines.

 

[kornball426]

Big blocks have more quench that small blocks... But that's still impressive. You don't have any detonation problems?

I have very little experience with high compression. Any powerful cars I have experience with blew up, or relied on cubic inches over compression. 😛

 

[larryo454]

Lets just say when u look at cams in a book and you are thinking of putting a new cam in your engine and you read the notes about the cams. Some cams that have high lifts and long duration thay say a minn and gears like 3.73 or 4.56 and 3000+stall.This is what puts less load on the engine at the low end with duration or overlap the more over lap you got the more compression you need a 11.5 with overlap at 250+dreg is like 9.8 or close. This is why you turn back the total timing so the engine don't detonation. My bbc on the street is set at 34 total timing on 91 pump fuel and at the track 38 to 41 total on mark4 racefuel.

 

[stomis]

Lets just say when u look at cams in a book and you are thinking of putting a new cam in your engine and you read the notes about the cams. Some cams that have high lifts and long duration thay say a minn and gears like 3.73 or 4.56 and 3000+stall.This is what puts less load on the engine at the low end with duration or overlap the more over lap you got the more compression you need a 11.5 with overlap at 250+dreg is like 9.8 or close. This is why you turn back the total timing so the engine don't detonation. My bbc on the street is set at 34 total timing on 91 pump fuel and at the track 38 to 41 total on mark4 racefuel.

Right just remember if your following this principal of dynamic compression with big overlap your timing needs to be dialed way back to account for the fact that your compression comes way back up higher in the RPMs.

 

[kornball426]

Yeah so I hear... Like I said I never had a car with enough compression to have to worry about it. I don't want to learn the expensive way.

But also I hear, that if you run a cam with lots of overlap it doesn't matter that much at the higher RPM's that the cam can't bleed off as much compression. The reason being when you're revving a motor it's not loaded as much as off the line, or low speed driving in traffic (stop and go). Getting started from a stand still is harder for an engine to do, than just keeping your car moving. And thats what worries me, that it'll start to ping and knock on hot days in traffic.

 

[Minion1186]

typically you shouldnt drive cars with race motors around town or in heavy traffic on hot days. I had some overheating isues with mine in 90+ degree hot summer days. Right now mine runs good in town since its been cold out.

I have 59cc chambers, and the timing advanced 2 degrees and the only problem(s) i've ran into were it seems to backfire through the header every once and a while and has a little less power than when i run the 50/50 mix.