I'm trying to estimate the Compression Ratio of the new engine I'm building.

455 engine bored .030 over
L2323F pistons
Heads milled .060
Piston deck height (I don't know right now but I assume around .026ish)
Head gasket thickness .032

I've run it using an online calculator and came out to around 10.3 to 1

The pistons look the same as the cast ones I have on a 455 advertised as 10.25 to 1, I just figured with all the machining that the ratio would be higher. Thanks.

 

I get 10.35:1, doable with enough cam and gear. .032 gasket=7.26cc, .026 in the hole=5.77cc, piston dish=18cc, chamber 70cc, (based on a stock figure of 80-.060 of milling)=101cc added to swept volume of 945cc then divided by the 101= 10.356.

I did Panos', 10.75:1+ with a 238/246 Hyd Roller. Ran 29 degrees timing on pump 93.

 

Thanks. The cam I got is 294/306 .554/.558 and was thinking Torker with 850 Holley or my vintage dual quad setup with 750 Carters. I need to work the rear some also, got 3.08 open end now.

 

What are the at .050 specs and lobe sep?

 

250/256@.50 110 lobe center angle? Same as sep?

 

That's a lot of cam for a 10.3:1 motor. What are your final goals?

 

To drive it once in awhile on the street, maybe take it to the track at times. Not looking for a daily driver, just something to take out and have fun tearing up the streets, legally.
I also have an older Crane Fireball cam. Specs attached. Has more duration, not as much lift.
As far as compression, I guess I'm all out of options besides different pistons to raise it to match the cam.
I guess something else I should have put in the equation is power brakes and auto transmission. I'll take any suggestions. I have a good set of "E" heads that have been worked over nicely. Thanks cutlassefi.

 

From what I'm reading the Fireball has less duration, not more. Don't confuse advertised with the @.050 numbers. The Crane has more advertised but less at .050. That means it's pretty slow vs. your other one.

Quite frankly I wouldn't use either one, the first is too big especially for power brakes and an automatic, and the Crane is real slow, not much better.

You can do a nice roller or flat tappet in the 230+ @ .050 range with good results. If you have a decent set of heads then get something with a bit of lift to take advantage of that.

Jmo.

 

Thanks, I'll look and see what I can find in that range.

 

Lunati, Comp and others do custom grinds, or I can grind you something if you want.

 

Found a Lunati cam with 235/235@.050, .540/.540 lift, lobe sep 108. Just might be the one.

 

Can you tell us why you like that one?

 

I guess I'm out to lunch on this. Looked at @.050 duration in the 230 range and the higher lift. RPM range okay, I'll need gears and converter. I'll admit it, I just hunted for the cams with the duration range, and narrowed it down to which had the highest lift. I kinda wish I was building the engine for my stick car with no power brakes and a 3.90 posi, almost everything would be fair game. I'd consider removing the power brake booster from my car if I had to. If I'm missing the boat here, let me know. I definitely appreciate your input. I'm looking to make the car street worthy but just barely. Thanks.

 

For the record I like Lunati stuff, used it before. What I'm not fond of is using a cam that has the same lobe profiles for both intake and exhaust, especially in a stock headed Olds. All the generic stuff does that as well. Exhaust doesn't flow too well on an Olds head so you need to favor that. You can do it by just getting something with more duration on that side but a better way is that as well as using a slower profile for the exhaust than the intake.

I'd do something like a 235/240-242 or so on a 110. Should give you good throttle response and decent driveability. But again try something with different lobe profiles for the intake and exhaust. You'll have to be careful if using the dual quad set up as they're not the most efficient design, they're a bit harder to tune for everyday driving and can be a real challenge if you have a big cam and still want good street manners.

On the other hand lift is good, except if your heads don't flow well at the higher lifts, then it's a waste of time and money. If you find a cam with less lift than you want, you can always use a 1.7 rocker instead, provided you haven't bought those yet.

I went into Lunati's cam library. Try this on for size; on the intake their lobe number H235 which is the same lobe you have above, adv. 285, 235@.050, .338 lobe lift. But for the exhaust do the UH21 which is adv. 300, 244@.050, .335 lobe lift. That gives you lift at the valve of .540 in, .536 ex. Notice there's a difference of 15 degrees on the advertised but a difference of only 9 degrees at .050. That will normally tell you it's a bit slower than the intake. Imo that's what you want. Grind it on a 110 in at 106 and you should be good. Run that by Lunati and see what they say. You'll certainly hear it and should have decent driveability. Just an FYI, I can do something similar with an Erson grind as well.

 

Thanks again "cutlassefi" for the info and taking the time to respond. I'll look into the custom grind with Lunati and search more for the duration combos as suggested, now that I know what to look for.
I don't think I'm going to use the dual quads, I'm thinking Holley 850ish and Torker. I do have visions of a High Rise Offy with the 750's I have but that may wait until I start my other car.
The E heads I have look like they'll flow well. The bowl area has been smoothed out. They have been milled on the exhaust side to make that center divider flush. Not sure if that was a good idea or not. The intake side was milled also.
Thanks again. I'll let you know what I find through a PM so as not to tie up this thread, course I started it
My goal is to get the car ready for our Spring Fling car show here in Southern Maryland. Out of 200+ cars there's maybe 1 or 2 Oldsmobile's and I hope one day to double that number myself.

 

In order to get you comp-ratio you need all the info.
head-CC's
piston- CC's
piston in the hole depth
head gasket thickness
head gasket bore diameter
bore size
stroke

Then use a online calculator to get your ratio.
Also did they take off the intake side the same amount they took off the head surface?
You may have to double gasket the headers to clear the block because they milled so much off the exhaust side to bring it flush.

Gene

 

I need to verify the piston in the hole depth, I had guessed .026 . The intake side was milled quite a bit also, usually there's a ridge oh maybe about 1/2" down from the top of the head, well that's gone. Have to use a thicker intake gasket for sure along with the exhaust side.

 

I'm running an iron headed, true 10.1 compression 461, 230/236 Comp Cam, P/B, and 4 speed. Brakes are right on the edge, and in hot weather I have to back my timing down, or run octane boost to prevent detonation. With an automatic I would be thinking about a wider lobe separation angle to try to build a little more vacuum.

 

I checked piston deck height and there's basically none, maybe .003. I used a straight edge and feeler gauge. I take it this is not enough or maybe need to use a thicker head gasket when assembled?

 

Have your E heads been milled?

 

The heads have been milled .060, no room to play.

 

Sounds like you're right at '0' deck ht., I'd look at a thicker head gasket, a quench distance of .040 is about right.

 

I will get a thicker one, was planning a copper one at .021 but to be on the safe side, at least a .040 thick one. I'd be in trouble if I had flat top or dome pistons.