Achieving Compression ratio target

[Anonymous]

I'm getting ready to start the build up on my '68 200 with the following setup:

'68 block
OZ head/intake w Holley 2300 500 CFM 2V
264/274 – 214/224 - .450/.450 – 110* CAM
full roller rockers
dual roller timing
HiPo balancer
Pacemaker headers (dual out)
New stock dished pistons

I've had the block bored .020 over and decked to .010

I need to pick my target ratio so I'm looking for suggestions. I want to run stock fuel..don't mind using premium octane. With the Schjeldahl's compression calculator (http://falconperformance.sundog.net/compcalculator.asp) i put in my numbers using their stock info and my bore and deck mods and the thicker gasket number (.055) and I get:

8.8:1 @ 118hp (I'm sure the HP isn't right with the other MODS I'm doing, right?)

I left the volumetric efficiency at 80%, but wouldn't that be going up significantly with the OZ head, larger carb, and headers?

Also, what kind of RPM's should I use in that calculator? Stock is set to 4000.

Now, since I'm going with the OZ head, I'll need an accurate combustion chamber figure to start from to know how much to mill that head. I plan on CCing myself or course, but until it gets here, what chamber volume will I likely be working with? Based on that, how much should I look to mill off? From what the "Handbook" says, .060 = ~ 1.0 compression ratio points.

 

[CZLN6]

Howdy Bryce:

You didn't say what tranny your are using, or what type of driving you are doing. The conservative, way safe generality for an otherwise stock engine we use is to use a goal CR that matches the octane rating of the gas you intend to use. 85 octane= 8.5:1 CR. But given your mods, in particular, cam, headers and .010" deck height, I believe you could safely run a 9:1 CR with an occassional tank of premium during the hot summer months.

As far as VE %, you can use whatever you want. Just know that VE is not a constant with any internal combustion engine. VE is lowest at an IDLE and highest at WOT and higher rpms, usually somewhere between peak HP and Peak Torque.

As far as RPM, What is your engine doing? Do you ever run it to 5,000 Rpm? If so put that figure into the calculation.

The generality of .060" = 1 point of CR is a good generality for USA heads. I do not know if it is good for an Oz head. Probably best to make several smaller cuts and cc each time to be certain.

Best wishes.

Adios, David

 

[Anonymous]

yep, of course I forgot something! Sorry.

Unfortunately, for the time being, the stock 2-SP Ford-O is going to have to stay. Based on another member's C4 swap issues with the driveshaft, universal joints, and rearend, it'll have to do for now. I was hoping to bolt a C4 on and just shorten the driveshaft if needed, but apparently there are more significant mating issues than that.

As for driving, it varies. Mostly I'll be cruising around town...highway driving fairly regularly, and of course, I want to be able to smoke someone at a stop light once in a while ! Especially if they are booming their bass!

@ 9.1 with my setup, what do y'all imagine my HP's would look like? Would I gain significantly shooting for more like 9.3-9.6? Would I be safe with those numbers (noting that a C4 is definitely in the future when the details are worked out).

Thanks again!

 

[Anonymous]

any other thoughts?

 

[addo]

Choose some flow numbers that resemble your head best (Az might be able to assist), select a cam that hybrids those figures and your intended usage/finished driveline.

The grinder should be able to suggest a static CR that will work with the cam. Consider 9.3 as a minimum.

(Remember Australians don't do this stuff by halves and if it breaks, well it was good while it lasted. :roll: )

 

[falcon fanatic]

Bryce,
The c4 swap has been completed and runs great. It was expensive having someone else do it. Most of the problem had to do with needing to massage the starter holes to get the proper alignment and figure out the kickdown linkage while retaining the stock throttle linkage. Not difficult problems if you alreqady have the engine out of the car. In my case the engine was in the car and i ended up paying for the trans to go in and out three times while the guys fussed with this stuff. Since your OZ head will require a cable throttle conversion, you can do a cable kickdown conversion while you are at it. Summit carries a Lokar kit for about $65. Should be relatively simple if you asseble the whole shebang on the bench and then slip it in assembled.

Driveshaft was an issue. Had to be shortened and fitted with the proper yoke and for some reason that cost me $250. Another member advised me that he once found a u-joint that would mate the later 8" driveshaft to the earlier 7.25" pinion yoke. That would have saved about $150 if you figure 75 for a used driveshaft of the correct length (53") and $25 for said u-joint from Napa. remember the 7 P´s of happiness: Proper Prior Planning Prevents Piss Poor Performance. I didn´t and i paid.

Still, my car drives 100 times better than before.

 

[Anonymous]

The engine and tranny will all be out so imagine it will be easier to do it this way. If I could come up with the magical U-Joint that would eliminate the need for a new rearend allowing me to be able to mate the C4 to the original (shortened) drive shaft, I'd go for it.


I'm going to PM you with some questions...

Now, where do we find the magical part?!

 

[Anonymous]

I'm sure you could find it at Napa, as FF said... You just have to find a pretty knowledgeable counter-person and or one who is willing to look into the books instead of the ol' "I can't find it in the computer"


A friend of mine had a '66 Stang one time with a 9", and it needed a rear u-joint... turns out it had the orig driveshaft and they got a 'conversion' u-joint to mate it to the 9".. We were lucky in the fact that he worked at Pep Boys for awhile, so they let us go behind the counter and look in the books... since we had no way of knowing what the part # of the u-joint was.. I happened to find it in the back of the U-joint catalog... they had a conversion chart and list in the back...

I know the 8" takes what is called a 1310 u-joint (my friends conversion u-j was 1310 on one side and 1330(bigger) on the other)... So you need something with 1310 on one side and the smaller size on the other (I dunno what they call that). But I'm sure it does exist....

You could also try a place that does drivelines... FF's price of the driveline sounds a bit high(depending on what they charged for the yoke)..

I had to get a d/l made a few years back, I just wanted to balance my original and have new u-j's put in... But they told me I they couldn't balance it since it was a 2 piece (with the rubber between the 2) since the rubber cracks and change the balance... So I just told them to do whatever was needed (since I happened to have a BIT of money at the time).. they wound up making a whole 'new' driveline... which cost me just over $90, but this was using the existing yokes... Being the balance was $40, the 2 u/j's was $40, it was just over $10 for the driveline I guess...But this was in '96 or '97, so I'm sure prices have gone up since then as well... I'm guessing they just took my old yokes and put them on another solid tube...

Let us know if you find the said u-joint, I'm curious if there's a part #, or what they call the smaller size (1310 or whatever)

 

[Anonymous]

So, the C4 tailshaft connects to a 1310 U-Joint? Is that a standard?

 

[Anonymous]

The yoke that goes on the output shaft of the tranny? I know on V8's it does (use a 1310) sorry I dunno about 6's