How much to mill, bore, and deck..gotta know now

[Anonymous]

OK gang. The block (1968 200ci) is coming out tomorrow and heading the machine shop. They are going to hot tank it, clean it up and flux it to make sure she's goot to rebuild. Assuming it is, i have some questions about how much to bore over, deck it if at all, and how much to mill the head.

I'm replacing the '69 head on her with a rebuilt head from a '77 (hardened seats, larger valves, etc). My I6 bible says to deck this head .060 to make up for the newer thicker gaskets. Makes perfect sense to me. This should keep me close to stock compression if I was just swapping heads. However, this block is going to be build from the ground up with FordSixParts peformance goods! Full roller rockers, hydraulic cam, lifters, push rods, a cam with a little more excitment to it, forged pistons, all new bearings, ARP bolts, high-po dampner, headers, + 2V carb + adapter. So yo see, I'm not looking to go back to stock. I want to make this little 6 sream. I'm no looking for stock compression ratios.

SO, question number 1:
the handbook also says it's better to deck the block instead of milling the head where possible. I understand the why's of this and what it means, but are they suggesting to deck the head .060 INSTEAD of the head if possible? Could I just split the differnce and do .030 on each (assuming i have .030 deck height now). Does anyone know what the "stock" deck height on a '68 200 would be?

Will replacement pistons (same rods and crank) change the deck height just by bolting them in or can I use an existing piston setup to get my current deck height? The pistons are already out, but I can easily pop one back in for measurements. BUT if new pistons will produce different deck heights, I'll have to wait to have them new pistons in hand to measure the new deck height to know how much I can remove...right? That'll put a real squeeze on things as the pistons take 3-4 weeks to make!

Here is what I'M thinking would be a good plan...please tell me if this makes sense!

have the head milled .060 to make up the gasket difference
Have the block cleaned up then have it bored and honed just enough to perfect the cylinders but not less that .020
Once that's done measure my volume (liquid filling the cylinder and combustion chamber) as a base reference for my new compression ration (new head and newly bored cylinders).
From that point decide how much to deck the block to reach a goal compression ratio. Assuming I have that much block surface to mill, take that amount off. If I don't have enough deck height to cut, can I take the difference off the head over and above the already .060 milling it had?

ex: my existing deck height is .040 and my target compression ratio requires I lose .060 more material from somewhere. Can I take the .040 off the deck bringing me to 0 deck height and then take the remaining .020 off the head (noting it's already had .060 milled)?

So, with all of that said, what is a good target compression ratio for me? This 200 is in a '63 Falcon Convertible with the standard 2-speed tranny (WILL be a C4 soon enough) and stock rear end (I think).

Thanks tons to all for all of the help!! You guys rock!

 

[addo]

You would ideally deck the block for zero deck height. That requires the pistons to be test fitted, then removed. So you do need the pistons.

The bores should be torque plate honed. This will really affect some holes more than others. Similarly, honing should be done with the water pump and timing cover torqued to spec.

That's probably about the guts of it. Try to convince a board member to run your intended combo on Engine Analyser or DD. The main reason is effective compression loss with a hot cam. You'll get a better idea of what chamber volume to mill up. With the thermal qualities of a forged piston you can probably go a shade higher in CR than for hypers.

Note well: This is going to be a long way removed from your current motor. Besides having the distributor recurved, you'll have to reasonably expect a few teething issues. Every engine is different and changing so much means the final outcomes are impossible to pinpoint, especially in terms of timing/carburetion.

Regards, Adam.

 

[Anonymous]

Thanks Adam. that'd be great if someone could run these numbers! I'm thinking about a cam with this profile (based on Mike's info):


274/274 (Adv Duration)
224/224 (.5 Dur)
.450/.450 (valve lift at 1.5)
.480/.480 (valve lift at 1.6)
.495/.495 (valve lift at 1.65)
110* lobe centers
1900-5400 RPM

 

[CZLN6]

Howdy Bryce and all:

Wow! You're really on the way.

Once the engine is disassembled, the minimum bore determined and new pistons have arrived, do a mock assembly using the new pistons fitted to the reconditioned rods installed with new bearings to assess deck height. Typically OEM deck height is .025". The new pistons will likely be down an additional .005". The only way to know for sure is to do a mock assembly and measure. Disassemble and deck the block for a goal of zero deck height.

Do not mill the head until the botton is finalized and rechecked. Take note of all measurements and write it down. Final bore diameter, deck height, if any, head gasket thickness, etc. Mill the head the amount necessary to attain your goal CR.

Assuming this is going to be a street driven engine, If you will do a good job of polishing the chambers and piston tops, you could run a CR of 9.4:1 to 9.6:1 with out much worry, using 93 octane gas in the hotest summer months.

Glad to hear the FPH is useful.

Adios, David

 

[66200i6]

Good luck finding an outfit that doesn’t already have the attitude “don’t worry about it, it’s only a sixâ€￾. I have tried to locate a boring/honing plate for the 200 250, none of the shops in the Puget Sound area use them. I am left with having one made, hence the hold up in my rebuild.

Good luck, Ric.

 

[Falcon62]

Personally, I wouldn't bother with torque plate honing, not because it isn't an important performance procedure, but because, like Ric has found out, there are none out there. The only ones I knew of were "rented" out from Clifford Performance, but I have no idea if they still do that.

Overbore only as much as necessary for the cylinders to clean up and no more. Your performance gain is nil in respect to potential cooling problems and cylinder wall flex. Concentrate instead on the good advice given so far.

If you drive your car with this engine you'll be replacing the Fordo sooner than later.