What year 200 for longblock?

[CZLN6]

Howdy back SAll:

The reason I asked about your goal CR is because stock type, short duration cams tend to build more cylinder pressure than a longer duration cam. If you are going for a higher than 9:1 you'd be more knock resistant at lower, lugging rpms with a little more duration- say 260 or more.

"RV" cams can mean many things to many people, Find out the exact specs.

You'd be better off having the builder do a zero deck height on the block then to go away from stock type, small dish pistons.

Personally, I like more CR, but it has to be done right and managed. What is your elevations?

Adios, David

 

[Anonymous]

Thanks David,(CZLN6)

I am at sea level. The builder said a Comp cam in the 260 range. Are you saying to stick with the stock pistons and mill the head? Can you define zero deck height ? ( i really appreciate you taking the time to answer my questions)

 

[Anonymous]

Can you define zero deck height ?

On pretty much all production engines, when the piston is at TOP DEAD center, it is still not all the way to the top!

The top of the piston is usually quite a few thousandths below the top flat surface of the block.

"Zero Decking" mills the top of the block down, so that when the piston is at TDC, the top of the piston is even with the top of the block.

 

[CZLN6]

HowdY:

Linc gave you a good description of "Zero Deck Height". Decking the top of the block is a typical process in a rebuild, to establish a level mating surface. Typically a block and head may be surfaced .005" to .010" to achieve a level surface. Zero decking requires that the crank and pistons be assembled to be able to accurately measure the "before" deck height to determine how much must be milled off the block to achieve "zero".

Zero deck height will improve the quench effect of this engine, which improves combustion efficiency. It also raises CR. Typically a 200 has about .025" deck height from the factory. Variables- replacement pistons are usually down in the bore another .005" to compensate for machining, aftermarket head gaskets are thicker than OEM steel shim type gaskets. All dimensions must be verified and planned for. The head gasket gives more than enough deck clearance.

The Comp 260 is a good choice. It will have .425" of valve lift, a fat profile and a 110 degree lobe center. This cam can help manage 9.2:1.

Adios, David

 

[Anonymous]

Thanks guys,

I feel pretty sure about the configuration for my long block except for a couple of things...Distributor, carb, and rockers. Are the stock rockers 1:6:1 as advised by CZLN6 ? What distrbutor do you reccomend? Please keep in mind there are no junkyards here, all the old cars get hauled away on a barge or sit in someones yard. But if given a model of donor car for these parts I can begin the search.

 

[CZLN6]

Howdy Back:

The stock rocker ratio is 1.5:1 For all 144, 170, 200 and 250 sixes. !.6:1 rockers are available in the aftermarket. With a Comp 260 you will not need 1.6:1 rockers. It will have .440 or lift with 1.5:1 rockers. YOu may want to upgrade to adjustible rockers.

If you could find a '78 - '80 Fairmont or Zephyr as a donor car you'd have a good head with a good fresh air cleaner assembly, the best OEM ignition, and cable throttle and pedal assembly.

As for carb, there are really only three options; a larger one barrel, a two barrel through and adapter, or a direct mounted two barrel or 3 one barrels on a modified log. All have advantages and short comings. Do some research and reading here on the forum and choose what will be best for you.

Adios, David

 

[WhitePony]

68bronco,

The distributor that you want is the DuraSpark II. This is the distributor on the late 70's Fairmont's like David said. There are several advantages to the DS2. First, you have several choices as to the electronic controller. You can use the box that was designed for the DS2, a GM module, an MSD 6 series, or a Mallory Hyfire. People here have gotten good results with all of these combinations. The DS2 can also be recurved to match your engine power/torque range. In addition, the DS2 can use the larger HEI plug wires.

 

[Anonymous]

All of whitepony's info bits are correct.
I would also like to add that the DSII just looks more "modern".
I can't quite stomach the antique look of a "points" style cap!!