solid lifter cam in '78 200? smog head improvements?

[aribert]

THis winter I am planning on pulling the head ('78 200, never opened up, about 55K miles on it) to milled it (and to open up the carb inlet port a bit). Several of the lifters take a while to pump up and since I have a solid lifter Clifford cam w/ about 30K miles on it from my previous 170 I am considering putting it in at the same time (assuming that the lobes/lifters are still good). Are there any issues to consider when converting from a hydraulic cam back to solid lifters? Solid lifter ticking is not an issue with me - I grew up with the sound.

What are the typical compression ratio break points for ocane levels of 85, 87, 91? And as a follow-up question, about how much will the head need to be milled? I am just trying to get a ballpark idea and know that I will need to check the existing chamber volume when I pull the head. I have a Bridgeport and plan on rough milling the head and then having the machine shop Blanchard grind the head for the finish.

I tried to go this route when I rebuilt my 170 a few years back. Along the way I made either a calaulation error or measurement error. I planned on a 9.3:1 CR and the 170 head was milled by a total of 0.135 inch (it had probably seen one or two light resurfacing prior). Still during the break in phase (at 192 miles) I seized the engine after less than 10 miles of freeway driving at no more than 70 mph. I do not want to go down that route again.

Your thoughts? TIA.

 

[CZLN6]

Howdy Back:

Q- "Are there any issues to consider when converting from a hydraulic cam back to solid lifters?"
A- Be sure to use with adjustible rocker.

Q- "What are the typical compression ratio break points for ocane levels of 85, 87, 91?"
A- What we recommend with a stock type cam is an 8.5:1 CR for 85 octane gas. 8.7:1 for 87 octane. 9.1:1 for 91 octane. Other criteria that effects CR and octane ratings are cam timing- higher with a performance cam, elevation, ignition and combustion efficiency.

Q- "And as a follow-up question, about how much will the head need to be milled?"
A- A '78 head will have 62 cc chambers stock. That equates to about an 8:1 CR on a 200. To get the chambers down to 52 ccs will require a mill cut of about .050". Other issues- What engine is this head going on? What head gasket are you going to use?

Q- "I tried to go this route when I rebuilt my 170 a few years back. Along the way I made either a calaulation error or measurement error. I planned on a 9.3:1 CR and the 170 head was milled by a total of 0.135 inch (it had probably seen one or two light resurfacing prior)"
A- Yikes!!!! We don't recommend milling a head more then .090" total.

Adios, David

 

[aribert]

David: Thanks for the reply

Answers to your followup questions - head to go onto 78 200 (for now - eventually to go onto a '66 200 (I want my PCV port - for most engines the road draft hole - back again).

Head gasket will be common replacement such as Fel-Pro - is there a preferred brand? If I understand the currrent head gaskets are thicker and require a greater ammount of head milling.