Head and Lifter Change.

[fxp]

I'm seriously considering putting a 250 head on my 170 engine as part of my rebuild. Obviously the head (and maybe deck) will need milling as per the sticky above to get the compression up to the 9.1:1 I'd be looking for to run on unleaded (91 RON in Oz).

I've had a couple of issues flagged with it above and beyond the compression issue.

Firstly concerned about valve to piston clearance. I'm looking to put in a new cam with 254/264 duration and .382/.408 lift so does the extra lift make this even more critcal? I've no idea what sort of clearance it would have before the skim. I'm reliably informed by Addo the chambers on the 250 head should be 56-58cc and I'm going to need to drop that to 50cc at least.

The second issue flagged was that the bigger valves and runners would slow the intake charge leading to loss of atomisation, and possibly pooling, leading to lean mix in pots 1 and 6.

Any opinions on this? Anyone out there done a similar swap? Or is it just one of those things discussed as a hypothetical possibility?

The other question is how easy is it to replace the solid lifters in the 170 with hydraulics? Was told it's as simple as taking out the solids and dropping in hydraulics. I'd like to hope that's so as it would make the cam upgrade easier for a start.

 

[Anonymous]

I doubt that a cam that mild is going to cause any clearance problems even with the higher comp. However always check clearances before reassembly. I am running a 200 with higher comp.,zero decking, a larger cam, oversize valves and flattop pistons; I had room to spare.
No I don't believe you can convert to Hyd. lifters if you have a solid lifter engine.
This is a quote from what i consider a fairly reliable source of info about the small six

Hyd lifters cannot be retrofitted into a 144/early 170 c.i. block. The 144/ early 170 c.i. engines MUST use solid lifters. The early blocks are not plumbed to supply oil to hyd. lifters. During the 1964 year all engines were fitted with hyd lifters.

If you have a stock engine with adjustable rocker arm you got what you got--solids--Good news is they don't need adjusting very often.
Dan

 

[63redtudor]

yappy, what year is your car/170? Like Dan said, the earlier motors aren't plumbed for hydraulic lifters. Just because your engine has adjustable rockers doesn't mean that you've got solid lifters. Both my '63 170 & '65 200 have adjustable rockers & they both also have hydraulic lifters. I've heard of other guys pulling off the valve covers of even later motors (with hydraulic lifters) & finding the adjustable rockers as well.
I originally wasn't sure about the '63 170 as the car was an early model car, but a few years ago when I had the head off I pulled one lifter. Hydraulic. Since you're going to be changing the head on the engine anyway, check & see what you actually have. You never know. Remeber, ford used (uses?) an empty bin policy & its always possible to end up with some odd stuff.
Edwin

 

[fxp]

It's an Australian 66 170. It seems only the 200's had hydraulics in 66 over here.

Thanks for the tip on the internal plumbing - that will obviously make a final decision if it isn't.