Couple more questions here....

[Anonymous]

Ok, there's a '79 Fairmont 200 I6 in the local boneyard. I can pick up the head pretty cheap. Would it be the same, better, or worse than the head on the 250 I6 of my g/fs '74 Maverick? I thought I read somewhere the '78+ 200s got bigger valves or something....

The Duraspark II works awesome. I can't believe how much better the girl runs! The guy that rebuilt the RBS before me killed the choke, and had the idle mixture super rich. I rebuilt it, set the idle mixture nicely, and the choke works, but I have one problem... from a stop, with the engine warmed up, if you nail WOT the car bogs for about a second, then up and off she goes. Is there any way to get rid of that bog on a 1bbl? From a fast idle, to WOT it doesn't bog.

 

[Anonymous]

yes it will give you more hp but you will need to have it milled

 

[MLINE]

Yes, the intake valves on the '79 head are 1.75". Your '74 head should have the 1.64" intake valves.

And an added bonus is the hardened valve seats.

 

[Anonymous]

Why must the head be milled? Are the combustion chambers bigger or something?

 

[MustangSix]

The chambers on the later heads are about the same size as the ones on the 74 head, so a switch between those won't make much difference in CR. As the others said, you will end up with bigger intake valves.

I'd probably mill it .050 to .060" anyway just to bump the CR up a little. That will bring your engine up to close to 9.0:1 depending on what size the chambers end up. That alone is worth several horses and better gas mileage and you should still be able to burn regular fuel.

 

[Anonymous]

don`t forget that the new gasgets are twice as thick as the ones that are on the car now so you would be losing hp in a way if you didn`t have it milled about .030 at the least 8)

 

[Anonymous]

hey wait a secont I think that I sounded smart for a secont don`t tell any one o.k.

 

[Anonymous]

It will have a bigger intake valve, which, if the price is right, would be worth it. You'll pick up gains there (especially with a good carb.) but, as mentioned, without milling (.030-.060)you may lose a little too. Buying that head, milling it .060 over .040 and using a good carb. will give you really nice results.

 

[Anonymous]

Ok, so I'm going to get the head. Now, in milling the head .060", just how far will the valvetrain geometry be affected, considering the new head gasket will be thicker than the original?

How thick are the new gaskets, crushed? How thick are the originals?

Just trying to see if I need to get new pushrods or not...

 

[Anonymous]

That's a good question on the push rods, your machine shop (or someone else on here) will be able to give you the best advice on that. But here is some more info for you:
Your 79 head will be great because it will already have 1.75" intake valves and 1.49" exhaust valves and hardened valve seats (for unleaded gas) - which are all things that people with heads before 1977 (including me) have to have added/fixed!
as far as the gaskets: Ford used a steel shim head gasket that had a compressed thickness of around .020-.025. Your new composite head gasket that you'll use in reinstalling it be between .035-.050 compressed (just depending on brand, etc.) = a difference of up to .030 (which means a loss in compression/HP - which is the reason to mill, in order to get that HP back (and then some!). Depending on how you build it up (flat top or dished pistons, how much you mill, what size gasket you use, etc.) your compression can vary from 7.5:1 to a possible 12.0:1.

 

[Anlushac11]

8)

With hydraulic lifters you dont worrly about valve lash like you do with solid lifters. IIRC the '79 head is non adjustable.

The difference in thickness between the steel shim and composite head gasket even if you mill the ehad is well within the ability of the lifters to absorb. Most of the guys dont bother doing anything except let the lifters absorb the slack.

However if you want to be on the mark, several places such as NAPA sell .060" shorter pushrods.

 

[CZLN6]

Howdy Doward and All:

Please read the sticky post at the top of this forum.

'74 200/250 head- 1.69" int, 1.39"ex, 1.75" carb hole, 62 cc chamber (aprox).
'79-'82 200/250 Head- 1.75" int, 1.39" exh, 1.75" carb hole, 62 cc chamber.

If you do mill the '79, re-establish the relief in the head for the oil transfer slot. It is at the rear on the passengers side. A composite gasket will help, but depending on how much you mill the head you may need to do some grinding.

To get the most out of this upgrade you should seriously consider having a performance valve job done the the '79 head before installing. It should include a 3 angle valve job, Milling, installing a center port divider and back cutting the intake valves. It should also include a thorough cleaning of the rocker arm assembly, inside and out.

Your RBS carb bog sound like too much or not enough accelerator pump shot. Either could cause your symptom. Check to make sure your accelerator pump is working by peering down the carb, with the choke valve open, as someone steps on the gas pedal or you work the linkage. You should see a stream of gas squirted into the carb throat. If you don't, you will need to fix the problem with your accelerator pump circuit. The RBS carb is not easily adjustable, it either works or it doesn't. You may also try to use a little more initial advance to cover the bog.

Hydraulic lifters more than compensate for the difference you're going to mill, and some of the machining will be traded off in the difference in the thickness of head gaskets that's already been discussed.

Adios, David