Is it worth it to mill my head?

[Anonymous]

I just bought a 66 200 to replace the 170 in my 66 bronco. The motor has all new fel-pro gasgets the head has NOT been milled for the thicker head gasget. I would like to just do the swap and not mill. Would this be a NOTICABLE loss in power?
P.S I did read the sticky!
Thanks![/i]

 

[addo]

OK, model the two options on a calculator by our own Dennis and Dave, authors of the Falcon Six Performance Handbook:

http://falconperformance.sundog.net/compcalculator.asp

Now you can put a price on that HP.

Regards, Adam.

 

[CZLN6]

Howdy Back HBuck:

Adam has outlined the plan for you to deduce the answer to your question.

In the mean time;
What is the head casting of the new 200? What is the casting code of the 170 head? It is possible that they are the same casting. That may provide the foundation for a future fix.

If it has a new Fel-pro head gasket, I've got to ask why? Was a valve job done? Milling to true the head mating surface is typically part of a valve job. Do you know any of the history of the 200?

The loss of CR will not only effect HP, but also reduce torque and economy. The extra cubes and longer stroke of the 200 will be very noticeable and add to the torquey feel of the rig, but know that you're leaving some potential behind.

The time to do the milling is when a valve job is done. Milling the head surface at this point may be the cheapest HP you will ever buy.

Keep us posted.

Adios, David

 

[Anonymous]

The coworker I bought the motor from had dismantled the motor compleatly and "looked" it over did a valve lap job, cleand and painted the motor and reassembled with all new fel-pro gasgets. I will look at the casting # tomorow. I think I might run it the way it is for the summer and then mill the head and do a valve job on it in the winter when it will be parked. then next year it will feel like I improved it right now I dont know what to expect from it. I see clifford has came out with a header for the bronco. I might just have to get one this winter also.

 

[CZLN6]

Howdy back:

I ran the numbers, out of curiosity.

Assuming that the head gasket is the only difference, you have lost .5 of the stock 9:1 compression ratio. Assuming 200 cubic inches and a 185 cfm, stock autolite 1100 carb, the loss of CR results in a loss of 6 hp. From 107 @ 4,000 rpm to 101, also at 4,000 rpm.

I thought you'd like to know.

Adios, David

 

[Anonymous]

what am i doing wrong I get 120 stock and 113 with a .050 compressed?

 

[Anonymous]

well I looked at the casting # and the head is off a 1970. I cc the head to be a 62cc and my compressed gasket thickness was .045 my deck hight was .020 and it has 7cc dished pistons and if I remeber right the gasket diamitor was .383 but not shure on that. I do plan on mill the head .075 to get it back to the 9.1:1 range. Is their any thing better about the 70 heads over the 66? Valve size? also if the amount I plan to mill looks off please let me know. thanks

 

[Anonymous]

the gasket bore diameter was 3.84. sorry

 

[CZLN6]

Howdy Back Buck:

I ran the calculator at 4,000 rpm becaust that consumes all of the 185 cfm of a stock Autolite 1100. To get more would require a higher capacity carb.

I only changed the gasket thickness from .025" to .050" The more exanct you are with measurements and input, the more accurated the results will be.

Your plans to mill the head .075" is about right on. Be sure to re-establish the oil transfer slot at the back of the head surface, and plan to use hardened washers on the head bolts on reassembly.

About the only real difference between your '66 head and the '70 head will be the difference in cc chamber volume and the diameter of the carb hole. The '66 is 1.5". The '70 will be 1.75".

Was the new gasket a Victor?

Adios, David

 

[kirkallen143]

I just bought a 66 200 to replace the 170 in my 66 bronco. The motor has all new fel-pro gasgets the head has NOT been milled for the thicker head gasget. I would like to just do the swap and not mill. Would this be a NOTICABLE loss in power?
P.S I did read the sticky!
Thanks![/i]

Just as a reminder, make sure your mating surfaces are true (head and block). I had only milled my head in my bronco and the block seems to have some warpage to it ('68 block and '75 head). Well anyways, I now have to build another block 'cause the rings are shot, so the block will be decked (minimal) to assure a good mating surface. Just something to watch for. Good luck.

Kirk
ps. if you really want to wake that engine up, put a carter YF-1 from a 240 inline six out of a 1974 f-100, it is an easy swap and nothing to it.

 

[Anonymous]

the new gasket was a Fel-Pro.

 

[Anonymous]

Is it worth it to mill my head?

If the engine is already assembled and ready to go in and you plan on leaveing it stock-I wouldn't bother.
If you intend on later mods that involve anything internal- I wouldn't bother till then.
If however you plan to upgrade the carb and exhaust -i might.
Even with the thicker head gasket you are likely running more compression than a later model 200 anyways and with more compression comes the need for higher octane, and often a little less compression gives a little more low end. I recently knocked down the compression on my high perf. Harley from 10.5/1 to 9.5/1 and it has a little more low end pull -and it starts a lot easier when it is hot.