Engine at machinist - got some questions?

[TxAgs66]

Hey all! It's been a while, but I am finally getting the engine work done on the car.

I originally wanted to just clean it up and put it back in the car, but a buddy convinced me to remove the head. We found a valve was getting burned up and there was a bit of play in the bearings. So, the head and block are completely broken down. I went by the machine shop today and the guy was super helpful.

Here's what I found out -
Block
Crank should polish just fine.
Block was already .030 over. He's going to go to .040.

Head
Head needs hardened seats on exhaust side.
Needs new valves
Needs to have valve guides re-worked.

Owner was a bit concerned at the spring compression that the 302 spring from Mike have. He was worried that they might wear quickly. Any thoughts?

So, based on the head, I am going to find a 250 head and have it re-worked.

Should I get new pistons or use the .030 pistons with .040 rings? Is that possible? Flat top or dished pistons?

Thanks for the help!

Jason

 

[CNC-Dude]

If the block is going to be bored .040 over you will also have to use .040 pistons, the .030 pistons will not be acceptable for anything but a .030 over bore. As long as the valve spring pressure is in spec for the cam type and valve lift you will be using, they should be fine.

 

[64falconsix]

Here is a discription of the different valve spring available and their applications. http://www.classicinlines.com/products.asp?cat=37 . Without increased rpm c apabilities of more carburation, performance cam or head flow work I would stay with a quality stock replacement spring. the mid 69 and later heads are the best choice as the intake and carb inlet are larger and if I remember correctly the intake valve size increased in either 69 or 72. But so did combustion chamber size. the 200 and 250 heads are the same. As for the pistons it really depends on what your plans are for your build, I run a dished sealed power cast piston and run right at 9 to 1 with the milled late model head on my 200.

 

[FalconSedanDelivery]

I NEVER have Hardened seats installed in a head that Never had them to begin with , I have Thousands of Miles on Stock to 800+ Hp Blown STREET Driven Combos and its NOT needed if its going in a RV or Tow Truck , MAYBE , if the work isn't spot on the head will be JUNK , I deal with cylinder heads that are NOT replaceable so that sways me a bit , but its your money ,

 

[CZLN6]

Howdy Jason and All:

You might want to look for a D7xx ('77) and later casting code 200/250 head. They will be sure to have the best of what you need; 1.75" intake valves, hardened valve seats, a larger diameter carb bore and increased intake tract volume. It will have to be milled to reduce chamber volume to '66 size and to compensate for the thicker head gasket now available, but milling is typically a part of a valve job. It will require a mill cut of about .075". I know that sounds like alot, but .025" is just the difference in gasket thicknesses- old to new. A mill cut of that much will get your engine back to the 9:1 CR range of a stock '66 200. The D7 valve springs will be adequate for most street engine applications. They can be shimmed .030" if more tension is needed.

I don't recall the details of your project. You might want to give us a reminder of what you're working with.

Adios, David

 

[JackFish]

Don't forget the 3-angle and backcut valve job.
Now would be a good time to install the oversized SI valves too if you're into that.
Pocket porting too.

 

[TxAgs66]

Thanks for the replies guys.

Here's the project -
1966 Mustang, 200 CI 6. Weber 38/38 DGES, Duraspark conversion, Classic Inlines 264/264-110 cam, double roller timing chain, dual outlet headers. All in front of a T-5. Unfortunately, it is a non-world class T5.

Here's what I have done so far-
1. Removed everything from car
2. Stripped paint by soda blasting
3. Broke engine down to get to cam. Decided to go ahead and break down the bottom end as well.
4. Repainted the car and getting interior back in. Damn windows are so stinking difficult!

Ok, so the block and head are at a machinist. He says that the block was at .030 and he is going to go ahead and bore out to .040 in order to clean up cylinder walls. There were a couple of scrapes that were pretty bad from the rings. He looked at the crank and thought it would polish out just fine. I believe he said it was .010 under.

The head is an original small log. One of the valves and seats had burned up pretty bad. The valve guide is also pretty rough as well. We also looked at the rocker assembly and it was pretty rough. The rocker arms are well worn and the shaft is sloppy.

So, my machinist really wants me to find a 250 head. I do to! He is going to put in hardened seats on the exhaust side. He also wants to get a new rocker assembly.

I am rapidly busting my budget! I am so tempted to just suck it up and get a CI Aluminum head and be done with the challenge.

Can someone refresh my memory of what cars had 250s?

Thanks,

Jason

 

[JackFish]

Again, 250s and 200s share the same head.
Anything in 1977-81 range should be good. Fairmonts, Zephyrs, etc...

 

[CNC-Dude]

One way I would look at it is if you are going to spend close to half the cost of the CI aluminum head on a log head, you still wont have a head that is half as good as the CI head. So if your already considering the upgrade, you can use this as a determining factor.

 

[Lazy JW]

One way I would look at it is if you are going to spend close to half the cost of the CI aluminum head on a log head, you still wont have a head that is half as good as the CI head. So if your already considering the upgrade, you can use this as a determining factor.

There will never be a better time to upgrade

 

[bmbm40]

I would not put money into a small log head.