Stock 250 cam in a 200

[Guest]

This has probably already been discussed, but I could not find it in the archives.
The vehicle is a 64 Econoline van used as a daily driver. I am going to start pulling a small boat and would like to have some more power on the lower end of the rpm range.
I am going to remove the 64 170 head and install a 250 head on my stock 66 200 block to improve the breathing. I plan on having the head milled .060 to keep the compression up, I already have a set of adjustable rockers from the 64 170 to go with it.
#1-What year 250 head is the preffered year for this swap? Largest valves, hardened seats, largest intake bore, etc?
#2-Will a 250 cam out of the same year 250 engine improve the low end performance, or do I need an aftermarket cam.

Dave

 

[CZLN6]

Howdy Dave:

The head you want is a 200/250 with the casting numbers D7XX or D8XX. the '80s casting will also work, but are encumbered with some extra milled openings that make it less desireable. The heads are from '78, '79 and '80s FoMoCo 200/250 engines. In these castings the 200 and 250s heads are identical.

The later cam would be an improvement over the '66 200. Duration moves up from 252 degrees to 256 in the later cam. Lift goes from .348" to .368"

For about the same money you could move up to a Comp 252H with .425" of lift and much faster ramps on the lobes to increase .050" duration quite a bit over a stock cam profile. That would be my suggestion.

You'd be doing yourself a favor if you moved up to a DuraSpark II electronic ignition system and late model carb too.

Adios, David

 

[Guest]

David czln6,
Thanks for the head and cam info. I will purchase the Comp 252H. I removed the points and condenser several years ago and replaced it with a Pertronix system. I have had no problems or failures of components with this system.
I hope you don't mind answering a few more questions.

Will the cam you suggested provide good driveability for daily driving?

You mentioned carb upgrades. This engine has a stock exhaust manifold and 2 1/4 single exhaust. What carb choices do I have available that would perform well with the 250 head and the 252H cam set up?

I have seen different numbers given for the amount to mill off the stock 250 head to bring the compression back up to 9-1. I will be using a Fel-Pro composite type head gasket. I would like to take as much off as I can and still run 89-93 octane fuel. Does the higher lift cam affect the amount milled from the head? Should I be concerned about crashing a valve through a piston? The pistons are the stock 200 dished center type.
Dave

 

[CZLN6]

HowdyBack Dave:

The 252H Comp cam will be an excellent daily driver. It will give you a stock quality idle, good vacuum signal and imporved perfromance over stock. You didn't say what trans you're using in your econoline, but this cam works well with an automatic trans.

Petronix is a good upgrade and it sounds like you're happy with it, but the stock '66 distributor has no centrifugal advance built into it. I guess I should have asked some questions before I suggested the DSII. Are you using the '66 carb and distributor Load-a-Matic system in your rig? If so the Autolite 1100 carb and the Load-a-matic distributor are designed to work together. When working as designed they give adequate performance. Give me some more details on your current system.

To prep a late model head plan on milling it .050" for the difference in chamber volume and another.025" for the difference in gasket thickness for a total of .075". You can safely mill these heads up to .090". Plan on using hardened washer under the head bolts on installation. There is no danger on valve/piston interference with this cam/piston combo.

Adios, David

 

[Guest]

David,
I am running the '64 170 head, distributor, and 1100 carb. When I go to the 250 head I intend to put a Weber carb and upgrade the distibutor to a later model.
Dave

 

[CZLN6]

Howdy Back Dave:

Your current '64 setup was/is holding you back in several areas; the 170 autolite 1100 carb has a venturi of 1.10" and a flow of 156cfm. The same carb from a '64-'67 200 has a venturi of 1.20" and flows 187cfm. You'd notice the difference.

The '64 distributor has vacuum advance only. Even with the Petronix conversion you're leaving improved performance on the table with no centrifugal advance. If you want to maintain your petronix conversion you might consider upgrading to a '68 to '72 distributor. It will have both vacuum and centrifugal advance and your Petronix unit should go right in. This will give you a stock appearance, if that's important to you. The DSII still has several advantages thought. be sure to use high quality plug wires.

The Progressive Webers have several advantages over the stock Autolites. They do take some tuning though, so be prepared. which Weber will you be using?

I think that you'll love the difference with the changes you have planned.

Adios, David