Stock Head Info

[Dstan]

I am looking for some info on a set of heads I have. I am rebuilding a 1968 383 and the heads that I got with them have a 250 casting number. I have done some googling and searched through old forums on here and all I know for sure is that they are 1968 383 only as the other big blocks got the 906 that year and that they are open chamber (I have ordered the tools to cc them and will soon). I am going to run them as they cam with the engine I bought and they already have 2.14/1.81 valves installed. I am just hoping to find out how they flow and if they respond well to mild port work.
Thank you for any info.

 

[PurpleBeeper]

I found this list of big block head casting numbers http://www.mymopar.com/headcastnumb.htm

It looks like 250 heads are '68 440 only & since the 906's were released that same year, and since the 250's have the larger 2.08"/1.74" valves, I "suspect" that those heads are identical to 906's, but may have come with slightly weaker valve springs ??? for non-high-performance 440's in '68 ???

From what I understand, the biggest benefit for flow on those heads is "pocket porting" where I believe you smooth out the area around the valve guides into a teardrop shape with the tail of the teardrop facing down-stream of port flow. Smoothing out the bowl area in general should help + port matching vs. gaskets. Polish the exhaust ports & leave the intake ports rough. You can still find some Direct Connection porting templates (pieces of plastic you cut out of a sheet) that are supposed to help you mill "just enough" out of the ports to improve flow. Also, for sure add some hardened seats to the exhaust valves to run on unleaded fuel.

This is just stuff I've heard & others on this board are much more knowledgeable than I am.

 

[lewtot184]

I don't think the 2.14 intake valve will respond well to just a template port job. they need more work than that to really pick numbers up. i'd suggest that you let a professional get the most out of those heads.

 

[1967coronet440]

88cc I believe Open chamber, probaly flow well under 200 cfm

 

[Garys1969RR]

The 906, 915, 452, and346 heads all flow within a few CFM of each other, in stock form. I imagine the 250s are similar. To get really good flow out of any of those heads, you will need to spend alot of time researching and grinding. Hot Rod mag had some really good articles on porting Mopar heads. Read those, follow the ideas, spend 40 to 50 hours, and you might see some improvement. Or spend $1000 on some after market alum heads, and you will he $$$$ and time ahead. Not to mention the lighter weight. Good luck !

 

[wyrmrider]

IDK if those heads have 915-906 ports or 64-67 516 ports- the rework is slightly different- stay away from the short side.
when the larger valves were put in were the throats opened with a cutter?- If so much less hand work

 

[lewtot184]

IDK if those heads have 915-906 ports or 64-67 516 ports- the rework is slightly different- stay away from the short side.
when the larger valves were put in were the throats opened with a cutter?- If so much less hand work

if the short side isn't re-worked with the big valves the head will flow less air than a stock valved head. the short side is the key to flow on the intake side with big valves.

 

[Garys1969RR]

Yes there is alot to learn about head porting. Short side radius, pocket porting, back cutting intake valves, push rod pinch area, etc. Spend some time learning about what to do before you pick up a high speed grinder.

 

[lewtot184]

for the home port job it's best to stick with stock valve sizes; unless you have some direct experience with big valve/short turn work. I've been thru this before with a set of big valve stage V heads.

 

[moper]

Pretty much all BB heads are similar in terms of performance. Porting is usually done in stages: I, II, III, etc. The biggest value, that meaning return on investment, comes from the valve job and the pocket clean up work. So if you're going larger valves, use a shop that has high quality seat and guide equipment, and have a 5 angle cutter valve job done. Then spend another $200-300 on bowl blending and gasket matching the openings and intake. It will be easy to reach 475-500hp with those heads and a medium sized street cam. After that it gets expensive.

 

[IQ52]

I found this list of big block head casting numbers http://www.mymopar.com/headcastnumb.htm

It looks like 250 heads are '68 440 only & since the 906's were released that same year, and since the 250's have the larger 2.08"/1.74" valves, I "suspect" that those heads are identical to 906's, but may have come with slightly weaker valve springs ??? for non-high-performance 440's in '68 ???

From what I understand, the biggest benefit for flow on those heads is "pocket porting" where I believe you smooth out the area around the valve guides into a teardrop shape with the tail of the teardrop facing down-stream of port flow. Smoothing out the bowl area in general should help + port matching vs. gaskets. Polish the exhaust ports & leave the intake ports rough. You can still find some Direct Connection porting templates (pieces of plastic you cut out of a sheet) that are supposed to help you mill "just enough" out of the ports to improve flow. Also, for sure add some hardened seats to the exhaust valves to run on unleaded fuel.

This is just stuff I've heard & others on this board are much more knowledgeable than I am.

1st of all, I believe that website to be wrong. I have never pulled a 250 head from a 440. I believe the 250 was used on the 1968 and only the '68 383, as I have pulled 250 heads only from 1968 383's.

Has anyone had a different experience? Please help us out if you have.

Having had the 516 and the 250 heads on the bench at the same time, they are much different than the other 1968 and later heads. They are closer in shape to the flat port 346, 452 & 902 heads than the 906 & 915, but do not flow as good, as cast, as any of them.

In a dyno test we did, we removed a set of rebuilt but stock 906 heads that were making 380+ horsepower and replaced them with a mildly ported 516 heads and jumped to 440+ horsepower. Well executed 250 heads should be able to do the same thing.

That is my take on it, others may see it differently. Yes, I may be all wrong, and all wet, as I have only been porting heads for 50 years.

 

[wyrmrider]

Good to know
I've used lots of 516s and must have but cannot remember the 250
I had a whole pallet of 516's back of the shop and evidently some scrap bandits threw them over the fence and down the road. I keep the 915's inside
Don't know why- market for them has dried up