Help with a 250 build

[Ron R]

Just picked up a running 1974 250/C4 out of a Maverick, The car had 120,000 on it and was clean, I yanked the front spindals for my Fairlane and the 6/c4 for my wifes 63 Falcon Vert. The vert has a ready to die 170/2speed. All I really would like is a stock looking but peppy 250.
I would like to keep the 1 barrel carb. Depending on how the 250 looks inside I plan on a re-ring and new berrings/cam/chain/oil pump and rebuild the head. If it needs a total rebuild then I will do that.
What all should I do to the head? what cam should I run?
I plan on using the stock exhaust manifold off the 250. I also have a good 170 head sitting in the shop. The Falcon also has a 200 head on the 170.
(old owner put it on).

thanks for the help
Ron R.

 

[Ron R]

How much HP could a guy pick up using a header and a good 2barrel carb? Should I have the 250 head "decked" to raise compression?
What was the stock compression for a 74 250? 8.5-1?

 

[addo]

Not a whole lot, would be the first answer. A carb, new timing set and split pattern cam will show more gains. Decking the block will have more profound benefits than skimming the head massively, but it's probably safe to take a good 20 thou cut. Measuring and calculation of the CR with your motor apart is the safer bet.

Cheers, Adam.

 

[Ron R]

Thanks

 

[wallaka]

Taking materiel from the head will have the added benefit of cleaning up the quench distance. The 250 was made with a massive .100 (at least) deck. The average is .125, or 1/8" or so.

There are some recent posts about exactly how much to take off, just look down the page or back a few.

 

[falcon60]

Taking materiel from the head will have the added benefit of cleaning up the quench distance. The 250 was made with a massive .100 (at least) deck. The average is .125, or 1/8" or so.

There are some recent posts about exactly how much to take off, just look down the page or back a few.

Taking material from the head won't change the quench distance at all. Taking it from the deck surface of the block allows the piston to be closer to the deck at tdc and improves quench. Quench distances of .040" or so are extremely beneficial in a performance aspect due to increased compression and reduced detonation. If you choose to "zero deck" a 250,mill the head as little as posible because the added displacement results in fairly high compression ratios and no head milling is necessary. With a 200, .050"-.070" head milling may be needed to achieve the desired compression even with a "zero deck" block.
This measuring and calculating and the added cost of machine work seem like a pain,but do pay off handsomely in the end. It's the difference between an average rebuilt engine and one that really runs.

Terry

 

[Ron R]

anyone ever run into a rubber bolt in freeze plugs on the side of there 250 block ? It looks like the cheep ones you get at smucks to fix a blown out one, But its all of them no just one.

 

[wallaka]

Taking materiel from the head will have the added benefit of cleaning up the quench distance. The 250 was made with a massive .100 (at least) deck. The average is .125, or 1/8" or so.

There are some recent posts about exactly how much to take off, just look down the page or back a few.

Taking material from the head won't change the quench distance at all. Taking it from the deck surface of the block allows the piston to be closer to the deck at tdc and improves quench. Quench distances of .040" or so are extremely beneficial in a performance aspect due to increased compression and reduced detonation. If you choose to "zero deck" a 250,mill the head as little as posible because the added displacement results in fairly high compression ratios and no head milling is necessary. With a 200, .050"-.070" head milling may be needed to achieve the desired compression even with a "zero deck" block.
This measuring and calculating and the added cost of machine work seem like a pain,but do pay off handsomely in the end. It's the difference between an average rebuilt engine and one that really runs.

Terry

Oops. I meant deck, LOL.

 

[Ron R]

Cool I have the 250 pulled and sitting on the stand now.
I just ordered my Performance six book. And I am forming a plan.
But I keep getting side tracked with this turbo six stuff.
I love turbos and have been playing with the Dodge Diesel 5.9 six for about 6 years now. Only problem is that they are big $$.
I think Im going to sit back learn a little more, build the 250 for the wifes 63, Then plan a 1960 Flacon build with a 200 or 250 turbo powered!!! Something low, and cheep.

Later
Ron R.

 

[Ron R]

Anyone know of a good Machine shop in the Everett area? or close?

 

[Anonymous]

If you choose to "zero deck" a 250,mill the head as little as posible because the added displacement results in fairly high compression ratios and no head milling is necessary.
Terry

Don't you mean "reduced displacement"? (by decking the block)

 

[ASMART]

Decking the block does not cause displacement in the since that there is more cubic inches. It would reduce the cumbustion chamber size though increasing the compression and quench effect.

 

[falcon60]

"If you choose to "zero deck" a 250,mill the head as little as posible because the added displacement results in fairly high compression ratios and no head milling is necessary. "

I am referring to the added 50 CI displacement over a 200 and the effect that has on the compression ratio with the same cylinder head.The 250 will be much higher compression due to the increased capacity.
Right,decking has no effect on displacement......it's still Pi X Radius squared X stroke X number of cyls.

Terry

 

[Ron R]

Got it, thanks,

So what about 1/2 should do the job

 

[MustangSix]

If you decide to deck the block, I recommend you do it so that you end up with a "zero" deck, i.e. with the piston level with the deck surface. Then adjust the chamber size and piston recess to reduce compression. Anything less than a zero deck will raise compression without giving you any quench, making the engine prone to knock. a zero deck with a composite head gasket gives a good quench distance.

 

[Anonymous]

I am referring to the added 50 CI displacement over a 200 and the effect that has on the compression ratio with the same cylinder head.The 250 will be much higher compression due to the increased capacity.
Right,decking has no effect on displacement......it's still Pi X Radius squared X stroke X number of cyls.

Terry

Ok, we're all on the same page. Yes, I know displacement doesn't change by decking, it was the effect on quench that got me befuddled.