Question about my 250 inline build and headers

I'm building my first inline and well its a whole new ballgame for me. Im waiting for the block to come back from the machine shop. Having the crank reworked, new freeze plugs, new cambearings and what not. I've already rebuilt the head. New springs, guides and valves. Ordered a 32/36 carb, air filter and 1-2 adapter, new big torque comp cam, hei distributer, glass packs and pipe. I want to run the stock single intake but I'm tired of the old exhaust manifold springing leaks constantly. Summit sells long tubes but will they work with the stock mounting style? Do I need to buy flanges or something? Kind of lost on the situation? Any ideas on header mounting? Thank you

 

Anybody?

 

The thickness of the flanges should be the same, or at least very close to, the thickness of the intake manifold. It's been a long time (1975-6) since I built a 250 six, and it seems to me there was some creativity involved in getting the bolts and hold-downs working together. I think you'll lose any improvement you might see by using an adapter taking a 2 barrel carb into a 1 barrel mounting. I just happen to have a NOS set of the shorter tube, universal fit Clifford headers and a Clifford intake for the late Chevy six I'm probably not going to be using in the near future. I am Butch/56sedandelivery.

 

Hello Dave, first off the avatar maybe throwing people off since this is a pre-49 all traditional hot rod website. That being said, there are plenty of guys here that love chevy inline six. I'm more of a Ford 300 guy but I'll help as much as I can. I'm really uncertain about the headers to be honest. But either way I don't think using the stock 1- barrel intake will allow you to really see the potential of the 2-barrell carb, the big torque comp cam, or the headers. If you want to do this right go get an aftermarket aluminum intake.
As far as the head? What size valves? Did you put in the lump ports?
It sounds to me like you have the potential of making some decent power for a street engine with the right combination. Have you gone to inliners international? Lot of good info there. Someone will chime in. Thanks.

 

I have a friend who used Sanderson block hugger for the 250. The look a lot better than the Fenton used on 235

 

Dave, here's a couple of ideas for you. If your exhaust manifold is the stock type, look at the surface that mates to the head. If it has corroded to the point where you don't have a good flange surface all the way around the exhaust ports in the head, you should replace it w/ a better one or with headers w/ a good thick flange. If it looks O.K., you could have the mating side surfaced at a machine shop. This will give you a better grip on the gasket between the manifold and the head. If the flange on the intake and the exhaust manifold are of two different thicknesses, you will need to make up a "washer" device to bridge between them that compensates for this difference, so that your fastener (bolt, or nut & stud) bear on them with an equal pressure.

For your intake, don't bother to run your two barrel 32/36 carb into a one barrel adapter on your stock intake, unless you know this is temporary and you can't afford better right now. Get a Clifford or Offenhauser single four barrel intake and a 2 barrel to 4 barrel adapter for that small Weber four bolt pattern to use with your 32/36 carb; you will get much better results with it. Or, eBay the carb, and get a 390 cfm 4 barrel, and run that on your 250". Either one will be better than funneling through your stock intake. Of the two intakes, the Offy seems to be more "streetable", or have better manners in traffic, while the Clifford flows better for wide-open throttle. I'm sure you'll get varying opinions on this. K6

 

Thank you all. My stock intake is temporary until I find one at a swap meet for a reasonable price. The old exhaust manifold is pretty poorly designed. It has a spot that is open to the bottom of the intake manifold. Its a 4"approx square made to warm up the intake. I actually tried machining the manifold smooth and the heating spot got off a bit. Now it blows that gasket and the new donut gaskets are junk. Well everything I buy new seems to ve lately. I know this is a pre era forum but I knew I wouldn't get a bunch of 18 year old kids saying to throw in a 350 or stroker. Nothing against small blocks but in all honesty there's no one in my neck of the woods running inlines. I've never seen one and I love the oldschool look of them, the dependability, and the ease of working on them. I've also got a 300 I plan to build next for my 67 f100 that will be a bit more radical. As far as lump porting, I thought about buying the kit to do it but wasn't all that sure I could do it without a vertical mill. Do they have a DIY at home kit? I rebuilt the head to stock specs but went with stainless exhaust valves to avoid stretching from heat. I'm not looking to even really get over 200 hp when all is said and done. Just a dependable little truck that can burn a tire when I want her too.

 

I've got Langdons cast manifolds on my 250 and love them. Just another option.

 

I am one of those guys who loves inline 6's.

I have been playing around with a 292 for the past 4 or so months. It has hei, hard valves, a couple extra bearings, and came with a truck attached. This is my daily and I make that high torque sticker earn its place. After messing with various one and two barrels that are now in my carburetor cabinet I took the plunge with a 390, offy, Langdons/stovebolt, and porters. One of the most impressive bolt on upgrades I have done in a while and worth every penny.

The cast headers seal perfectly and won't deform. The offenhauser is water cooled and the 3/4 hoses are to hot to touch within a minute. I did a lot of research and test fitting (mostly exhaust) while buying everything over a month. It all lead to a 20 hour install including the exhaust and linkage.

Note that some offenhausers use exhaust heat and some use water heat. The aftermarket suppliers won't tell you the difference. If it has shiny plugs at the bottom that's exhaust heat. You can seal the plugs easily or pull them out if you do get a exhaust heat intake and want to use it with water. Water heat is better for the aluminum. Make sure to get the water heat plate when you buy your headers.
If you go with 2.5" exhaust(like I did) you will need to taper one of the pipes 1/4 of an inch to clear the other where they come together. I have a bit less then 1/8" gap between the two after doing this. 2.25" pipes would have cleared and is what the headers are designed for. I had most of the 2.5 stuff from another build.

Personally I do not feel that lump porting is worth it in a engine that will see street driving.