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Old 07-29-11, 10:24PM   #1
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Join Date: Jul 2009
Location: Butler, PA
Posts: 56
Default SD 389 build has finally begun....

Well, the divorce is now final and life begins again. I've pulled out all the components I've been accumulating for the past couple of years and have decided to do something a bit different. As the cost of building a true SD 421is outside my budget, I've decided to take a step back and build an authentic recreation of an early Super Duty motor, the SD 389. My original plan was to put a blower on this motor, but I decided to back off that direction and stay with a traditional high compression set up. The block is at the machine shop for cleaning and baking, the heads have been disassembled. And I have my first two problems that I need input from the group. These are 306 heads.

Attached are pictures of the combustion chambers showing the most and the least damage caused by sitting water. I have been told (and I don't know if it is true or not) that there is enough room in these heads only for either an intake or an exhaust seat, but not both. Can anyone either confirm or dispute that statement. I would like some input on how to correct this problem, including where to send these heads for machine work.

Problem 2 is the pinned in studs. The shop were I took these to be cleaned and magafluxed had no idea how to pull these studs out. So I told them to do nothing with them. My original thought was to remove these studs and substitute an contemporary screw in stud. What are the thoughts here? My plan is to use the McKellar #8 cam I have but to substitute new valves, springs, lifters, retainers and rocker arms. I have an original set of NOS pushrods I want to use here.

Next question.....can I get some input on which manifold to use. I read John from The Carburetor Shop's article on tripower and a V-8 engine and came away from that with the notion that if you want a set up to go fast you use a single four-barrell or a dual four-barrel setup. Well, a dual four-barrel was not available in 1961, so that is not a choice for me.

Here are some of the specific parts to be used on the build:

1961 4-bolt Trophy Block at standard bore, new studs to replace all bolts
1961 540306 heads
1961 SD manifold (based on input from the group)
1961 SD389 distributor
NOS McKellar #8 camshaft
Ram Air V 3.75" stroke crank. The crankshaft is currently on its way to Henry Velasco to be reconditioned back to factory specifications. Henry's shop did the original machine work on this crank. I had the crank X-rayed before I sent it to California and it checked out ok. The picture is the way it looked when it came to me from RacingJunk.
NOS Ram Air V or SD-455 rods

I have a 1961 era set of NOS forged AL pistons. What is everyone's thoughts of using these for this build?

Also, the heads for this build came off a 1958 Pontiac that was used for dirt track racing in South Carolina. The guy had them set up for reverse flow cooling. I have all the components needed to duplicate the reverse flow set up. I know it is not bone stock, but I'm not really that concerned with having something the way it came from the factory. I only want it to be period correct. So if this would have been a modification that would have been done back in the day, it's open for inclusion here. What are everyone's thoughts on reverse flow cooling?

I still need an early SD harmonic balancer. Can anyone help me out here? I know these are not cheap.
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Starman16002 is offline   Reply With Quote
Old 07-29-11, 11:44PM   #2
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Join Date: Jul 2002
Location: long beach,california
Posts: 1,834

late 61 the 991 dual quad intake was avail.I would run it with the stock size valves.You will want to clone a set of carbs as originals are stupid expensive,like 4-5 grand a set.Unless you are going to use a huge roller cam I would stay with the pinned studs.They were very good.If you need help with carb info PM me.Tom
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Old 07-29-11, 11:45PM   #3
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Join Date: Jul 2002
Location: long beach,california
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I have a SD balancer but dont want to part with it at thiis time.Will keep a eye out for you at Norwalk.Tom
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Old 07-30-11, 01:44AM   #4
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Join Date: Jul 2009
Location: Butler, PA
Posts: 56

Tom - everything I've ever seen regarding the 991 manifold said it was used only on the SD 421 engine, not the 389. As I said, I'm not adverse to making a period correct swap.

And I know what you are saying about the original carbs. A set just went on eBay for $4,250 that needed some work. I don't have that kind of budget for carbs.
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Old 07-30-11, 06:12PM   #5
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Location: long beach,california
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I know I and others ran the 991 as soon as theywere avail.Just not NHRA legal.Tom
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Old 07-31-11, 03:37PM   #6
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Join Date: Aug 2005
Location: Mcinleyville CA
Posts: 521

Just do what Smokey did.
"His" SD 421s were SD 389 blocks that had a cut down 421 crank in it.
He knew there was utterly no reason on the face of the earth for a stupid huge 3.25 main bearing.
Just go out and buy a modern 4" stroke 3" main forging and be done with it.
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