All Big Six Pedestal rocker build. Is it a good idea?

Relates to all big sixes

Motorboy

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Hi all! Today I had a surprise. I almost have the transmission buttoned up, And the weather was nice for a change here in PA, so I decided to wash off the engine since that’s next on my list. When I removed the valve cover I was surprised to see pedestal rockers. I assumed the engine was original (80 f250). I couldn’t get a casting number on the head (Maybe I’ll be able to decipher it once it’s off) but I’d bet it’s an efi head.

Anyway this changes my plan a bit. My original build was based on Keystoner16 https://fordsix.com/threads/300-rebuild.80112/ and similar to Macguyver’s https://fordsix.com/threads/ole-blu...4x4-300-6-3-od-trans.81388/page-5#post-640126 builds. Larger valves, rolling rockers, mild cam. I’m assuming this head has the shorter 4.75 valves.

I like the idea of using the scorpion rockers, but they have a much higher ratio. This is my first time building a pushrod engine so I’m green with the rocker arm geometry thing. Would this be a good idea, or should I get my head machined for studs and go with the Harland Sharps?
 

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pmuller9

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It can also be the 1985 to 1986 carb head.
We need a picture of the exhaust manifold side of the head.

Yes it will have the shorter 4.75" valves.
If you convert this head to stud mount roller rockers you will also need pushrod guide plates.

Roller rockers resized.JPG

If you go to the longer valves you can use the Scorpion roller rockers for the moderate cam profiles.
 
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Motorboy

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It can also be the 1985 to 1986 carb head.
We need a picture of the exhaust manifold side of the head.

Yes it will have the shorter 4.75" valves.
If you convert this head to stud mount roller rockers you will also need pushrod guide plates.

View attachment 5548

If you go to the longer valves you can use the Scorpion roller rockers for the moderate cam profiles.
So if run the longer valves (4.8 inch as I remember) with the scorpions, I assume I'll need custom length rods, but will I need guide plates as well? or is that something I measure for later?

For all intensive purposes I'm an keyboard expert on this engine. I've read a lot, but have no hands on experience.
 

pmuller9

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Pushrod guide plates are only needed for the stud mount rockers like the Harland Sharp.
It keeps the rocker arm from turning off the valve stem.

The pedestal mount rockers like the Scorpion are locked from turning so they do not need pushrod guide plates.

Either the Harland Sharp or the Scorpions will need longer pushrods.
That's something you will measure after the engine is assembled and it is time to install rocker arms.

Are you going to install larger diameter valves?
 

Motorboy

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Ahh.. thanks for the info. I was a bit confused as to the purpose of guide plates. That makes sense.

Well since I was planning on running a fairly mild cam and getting my power gains from valve and head work, it seems going with the scorpions would work well for me as I won't have to mess with guide plates and a lot of extra machine work. I assume with this set up I'm restricted by valve lift. I remember reading somewhere these heads don't do well with lift beyond a point. I can't seem to locate the sicky. Any guru advice on what i should keep below?
 

pmuller9

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The valve spring retainers will hit the top of the valve guides around .500" valve lift.
It is possible to trim the guide down for more lift.

Are you going to use larger diameter valves?
 

Motorboy

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I was planning on running 1.94 and 1.60 valves, cleaning up and blending the intake bowls and polishing the exhaust. I hadn't decided on a cam, but I was eyeballing the Howads 280026-08 or the Erson E270101 as a good candidates.

A few years back I put on an offy cseries intake, efi exahust manifolds, and a 2150 with 1.08 venturi on it. This was a great running set up, and totally adequate for my needs, but i've gotten hooked on the idea of building up this engine, and since then the pan gasket and a freeze plug started leaking, and the 3-4 syncro on the trans went, so i was pulling it anyway.....and you all know how it goes from there.
 

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pmuller9

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There have been problems lately getting the 4.810" long 1.94"/1.60 valves from VI.
Just use the 1.910" long SBC 1.94"/1.60" valves instead.
There has also been a problem getting Erson cams for the 300 six.

The Howards 289926-08 has a 108 LSA which has more overlap than the other comparable cams.
It will have a rougher idle but will provide good low end and midrange torque especially with a long tube header.

If you want a smoother cam in the same range look at the Schneider 131H which has a 112 LSA.

Could you post a picture of the exhaust port side of your head?
 
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Motorboy

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Here are pics of the port side. I had to get back to the shop to take them. the morning light was just right to get a better pic of the head casting.
 

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pmuller9

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That is not an EFI head or block.
It is either a 1985 or 1986 engine that used a carburetor.
The combustion chambers have a 76cc volume.
 

Motorboy

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Thanks Pmuller! Is there a good sticky or thread on using the Chevy Valves? I'd prefer to read up before asking a lot of redundant questions.
 

pmuller9

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There's no specific thread on using the longer Chevy valves so here is what you need to know.

The longer valve will move the rocker arm higher.
You will need to determine at what rocker height positions the roller tip to travel across the center of the valve stem tip.
Once you have that then you can measure to see what pushrod length you will need.
The longer valve also moves the valve spring retainer higher and depending on the spring pressure needed for the cam the valve springs may need to be shimmed.

We can cover how to do each of those measurements later.
 

old28racer

Famous Member
This is a picture of the welded sbc adjustable guide plates pmuller9 is talking about. they are for 7/16" rocker stids and 5/16" heat treated push rods. They were welded in a gig for all 300 studed heads. They are for sale, never used. Message me as I have a set of original Ford refurished EFI Exhaust Manifolds (front & rear) also for sale.
300-Motor-141.jpg

300-Motor-142.jpg
 

Motorboy

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There's no specific thread on using the longer Chevy valves so here is what you need to know.

The longer valve will move the rocker arm higher.
You will need to determine at what rocker height positions the roller tip to travel across the center of the valve stem tip.
Once you have that then you can measure to see what pushrod length you will need.
The longer valve also moves the valve spring retainer higher and depending on the spring pressure needed for the cam the valve springs may need to be shimmed.

We can cover how to do each of those measurements later.
Thanks! I don't post much here but if you could see my bookmarks bar it mostly threads here.

Well done anticipating my next question. (it's like you've done this a few times :)) What springs should I be looking at? Something tells me I won't be shimming the stock ones out that far. Or is that something I measure for after I get the head machined for the valves?
 

pmuller9

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After the head is machined for the valves you will install a retainer and measure the distance under the retainer to the valve seat on the head.
Your measurement will be around 1.800" with the Chevy valve.
You will take this measurement for all 12 valves and record them

1614401284878.png

The stock spring has a seat pressure (when the valve is closed) around 80 lbs with a spring rate of 300 lbs per in.
You won't need much more than that for a midrange hydraulic cam.
We like to see seat pressures between 100 and 110 with a little more spring rate.

You will only need a single coil spring that fits the head.
Notice the raised ring under the valve stem seal.
That is cast as a spring locator so the ID of the spring has to fit around that ring which is just under 1.000" in diameter.

One of the springs that will fit the bill is the Comp 942.
Use with the Comp 768 retainer.
It has an ID of 1.027" and a seat pressure of 98 lbs when installed at 1.750" with a 339 spring rate.
You would shim it a little tighter than 1.750" just to get the seat pressure over 100 lbs.
 
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Motorboy

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Thanks for all the info! Before I whip out my credit card and start buying parts, let me run a general list by you.

  • My fist order of business is to find a good machinist in the Philly/Allentown area. Of the 2 i knew 1 passed away, the other retired to Florida.
  • Next disassemble, clean, and check over what i'm working with. Despite the gasket and freeze plug leaks, this block seems pretty healthy (see pic of compression when pulled) But I've taken apart healthy running engines only to find there was a crack or flaw somewhere and i was better off hunting down a new one.
  • Once I can conform i got a head worth working with, I can order valves, guides, retainers and rockers. (any suggestions would be appreciated) I've herd a lot of talk on stem seals, viton, was name i see a lot, is that something i should look into?
  • I'll order pistons once i cc and measure the ones i have. I have no plans on altering compression much.
  • Then it's off to my new machinist.
  • Once the head is cut, i can blend the intake side a bit and polish up the exhaust. measure for springs. Order up cam, springs, shims, gears and lifters.
  • Assemble block, Measure up for pushrods.
  • Final assembly.
Am I in the right ballpark?
 

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pmuller9

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The head:
The machinist will determine if the head need valve guides. Usually the head is good in that respect.
Viton metal jacket seals require the top of the guides to be machined with a cutter so the seals snap in place.
They are the seals showing above in post # 18.
Your machinist should have the cutter and the seals.
Do all your grinding in the bowls and ports before you send the head to the machinist.
If you do it after you might hit one or more of the newly machined valve seats.
After you get the head back you may want to do a little blending in the bowls or not

The block should have the freeze plugs removed and all the plugs for the oil gallery.
Keep track or take pictures of where you remove oil passage plugs.

Optional but recommended is inspect the inside of the crankcase for sand/iron lumps and deposits in the inside corners and grind them away.
Grind off all flashing you find in the block especially in the cam tunnel.
Radius all edges inside and out.
Excellent example starting with post #121.

The machinist will determine what size overbore the block will need.
Once you know that then you can order pistons.
Use the Speed Pro H519P hypereutectic pistons.
Machine off just enough to clean up the block deck.
The machinist will install the new cam bearings.

The pistons will need to be pressed off the rods then the rods get resized with ARP rod bolts.
The rods will need to be balanced so all the small ends and large ends weigh the same.
The new pistons will also need to be balanced so they all weigh the same.
Then the machinist will press the new pistons on to the rods.

The crankshaft journals will need to be turned and polished.
Then the crankshaft gets balanced.
 
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