Have you ever noticed that a Thickstun PM-7 is offset?

Is it possible that it was offset to compensate for fuel throw inside the manifold at the track, you know centifical force , like the track guys leaned carburetors to the left on fab intakes, for the same purpose? maybe? This is why open plenum ram injection isn't used in drag racing anymore. The g forces cause cylinder wash at the rear of the engine . maybe? i, well it was designed as a racing intake, no? my 2 cents.

 

I want to see your cut-aways! In fact, I double dog dare you to do it.

 

Now I know why everyone runs a small block Chevy.

Flatdog, please post up some cutaways. Sound interesting, and might help a lot of people here build better flatheads. You can't corner the market!

 

Gunna do it when is Tech week?

 

Get out that camera, Flatdog! The screensaver in Flatdog's BRAIN is a cross-section view of a flathead port!

Now: Crank is offset to RIGHT .265, cam is offset differently by a trivial amount.
R&L valves are canted differently, differently differently '32-45 and '46-53 just to make life exciting.
Cylinders also offset, probably not directly relevant here.
There are good cross-sections in Service Bulletins, Blown '49 sells even better big posters of late crossections, cleaned up and very sharp. If you don't have both you ain't trying.
This is tech week, so let's start a tech first on HOW to explore this and find the facts, then on the whyness of it all. Flatdog I'm sure knows, but I know his answers are gonna be CRYPTIC and INTRIGUING.

Now--I can see some of the offsets clearly on the various available cross sections. I am not secure on exactly how the visible top and bottom surfaces of the block and openings for pan and manifold relate to centerline of block and centers of shafts. In fact, with every damn thing offset, I am not entirely sure exactly how I would even DEFINE centerline of the block...so I gotta see it and feel it myself.
This is a how-to on exploring this stuff, what I did this weekend and what I need to do further. I never really got to looking at this before, since I can't change any of it, but this post brings up the issues as TUNING factors we can actually use.

Finding what's where...looking for the axis mundi in an offset world.

First--line up a nearly bare block, a 59Z serving as home for 10,000 spiders in this case, a Thickstun for its massive offset, a stock (Canadian WWII military) manifold to explore.
Top of block first: I installed tall studs in 4 center area manifold bolt holes, tall enough to make stock and thickstun measuring easy. Dropped a tall piece of 3/8 rod into pump pushrod hole (cam centerline!). This is sufficient to study SOME of what's happening.
Bolt holes themselves and adjacent intake ports seem symmetrical in terms of the visible flattop of the block. Exhaust crossover holes appear slightly offset to Left. Stock manifolds shows carb offst to L by about 1/4", Thickstun close to an inch.
This blasted block was never drilled for its manifold locater pins, so that introduces some shakiness. WTH??
Port openings, probed at opening with angle finder, appear to start at same angle L and R, but of course must differ farther in because of valve angles. This is tough to measure, so Flatdog's cross sections will be VERY useful. It would also be helpful to put magnetic or otherwise stuck straight edges on the valve tops to make angle clear in relation to topside.

Next--need to borrow some muscle and get that block jacked up a bit so I can get at bearing saddles and pan face. Need here is to ID main center and study pan opening from there, determine plane and measure 90 degrees up to properly identify crank and then cam centers on top of block. This stuff will become more clear as I can actually SEE some lines on the block. I can only steal a few minutes at a time when I'm at home due to wife's medical stuff.

So...where to go from here, once all the different centers are drawn on block? Port axes will be important...but will take some thought, as they are deep and dark and all shapes are complex, not solvable with ruler and square...bring on the cross sectons.
Wish I had a manifold, or several, milled down to the bottom inch to make looking at those transitions easy. No, I don't want anyone to offer to mill down my Thickstun...

 

Bruce:

Let me know if you need some muscle to move that block around for this experiment. I could swing by afterwork one day.

 

That would be great...first, gonna nab four angle iron legs for the old lump to get it up as a fitting block. Want to clearly establish all 17 centerlines on this sucker.
Bangers are offset too, but hurt my head less...
Anyway, this is just one of about a million places in which you realize how much nearly invisible complex thinking went into the flathead. A simple lump of iron with more secrets than the Great Pyramid, a simple lump of stone...
And remember...there ain't no reason they could not have shoved the cam center to where the valves could have had same angle, is there?? Somebody was thinking something there.
So a flathead turns out to be like a big-block Chevy, with two different intake port types. Tuners have used such things to do other things...ever wonder about those BBC race motors with the Hilborn stacks on the two port types different lengths??

 

Ummm...this week, conveniently.

 

Joe Abbin recently did back-to-back dyno testing of PM-7, Edelbrock Super, & Edelbrock 3x2 on the engine he built for Honest Charley (I think).
He said the 3x2 made the most power, but of the two 2x2s, the Super actually made more power.

I don't care, I'm running my PM7 because it looks better!

 

My son is running one of these manifolds on his 27T roadster, on an early 21-stud. When
he made the radiator support rods, he came off the original T bracket on the firewall, then split before the carbs using two rods that were symetrical and passed one on each
side of the carbs, then to the usual two places on the (shortened by Walker 28-29 A) radiator. It was then that we noticed the offset to the driver's side... After standing
around and scratching our heads and looking things over, we decided that the carbs
were offset to the left to make enough space for two of the manifold (hold-down) bolts
on the RH side, for which there would be no room if the risers were centered.

 

For the sake of clarification we need to define left and right in our descriptions! In my above posts I used left and right when viewed from the front of the block. If I understand Bruce's post correctly some of his info suggests the the drivers side is left and the passenger side is right.

Help me out here guys.

 

When talking automobiles, everything is the Driver's perspective. (Driver's left, Driver's right).

Anyone seen the tech post on the cut-aways yet???

 

Yes, I've always been told in car work left is US Driver's side always. In effect, the car has its own left and right like a person, so when you say "Left front tire" it means the same thing to all hands.

 

Thanks guys I thought it was always that way so you will need to reverse your hands for my initial posts.

 

We could just go Navy and call it port & starboard - then there'd be no confusion!

 

Hey,

Nice car but have you guys noticed how off center the air cleaner is? Throw the whole thing out and start over!

Kidding.

I think we all have a few of those little details that drive us crazy on our cars.

don't spend to much time looking at it when you are driving or more than that will be "off center".

 

Hi Richard, Mike from Yorba Linda here. Good to see you posting here.

 

This is the first time... Apparently the simple explanation is too simple? R.

 

It is interesting...I think I did notice the Thickstun had a full complement of bolts. Most aftermarket manifolds dropped a few, I guess largely because of interference from both runner design and fatter casting at runners. An Occam's razor explanation. Or Occam's 9/16" wrench maybe...

 

I love mine so much more now.
It might just be 'cuz it's driving so many HAMBers crazy

 

The towers are over about an inch.

 

I was told by an old John Deere parts counter guy that left and right orientation is from the perspective of standing behind whatever you're working on. The only exception to that rule is a manure spreader - that you stand in front of!