Unquestioned Flathead "Truths"-Questioned.

Seems like there are a bunch of things surrounding flathead builds that are unquestioned "truths" that sometimes seem suspect to me...

The one that has been nagging me lately is the one that says you have to replace the fiber cam gear with an aluminum one.

I've been looking at the like-new fiber cam gear with the metal insert that came out of my 8BA and thinking that a cast aluminum gear probably isn't that much stronger.

I would think that if you had enough pressure on that gear to break the fiber teeth, you'd be in trouble with the aluminum teeth as well.

And if it broke, so what... You're not going to **** a valve.

Maybe on the early motors it's an necessity to change them but on the later motors with spiral gears, it doesn't really seem necessary to me.

Another thing I was thinking is that with the relatively low valve spring pressure and relatively wide lifter face, the pressure on that big cam gear probably isn't that great.

But then again, I'm just thinking out loud.

Discuss...

 

I think the MAIN reason it is suggested that an aluminum gear be used (in place of the fiber) is when a different can (other that stock) is used with; say, double valve springs, the aluminum gear WILL take more of a beating.

Ford DID change to an aluminum gear in the later years.

 

My fiber gear has over 200K on a stock 51 flatty. Increased valve spring pressure could warrant a' lunimum one.Sparky

 

I was cruising down rte 81 about 55 MPH right in front of the Walker muffler plant just a grinin' in my 36 beater P/U with an 8BA....BLAHHHHHHhhh Just like you turned the key off. No warning, no horsin' around just cruising along. It was a nice Sunday afternoon spent waiting for my buddies trailer to come the 2 hours to retrieve me. It wasn't cold and rainy. It wasn't 2 in the morning but I'll use an aluminum gear on all of my motors...thank you very much. It ain't a wives tale to me.

Their only advantage that I know of is that they are supposed to be quieter ...quieter?? This thing is a hot rod!

 

Two datum points on stockers: One fiber gear retired intact at over 200,000.
One suddenly failed at very low mileage.
Ford used aluminum in many stockers, late and early--all flathead gears are spiral cut. Decent ones don't make any difference in noise detectable in an early Ford, and are stronger for sure.
The DO NOT USE case would be repro fiber, if anyone makes them. I know the Model A repros are like paper mache'.
I would definitely use aluminum for even a small increase in spring pressure.
My gear failure baffled me--I was busy checking ignition. But an old crusty mechanic recognized the key symptom immediately--vac wipers popped on for a second at point of failure!

 

hey hey,

if i had unlimited money, id make a Myth Busters series just on the flathead. nothing but busting flathead myths all day long, i think i could do an eppisode a day for a solid year.

seems like everytime you ask about a fleathead issue you get 100 different answers and all of them claim to be true!

what id like to see answered before my very eyes:

1. 2 x 94's with the stock dizzy and made to perform.

2. HP gains from a reg dual manifold compared to a "super"

3. the endless porting/relieving merry go round.

4. special valve springs on the isky cams?

more then anything i'd take my endless supply of money and do real world hop up performance tests. take that stock motor and swap on the duals and lets see how much it bumps up HP and torque. then those heads. hot ignition. different cams. porting. different HP figures for the same motor and different cams, or same cam and different makes of head. endless fun.

Danny

 

I think Petejoe solved the 2-94's with stock dizzy about a year ago; but then I could be mistaken (maybe it's a myth in my mind )

 

Danny,

In my discussions with Mike Davidson, I get the distinct impression he's done all this, which is why he's so "thingy" about block relieving. He's done the saw the blocks and heads apart, flowed this vs. that etc. Wouldn't hurt to give him a call. Be cheaper than a reality show!

(I'd like to work on Myth Busters, that has to be right up there with other best job in the world contenders).

 

I was under the impression that it wasn't teeth shearing off the fiber gear, but the gear slipping on the metal core. I could be wrong. Back in the day, I never used anything but fiber gears because I didn't know aluminum gears existed. I don't think failure of fiber gears is very common.

 

You could probably make quite a bit of cash off of a book about that, then again theres that initial investment problem...Jay leno maybe?

 

Hey Guys,

Yeah I think I'll need to marry Leno in order to get the capitol required.

The real problem with anything flathead related is lack of hard data. There must be a million before and after dyno readouts for SBC engines but I've seen one for a flathead. I'd love to know just which parts combination get the best result. Which cam, heads and intake etc etc.

*day dreams*

Danny

 

Good questions, and I had thought about the fiber cam gear too. I had planned to use mine, but after I ordered a cam and HD springs, and all new valves, ect, the price was cheap and the benifits seemed to be there, I threw a new aluminum gear in. I'd do it again.

 

Jim, the teeth sheared off on my fiber cam gear. It was the typical used motor transplant with unknown mileage. I'm guessing it was alot. I slapped a replacement aluminum gear in it and was back on the road again.

The plastic tooth GM gears always seemed to shear on start up (my experience anyway) with all the torque trying to turn the cam and valve train.

It just seemed funny to me for the teeth to let go while cruising. I guess they just got tired.

 

I've seen 2 94s and stock dizzy...

Mine!

On a dyno!

Ran fine. Did start to fall off in the upper RPMs but just after 4000 or so. Not a huge deal for a street flatty.

I may cheat and hide an MSD box in there somewhere.

I've also heard tell from multiple sources that a Super Dual will add 1-5hp over a regular. But that you have to think about intake design...

If you were to pit the best super against the worlds worst regular you might see some bigger numbers. The converse is true also...

One of the people who told me about the Super vs Regualar thing was the one with the dyno that my dizzy was tuned on. Take 1-5hp to the bank... Trust me on this one.

As for porting and relieving...

Everything in moderation. I've seen flow numbers that state that relieving doesn't help enough to warrant the potential problems it can cause. Why not just design the heads better?

Porting on the other hand can be very helpful. It's hard to picture untill you start grinding but once you're "in" the ports you'll see what makes the biggest difference. Short side radius on the intake ports and clean up the exhaust... And don't go nuts on a driver.

And valve springs?

There is no reason to load on the pressure on flathead valves. The cams that actually work in a flathead aren't extreme enough to warrant a heavy spring and the cams themselves aren't stout enough to handle the extra pressure. You'll send that thing whipping around in there if you put double springs on a flathead.

Answer your questions? It wouldn't have for me 10 years ago but I've done my homework and am pretty confident in what I've learned and who I learned it from.

Your results may vary...

I'm using the fiber gear. I'll let you know how long it lasts.

 

That think might just outlast us all...

Danny

 

Ole' Henry was tighter than a fishes date, so I'm guessing if he decided to change them it was probably coz it was costing him in warranty work?

I'm going to put an alloy one in my new motor, why? well, for start I have one, secondly alloy HAS to be stronger than fibre.

and lastly, this aint going to be a stock motor I want to be able to rev this thing, its going to cost me money to build and the small difference in the fibre to alloy I dont see the question need be asked.

also it just wouldnt feel right putting a stock piece in a hotrod motor

 

Hey Mate,

the only pleasant suprise I got from my motor is the fact it already has a alloy timing gear. bonus. lol.

Dan

 

I dont mean to hijack, but then again maybe this post is for ALL questioning?

whats the conflict with 2 94s and a stock distributor?

 

Vacuum signal.

 

Thanks Tommy. Mine never failed, so I was just working hard on resurrecting old conversations from my half dead memory cells.

 

The gears are different on early and late flatheads. Early flatheads had the pitch of the gears such that the thrust was against the block and late flatheads thrust against the timing cover. I really don't think the difference is worth fretting over except that gear thrust needs to match the timing cover because the early covers don't have a surface for the gear to thrust against. All that being said, I really wonder how much thrust their is and if the early distributors would handle the thrust from a late cam gear. Any experience out there?

 

Hope I'm not hijacking your thread, but what's the rev limit on a stock flattie? And what is a good highway rpm? I've been running mine at 3000, I thought that would be safe, will it take more, or is that too hard? 3000 rpm is about 60-65 mph.


JayD

 

2 carbs and stock distributor is a problem on '49-53 due to drop in venturi signal strength--this is compounded by the difficulty of determining actual working curve of the distributor without a dyno--it can be done, I think, but with difficulty. You can't just rev the engine up in your driveway and find out anything useful about curve.
Early engines do have thrust surface forward--the difficulty with late gears is that sometimes the distributor runs out of end play before the cam does, and trouble ensues quickly.
I only have one early dyno run on a flathead mild hop-up, which I've posted here before, from an old HRM or Car Craft. Most recently published stuff is actually air dyno printout probably based on guessed numbers and software really meant for SBC use.

 

no you have spark...it backfired

 

Yes, the direction of the helical tooth determines the direction of thrust.

On the question of 2-94's, the vacuum signal does play into how well the distributor advance functions. Two 94's is going to effect the vacuum signal to the distributor. ON LATE Flatheads, '49-'53, the stock arrangement has the distributor advance signal coming from the carb ABOVE the ****erflys. I have read (somewhere) that Jere Jobe says that the vacuum signal needs to come from the carb, because if it comes from the manifold the signal is reversed (?) and the advance does not function properly. He is also supposed to have said that the new billet distributors from Mallory or MSD do NOT have the proper advance curve for a flathead. Mr. Jobe is supposed to be a Stromberg '97 guru and also has worked a lot with flathead distributors. I understand he has finally settled his shop in Montana and is back up and running fully again. He may have done some dyno runs and he may be a source through his website.

I haven't dug deeply into this aspect of flatheads yet as I'm not at the point of rebuilding and running my engine yet. I have an interest as I'm sure that a lot of flathead overheating problems is caused by improper ignition advance.

 

Discussing the '49 distributor as "Vacuum advance" confuses things by bringing a familiar term to bear on an unfamiliar device.
The distributor vac line hooks to the carb, connecting to two utterly different sources of pressure drop (vacuum) signals:
A hole going down connects to vac right above the throttles, exactly what is called "ported vacuum" nowadays. This source delivers near zero advance at idle and lots of advance at part throttle, a perfectly good arrangement.
The p***age going up or maybe it's just over in the carb connects with the narrow part of one venturi. This line delivers pressure drop that is called nowadays "venturi signal", the Bernoulli (spelling?? WTH??) effect that a venturi is designed for--pressure drops in accordance with airflow, so this signal effectively increases in proportion with RPM and is meant to act just like centrifugal advance: At high speed or large throttle opening, the ported vac advance drops dead and the advance coming from the venturi signal goes up in proportion to RPM. There are also sort of feedbacks between the two signals, deliberate internal leak effects, that I have not attempted to even think about. The whole mess is fully described in various Ford and Holley (the designer!) books.
The big problem is that venturi signal is a very weak force, barely able to approach proper advance on a good stocker. Springs resisting the vac are adjustable, but must be able to cope with both systems! Early rodders noticed in 1949 that some new Fords actually accelerated better at part throttle than full due to problems with this stuff, and the old flattop Mallory became practically standard on late Fords owned by rodders. Even the factory specified curve is weaker than seems desireable, and many cars can't approach that.
When a second carb is added, the venturi flow becomes effectively 1/2 stock at full throttle--think about that.
Ford specified setting up the thing on a distributor machine with vac pump set to specified levels...but do those levels exactly match YOUR engine??
I think only way to determine curve in action is to record vac levels IN THAT LINE under varying operating conditions, then duplicate those signals with a hand pump on idling engine and see where exactly advance goes. Once you get that right, I would think you need to repeat the process to refine it, as the vac readings you read were likely a bit wonky due to the incorrect advance!
The thing can probably be flogged into adequate full throttle advance, probably at the cost of excessive part throttle advance, with a LOT of thinking and tuning.
Don't forget to conduct a flotation test (BuNavOrd test procedure 1943-787B) befor messing with other aspects of the lovely device...

 

Long intake runners are BAD on a flathead.

The mixture is cool and slow enough to begin with.

The one good thing about tall intakes is they can help smooth out a rough engine. More intake valume can smooth out a rough idle or compensate for the fact that the regular dual configuration places the carbs in less than optimal locations.

Jere Jobe set up my intake and dizzy.

I would never attempt to 'tune' a 49-51 stock dizzy myself. He does it on a dyno and has the experience necessary to pull it off. It isn't easy and probably won't run quite as well as the MSD distributer, but it's a vintage part and it was a fraction of the cost of a new MSD dizzy or of a old Mallory. I think it looks better than the MSD as well.

 

O.K. how about some more details on your engine setup, please. Like carbs, intake manifold, cam, displacement, dizzy, etc.

For my engine I was looking at the following:
Dual 97's on a super dual manifold (don't know the manufacturer yet)
Isky Max I cam,
Stock 239 displacement unless I can find a good 4 inch crank
Offenhauser or Sharp heads
Stock dizzy possibly modified with dual points setup.

The more I research, read and listen to the "experts", the more it sounds to me that I should hire Jere to set up my intake, carbs and ignition.

 

I highly recommend Jere Jobe's work. I put a Jobe-built '42 distributor on a flatty that hadn't run in at least 20 years. The engine popped off as soon as gas hit the carburetors. I didn't have to do anything to the distributor except bolt it on.