New to the Flathead game and need advice

[Rick Gibbs]

Hello Everyone, I am new to the Flathead V8 game and could use some advice. First I got the truck from an individual that had done a lot of the restoration. He was very very meticulous about what he was doing and did a very good job. The family said the truck’s engine was said to have been rebuilt about two to three years ago and is doing very well for the truck. I have placed a Oil filter system on the truck.. what oil do y’all recommend? This will be the first oil since the oil filter system was placed on the truck. It is a weekend driver and special events. Question 2 The transmission was not rebuilt and I am getting a stuttering in the truck when starting off. Some say it is the clutch and needs to be adjusted. One person has told me to change it out with a S10 transmission. I like the original transmission but would like to cruise at 60 mph with a low RPM and they say a S10 transmission will give me that. The truck currently will go 45 mph to 50 mph but it is turning a high RPM to get to 50 mph. So my current game plan is to run none detergent oil something like a 10w 40, change out the rear gearing ( key note is I have never attempted to change out any rear gears in my life and the master “my dad” has passed.) I have looked at rear gears from speed way motors. I have just changed out the point distributor with their product and could not be happier with it. If I change out the rear gearing I would want to keep the old transmission and get the old transmission rebuilt with new clutch and pressure plate etc.. What does everyone think? Sorry for needing so much advice from the group already. Thanks in advance for the help.

[Rick Gibbs]

Sorry did not even say what the truck is.. it is a 1940 ford 1/2 ton with the original engine engine and transmission that come with the truck when it was built.

[JSeery]

Welcome to the Barn. Mac Vanpelt is a good source on transmission questions and parts (and information on flatheads in general). http://www.vanpeltsales.com/

[tubman]

Any commonly available 10/30 or 10/40 DETERGENT oil will be fine. It would be a mistake to run non-detergent oil in a rebuilt engine. Today's oils are vastly superior to what was available when these vehicles were new. You want the detergents in the oil to keep the engine from sludging up. You can add ZDDP or run a high ZDDP oil if it makes you feel better, but that is not necessary either. Because of there design, flatheads need much less valve spring pressure than modern OHV engines so they are not as susceptible to camshaft damage.

As to the transmission, what you are describing is probably clutch chatter. This is usually caused by motor or transmissiom mount problems. This series of flatheads has what are called steady rods or anti-chatter rods that run from the frame to the rear of the engine. Make sure they are installed (some people mistakenly remove them) and are properly installed. A T5 five speed transmission is a good addition to one of these vehicles. The overdrive fifth gear improves the driveability greatly. However, there are obsticles involved, such as the need for an adapter, speedometer hookup, and some of the available transmissions have internal gear ratios that are not really suited for everyday use. There is a ton of information on the internet about this swap, so you can do a bunch of research before you make a decision. You say that you are satisfied with transmission, but do not like the limited top speed. In this case, you should consider changung the stock rear end (whish probably now is a 4.11 ratio) to 3.78, 3.54. or even 3.25 gears that are available. You probably wont be able to haul heavy loads as well as with the 4.11's, but the highway performance will be greatly improved.

[WABOOM]

15w40 diesel oil with the SN specification is what I chose to use in my flathead.

[Rick Gibbs]

Sponsored Links (Register now to hide all advertisements)

This is awesome input so thankful.

[19Fordy]

Rick, Before you go buying and installing new rear end gears ( a complicated job) converse with folks who already have a 40 Ford truck like yours and learn as much as you can about them. First find out what gear ratio is in the rear end. Sounds like it might be 4:11. In that case 3:78 is more desirable for highway.
You can still use the stock transmission. MAKE A PLAN first and then follow it. Otherwise your truck will become a money pit.

[tubman]

One other thing about a T5. It usually requires a rear end change because the back of the transmission is incompatible with the closed driveshaft system used by these Fords. A couple of the guys on here ("V8COOPMAN" and "Heard") have developed a method of using the original rear end and you should review their thread. I think it's here : https://www.fordbarn.com/forum/showt...ghlight=closed.

[Rick Gibbs]

Currently weighing all my options to evaluate the cost. The rear gearing has to be 4:11 and is there a way to adjust a clutch on these old transmission or evaluate how much clutch is currently left to be used. Sorry if seems to be a stupid questions. I am a person that ““always measures twice so I only cut once “ type of guy when it comes to this truck. I figured out how to get the picture to show up under my name.

[tubman]

There is an adjustment on the linkage under the floor. Remove the floorboards and it should be obvious. While you have it apart, check the steady rods and rear transmission mount.

[Rick Gibbs]

Thanks for all the advice and help I will let everyone know what I find and do moving forward. This has been great!!

[19Fordy]

Rick, While you're under the truck adjusting the clutch, pay close attention to how much "play" there is between the clevis, the pins and rest of linkage parts. A tiny bit here and there all adds up. If you need instructions, i can email you instructions of how to adjust the 1940 clutch. I take photos of the pages and send them with the diagrams. PM me with your email address if you need them.

[Los_Control]

No expert here, I am going to guess what you really want to start with is gearing in the rear end.
Almost ashamed to say, I have a 1949 dodge with a flathead 6, 3 speed on the tree and stock 4:10 gears in the rear. It will do 45-50 mph.


I know my 218 6 cyl if I installed a 3:73 gear ratio, it will run 65-70 mph and have plenty of torque to pull a hill in 3rd gear on the freeway. If I used 3:55 gears, just a little to tall and on hills not enough torque and going to have to down shift ... not ideal on the freeway at slow 65 mph with a 3 speed and traffic running 80 mph.


Hope you see where I am going here, 4:10 is to low, 3:55 is to high, 3:73 is just right ... listen to the smart people here guiding you to a rear end change, and learn what gear ratio works for them with the torque of your engine. Then later swap the transmission if you think you want to.



For me, is as simple to buy a ford explorer rear end from a junk yard, spring perches from tractor supply and a new ujoint ... for you is different because you want to keep the big bolt pattern on the wheels ... I am just ignorant on the ways to swap the rear end in a 1940 Ford truck and use original wheels.

[Rick Gibbs]

Los Control you are correct about needing not to down shift in traffic. I sometimes think Alabama has not speed limits on major highways the way some drive. There has been so much done to the truck already, I think the easiest thing to do is change the rear gearing. I will keep you posted on which way I go. Thanks for the input. Every bit of advise helps.

[Rick Gibbs]

19Fordy I sent you a private message in hopes to get that information. Let me know if you don’t see it. I may have done something wrong being new to the site. Thanks again for all the help and advise.

[Mart]

I have a 41 pickup with 3.54s and 6.50 tyres. It drives very nice, but I do like to cruise 50 mph. 55 occasionally.
Forget the S10 trans unless you want to completely rework the truck with new rear suspension, axle, etc. etc.

Clutch chatter is probably more to do with engine and trans mounts and engine steady rods than clutch adjustment. If the clutch engages at the top and releases somewhere the adjustment is ok. You want about 1" free movement of the pedal before the linkage takes up the slack. You need a good pedal return spring and the pedal needs to return smartly.

Personally I think you need to bear in mind it is 80 years old and wasn't designed to cruise at 60 mph. The aerodynamics, beakes and wind noise are not condusive to high speeds.

You might be able to locate a complete rear end with good 3.54 or 3.78 gears and swap it in.

Or just take care of the clutch chatter issue and be prepared to sit back and relax and travel at a speed that is more comfortable.

What size tyres do you have? It's all part of the formula when talking about gearing. If they are the wheels and tyres in your avatar they might be smaller than stock and adding to the revvy revvy feeling you have.

Mart.

[Aarongriffey]

That’s the first I heard about a flathead not needing sink in the oil. Makes sense though.
Yesterday I changed oil and filter in a ‘49 Dodge flat 6. Couldn’t find oil with sink so I bough a tube of the additive. If I change oil for him again I won’t worry about the sink.
When they first stopped putting sink in most oils the story was that after the cam was broken in you did not need to use or add sink.
Oh, and as for that SUPER TEC oil that Walmart sells, we’ve been using that in my wife’s Corolla (10-30) since it was 6 months old and now once in a while I have to add oil and it’s only got 278,000 miles on it!
There was an article about that oil on one of these forums some years ago by an oil engineer. He said it was the best you could buy for the money. But didn’t say what company actually made Walmart’s own brand of motor oil.
We now use 10-40 dollar store oil in the old Toyota. Wish we’d have used AMSOIL from the start, but I didn’t know about it back then.
In my F1 I use 10-40. It gets hotter than hell here and sometimes almost freezing.
I’m not fussy about what brand,or weight, oil but I just want to use ONLY detergent oil.
I’ve seen too much sludge and stuck rings in engines owned by guys who “were told” they should use only non detergent.

[Aarongriffey]

I typed with z in front of sink each time but my stupid iPad changes it to an s.
It just did it again in the above sentence.

[my4dv8]

3.25 gears will be too tall for anything less than a built motor . 3.54 gears will be much better. what size rear tyres do you have, just to complete the calculations on RPM at 60mph.Its a little more involved changing rear gears on these banjo axles . But with the right advise you can do it.

[my4dv8]

Try zinc .

Originally Posted by Aarongriffey

I typed with z in front of sink each time but my stupid iPad changes it to an s.
It just did it again in the above sentence.

[tubman]

Just for information's sake, any oil with "50" as the last number of the weight has sufficient zinc for just about any need. For that reason, I run Mobil-1 10/50 in the hemi in my race car with an Engle roller cam.

[Ggmac]

Just something else to consider on your gear ratio is the size of your tires . They look to be a bunch shorter than what would be original . Take into account the diam. of current tires vs original. The ratio is stamped on the center housing .

[paul2748]

I have been told that oil with any oil with "40" is the same deal. In fact, a noted YBlock engine builder uses Valvoline conventional 10-30 and 10-40 in all his engine builds as they have enough zinc.

Originally Posted by tubman

Just for information's sake, any oil with "50" as the last number of the weight has sufficient zinc for just about any need. For that reason, I run Mobil-1 10/50 in the hemi in my race car with an Engle roller cam.

[JSeery]

Originally Posted by Aarongriffey

That’s the first I heard about a flathead not needing sink (zinc) in the oil. Makes sense though.

The additives came along with higher valve spring pressures with OHVs.

[WABOOM]

Originally Posted by Aarongriffey

Oh, and as for that SUPER TEC oil that Walmart sells...

There was an article about that oil on one of these forums some years ago by an oil engineer. He said it was the best you could buy for the money. But didn’t say what company actually made Walmart’s own brand of motor oil.

Warren Distributing Oil Company.

[Rick Gibbs]

Sponsored Links (Register now to hide all advertisements)

I think I should clarify, sorry new to the forum. But what I am trying to get in the gearing is turning a lower RPM at 50 mph and will go to 60 mph if I needed to. I would tear my engine apart trying to get to 60mph right now because it is running so hard to get to 50 mph. I just don’t want to strain the engine so hard cruising at 50mph. I hope that makes more sense. The idea of changing the whole rear axial is a good idea .... but I have already completely reworked this axial including new paint and coating. I thought the gearing would be good and the hands on work renewing the gearing was done by a friend. I wanted it to be done by someone that does it every day. The tire I am running is 255/55/18. They way the truck currently sits I don’t think I got any room to go bigger. Chatter has only started recently but I have gotten more play in the shifter . So since I am always fine tuning the truck I was going to check on the linkages and make sure the clutch is adjusted right. “Great help 19fordy” that is very good info he sent me. I am going to check all the mounts under the truck tomorrow while I am checking on the clutch. Speedway has gearing for sale I think it was 3:57. Do y’all think that would be right ratio?

[Mart]

255 55 18 is approximately a 29" combo. That should be roughly equivalent to 6.50:16.

The 3.54 gears are a great swap into these old trucks, that's what I have in my 41.

Mart.

[Rick Gibbs]

mart you are speaking Greek to me. Lol I think if I am following you right. Stay with the tires I got and get the gearing ratio I found at speedway. I don’t understand the 6.50:16 and 29 combo you said. Sorry if that is a stupid question.

[JSeery]

Rick, engine rpm, gear ratios and tire sizes are all related. The easiest way to reduce engine rpm is to increase tire size. In the rpm formula tire size is in diameter. Mart is giving you a tire size (the numbers on the side of the tire) that is equal to a 29 inch diameter tire.

Smaller tires will increase the engine rpm, larger diameter tires will reduce engine rpms. A 29 inch tire is a common diameter for these vehicles.

You can play with the numbers and see what you like, here is the RPM formula:

RPM = (MPH X Trans Ratio X Rear Axle Ratio X 336) / Tire Dia

In high gear in a 1:1 ratio transmission the Trans Ratio is 1, so:

RPM = (MPH X Rear Axle Ratio X 336) / Tire Dia

Now on the question of destroying a flathead engine with RPM, most likely not going to happen. 4000 rpms is very doable by about any flathead.

The MPH formula is:

MPH = (RPM X Tire Dia) / (Rear Axle Ratio X 336)

(4000 RPM X 29 inch Tire) / 4.11 Axle Ratio X 336) = MPH

So, MPH = (116,000) / (1380.96) = 84

At 3000 RPM the MPH would be 63

At 2500 RPM it would be 52 MPH.

Most people are not accustom to the sound of an engine running at higher RPMs because most modern engine are geared to run at lower RPMs. The design of the valve in head engine is very sturdy and the engine will be limited by the breathing capability of anything near stock engine. The engine is not going to be capable of high enough rpm to do any damage.

[Rick Gibbs]

Thanks, knew they were all related , never have worked the formula. I now understand the “29” and what it meant. Thank you

[Rick Gibbs]

Thanks, knew they were all related , never have worked the formula. I now understand the “29” and what it meant. Thank you

[38bill]

My pickup has 29" dia tires a 3:54 rear end and a T5 transmission. I love the T5's overdrive and it was basically a bolt in swap with the existing floor shift. There are adapters available for the banjo rear end that convert them to a open drive shaft so you can keep your existing rear end. I agree with JSeery about the sound. I finally installed a tach and found the RPM's to be much lower than I thought even though it seemed like the motor was really wound up. Post some photos of your truck please.

[Rick Gibbs]

Yes sir, I will add some picture to my album soon. Having connection issues at the moment.

[Hoop]

Deleted by Hoop

[Rick Gibbs]

So this is a follow up post and new question. Adjusted all the linkage on the clutch and checked out all the mounts related to the chatter question. Truck much much better. Thanks to all that helped. New question is about the oil. So I got lucus old motor oil with zinc 10w40. Oil pressure 40 psi when engine is cold. When it warms up to 180 temp. My oil pressure goes to 10 psi to 20 psi. The psi will increase when warm with higher RPMs but just sitting still will go back down to 10 psi. Do I need to run a heavier oil weight like a 20w50 during hotter days. Temp running well over 90 degrees on a daily basis in Alabama. Thanks for the help in advice.

[Mart]

The oil is fine, don't worry about it.

Mart.

[JSeery]

Originally Posted by Rick Gibbs

So this is a follow up post and new question. Adjusted all the linkage on the clutch and checked out all the mounts related to the chatter question. Truck much much better. Thanks to all that helped. New question is about the oil. So I got lucus old motor oil with zinc 10w40. Oil pressure 40 psi when engine is cold. When it warms up to 180 temp. My oil pressure goes to 10 psi to 20 psi. The psi will increase when warm with higher RPMs but just sitting still will go back down to 10 psi. Do I need to run a heavier oil weight like a 20w50 during hotter days. Temp running well over 90 degrees on a daily basis in Alabama. Thanks for the help in advice.

That's about normal for an engine with a lot of miles on it.

[Rick Gibbs]

Thanks a lot guys, totally appreciate it