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Old Flatheads and today's gas


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In my upcoming rebuild of my flathead 6 (217.8) I was thinking I should at least go with hardened exhaust valve seats.

A few questions:

-Anything else should I do in the rebuild considering today's gas?

 

Up to this point I have been using gas additives- a lead substitute, and Seafoam, and adding some Magic Mystery Oil to the current 30W non-detergent oil I use.

I will probably change to a detergent oil after rebuild.

-Is there a recommended oil weight? I am in the Phoenix AZ area, so no freezing temps- just hot in the summertime, so multigrade not really necessary (?)

-Should I continue to use any gas additives after rebuild?

-Octane rating- 87 good? Any advantage to higher rating considering these are a low compression engine?

 

Regarding compression- Mill the head .040 to .060 for a bit more?

Thanx much!

   

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I'll chime in with what I know, read or heard. If fresh rebuild, I would use synthetic oil because the oil is more consistent and usually better quality. Adding an additive has ZDDP is good as to not wipe out the cams. If the head is stock, milling the head .060 is safe. Oil weight I would look at 10w-40 (thinner oil so it's easier to reach areas when its first "cold". If you were gonna put stress on the motor, 10w-40 to cushion the bearings more.

 

As for octane. It's best to find a low octane full with no ethanol in it. The ethanol eats at seals in the fuel line. Higher octane burns slower then lower octane. With low compression low performance cars, you get more power out of a lower octane fuel.

 

I heard before the valve seats are already hardened?

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OK, now you have enough votes that the seats are already hardened steel.  I'd plan/budget for replacing the exh guides.  They are usually worn more than the intakes.  Check when you get in there, but just be prepared. 

 

valves themselves, 50/50 chance the exh will be too thin when ground.

 

Oil, my preference having lived the the valley of the sun, would be a qualty 15w40 diesel rated oil.

 

I'm lucky I guess as I have 4 stations within 5 minutes that have no ethanol fuel.  that said, IMO today's fuel is OK for the engine mechanicals, not so much for hoses and other parts.  87 octane will be fine unless you go wild on milling the head or advancing the timing.

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Valve guides don’t always have to be replaced.  Depends on how much slop is in them.  Your machine shop can guide you on that.   And a silicone bronze guide liner can be installed quite easily and probably save a bit of time. 

Oil?    I’d probably see what the bearing relief is after machine work.   0.0025”- 0.003” clearance I’d use Valvoline VR-1 20w50.  It has everything a flat tappet cam could need, and you’ll get arguments about if or not our whimpy spring valve train even needs it.  For my $ I’m happy to spend a little extra for the peace of mind. Few of us drive 3k-4k miles a month in these old cars.   You won’t be doing multiple oil changes per year.

 

You can read my (and other’s) multiple build threads throughout the forum and get some solid guidance.  

 

http://p15-d24.com/topic/43897-time-for-an-overhaul/?tab=comments#comment-467033

Edited by thebeebe5
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Good info on ethanol and rubber. Didn't have to consider ethanol back in the day. Don't want a car-b-q. Will be careful on rubber.

Great advice from all and I sure am going to appreciate those build threads. Sure will help me on my flathead 6. Rebuilt a couple flathead 8's back in the 70's and a couple OHC motors after, but this 6 is a new one for me.

Thebeebe5?  great tip on your thread re the outfit in Phoenix- to get the block cleaned out if I run into difficulty getting the water passages sludge and caking out. They're not that far from me here outside of  Queen Creek. BTW, your '37 looks really cool.

Thanx, all!

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3 hours ago, '41 Fat Bottom Girl said:

 

Thebeebe5?  great tip on your thread re the outfit in Phoenix- to get the block cleaned out if I run into difficulty getting the water passages sludge and caking out. They're not that far from me here outside of  Queen Creek. BTW, your '37 looks really cool.

Thanx, all!

 

 Give a shout if you need any additional advice. Also, if you need any machine work I know the place to go. 

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STP contains zinc.  I would stay away from full synthetics as they like to find places to leak. Been running 15 w 40 diesle oil for 40k since my rebuild. Traveler brand from TSC, the rottella last change. Just heard an advert for rottella gas engine oil on the radio yesterday might be worth a look.

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Hi, Below are my2 cents worth...  James.

 

1. I run straight 30 weight in a new engine and at about 40K miles I switch to straight 40 weight.

2. In a stock cam or close to it engine I never worry about adding Zinc. The guys/gals at the ANSI, when they tested the zinc no-zinc oil in production engines they maintain (which are as documented engines as they come) found that zinc did not do a thing. I also know some people who took cams/lifters, when this issue surfaced, and found out the cams and lifters were soft when they had them Rockwell tested. So chicken or the egg? With about 60K on my 251 in a car that outweighs everyone else around here my cam which was NOS looks just fine and never saw any zinc other than break in grease.

3. The ethanol in the gas can cause issues with the bore the brass plunger runs in on the Carter 1BBL's. Check it once a year. (search for my old thread on this).

4. Don Coatney has posted the mill chart on here a bunch of times.

5. If you decide to run more than 7 to 1, I run about 8 to 1 use Premium fuel. I have had evidence of some knock-ping under heavy load (again on a 5000 pound car) pulling up hills.  It is VERY subtle. One thing I noted on runs up a big hill, on days with temp and humidity the same, is that I am getting a little more power with premium. Now theoretically that is not supposed to happen. However, if there is any unheard detonation then a pistons forward momentum will be slowed by the early flame front. So, if you add premium and pick up some power it may be due to detonation. One can always retard the timing and run regular. In my case I need all the power I can get.

6. Guide wear is more of an issue that valve problems in my experience.

7. I just set up a PCV after running the new engine for 15 years and 60K miles. The oil stays cleaner longer and there is no visible blow by at stop signs!

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Sorry if I am taking this off topic....

 

James - 

Do you have a picture of your PCV set up?  I found mine sucks a little oil on long decels.  My engine is fairly fresh with good compression, I am probably going back to the draft tube....

IMG_1984.jpg.9d80b8bd7fd1146923752e65e21ef2bc.jpg

Edited by Adam H P15 D30
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I was thinking of getting rid of my draft tube also when I do my rebuild. I anticipate some oil in my future PCV tube because of the usual minor drip I had from the crankcase down tube with past and current flatheads. Always seem to have a bit of blow-by no matter the engine condition.

I was thinking of fitting a crankcase filter screen (Dorman #47064 and Motorcraft FA1068 are a couple available) between the draft tube (stubbed out raised up in vertical position as Adam has in his photo) and the PCV valve. To contain the filter in some sort of housing I would have to get creative with a piece of suitable I.D. rubber tubing and fittings both ends to attach PCV hose, or do something like that. 

Another thought I had was an oil separator (Steeda makes one for Mustangs I was thinking of) and put it in the line between the PCV valve and carb base. I suppose the possible advantage with  that is it visible whereas the screen at the draft tube would not (for maintenance?)

I will have to look on this forum to see if there are any posts on the subject.

If not, maybe some of the members have had some preventative fixes. Interesting you brought that up!

Great stuff...

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I've got to agree with James on the fuel recommendation.  When we built my motor it came out almost 9 to 1 with the aluminum head, and my machinist said the L-head motors are prone to knocking anyway, so he told me to run 91 octane (the best you can get in California).  Even so I could occasionally hear pinging under full throttle.

 

Marty

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