Stroke Recommendation

[Scotty's 52 F3]

My truck runs and drives but I'm collecting parts for my engine rebuild. It's going to be a mild street engine in my F3. Looking for good torque. I have 32" tall tires, a 3.73 rear gear and the T98 4 speed.

Walt DuPont fixed me up with an EAB cam and I have a set of EAB heads. I have no idea what the bore is or if the crank has ever been turned.

I'm running a stock Holley 94, stock single exhaust and I modified an old Accel dual point with vacuum advance. I don't mind running a small 4bbl if needed and might go dual exhaust just for the sound?

I have JWL's book but, I'm staying closer to stock. Bigger bore and more compression is my basic plan. IF.......my stock crank needs too much work or replacement it seems a new Eagle is the way to go based on reading posts here. Same price for longer stroke so any recommendations?

Scott

[old Tom]

If you go with 41/2 you will have to notch the block so I would try 41/8 It will give you more piston speed but will provide plenty of low end torque

[Scotty's 52 F3]

Thanks. Does the 4 1/8 need different rods or just the correct piston?

[rotorwrench]

It depends on whether you buy a purpose built 4 1/8 crank or make one out of a standard 4-inch crank by offset grinding it.

[Scotty's 52 F3]

All I have is my stock 3.75 crank. If it is OK, I may just stay stock to save some bucks.

If I need a crank...... I need to figure out what to get. Trying to get the most return on money spent on a relatively stock build. If going longer stroke is huge money for little torque improvement, I'll stay stock stroke and take what I get with a larger bore and more compression.

This is my first Flathead build so trying to plan ahead as far as "bang for the buck".

My truck weighs about 3500-3800 lbs if I remember my last scale ticket. When I had over a ton of rock in it I had to use granny gear to get going. Empty it is a good gear ratio to the power I have right now. I can take off in second gear just fine and top out about 65 MPH. I have a good amount of blow-by based on the smoke coming out of the draft tube so I'm planning my rebuild.

Scott

[34PKUP]

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Originally Posted by Scotty's 52 F3

I have a good amount of blow-by based on the smoke coming out of the draft tube so I'm planning my rebuild.

Scott

Install a PCV system to eliminate the smoke coming out of the draft tube.

[19Fordy]

Keep it stock and you will be a happy camper.

[richard crow]

19fordy has it right

[tubman]

I'll disagree with the last two guys. If you need new pistons, why not get a set of .125 over? In most cases, they're the same cost as the rest, and you'll be paying about the same amount for the actual cylinder work. 19 more cubic inches for essentially no extra cost. That's 3 cubic inches more than you get with the vaunted Merc crank. I've never heard of an 8BA block that wouldn't go 1/8" over (most will take 3/16") so there's plenty of room for another overhaul in the unlikely event it will ever be needed. I've had 2 8BA's with 3 5/16 bore (one 258" and a 276"), and never had a lick of trouble. I think the extra cubes would be even more appreciated in a heavy vehicle like your truck.

[Scotty's 52 F3]

My water jackets look really good after I flushed them. Hopefully I can bore without too much worry. Thanks for the advice!

Scott

[19Fordy]

Looks good. Did you notice the steel wire that was used to hold the cores in place when the block was cast? Pretty neat. You can snip it off with wire cutters.

[Scotty's 52 F3]

Yeah, I saw the wires. This is what my water jackets had in them before I flushed the system. I was relieved to see the block doesn't looked pitted. Where I can see anyway.

[Scotty's 52 F3]

I don't think this engine has been into. I haven't had the heads off so I'm guessing. Still had original T-stats, one water pump had sleeve bearing and oil cup. Intake didn't look to have ever been off. Valley and oil pan"were" sludged up big time, clean now.

After a good clean up, new water pumps, radiator serviced, carb rebuild and tune up, it runs pretty good. I have decent oil pressure, doesn't over heat and no tics or knocks so I've been driving it every day.

Compression is different on all cylinders and it has a blue tinge to the exhaust and the draft tube smokes pretty good.

My fear is finding all the scary cracks people seem to find after they tear it down.

Hopefully my crank is ok. If not stock ones are cheap. After reading everyone's input I think I'll stay stock stroke and save some money.

Thanks!
Scott

[Kurt in NJ]

When I put the 49 merc in the 46 tonand1/2 truch it made all the difference, it went from I think I can to no hill too steep, the vacuum came up and kept the 2speed rear in and the dual pump kept the wipersworking all the time---that little bit of stroke made a big difference, even fuel mileage went up,

[Ol' Ron]

For around 2 grand you can get a 3/5/16 bore X 4 1/4 crank assy from Gary. Another coupla hundred bucks, and you can have your block bored. Put a the crank assy in the block. Use the stock heads intake valves etc. Thei 294 ci engine witll produce more torque than your trans and rear end can uz. Very inexpensive build.

[Scotty's 52 F3]

Thanks Ron, Gary? GoFast?

[Lawson Cox]

I wouldn't recommend to anybody that they have a stroke. Bad stuff.

[3twinridges]

I think this was asked in another thread but the answer was not clear. Running a 4" crank and Merc pistons, you can use the stock rods. But what if you amp that to 4 1/8 with Merc pistons, can you still use stock rods?

[Scotty's 52 F3]

I guess I didn't specify. I didn't mean Hemorrhagic or Ischemic so recommendations for a FLATHEAD V8 STROKE! Smart guy!

[flatheadmurre]

Originally Posted by 3twinridges

I think this was asked in another thread but the answer was not clear. Running a 4" crank and Merc pistons, you can use the stock rods. But what if you amp that to 4 1/8 with Merc pistons, can you still use stock rods?

The aftermarket cranks come with 2 different sizes of the rodpins to give you the choice...but if buying a rotating assembly a prebalanced setup is not a bad choice.

Are the merc cranks getting so hard to find nobody considers them a good choice anymore ?

Merc crank and EAB heads is a lot of bang for the buck in my book...

[Lawson Cox]

Originally Posted by Scotty's 52 F3

I guess I didn't specify. I didn't mean Hemorrhagic or Ischemic so recommendations for a FLATHEAD V8 STROKE! Smart guy!

I should have put a after my post.

[Scotty's 52 F3]

Are the merc cranks getting so hard to find nobody considers them a good choice anymore ?

Merc crank and EAB heads is a lot of bang for the buck in my book...[/QUOTE]

I haven't been able to find a Merc crank and it seems the guys that do have to pay big for one. Then have to pay the machine shop to prep them. Shipping is also expensive if you can't find local.

If I happen to find one for a reasonable price, I will grab it.

Scott

[tubman]

Remember guys, .125" over pistons (which adds little if any cost to the build) results in a 258 ci engine, while the Merc crank option that is hard to find and evermore costly, only gives you 255 ci.

[rotorwrench]

The 49 through 53 Mercury 4-inch cranks are less expensive than the Scat types. There are the early ones with the small bore in the center of the flange end and then there are the ones for the later automatic cars that have a larger bore back there. The last one I purchased a few years back was $250 and it was already ground .020" mains & .020" rods. One that needs to be ground should not break the bank but I would want to know how much wear is there and see photos of the journals if you can't look at it yourself. I would stay away from one that had any damage to a journal unless you can verify the extent of the damage.

[tubman]

"rotorwrench" : not to be argumentative, but define "a few years back". I find that these days, when I use phrases like that, I realize I'm talking 10, 20 years, and things are much different now than they were just 10 years ago. Or maybe things are better in Texas; I know in Minnesota, the last couple of Merc cranks I saw advertised must have been cast from silver.

[3twinridges]

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Having just gone through this, I would say the going price on a Merc crank that is a gamble is $325, and one that has been checked out by a machinist is $400. Shipping is also a problem and adds to that price.

[Scotty's 52 F3]

Thanks for all the input everybody. If I find a Merc crank locally for a good price I'll grab it. If not, guess I'll use what I have.

Scott