8BA rebuild - do I want a Merc crank

[cederholm]

Come on John, you know you'll never use it and would love it to go to a good home.

~ Carl

Originally Posted by JM 35 Sedan

If I were building an 8ba or a 59 series engine, I would definitely use a 4" Merc crank, since I bought one about 10 years and it's still sitting on the shelf . Now in your case, if you can find one at a reasonable price with good rod and main jounals, I would so go for it....why not!!

[cederholm]

Okay, okay, I'm hearing you guys loud and clear. ...the search begins.

~ Carl

[Bored&Stroked]

I prefer to use original Merc cranks - just like the way they balance out. With that said, I don't like to buy a core that needs to go to .030 straight out of the gate. If you can find one that is STD/STD and needs a regrind, that is what I'd look for. Yes - a bit harder to find and usually a bit more expensive, but that is my approach. You can use the stock 8BA rods (though consider the cost to rebuild/resize them - might just buy a 'new' set from SoCal). You'll need pistons with the correct 'pin location' for the 4" stroke - everybody has them, not a big deal. I REALLY like the 1.5, 1.5, 3.0mm ring packages that some piston manufacturer's have (only in certain bore sizes). It is worth talking to the piston suppliers to see if they have something in a bore size you'd like. I used Ross forged pistons recently - 3 5/16 bore, with the metric ring packs (my favorite high-performance piston size). Good luck!

[flat 39]

I got over 25,000 miles on my 4" Scat crank. However, it was more difficult to balance than a Merc crank. The balancer had to add heavy metal to get it to balance.

[Ol' Ron]

I have an unusual Engine in my truck. It started life many years ago as a 276 street engine, L-100, 4bl. heads, etc. I put it in storage with out the spark plugs installed and yup, got educated. Several sylinders were badly rusted.. Afew years later I needed an engine for my truck so I called Eggy and they said they had .020/.030" over pistons for the 3 5/16 bores. The .020 pistons came with Metric rings for a Volvo. This saved the block and I put it back together with a EAB cam and milled heads. Merc intake bored for a 2BC carb ab]nd a distributor bt Richard. The torque is increadable. I climbed the Weston hill (14%) tryingto hold 50MPH in OD. Went over the top at 43 (1300 RPM). What a joy to drive. Trans is an F150 3 spd with OD, rear 3.73 Spicer. I call it a 280 flathead, stock merc with just a set of pictons

[cederholm]

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Flat 39, so even thought the crank is said to be balanced from Scat, you're saying it still needs a trip to the machine shop?

Please forgive my novice engine building questions, this will be my third motor rebuild and first flatty.

~ Carl

Originally Posted by flat 39

I got over 25,000 miles on my 4" Scat crank. However, it was more difficult to balance than a Merc crank. The balancer had to add heavy metal to get it to balance.

[GOSFAST]

Originally Posted by flat 39

I got over 25,000 miles on my 4" Scat crank. However, it was more difficult to balance than a Merc crank. The balancer had to add heavy metal to get it to balance.

This is one of the "main" reasons we avoid the Scat cranks, we've had similar issues with balancing their shafts on the Chevy's as well.

It is NOT good practice to have to add "Tungsten" (heavy-metal) if it can be avoided. Every Eagle (Flathead) shaft we've balanced here needed between 100 and 200 grms REMOVED (not added) from either end. That's a total of about 300 grms from the shaft.

This makes the overall balancing operation much easier than drilling holes and adding metal!! It's also more desirable to make components (this includes the crank) lighter when possible, NOT heavier.

Thanks, Gary in N.Y.

P.S. This is not meant to be "knock" on Scat's products, simply makes the job less labor-intensive with Eagles. We use nothing but the Scat rods, never (so far) the Eagle's??

[Ol' Ron]

I have a 294ci crank assy from Gary that's turned over 5k on several occasions, with no problems. I recomend his crank assys as a well balanced, economical investment.
Well worth the price.
When I build a street engine I like to get the rods with the crank, this way I don't have to balance it, as the factory balancing is very good. Unfortunately, re builders don't balance their engines and therefore the connecting rods are all over the place. Balancing has become a major problem with the flathead. Most have no idea how to balance the rod. and the cost is getting to the point where buying a crank assy from Gary is well worth the satisfaction that it's done right.

[Bored&Stroked]

I hear yah Ron - that is why I balance my own rods (if they are flatheads)! You have to have the necessary tooling/jigs and a lathe . . . it isn't just done on a damn belt sander!

It is not as much of an issue with rods like the H-Beams . . . they are a modern design and 100% CNC, so they are dang close 'out of the box'.

SCAT Rotating Assemblies: Hey Gary, have you ever used one of their 'balanced' rotating assemblies? If they required heavy metal, then that is what would have to be in them . . . OR . . . are they balanced correctly at all???

Just wondering - never used one!
D

[drolston]

As noted above, the SCAT rotating assembly I put in my 59A was advertised as "balanced", but I would never put that much $ in parts without having the balance checked. The race machine shop that did mine said my SCAT kit was pretty good out of the box. They also balanced the flywheel and pressure plate together.

[richard crow]

if you want a nice smooth cool runing eng leave it stock.the a is light & will be fast take the crank money & put it toward a good over drive.

[GOSFAST]

Originally Posted by Ol' Ron

I have a 294ci crank assy from Gary that's turned over 5k on several occasions, with no problems. I recomend his crank assys as a well balanced, economical investment.
Well worth the price.
When I build a street engine I like to get the rods with the crank, this way I don't have to balance it, as the factory balancing is very good. Unfortunately, re builders don't balance their engines and therefore the connecting rods are all over the place. Balancing has become a major problem with the flathead. Most have no idea how to balance the rod. and the cost is getting to the point where buying a crank assy from Gary is well worth the satisfaction that it's done right.

Hi Ron, thanks for this post, makes all we do worthwhile. We machine/build every unit as if it were my own. Same quality/detail goes into every job.

Originally Posted by Bored&Stroked

SCAT Rotating Assemblies: Hey Gary, have you ever used one of their 'balanced' rotating assemblies? If they required heavy metal, then that is what would have to be in them . . . OR . . . are they balanced correctly at all???

Just wondering - never used one!
D

Hi Dale, if we were to order any prebalanced kits we would end up with a combination we wouldn't be all that "happy" about. Example, with the Scat kit we would NOT choose their crank, with an Eagle kit we would definitely NOT choose their connecting rods, and now not all are offering the Ross pistons which we've been very comfortable with for many years now. So we'd much rather "build" our own kits. Also, with respect to being "prebalanced", we would have to make up the bobweights and run the shaft up anyway to confirm it's balanced where necessary. If we're going to be rechecking every prebalanced ass'y anyway it just pays for us to do the in-house balancing from the beginning!

On a side note I would not try to balance the OEM rods to within a few grams, being "out" by that small amount will not make any difference in the larger picture. We've disassembled many factory Mopar units, both SB's and BB's, that had as much as a 35 gram spread between the 8 rods in the same unit. Never affected the overall performance in the end, and never heard a customer with a vibration complaint either from the day it was purchased as a new ride.

(Add) Strictly from a business standpoint we would much rather have the kits we sell to be balanced by the customer's own shop. There's a couple of very sound reasons for this statement if you think about it?? Will expand further on this if necessary.

Thanks, Gary in N.Y.

P.S. Ron, stay healthy up there, tell everyone we said "hi"! Hope Bob and his family are all well? Just realized it's been more than 5 years now since I met you guys!! I guess "time really flies when you're having fun"?

[flat 39]

Cederholm,
I used the Scat crank with 8BA rods and .060 over pistons. I do not know how well there complete assemblies are balanced. I did this 10 years ago and do not know if they even had complete rotating assemblies back then.

[cederholm]

So much great info guy - glad I joined FordBarn! Hopefully someday I'll have the knowledge to be able to help some other noobie.

~ CArl

[Ol' Ron]

Gary, Everything is working great now, engine has over 5K miles on it6 now and is in use almost every day. However , the beginning wasn't as smooth, The owner got it running after we assembled it, Unfortunately, he didn't understand detonation. After driving it for a while it over heated and made strange noises. He lives only 1/2 hour away so he picked me up and I went over to his placed where we drove the truck. At forst i5 seemed to bo OK until he started to electorate and the detonation was serious. I back off the dist alittle but that wasn't enough so I backed it off some more and now it was just a slight ping. Engine ran fine.. I was concerned about the ring lands, so we pulled a head and found a score in #5. Pulled the piston and found the lower rale had bent out of the ring grouve. II called Ross for a .010 oversize piston and they said I'd haave to buy 4 of them, so we sleeved that hole and put it back together. The ring problem was my fault, and we wouldn't have fount if the engine hadn't detonated so badly. Since then I have realized that the later engines don't make that nice pinging noise we love to hear when everything is running right. Computers have eliminated that. Life is a series of learning experiences, that's why us old farts are so smart.

[flatjack9]

Ron, what grade of gas was he using?

[mountstimothy0]

Originally Posted by cederholm

Okay, okay, I'm hearing you guys loud and clear. ...the search begins.

~ Carl

I've also been told if you have a 4" mercury crank that the wrist pin on the piston needs to be higher as not to hit the heads due to longer stroke. I'm sure if I'm wrong the more experienced guys will chime in and correct if I'm wrong. And please do so if I am thank you

Sent from my SAMSUNG-SM-J120A using Tapatalk

[Ol' Ron]

Yes, a Merc crank must use Merc Pistons.
AS for the gas in the 294 It was regular. I build all my engines to use regular, more power and economy. At 8.5 CR, why run the expensive stuff?.

[JSeery]

If you use U.S. flathead Ford rods you need a piston that matches up with the stroke. A longer stroke requires the piston pin to move up in the piston. I believe there are French rods that are shorter than the U.S. rods that allow you to use the existing piston pin location with a stroker (4") crank.

[Bored&Stroked]

Originally Posted by JSeery

If you use U.S. flathead Ford rods you need a piston that matches up with the stroke. A longer stroke requires the piston pin to move up in the piston. I believe there are French rods that are shorter than the U.S. rods that allow you to use the existing piston pin location with a stroker (4") crank.

At one point you could buy 6 7/8" rods (instead of the standard 7" rods) - to account of the additional 1/4" of stroke (moves the pin down 1/8" - which is 1/2 the total stroke difference).

What I can't comment on is whether or not the piston SKIRTS for all the regular 3 3/4 stroke pistons will clear the crank on the bottom side. This is something that one has to know.

I'm not sure if they are still available, but unless you really want to do this, I'm more in favor of getting the right pistons (so some poor guy in the future isn't all confused about why these pistons are in this engine!).

Good luck!
B&S