Flatty rebuild advice........

I see absolutely no reason for special rods in a 5,000 RPM motor...the stock floaters had very successful lives in race motors pulling far higher revs than any street flathead and at higher loads. Do you realize that Ford floating rods were transplanted into early SBC's and other OHV's for most of the fifties to cure their high RPM rod failures in race motors?? The ohv's later cured their rod problems with much stiffer and heavier rods or race only m***ive aluminum ones...the Ford rods cured the problem by eliminating the cause rather than by strengthening a poor design.

 

No typo - more like brain fart - I used to be a diesel mechanic too!!

Well, they're still superchargers. I don't know what amount of "boost" they made - I think it was minimal, actually. Static CR in the GMC diesels was pretty high already. But even breaking even with a supercharger - in other words, not boosting, but eliminating vacuum, you see a significant power increase.

But it is - the increase in blower displacement is linear with the increase in cubic inch displacement - hence the length increase.

Yes. Mike has said several times that he gets most, if not all, of his porting tricks and tips from Bing.

I've seen pics of a factory rod twisted like a candy cane!

 

They didn't twist under normal combustion at 5,000 RPM! Probably done in by detonation, ususally with fuel. The point of the design is that with locked bearing rods, rod stretch at high RPM (worst stress is on EXHAUST stroke) stretches big end, pulling parting line of rod and bearing inward where they cut through the oil film and cause immediate catastrophic failure OR that detonation pounds the crank down against bearing, also causing the parts to curl inward. This is how rod failure plagued the early racing OHV V8's once they were hotrodded enough to spin a lot faster than Detroit had expected. And why the Ford rod was used in many early racing OHV-V8s until stronger rods were developed for them. Making the locked rods stronger mean more m***ive at the parting line, hence heavier and bulkier. The Ford rods sidestepped the whole issue because the floater allowed things to keep spinning well into the stretch...
Detonation is another issue, called out by Yunick as fundamentally non-survivable...with the high forces, strengthening one part just moves the failure elswhere or delays it a fe seconds.

 

No, Bruce, I wasn't very clear - this was purposefully done to demonstrate the strength of the rod. Kind of like the axle that I've seen twisted...

 

F.E.:

I'm glad you clarified what you ment by that. I was thinking this thread was going to turn into one of those never ending "what if" threads.

I think JWL's book does a good job of delinating what things cost, if it's needed, and the expected outcome.

H-beam rods ($1,600 Crower or Cunningham's) are certainly beautiful pieces. Worth it for a street motor? Debatable.

Can't speak about Speedway's or CAT/Eagle rods.

Sit down, write out what you want, plan a realistic budget for your build.

You'll either get it done with your current budget, need to save for it, and most importantly you need to finalize what you want to do for these decisions should be made before your block goes under the knive at the machine shop.

Best of luck and keep 'um runnin'!

 

I have heard, can't say where, that late rods were good for up to 350 HP 5200. Is that true??? Sertainly more HP than one is likly to see on the street.

 

Yeah, I'll be going with the 21A rods.

Thanks again for the help guys!

HC.

 

As the Fonz usta say .....

"CORRECTAMUNDO"

Rat

 

21A rods, with a correctly setup crank shaft --> good radius/fillets on the journals, .002 or so rod clearance, fairly large rod side clearance (don't have the numbers handy, but seems to me about .010 to .013), correct bearing setup (think rubber hammer!), CAD-Silver bearings if you can find them and lots of oil flow . . . is the way to go if you're looking to run 21A rods, high horsepower and higher RPMs.

Make sure you have the rods shot-peened/stress relieved, have a small chamfer ground where the big-end caps meet, have everything balanced and you'll be amazed how these lower-ends will work. I ran a blower on mine and tached 6800 through the traps (1/4 mile drag). If you're running a blower, it is not a bad idea to put steel main caps on it or a Doug King girdle if you really want to tie the lower end down.

 

Dale:

Right on, brother!


Also, a pro shop built motor doesn't always mean you'll have a good motor.

Ask the Rolling Bones fellas about that one!

 

I've been looking around and comparing prices the last couple of days and these are what I've found with the best prices:

4" crank from ****. they've got the 2000 one and the 2138. Are they the pin size?

Super Dual Intake from summit but I'm still thinking of going with the PM-7 from auto riley which is the only place selling these PM-7's which I've found.

400jr cam from speedway or from reds headers (he's just getting back to me with prices).

Aluminum 3-ring pistons from speedway. I'm pretty sure they are cast.

Edelbrock 65cc heads from summit.

Offenhauser heads with .425" from reds headers.

Navarro heads from Navarro engineering.

1.6" valves from reds headers.

Dual rebuilt carbs from down under.

I've been told that the 21A rods won't work with a **** 4" crank.

What's the go with that???????

What do you guys think up to now?

HC.

 

For a street engine, I'd run standard 8BA-style rods. They're plenty strong and you can get brand new sets of French ones for about $125 from SF Flatheads - can't beat 'em for ease of installation on a mild street engine (or even most "hot" street engines).

True, the full-floating bearings of the early rods offer a lot of protection, but are expensive to get bearings for and can be tricky to set up the bearings - you'll want to find a shop that is not just familiar, but fluent in them.

If it were me and I were on a budget:

Stock Merc 4" crank
Stock 8BA-style rods
Cast pistons from Patricks
Stock EAB heads
Max-1 or 400Jr w/solid adjustables
Zephyr Valve Springs
Edelbrock Super Dual w/2 x 94 carbs
W-type headers (if they fit - otherwise, Red's for my application)

Next upgrades would be:
1.6" SBC exhaust valves from Summit
Street Port, Polish, & Relief job
Ross forged pistons (quality is far superior to cast, but you pay for it)
Edelbrock heads (better QC than Offy - otherwise, not much difference)

 

Thanks for that Ernie.

I think I might be taking a bit of a different approach to what I started off with.

It'll be a long term project so I don't mind it sitting for a month until I can get some more money into it. You with me?

I'd love to do it slowly, surely and very street worthy.

Does anyone know where to get the PM-7 intake from anywhere either than auto-riley?

Who can tell me a bit more about the Navarro heads in terms of compression and comparison to the edelbrock and offenhauser heads.

Thanks.

HC.

 

For street use, there's not enough difference between any of the commonly available heads to make a hill of beans difference - use what you think looks best.

The PM-7 was being reproduced by Tony Baron, I think. Not sure who else distributes it. It's a decent enough intake - again, for a street 2x2, there's not a lot of difference between any of the regulars and only a minor improvement going to a super. Use what you like.

 

I agree with Flat Ernie --> it pretty much comes down to what you like as far as looks, brands, etc.. AND how much you want to spend. I love Navarro stuff (now H&H) - just because the machine work was always really nice -- hopefully H&H is keeping the quality where Barney had it. You always paid a bit more for Navarro - some could afford them, some couldn't. Tony Baron's heads are a work of art . . . really nice machine work, hold tons of water, etc . . . but you'll pay an extra $400 or so for them.

Certain manufacturers have better machine work (especially in the valve pocket areas), others rely on the casting patterns. I recently worked with a new set of Edelbrock block letter heads -- nice quality NC machine work, but fairly large combustion chambers overall. You need to know what combustion chamber volume you desire (given your bore, stroke, relief work, valves, etc).

Compression is a very valuable thing on a street motor - total high-end "Bonneville Flow" is not as important. For this reason, you'll probably want a milder relief (smaller transfer area), tight piston to head clearances and a final compression ratio of 8.5 to 9.5 to one (depending on your gas situation). Also, don't scrimp out on your ignition - a really good ignition makes a difference on a flathead. If you're not too hung up on "traditional looks", then consider a MSD, maybe a mag, etc.. . . . can really make a difference. On my next race motor I'll probably run a MSD unit - with adjustable timing, boost retard, etc..

 

I would recommend doing your homework and shop around. I found a guy on E-bay who is a dealer for Ross pistons. His price was $360 + $12 shipping. This includes Grant rings.

Patrick's price for 3 ring pistons & rings was around $300.00 + shipping.

The extra money was money well spent IMHO. Especially if you have any thought of putting a blower in this thing anytime in the future. Of course you'd have to do do other mods. (cam, heads, etc.) to benefit the addition of a blower, but atleast you wouldn't have to change pistons at that time.

Also, don't believe the hype about forged pistons needing huge clearances. I think Ross recommends a non-blown motor honed with a torque plate at .030" wall clearance. Don't quote me, I'm not a machinist and I'm going off memory.

Also, check this out. If you call Ross and give them the run # off the box they will give you the measure of the pistons you bought dead on.

I didn't believe. Machinist had his mic'd out while he talked to them. He said the number out loud and then mic'd with his digital gauge. Dead on. Pretty cool.

 

Hey dude, build yourself a good, solid, decent stroker motor, not going too big, a decent cam, the 2x2's are cool and some headers......you cna almost run the same engine with a 4-71 @ crankspeed or the 3-53 @ a little over.....
Just read up on where you want to go cause theres tons of lit. out there and a bunch of us have run setups like this before.....so you have a ton of experience to draw from..........

 

I just looked at back at your post. I'd check with your machinist first before I bought the pistons from Speedway.

PM-7 is certainly a cool piece. I own one and love it. Don't rule out the new repop'd Edelbrock Slingshot. Sure hard to be for coolness factor and it comes in at about $250 clams less than the PM-7 from Vaphead (Eric)

I know a real decent shop who will not use Speedway pistons no matter what. He said he has found too many of them are so far off from each other in wieght and size that it acutally winds up be cheaper in the long run to go with a set of Ross-like quality pistons after you factor in his labor.

Just a thought....

 

I totally agree . . . there is absolutely no reason to scrimp on pistons! As a matter of fact, when you order pistons from Ross, try to order with the upgraded ring package -- the modern rings are MUCH better than the Grant **** that most people just order and don't think about. Spend a few bucks more and have a much better piston/ring package. When is the last time you heard about anybody running ole' Grant rings on anything other than a flathead?

 

True, I wish I did do this upgrade and also upgrade to lighter pins.

 

Are the 'High pressure oil pumps' like the ones from SF Flatheads the ones to go with????

HC.

 

Those French ones are odd. Not sure why you need more pressure. More volume maybe. More pressure debatable and sometimes causes more harm than good.

Those original style silver-cad bearing will flake with too much pressure.

To get back to your question and all things flatheads: depends on who you talk to. If you are planning to run a full pressure system with an external modern type spin on filter, yeah maybe.

Without all that ****, no. Change to oil every 1,000-1,500 and you are good to go.


I know you are looking to do this right, but don't over complicate this thing.

They are not a complicated motor. Look back to history like Bruce pointed out.

Guys ran these things HARD at the lakes and drove them home. Their lakes race cars were their only transportation. All of these ran on stock Ford oil pumps. Maybe stretched springs to bring the pressure up a bit, but nothing hi-volume or hi-pressure.

Keep it simple, brother.

 

Lots of good advice here. I've built a few flatties and learned a few things the hard way. **** rotating ***emblies weren't available a few years back, I always found the 4" Merc crank, .125 overbore,ross pistons or hypers from Egge and 8BA rods to be a good combination on the street. Two things I would stress regarding boring .125 would be to do a sonic bore check to verify cylinder wall thickness and check for core shift and DO NOT bore without the use of torque plates. The head bolts/studs are very close to the cylinders and they WILL distort the cylinder walls when torqued.
The 8BA rods are very tough. Ford used a very high quality vanadium steel in these rods. A standard pressure/volume oil pump will work fine.
My last 276 flattie used a steel billet 4 bolt splayed center cap with pinned front and rear mains provided by Dave Tatom. If you want to spin 5500-6000 I'd recommend something like this for your bottom end.
Compression is always a discussion when it comes to flatheads. Gaining compression through increased displacement is O.K., but you want to have space above the valves and a decent transfer area. That's where the rub is with a flathead. High compression heads and/or milling the heads pinches off this transition area and can negate good port work. If installing 1.6 valves (highly recommended on intake) be sure to do some head work to unshroud the valves.
If this is your first time porting a flathead, don't get carried away! There's water around them thar ports (don't ask me how I know!). Remember, a flathead is just an underhead valve engine. Don't hog em out or lower the port floor. Most of the work is in and around the bowl and the short side radius. If you're conservative you may leave a few horses behind, but trust me, it really feels ****py to be looking at a water jacket from inside that eighth intake port (I don't wanna talk about it).
As far as breathing goes, I borrowed an idea from the old Harley Davidson flathead flattrack racers on my last build, using a stepped transfer area over the intake valve and a partial ramped block relief from the intake to the squish area. I believe H-D commissioned M.I.T. to design this in an attempt to stay compe***ive with the OHV British bikes. These customized Offys produced my best running flathead.
Along with the above mentioned stuff I ran an Offy 4bbl manifold, Unilite ignition, ported Fenton headers and a cam I would dearly love to get hold of again, a Harman and Collins 408 ground from the original master. This combination produced a nice power curve that revved willingly to 5800 6000 rpm. Even in my heavy 47 Merc sedan with a Cad-LaSalle close ratio 3 speed this thing would surprise many people. In a light car like a model A it would be a lot of fun.
Sorry about the long post, I sold the Merc about 8 years ago and now run an SBC because flatheads became to big an obsession. The Merc was merely a life support system for a flatmotor. I do miss having one. Hmmm, maybe I'll finish that port job on the standard bore 8BA block under my bench! Cheers and good luck to you. The flathead road is never short or easy.

 

Right on. Thanks for giving some input on H&C cams. You see them around but never hear of anyone running one.

So true about the porting. Sorry to hear about your mishap in hitting water. Barney Navarro was also a believer in the H-D type of step and unshrouding.

If it wasn't for all those head bolts, we'd be able to do that as well in our flatheads.