Board index Flathead Power-Technical Questions, Answers, and Suggestions Pans Building an '88 inch pan

Building an '88 inch pan

Post Fri Mar 09, 2018 7:13 am

Posts: 1704
Location: Interlaken, NY USA

Greetings, been awhile since I posted on the Forum, but I've come to the experts today for opinions and, I guess, advice. Building a 55 pan for a friend, in the planning stages, and want to run the idea past the accumulated brains of the forum. Especially the ones that are in better shape than mine, due to less mistreatment in our youth :lol:
Here's the deal: My buddy has been riding a '50 pan/shovel bobber for 5 yrs now that I built for him, 84 inch, old Sifton 412 cam, moderate compression. Health reasons say he needs to move to a swingarm, and he wants to go straight Pan. We've got a 55 aftermarket left case and a 62 right case. Have no idea who made the left case, most distinguishing feature is the lack of reinforcing ribs, a smoothed surface and obvious extra "thickening" of the case material. In other words, it looks plenty strong, with a Timken bearing setup.
We want to go '88 inches with this setup for more poop. I plan to use T&O torque monsters, stock bore.
Don't want to go to ridiculous compression, mid 8's? and a cam that will do two things,
relatively late inlet closings to make for easy kicking(hey, we're all getting older here ya know,)
and not give up too much low end grunt to the god of top end speed.
He and I both like the way the good ole Sifton 412 did just those things in his pan/shovel.
I also like the way my Andrews "B" works in my own '65 84 inch pan.
Having said all that, I guess the points for discussion are:
Can a 88" pan be a reliable high mileage engine?
And what would be some cam recommendations to meet our dreams?
I say dreams 'cause I only don't want to give up low end and do want to gain high end power :lol:
What do you think,
(Disclaimer, all comments and recommendations may be cheerfully ignored and I'll end up doing what I damn well want to anyway) :D

Post Fri Mar 09, 2018 12:45 pm
Pa Site Admin

Posts: 6109
Location: Ohio USA

Love your humor DD. Thumbs up Bro !

Post Mon Mar 19, 2018 1:32 pm

Posts: 3385
Location: Central Illinois, USA
And you should, DD!

I'm fine with all of it, except the Andrews B.

(I'm still living in the last century, sorry.)


Post Mon Mar 19, 2018 6:19 pm

Posts: 1704
Location: Interlaken, NY USA

Thanks Cotten! Am open to suggestions as to "last Century" cams, I'm always scrounging cams at the AMCA meets, those boys sell 'em cheap, not original equipment, you know :D

Post Tue Mar 20, 2018 7:39 am

Posts: 3385
Location: Central Illinois, USA

Andrews quality control probably improved since my experience with them.

The (real) Sifton 112s were great, and I loved one in my 86"er.

Its around here somewhere...


Post Tue Mar 20, 2018 5:19 pm

Posts: 1704
Location: Interlaken, NY USA

Interesting you should say that about Andrews quality control. My first "A", bought maybe '75, I ran a couple of years and then checked it out with a degree wheel. lobe timings were off, and called and complained. At first they wanted to just brush me off, how could I possibly have the capability to find fault with their product. But, they eventually believed me, and replaced the cam at about half price, if I recall.
Yeah, a class operation would have warranted it for free, but it was a couple of years old, so, I wasn't complaining.
Been lucky ever since.

Post Tue Mar 20, 2018 5:45 pm

Posts: 3385
Location: Central Illinois, USA
Let bygones go, DD,..

And assume productions improved over the years, or they would have went the way of so many others.

Andrews tranny crap HAD to have improved!

Hell, its been nearly thirty years for me... I think.
But I bet I still have Andrews inventory in stock.

Ebay is my exit strategy.

PS: I faintly remember talking to the real Sifton company, and learned I was pressing OEM gears on their billets wrong by going by the marks.

Everybody said they ran great.

Post Sat Apr 07, 2018 4:20 pm

Posts: 807
Location: Pa. , USA
DD, not a pan pro by any means but always understood the heavy wheels and longer stroke is for low end torque and wider cam duration for rpms, I'm currently getting started on a similar project '50 pan bottom/ shovel top that owner wants to go back to all pan, have the heads but need to ask you guys in the pan loop, is anybody making decent pan cylinders ??
Vintage roadracing, Class C, AHRMA # 335

Post Tue Apr 17, 2018 8:45 am

Posts: 165
Location: Carver, MN

Hi DD,
Here are a few of my thoughts off the top of my head.

I’ve never personally tried a set of the heavy flywheels in a stroker, but they might make it easier to kick start so that could be a plus. The extra weight of the heavier flywheels stores more energy than their lighter counterpart, so although they do not increase torque, they give that illusion. The added cubic inches of the longer stroke will add torque across the RPM range, but the longer stroke will also increase piston speed which has the effect of helping the intake tract move more air – a good thing in breathing limited engines. You probably won’t have a lot of choices for compression ratio, since stroker piston availability isn’t what it once was. I see S&S shows 9.1:1 and 10.8:1 as their two choices. I wouldn’t let the 9.1:1 scare me too much since that is based on heads that are “virgin” in regards to chamber volume. Chances are very good that the heads you use will be quite a few cc’s larger than that, resulting in a more acceptable ratio. It’s not unusual to see an extra 10cc in a head that has had multiple valve jobs over the years.

Due to the long stroke, I think you could go with a fairly long duration cam without noticing much loss of low end power. As for reliability, I have run 4-3/4 stroke engines on the street with good results and what I would consider good longevity. Remember, the larger engine will not have to be run up as far in the RPM range to make good power and more top end (higher gearing?) and that can translate into a “break even” for longevity. Of course, the other side of that is that the power of a stroker can be addicting, causing the rider to run the bike harder all the time, with a resultant reduction in engine life.

As for Tim’s question regarding aftermarket Pan cylinders, from what I have seen its not a big issue. The amount of meat in a Pan cylinder is enough that I don’t think they are susceptible to being weak like an aftermarket Knuck cylinder. I have a set of generic aftermarket Pan cylinders on my 99 cubic inch Knuckle nostalgia drag bike at 12.8:1 compression ratio on ethanol which seem to be surviving just fine. The only thing I did to them (besides turning the fins down to lighten) was to bore to +.010 to insure the bases were perpendicular to the bore.

Post Sun Apr 22, 2018 9:17 am

Posts: 807
Location: Pa. , USA
Thanks Lee, we'll try the aftermarket as availability for good used cylinders is limited, wondering about your street strokers, are you running cast or forged pistons and at what skirt clearance ? thanks again, Tim
Vintage roadracing, Class C, AHRMA # 335

Post Mon Apr 23, 2018 9:27 am

Posts: 165
Location: Carver, MN

Hi Tim, I would have no qualms about running cast pistons in 95% of street strokers since most rarely see the demanding conditions that would require forged pistons, however availability of anything except forged stroker pistons is (as far as I know) pretty much non-existent these days.

Skirt clearance would be need to be determined by the particular piston and the application. Personally, I use the recommendations of the piston manufacturer as a baseline and adjust from there. For Pans and Shovels I would go to either the middle or loose end of the manufacturer's recommended clearance. For a Knuck I would go to at LEAST the large end of the suggested range (due to more retained heat) and usually a bit more. For Evo or Twin Cam the manufacturer's minimum spec is normally fine due to the aluminum cylinders. Whatever the application, a little extra clearance may cost you a little bit of ring life due to piston rock, but too little clearance will always result in scored pistons. If the pistons do not score, the clearance was not too small. The trick is to determine what that point is, and since nearly every engine combo will produce slightly different amounts of heat, you are safer to set them up on the loose (safe) side. Teflon type piston skirt coatings can muffle any noise from the extra clearance in a cold motor.

Post Mon Apr 23, 2018 11:28 am

Posts: 3385
Location: Central Illinois, USA
[quote="Lee W"]...For a Knuck I would go to at LEAST the large end of the suggested range (due to more retained heat) and usually a bit more..../quote]Lee!

Why would a Knuck retain more heat?

Thanks in advance,


Post Mon Apr 23, 2018 12:07 pm

Posts: 165
Location: Carver, MN

Hi Cotton,
Heat soak from also having cast iron heads vs Pan and Shovel aluminum heads. ...and no I don't have any scientific proof; purely anecdotal in that over the years I've seen way more Knuckles and Iron Sportsters with scored pistons. What are your thoughts?

Post Mon Apr 23, 2018 1:58 pm

Posts: 3385
Location: Central Illinois, USA
Well, Lee...

We get into armchair engineering now, so I will try to only report what I observed, prejudiced by what I was taught, of course.

Toss Sportsters out of the conversation right off the bat, as the loose nuts on the handlebars made them an extraneous variable.
("It ran great 'til it got a hole in a piston...")

Comparing Knucks to Pans and later designs would rob them of their honor of many more years of honest abuse, and frankly, admirable survival.
You know how I harp on manifold leaks, and and until modern times, the "plumber's design" was treated with contempt, often to the point of disaster.
So toss any comparisons after '55.

As I was taught, internal combustion engines have an optimum temperature for efficiency, and our cast iron cylinders are where the work gets done, even if the heads' material varies.

Heads are anvils that pistons crack hydrocarbons upon.
Hot cast iron heads held an advantage for low octane fuels, at road speeds most common before Eisenhower's Interstates.
Heat dispersing aluminum heads took advantage of the high-octane fuels of the time.

Now what fuels have we?


Post Mon Apr 23, 2018 5:04 pm

Posts: 165
Location: Carver, MN

Okay Cotton, lest I be misunderstood, I certainly was not arguing that Pans or Shovels were superior to Knuckle heads. My only point was that for the pistons to survive, it is my opinion that Knuckles will benefit from more clearance than their later cousins. I do think that an aluminum head, by cooling quicker than cast iron, would have to pull some of the heat out of a cast iron cylinder by conduction. How much is probably a matter of conjecture. I don't doubt that the cast iron head is more efficient than aluminum: that seems to be commonly accepted, and as a matter of fact it is said that aluminum heads require more compression ratio than cast iron in order to produce the same power levels due to cast iron retaining more heat.

Do you think modern "P4 gas" (to use your term) produces less heat than the high octane of yesteryear? I suppose that may be (especially when ethanol is added) but I don't know that from any research that I have done and I really don't know how it compares to the gas available in the '30s & '40s.

So if the gas we have now is comparable to what we had in pre-Panhead days, then to keep the optimum designed running temperature, wouldn't we need to keep the Knuckle and early Pan motors at their stock 6.5:1 (low compression) and 7.0:1 (high compression) ratios? But then, that would assume that stock compression ratios resulted in optimum efficiency. I sure don't have all the answers, but like you, I base my ideas on a combo of the reading of trusted sources, armchair engineering, and personal experience.

Post Mon Apr 23, 2018 7:26 pm

Posts: 3385
Location: Central Illinois, USA

All bets are off with today's fuels.

But the cylinder portions of V twin designs should be very similar, with flattys a hundred degrees hotter at the head than OHVs.

Everything else is a give'n'take;
Why were "billet" aluminum heads the rage for import racers last century?

Rap a hammer on a cast iron cob, and then a aluminum chunk.

Which rebounds more energy?


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