I'd like your learned comments on this please.
Presently I'm part of the way along to building a speedster and because I'm just about to start on the engine/trans, I'm looking at the cheapest way to add horsepower. The claims in catalogues make it sound easy to double the output just from add on stuff. For example; Z head (or Sherman)= 7HP, High volume intake manifold and dual exhaust manifold = 5HP, 280 Stipe Camshaft = 2HP, A Crank (or Scat) = 5HP, which totals 19HP.
Then there are things like oversized valves, distributor, carb/s etc, which I haven't taken into account.
Short of spending a bucketload on one of Mark Chaffins fantastic Rajo OHV conversions, what are my alternatives?
I would really appreciate any conversation, advice and opinions on this please.
A good buddy hit a winner with the following - Sherman head, Scat A journal crank, Stipe 280 cam, dual exhaust manifold, larger than stock valves, and a pair of the modern Kohler or whatever replacement carbs. No dyno numbers but it sure runs strong. The prior iteration in this car had the same setup but a Z head and non-counterbalanced A crank. The new crank and especially the 8 to 1 Sherman head gave a great performance boost (both seat of the pants and acceleration and speed measured with a GPS). A flat head can run really strong. His full fendered 21 roadster PU will climb any hill and scoots on down the road at well over 60 MPH. How fast do you want/need to go. An overhead setup sure looks great and most perform really well but it kind of depends on how much money you want to spend. I'd never go overhead without beefing up the bottom end so if money is a significant factor, consider the cost of a good performance flat head vs. that sexy OHV setup.
Quickest, easiest, most "bang for the buck" is more compression,......which means a "Z" head!
That's exactly the sort of responses I'm hoping for. Much appreciated.
Rob if your not concerned about engine longevity I would say nitro is the cheapest way to go.
Actually I think Harold is correct, Z head, different carb and then a cam. When you start talking "A" cranks, different valves, cams etc it will not take you long to spend what Mark's RAJO cost. If you can do your own machine work that will help but Model T HP is not cheap regardless.
I wonder if someone can explain to me Walt's observation that changing a engine from a A crank to a A dimension Scat crank will gain ANY HP???
Now the Sherman head I know will make for a gain over a Z head.
With a flathead T you rapidly run into a limitation because of the "siameze" intake ports. It limits the amount of cam duration that you can effectively run.
Some years ago I built a A crank counterbalanced pressure oiled T block and used a 5/16" lift long duration camshaft, Sherman head and Stromberg 94 2 bbl carb. This car would exceed 100 mph, way to fast!!
Z head, Stromberg OF carb.
The Z head helps but the Sherman is another step well beyond the Z for performance. If you go beyond the Z head you should seriously consider beefing up the crankshaft. Well, unless you like replacing them. Breaking a T crank is a matter of when rather than if. Serious HP increases diminish the mean time to failure of the crank.
For more HP than a typical touring motor, I'd be planning on a stronger crank first. Your money and of course your mileage may vary.
Should have also mentioned depending on the cost of a machinist, you could just mill the head or block, make your own headers and intake. I'm sure your are already well aware that shipping will just kill you to get parts. You have a few guys over there that know about getting speed out of a T. By the way you have a beautiful Touring car.
I don't see the Scat crank adding HP over the A crank other than whatever tiny bit may be gained from being counterbalanced and possibly balanced better than the average A conversion. I would want it for the modern manufacture and counterbalance. Depending on how the motor will be run, an A crank could be equally satisfactory.
The Scat crank made for a T with A stroke, will give more power, but it is also a stronger crank. It is quite expensive. However, you will need to weld a flange on an A crank which will add to the cost of using one and also a possible location for future problems.
Once again, thanks for the suggestions and advice.
Believing that a crankshaft is the heart of any engine, I have already decided to use either a good Ford A crank or a stroker Scat crank. I also have a really nice little Stromberg OF that Stan Howe has already wielded his magic upon.....hmmmmm.
Regarding freight costs, that's just something we here in the Antipodes have learned to deal with and expect. I wouldn't have embarked down this path if I wasn't prepared for it.
Machining? I have a brilliant T engine expert, who is coming out of retirement just for this engine. He's responsible for the engine in my Tourer....which is also brilliant.
"However, you will need to weld a flange on an A crank which will add to the cost of using one and also a possible location for future problems"
Please don't do this, it WILL fail!!
I know of two good proven solutions that you can do;
In no particular order
1. Move the block ahead 5/8" on the pan. It is probably easiest as follows. Start with two pans and cut and weld them together to stretch the area where the block sets. You will now need to move the front engine mount from the outside of the pan to the inside and it will all fit. drill a couple of new block mounting bolts and all done. Oh and you will have to dent the sides of the pan for rod bolt clearance, but you will have to do this with a Scat crank too.
2. And option two. Carefully machine off the rear flange and machine a gentle taper (I use 3/4" per foot) on the back end of the crank. The object it to shorten the crank 5/8". I make a new flywheel mounting "hub" out of 4140 steel that is 1" long. I machine everything so when done I heat the "hub" to about 500 F and press it on the taper just nice and snug. After it is cooled I machine the hub all nice and true and drill holes for the flywheel (countersunk from the engine side for socket head bolts).
To install it you will need to shorten the rear main bearing, but it all fits and it is STRONG and fatigue proof.
Personally I drill the crank for pressure oiling. It is only a couple of hours work with a NEW 5/32" by 6" long drill bit. The important thing Is to be very careful as the drill bit is breaking out the far side. I prefer to not actually drill out, but feel when it just starts to "dimple" out and stop and then drill back in with a centre bit.
As it sounds like you have a skilled machinest to help you, I would be please to provide pictures and detailed measurements off list.
Thank You Les.
When the time comes, I'll do that.
Once again, to all who took the time to answer my post, "Thank You." Its very much appreciated. Lots of good and some great info there.
At what RPM do you want to make power? A stroker crank will make more low end torque, but short con rods mean greater angles: bad for efficiency and wear. Stock stroke avoids those things.
For higher RPM you will want better breathing. I believe the OF is too small, and would use a 1 or 2 series Stromberg. I would shoot for peak power well above 2,000 rpm.
Stock gearing gives 40 RPM/mph.
You should develop max HP at top design speed. Choose your target top speed and work backwards to get your max HP RPM.
As always, you're a wealth of information.
If you use a A crank with A rods then it avoids the issue you are talking about and pistons are available for this design. I have heard of guys welding A rods to T rods and getting away with it. Not my choice, but it has been done with apparent success.
When I say apparent success, you don't really know until you have driven it some distance. My first conversion, I welded the crank flange on and it ran for probably close to 10,000 miles and would rev nicely to 4500 rpm. BUT the weld did eventually break.
Using my press on method I have repaired broken welded on ones and didn't even have to redo the bearings
What about switching from iron to aluminium pistons?
That was going to be my first modification down the road, as it were.
Compression as mentioned is a key factor. Then improved carburetion & exhaust. All bolt-on's. Problem is the standard T crankshaft which is by far the weakest link in the more power club.
Z head & Stipe 250 cam.