Rebuilt Engine Options

[David in San Antonio]

The Wretched Roadster’s rebuilt engine is almost ready. Faced with some alternatives. Described as Touring Engine.
It will have counterbalanced crank, insert bearings, lightened flywheel, adjustable pushrods.

Q1. Head: 5.5, 6, or 6.5:1? I figure 6.5:1 but wonder if it will require premium gasoline, or will it be sufficient to just not advance the spark as much? I have been running non-ethanol fuel, 87 octane. Higher octane would mean fuel with ethanol.

Q2. Model A clutch or early V8? What advantage is the early V8 clutch? Is it easier or more difficult to service at home? I lean towards the original, I’m thinking that Model A parts are easier to locate. Yea or nay?

Q3. Regrind my original camshaft or new one?

Thanks in advance. Sure looking forward to getting back out there!

[Herb Concord Ca]

I'll start and I'm sure others will chime in. I'd get a 6.0 to 1 head, the 6.5 should run just fine in 87octane gas. I prefer a V8 clutch have that in both my A's, both have 5.9 Brumfield heads. You want as minimum a reground Model B grind, others are available. You didn't mention carbs, I have Marvels on both my A's.
Next!

[David in San Antonio]

Herb, thanks for going first. Why do you prefer the early V8 clutch?

[Herb Concord Ca]

In was in my first Model A when I got the truck, have been told they are easier to operate that a standard clutch.

[40 Deluxe]

Originally Posted by David in San Antonio

The Wretched Roadster’s rebuilt engine is almost ready. Faced with some alternatives. Described as Touring Engine.
It will have counterbalanced crank, insert bearings, lightened flywheel, adjustable pushrods.

Q1. Head: 5.5, 6, or 6.5:1? I figure 6.5:1 but wonder if it will require premium gasoline, or will it be sufficient to just not advance the spark as much? I have been running non-ethanol fuel, 87 octane. Higher octane would mean fuel with ethanol.

Non-ethanol premium gas is widely available, at least in some states. It may not be advertised on a sign, but ask the clerk or check the pumps. Also there are websites showing the locations of stations selling pure gas.
Stations near popular boating areas often have premium ethanol-free gas to feed high compression big block inboards. Recently small aircraft have been approved to use automotive gas. This would be ethanol free to prevent planes from falling willy-nilly out of the sky (due to vapor lock and water contamination, etc.). Ethanol absorbs moisture from the air and makes a nice corrosive sludge, whereas water does not mix with gasoline but settles to the bottom of the fuel tank. Part of a pre-flight check is to drain some fuel into a glass bottle to check for water. Doesn't work with ethanol. You won't know about water in your fuel until you're about 50 feet off the ground and the engine quits!

[nkaminar]

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The V8 clutch has less tendency to chatter. It is easier to push on the peddle. Your lightened flywheel may not be drilled and tapped for the V8 clutch.

The compression ratio is important but also the combustion chamber design. It has to allow the engine to breath. I think the Snyders 6.0:1 head has a good combustion chamber design. You will not need high octane fuel.

The Burtz cam is one of the best. I am not found of regrind camshafts because of the reduced diameter. I think it effects the profile. I may be wrong but why not go with a new one.

Aside from the higher compression head, a larger carburetor really helps. The Weber down draft provides good economy plus lots of power at the upper end when needed.

[Wello]

On my recent rebuild I went with a 6.5 Burtz head and a Burtz cam. I am more than happy with the results. The car runs fine on 87 octane but it seems to prefer 89 octane. That may be due to the gas mixture in my area.

[BrianH]

Dave, you might look into the BURTZ cylinder head 6.5 to 1 and the BURTZ camshaft 340 lift and more duration.
A Model B carburetor and manifold would be an improvement over stock.
The clutch is whatever your left leg desires.

[Bruce of MN]

With at least the 6:1 head, you need to manipulate the spark advance lever more to suit the engine’s needs. Also maximum advance is less. I have gotten used to it and it is as comfortable as double clutching now.

[Synchro909]

I run a 6:1 head on my Burtz engine and made a stop I screwed to the side of the distributor (with a screw like a throttle stop on a carburettor). The stop restricted the advance to 22° which was fine on the open road. Around town it was a very different story. I soon got sick of working the lever as I increased revs in the lower gears, pulled it back when I changed up, only to repeat the process every time. I went the an ignition specialist and asked for a distributor with mechanical advance maxing out at 22°. What I got also had vacuum advance. It transformed the car.
In short, I'm saying either a 6 or 6.5:1 head will be fine (IMO) so long as you pay attention to the ignition timing. I'd also use the V8 clutch and probably a reground camshaft the same as the one I have used in my Phaeton for the last 70,000 miles.
Although the OP didn't mention carburettor, I'll give my 2c worth anyway. I'd use either a Webber 32/36 carby or a Stromberg 97 and hang on tight.
With the oomph that engine will have, I'd use either a higher ratio diff or better still, a O/D.
Also pay attention to the brakes and tyres.

[Gene F]

I had a Brumfield super head on one of my engines. I can't recall what ratio that was. That thing had hardly no spark advance with a touring cam. Ran fine on 87. BTW, higher compression heads actually run cooler for some reason.

[Synchro909]

Originally Posted by Gene F

I had a Brumfield super head on one of my engines. I can't recall what ratio that was. That thing had hardly no spark advance with a touring cam. Ran fine on 87. BTW, higher compression heads actually run cooler for some reason.

It's because the higher compression results in more efficient combustion. That shows up as more grunt and less wasted energy (heat).

[Jim Brierley]

V8 clutch, the flywheel must be machined, so it becomes flat, and lighter, or better yet a diaphragm clutch, much smoother. The Burtz cam is very nice, but a regrind is MUCH cheaper, and can be easily and safely reground to any spec you may want, I run regrinds at Bonneville, as do many other guys. A 6.5:1 head will easily run on regular gas without problems, you just need to run a little less spark advance.

[CarlG]

Originally Posted by Jim Brierley

..., or better yet a diaphragm clutch, much smoother. ...

That's what I have, works great.

[JayJay]

Originally Posted by CarlG

That's what I have, works great.

Anyone have a recommended source for the diaphragm clutch for a Model A? I have a Burtz flywheel that is drilled for a V-8 pressure plate.

[Bruce of MN]

There have been other threads here that have more detail.

[David in San Antonio]

Thanks for the feedback everyone.
I’m choosing the Burtz 6.5:1 head, Burtz cam, and early V8 clutch.
Improved carburetion will wait until I see how these upgrades perform.
The rebuild was due to a huge oil leak, not a lack of performance. In fact, the old engine pushed the roadster to 60mph (not uphill), though 45-60 took a while.
I showed my girlfriend this post and all your responses and she said “That’s quite a resource!”
Thanks again.

[Dodge]

Jay Jay,
Are you looking for the V-8 clutch? If so Dennis Carpenter or Mac Van Pelt for them.
If your going to re-drill for the diaphragm clutch its from a 2.3 Ford Ranger.