5.5:1 vs 6.0:1 heads

[8EL]

It is fairly simple to determine that increasing the compression ratio on the little Ford 4 cylinder A engine will make the car more drive able due to the additional power it will develop. But by how much? What are the comparisons to be made between the two aftermarket iron heads offered?

The low range torque curve for the 6.0:1 head was a little flatter than the 5.5:1 head, power output was negligible for the two, about 3.5 HP. For an engine with insert bearings and given that the cost for the two heads is the same, the 6.0:1 head would probably be the way to go.....But what of the exhaust note between the stock and higher compression heads? Are they the same?

I know that the 10.5-11.0:1 V8s from the 60s had quite distinguishable exhaust sounds over their low compression 8.75:1 counterparts. But ignition, valve timing (camshafts), carberaturion/induction, and exhaust was also different for these old fire breathing dragons.

I guess I want it to sound like a Model A, those who are using these heads, which one is it, and what does it sound like??

 

[alexiskai]

Use the 6.5:1 Burtz head. Better cooling, more power, correct size, similar price. End of story.

 

[8EL]

Use the 6.5:1 Burtz head. Better cooling, more power, correct size, similar price. End of story.

Are you using one of these heads? If so, are there any differences in the sound of the running engine?

 

[BRENT in 10-uh-C]

FWIW, an original muffler and exhaust system has different tone than what an aftermarket Aries muffler has. Yes, compression ratio affects the idle quality but is less detectable at higher RPMs. The increased compression just 'hits harder' for each stroke at idle over a stock 4¼:1 ratio. The caveat is most hobbyists today have no clue what they originally sounded like.

 

[Bob Bidonde]

I have a 6:1 head on my Victoria and it sounds like a Model A at idle.

 

[8EL]

I have a 6:1 head on my Victoria and it sounds like a Model A at idle.

Thanks bob, that is what I was wanting to know. The Model A has a very distinctive "cackle" and I would not want to affect that. The 3.54:1 ring and pinion I recently installed is requiring a little more "twist" than is currently available prompting these considerations.

I would imagine that you are realizing better fuel millage to boot. The last tank with the new final drive changes yielded 14.6 MPG.....I think we can do better...

 

[nkaminar]

There is more than compression ratio to flathead head design. The air must turn to flow down the cylinder during the intake stroke and out during the exhaust stroke. The design of the squish area determines how well and how fast the combustion takes place. In my opinion, the best head designs are those for flathead Harlies and racing Briggs and Stratton engines.

 

[8EL]

FWIW, an original muffler and exhaust system has different tone than what an aftermarket Aries muffler has. Yes, compression ratio affects the idle quality but is less detectable at higher RPMs. The increased compression just 'hits harder' for each stroke at idle over a stock 4¼:1 ratio. The caveat is most hobbyists today have no clue what they originally sounded like.

Yes, I would expect so Terry....I might fool them, but I remember what they sounded like....Thanks

 

[AzBob]

I have a 6:1 head on my Victoria and it sounds like a Model A at idle.

X2.
6:1 Snyders head on mine and sounds like Model A at idle as well.

 

[8EL]

X2.
6:1 Snyders head on mine and sounds like Model A at idle as well.

This is the head I am seriously considering. You both indicate that it sounds like a Model A at idle peaking my curiosity, does it sound noticeably different at other throttle positions?

 

[AzBob]

This is the head I am seriously considering. You both indicate that it sounds like a Model A at idle peaking my curiosity, does it sound noticeably different at other throttle positions?

FWIW, other than "sounds like a Model A at idle", I am going to disqualify myself for the "does it sound noticeably differently at other throttle positions?"

I have a Weber carb and cast iron exhaust header with Aries plain steel muffler. Other than idle sounding the same (to my ears) as an original 4.2:1 setup, it seems to sound the same under lower rpm load with the characteristic "cackle." At cruising speeds, IMHO, seems to have an overall smoother sound. This is of course subjective as I have never heard my Model A drive by.

 

[GeneBob]

I went with the Snyder's 6:1 a few years ago and liked it. It is a good head. I have since gone with a Lion III head and I think it is smoother than the Snyder was.
If I were starting from scratch now, I think the Burtz may be the way to go. Higher compression and better water passages would be the deciding factors.
We have come a VERY LONG WAY from the 1930's gasoline and engine rebuilds. Take full advantage and improve the efficiency of your engine.

 

[CarlG]

I have the Snyder 5.5 head with a cast iron header and Aires muffler (not stainless) and it sounds like a Model A.

 

[Gene F]

Thanks bob, that is what I was wanting to know. The Model A has a very distinctive "cackle" and I would not want to affect that. The 3.54:1 ring and pinion I recently installed is requiring a little more "twist" than is currently available prompting these considerations.

I would imagine that you are realizing better fuel millage to boot. The last tank with the new final drive changes yielded 14.6 MPG.....I think we can do better...

Stock exhaust pipe, and the big heavy flywheel will retain that "lope" when you idle her down. JMHO The higher compression heads run cooler - go figure... However, the car doesn't really have as much appeal if you do not drive it. Nothing like going to the hardware store, post office, or any other errand, and having someone ask about your car, or say "nice car".

 

[ndnchf]

Snyders 6.1 on mine and it too sounds like a model A should at idle.

 

[Big hammer]

I have a Synders 6.0 -1 head, 330 touring cam, larger intake valve’s, and Aries plain steel muffler. All of the old timers comment your A is so quiet, I’am not old enough to know if it sounds like stock, Aries says there made to Ford specs , retard the timing lever and it will cackle ! and adjust the idle at a slow idle.

 

[8EL]

All very useful information, thanks fellas.....

 

[nkaminar]

My current Model A does not sound like the Model A's of my youth. But nothing does because of my bad hearing.

 

[8EL]

My current Model A does not sound like the Model A's of my youth. But nothing does because of my bad hearing.

Heard that....no pun intended??

My wife says I have selective hearing, in her case I always have, it's just now I can realistically use the excuse.....