Ah, sweeet success!

[Anonymous]

Two years after the blunder, it feels SO good -

When I rebuilt my 3.3L/200 CID 2 years ago, I had to put in the Victor head gasket that you get at NAPA. I knew the resulting compression was low, but did not realize just how much these engines rely on their squench bands for higher RPM performance - boys, it's CRITICAL!

When I took out the head gasket, I found it had only compressed about .006" on average, going from .050" when new to .044" afterward. This meant that the compression ratio was only 7.7:1 (original was 8.25:1), but more importantly, the squench height was
(.044"+.025" deck height)=.069", which is to say, no squench at all, since anything over .040" is pretty useless.

Today, I got my engine back together with a .010" head mill, the steel FoMoCo head gasket (thanks, Mustangaroo - ) and a Clifford exhaust port divider. The compression is now 8.6:1 (58cc head chamber) with the .018" thick steel gasket.

My 'test hill' is a very steep 12 degree hill, 1/2 mile long, near my house. Before this modification, I could pull this hill at WOT at a mere 32 MPH (30 MPH before the first rebuild). Today, I bettered that climb by 14 MPH, at 46 MPH and still accelerating when I ran out of hill!

I know from building racing motorcycle engines for years that the squench band is the secret of passing the 9,000 RPM mark, even up to 18,000+ RPM (yes, that's not a typo-), but those are all hemi-head engines. Now I know that the secret of getting better high-RPM efficiency in these 3.3L heads is in the squench, also, despite the bathtub-shaped 'wedge' these heads have.

Oh, one other thing I did - I ported the intakes on just cylinders 1,2,4 and 6 to and matched the new valve seats into the port shape, to balance the flow better. I also unshrouded the valves on all chambers just .030" or less and rounded off the sharp edges that the valve job caused where the new seats were cut into the heads, all with my trusty Dremel tool. I also rounded the boss where the sparkplug protrudes into the chamber, because each chamber's shape was different in this spot. Now they are all similar.

After I start driving it regularly, I'll post the MPG numbers. Before the first rebuild, I was getting 15-16MPG on 85 octane. After the rebuild, it dropped to 14-15 MPG, disappointing at best. Water injection brought it up new 18 MPG on a good day. Now, I'm hoping to reach 18 MPG on 85 octane alone - I'll let you know!

Thanks, too, to Dave - CZLN6 -- - you're the greatest!

 

[Mustangaroo]

One other beneifit of squench with the thin gasket is I'm now running 10:5.1 Compression Ratio on 91 octane and no pinging even with it over 100* here in Bakersfield, California this summer. Any yes I'm running about 10-12* advance!

 

[Falcon62]

Mark - Just curious, why didn't you port all the intakes?

 

[CobraSix]

Actually, that's good news about the low compression. Something I'm worried about when I start looking at superchargers...need it below 9:1 from most places I've read, prefer to be below 8.5:1.

Slade

 

[Anlushac11]

Mark - Just curious, why didn't you port all the intakes?

Ak Miller recommended porting the two end ports since traditionally they receive the worst airflow and anything that helped them breath better was helping.

 

[Falcon62]

I can understand that, to a degree, but while optimizing everything else at the same time it seems self-defeating to leave two intakes 'as casted'.

 

[Anonymous]

Hey, Falcon62;

My goal here was 3-fold:
1. Improve MPG. I want 20+ MPG in around-town driving, auto tranny.
2. Smooth out the engine (these sixes run rougher than most).
3. Get more power at higher RPM without giving up the low end. It's the low end that climbs these mountains around here (I'm in Colorado).

After much study, I decided the only way to do all 3 of these is to balance the flow across all of the cylinders. I also know this to be true from working with multi-cylinder motorcycles for over 30 years: these are typically 4 independent engines on one crankshaft - the ultimate tuning environment. Then, after looking down the intake's throats for a while, I discovered that the diameter of the 2 center cylinder's throats are larger than the others. Add to this the fact that they are very close to the carb and it's not hard to figure where the lion's share of the flow ends up.

The Clifford port divider does it's thing above about 1500+ RPM, but below that, it's all about intake cross-section area. I actually made the #1 and #6 ports larger than the #2 and #4, just for this reason. The smallest now are #3 & #4, though not by much.

The only thing I would do differently, should I do it again, is to back-cut the (or buy 30-degree) intake valves and recut the intake seats to match the 30-degree flow. This works so well in bikes and V8s that it's become the hotrodder's first choice these days: even Ford, in the legendary 1964 427 SOHC engine, found the 30-degree trick to be worth over 25% in increased flow at low engine speeds.

And, like it or not, these sixes must be considered "low speed engines" with the cast-on intakes, because they will never breath well enough in that configuration to be reliable high-RPM units. That's not a bad thing: more than 99% of your driving will not be faster than 4500 RPM, anyway...
...and, every 1000 RPM you 'lose' becomes another 20,000 miles you 'gain' in low-maintenance longevity. I like my little 6 enough to want to keep it that way for a long time!

 

[xctasy]

Mark P said

and, every 1000 RPM you 'lose' becomes another 20,000 miles you 'gain' in low-maintenance longevity. I like my little 6 enough to want to keep it that way for a long time!

.

Wow, wise man!

The fact is, you're right! That's why Fords last, there under no streess at all.