Static vs Dynamic Compression Ratio Questions

[colnago]

71cc and Jacksdad,

I certainly understand what you're saying, and I agree to a point. It really isn't the logical choice to rework my current engine. The time, money, and effort can certainly be directed toward my final solution. I can't really explain it, but I really want to get this engine performing as best as it can - to a limit. I know that it will never perform as it could, unless I build it up from scratch.

I want to continue learning from this. I want to see the outcome of using a cam with a shorter duration. I made a poor choice from my original cam; I don't mind swapping in a more appropriate option. As long as I'm at it, I'll do what I can to increase the compression. If I end up with a lackluster engine ... meh, it's only time and money, and maybe I'll learn something along the way.

Thanks for your input. I really appreciate your advise.

Joseph

[8ton]

Sounds like you could get by with a bit more tuning, before ripping into the long block. You are running edelbrock carb right? At what vacuum does the enrichment come in? A vacuum gauge in cab, and staying out of that vac range will help mileage alot, although will serious slow you down. It doesn't take much pedal at all to drop vacuum to 3-4" from a stop.

What is the advance curve on your distributor, initial and total timing? Are you running ported or manifold vac? Are you running a big cap with low resistance wires? What plug gap? Have you tried a projected plug like Motorcraft SP435?
My 360 likes as much timing as possible. Get a crane adjustable vac advance, and drive around with a timing light, 1/2" wrench, some pliers and a Allen wrench and bump it to the max.

Have you tried a 4 hole carb spacer?
How about an adjustable timing set? 2*-4* advanced should bring your power band down some.

How about some of the $150 headers and an exhaust rework? You could replace them with nice ones in 2-3 years, and not be out much.

Your mileage and throttle response should both improve with all that, and cost significantly less You could still swap head gaskets/cam afterwards if still unhappy.

I drive my 360/c6 powered 100 several days a week, so I understand the frustration of poor mileage and lame power. Double digit mileage IS possible, but you have to work hard for it. The best mileage gain I have made is carpooling with my wife in her Volvo.

[Jacksdad]

The best mileage gain I have made is carpooling with my wife in her Volvo.

[colnago]

Sounds like you could get by with a bit more tuning, before ripping into the long block. You are running edelbrock carb right? At what vacuum does the enrichment come in? A vacuum gauge in cab, and staying out of that vac range will help mileage alot, although will serious slow you down. It doesn't take much pedal at all to drop vacuum to 3-4" from a stop.

The Edelbrock secondaries are mechanical, not vacuum like the Holley. Cruising, my vacuum is 13" - 19", with jumps above 20" at times. I do have an in-cab vacuum gauge. You're right, it takes very little pedal action to see the gauge jump.

What is the advance curve on your distributor, initial and total timing? Are you running ported or manifold vac? Are you running a big cap with low resistance wires? What plug gap? Have you tried a projected plug like Motorcraft SP435?
My 360 likes as much timing as possible. Get a crane adjustable vac advance, and drive around with a timing light, 1/2" wrench, some pliers and a Allen wrench and bump it to the max.

I just got a new distributor from Performance Distributors. It's the Duraspark version. I haven't had a chance to map it out yet, and they didn't provide one. My initial timing is 15 degrees BTDC, which puts my total advance (without vacuum advance) at 37 degrees BTDC. Ported vacuum right now, but I have no problem with switching to manifold. Plug gap is 0.035", although I've been told to increase it to 0.050". Yes, low-resistance 8mm wires. No on projected plugs. I haven't done anything to adjust my vacuum can ... yet. But I will.

Have you tried a 4 hole carb spacer? How about an adjustable timing set? 2*-4* advanced should bring your power band down some.

I have run a 1" 4-hole spacer for years. I just changed to a 2" 4-hole spacer. It _seems_ to be more responsive, but I'm not currently driving it much, so it's slow to see how changes affect things. Currently, the cam is installed straight up, and I currently have a non-adjustable timing set.

How about some of the $150 headers and an exhaust rework? You could replace them with nice ones in 2-3 years, and not be out much.

I'm afraid the cheaper headers would be a fitment nightmare. That's why I'm looking at the Sandersons. I know those will fit. Any of the $150 versions SAY they fit, but I've not heard from anybody who has used them and had them actually fit. I do expect that my biggest gains will be when I install headers.

Your mileage and throttle response should both improve with all that, and cost significantly less You could still swap head gaskets/cam afterwards if still unhappy.

I don't disagree at all.

I drive my 360/c6 powered 100 several days a week, so I understand the frustration of poor mileage and lame power. Double digit mileage IS possible, but you have to work hard for it. The best mileage gain I have made is carpooling with my wife in her Volvo.

Frustration? No. Hope and expectation? Yes. The best mileage gains have been over the last four weeks. I've been riding my bicycle to work.

Joseph

[8ton]

Enrichment is when power valve (Holley, autolite) opens or when the metering rods (abf, q-jet) rise up to the thinner part at low vacuum. This adds extra fuel under acceleration. It is controlled by color coded springs, dictating what vac they activate. If it is enriching at 10.5" you may see better throttle response, but worse mileage, and if they enrich at 3" it may ping pulling a load at part throttle. You need to know what you have to avoid driving around dumping fuel, and can play with it to maximize this balance.
It sounds like your driving vac is similar to mine.

The stock spec for a duraspark 360 is a .042-.046 gap at 12* initial, set at 500rpm, idle at 800. Try gapping your plugs in this range, I doubt you will have any problems.
I tried the 800 idle and it was WAY fast.
The projected plugs are what ford made for the 300 6 as it went efi. They do not interfere with flattop pistons. I haven't determined if they help or not though...

The summit roller adjustable timing set is $35-$40 and is USA made (or was a couple of years ago)

My flowtech headers were not a nightmare to fit, they are just tight AF around the starter, and after a few times on and off over the years have developed warped collector flanges from over tightening. Oops!

[colnago]

Ah, gotcha on the enrichment. Right now, I have the orange springs in. I've played around a lot with the needles/jets. It seems that my engine likes things a bit on the lean side, but I live at 2,000' altitude, so it might not be super-lean (that also lowers my vacuum about 2").

As far as idle, my current setting is 600 RPM. I haven't done anything with the plug gap yet. I need to increase the voltage to the coil (it's still going through the ballast resistor). I have the relay and wiring; I just need to get off my rear and git 'er done!

I checked out the Summit timing set this weekend. Looks like a good set, and it's received a lot of good reviews.

Good to know about the Flowtechs. I will have to check them out.

Joseph

[colnago]

Well, I just bit the bullet. For better or worse, I'm going with the Lunati, and Mr. Gasket 0.020" head gaskets/shims. I did get the Summit timing set, instead of the Lunati (note to tnlprt: I also purchased a degree wheel, but I'll keep the Edelbrock carb). Next year, I'll get the Sanderson headers.

Thanks, everyone! Good or bad, I'll post my results when it's all installed.

Joseph

[DuckRyder]

So, hows this going?

[colnago]

I've got a box of pretty parts sitting on my work bench, waiting for the time. My son is changing apartments, so I don't want to disembowel the old girl until I know she can be down for a couple of weeks. I was planning to go back to my "S" intake manifold, but I hoovered it up, so I have to figure out how to un-booger it (or keep using the current "T" manifold; there's probably no difference between them).

Joseph