[Chief of the 60's]

Originally Posted by carbking

The first thing to check is your numbers.

If you have a highway handy with mileage markers, do a 20 mile run and check your odometer against the mileage markers.

Rear gear change or tire diameter can greatly effect the accuracy of the odometer.

Jon.

I got a local sheriff to run radar on me. You are not getting more accurate than that. He was more than happy to take time out to help.

But you cannot take 1 speed check due to the crude mechanics of a speedometer/odometer. You need at least 3 tests in the upper mph's for accuracy. 40, 50, and one more of 60 or above will give the best results. I chose 65 as my final test as that is generally the fastest speed usually traveled on roads.

[footjoy]

At this point I am not focusing on speedometer I think the problem is fuel or fire.

I have a 68 intake and a 71 7041264 quad that is in rough shape in the basement, but I don’t have the 500 or what it takes to restore the carb..

So when I have exhausted everything in timing and advance I will look into the quad. I have had Holley spreadbores that got 18 mpg

[Chief of the 60's]

One cannot obtain accurate measurements without accurate instruments. What good is measuring 1 foot with an 11 inch ruler.

[tom s]

If you have a smart phone its easy to check your speedo on a straight road.I use WAZE.Tom

[Formulajones]

I was going to say, with all the tech today it's pretty easy to see how accurate your speedo is. Like Tom said smart phone apps have it. I use a GPS that has a MPH feature and I find that to be spot on. It also calculates mileage for comparison to your odometer and see how the MPG calculations differ. Just about everyone has a GPS these days don't they?

Definitely something amiss. 11 mpg out of that combo is pretty bad.

I don't even have overdrives in our classics here and I'm getting anywhere from 14 mpg to 17 mpg with bigger engines and 3.31 to 4.10 gears in various cars.

Even my fathers 69 GTO with a 724hp 571 cubed Pontiac engine with a loose converter, no overdrive, and 3.73 gears is getting right at 10 mpg.

A wideband comes in handy here for light and part throttle cruising AFR's and will give you an idea what area of the carb needs attention.

[tom s]

If a car has too high a final gear it can lug a engine and it will hurt the mileage for sure.All 3 of my cars are setup up to be about 2000 at 65-70 MPH.Tom

[footjoy]

I have checked with my Garmin gps the speedo is 1 mile slow at 70 and the tach is 2350

[footjoy]

For cruising at 2400 I am curious should I be all in at what 2800, 3000 or 2600 rpms ?

Thanks

[Chief of the 60's]

Originally Posted by tom s

If you have a smart phone its easy to check your speedo on a straight road.I use WAZE.Tom

Originally Posted by Formulajones

I was going to say, with all the tech today it's pretty easy to see how accurate your speedo is. Like Tom said smart phone apps have it. I use a GPS that has a MPH feature and I find that to be spot on..

GPS "spot on"?????

That is why people get lost, drive onto train tracks and drive into lakes.

I already know "GPS" does not fly in front of a judge in court.

[dataway]

Yep, the GPS reading will be very accurate on a straight road taking about a 1 mile sample. It's the most used method for calibrating aftermarket "adjustable" speedometers, or speedometer correction boxes used on late model motorcycles that use sprocket sensors for calculating speed (gearing changes throw off the OEM speedometers).

[Formulajones]

Originally Posted by dataway

Yep, the GPS reading will be very accurate on a straight road taking about a 1 mile sample. It's the most used method for calibrating aftermarket "adjustable" speedometers, or speedometer correction boxes used on late model motorcycles that use sprocket sensors for calculating speed (gearing changes throw off the OEM speedometers).

Yep, and from there just do the math and make the necessary corrections. It's pretty simple really.

[400 Lemans]

http://forums.maxperformanceinc.com/....php?p=4304819 My thoughts, just in case Crower 60243 wasn't degreed in initially.

[footjoy]

Originally Posted by 400 Lemans

http://forums.maxperformanceinc.com/....php?p=4304819 My thoughts, just in case Crower 60243 wasn't degreed in initially.

Well what can you do to correct this I don’t know if the engine builder did that. With out pulling motor a part.

Thanks

[footjoy]

If a cam is put in dot to dot and it should have been advance 4 degrees, is there a fix without pulling the motor. Like maybe timing adjustment?


Thanks

Greg

[tom s]

Greg,I just did that last week.My 068 was put in straight up.My timing set has a 4 degree advance and a 4 degree retard keyway.I just pulled the front cover and moved it to the 4 A keyway.If you a smart phone I can text you the pics.PM your number.Tom

[footjoy]

Originally Posted by tom s

Greg,I just did that last week.My 068 was put in straight up.My timing set has a 4 degree advance and a 4 degree retard keyway.I just pulled the front cover and moved it to the 4 A keyway.If you a smart phone I can text you the pics.PM your number.Tom

I will pm my text number

[Chief of the 60's]

Originally Posted by tom s

Greg,I just did that last week.My 068 was put in straight up.My timing set has a 4 degree advance and a 4 degree retard keyway.I just pulled the front cover and moved it to the 4 A keyway.Tom

Interesting. What were the results after altering it from the factory setting?

[tom s]

im told it should pick up about 15-20 lb pumping comp.Hope to pump it tomorrow.Tom

[chiphead]

Which #15 heads do you have? There was a '68 high compression 72CC head and a '70 moderate compression 87CC head for 455.

Cams should always be degreed for best efficiency and performance. Correct ICL for each engine may be different depending on compression and engine size.

What kind of idle vacuum does this engine have?

[footjoy]

Originally Posted by chiphead

Which #15 heads do you have? There was a '68 high compression 72CC head and a '70 moderate compression 87CC head for 455.

Cams should always be degreed for best efficiency and performance. Correct ICL for each engine may be different depending on compression and engine size.

What kind of idle vacuum does this engine have?

87cc heads about 14 inches of vacuum at idle with flat pistons with 4 reliefs.