High MPG SBC Build

[thirdstreettito]

OH ok, thank you for clearing that up. So, what's wrong with using a hydraulic flat tappet cam? Pros and cons?

[Warrens69GMC]

Originally Posted by InfernalVortex

Flat tappet cams were fine for years and years and years. It's the modern oil that's killing them. The advent of roller cams in more modern engines are why the modern oil isnt formulated with them in mind also. But roller cams allow for much faster valve lift rates in addition to being more reliable. The ratio of duration at .003 and duration at .050 basically determines your drivability at a given power level. Duration above .050 lift is the duration significant enough to give you actual airflow and power. Duration between .003 and .050 basically is just lost efficiency, overlap, low vacuum, etc. This is an oversimplification, but you get much more drivability for the amount of power you make with a roller cam that can ramp those valves open at breakneck speeds. If you dont understand what all the numbers are about, just know that roller cams WILL make more power.

The other element of roller cams is beyond measurements, not only do they open faster, even with the same duration at .050 of a flat tappet cam, the valve will be at higher total lift in most cases, but it will also be near and at maximum lift for a longer amount of time. The valve is open farther, and longer, even with the same duration.

From ThirdGenration.org

[djracer]

If you use the Flat Tappet cam run Diesel oil till its good and broken in! Rotella or Dello

[Warrens69GMC]

Originally Posted by djracer

If you use the Flat Tappet cam run Diesel oil till its good and broken in! Rotella or Dello

Why is that?

[djracer]

Its has the additives that regular oil is lacking these days.

[Warrens69GMC]

With the CJ-4 standards the are well below what our oil used to have for Zinc. Or are you talking about soot control? Or something else??

[fastwillie 696969]

does those rings need filing

[Captainfab]

The diesel oils available these days do not have sufficient ZDDP content to support a flat tappet cam.

Originally Posted by djracer

Its has the additives that regular oil is lacking these days.

When breaking in an engine with a flat tappet cam, you must run a good break in additive for the amount of time recommended by the cam manufacturer. There seems to still be some debate as to what oil to run with a flat tappet cam after a break in period. Some say you still need an oil with at least 1400ppm ZDDP, and others say that you don't.

There is a good thread on flat tappet cam compatable oils in the 'Engine and Drivetrain' section.
Here it is......
http://67-72chevytrucks.com/vboard/s...d.php?t=381780

[Warrens69GMC]

Originally Posted by Captainfab

The diesel oils available these days do not have sufficient ZDDP content to support a flat tappet cam.

Exactly.

[Marv D]

Wow what a overthrashed subject. The last time this came up a member brought to light that Motorcycles are not subject to the same level of emmissions crap as cars and truck. Motorcycle oils have higher levels of the taboo high pressure lubricants than API approved gas or Deisel oils.

(and yep Keven,, Rotella and Delo was hit a a year or so back also,, better than gas engine approved oils, but have reduced the ZDDP there too)

In the end, a roller cam is far cheaper than rebuilding your engine because a lobe failed. When the ground up lobe and lifter debris is flying around in the crankcase, and going through your oil pump,, finding it's way to the cam, rod and main bearings,,, the math then adds up.

Only alternative I can say is an absolute positive solution to the ZDDP missing in street grade oils,, thank God we still can have OFF ROAD classification. Offroad / racing oil can't be sold over the counter for your street car but has everything you need for flat tappet cams, and more. I know a guy who knows a guy who can score you some,, but it ain't gonna be cheap

LOL

http://www.jegs.com/i/Royal+Purple/831/05021/10002/-1

[thirdstreettito]

I was going to use Shaeffer Supreme 9000 oil anyway. Also, I cant go higher than .50 lift because of the heads, I'll have to get them machined if I want to go higher.

[C-10 simplex]

As someone who has done/is doing scientific testing regarding mpg (will provide links later maybe) i would suggest based on your plan(s):


1) concentrate on actually saving money on gas first before anything else; i.e., mobil has/had a card that offers .15 off pump price. This is fast easy cheap way to save on gas. If that is no longer available, there are a slew of credit cards that offer 1-2 maybe higher % off any purchase. Also, look into a sam's or costco membership.

These 2 things alone may account for up to $2 off every fillup. This is immediate savings requiring no investment. (i know sam's and costco require a membership fee, but i'm talking about the credit cards)

2) Based on recent observations, aerodynamics really helps. In fact, i think it's more important than weight reduction. i just apparently jumped about 1.5- 2 mpg just by adding a tonneau cover. i think aero is much cheaper and easier than engine work.

3) Don't be too quick to condemn the engine. Of course a 350 in a truck isn't not the ideal combo for high fuel mileage. While it's true that you can make big gains by switching engines altogether or modifying one, it's all about the total combination AND i think there are better (cheaper) ways to improve mpg first.

My point is do other stuff first, THEN work on the engine because the payoff is better with other things.

[thirdstreettito]

There isn't much I can do for aerodynamics, it's a suburban. lol

I go to sams when I'm near it(20mi away), also, I check online for the lowest price withing 15mi of me, then go fill er up there.

I will be getting 33x10.5R15's soon, they are higher load range tires and taller, so they will help my high speed mpg and rolling resistance.