View Single Post
  #8  
Old 02-12-2014, 07:58 PM
ccracin's Avatar
ccracin ccracin is offline
Senior Member
 
Join Date: Sep 2006
Location: Rostraver, PA
Posts: 2,067
Thanks: 0
Thanked 4 Times in 4 Posts
Default

Quote:
Originally Posted by Ron Sutton View Post
[B] If they can afford $200 to put the car on a chassis dyno, you can get the last 20hp of the engine by fine tuning the jetting & timing. Tune for optimum power from 4700-6300 & give up some in the 4000-4300 range so it doesn’t spin the tires easily. This allows the driver to roll the throttle on quicker and get the acceleration cycle started earlier. This is key both to good lap times, but also setting up passes. You can’t pas someone if you can’t get off the corner well enough to get along side them.

Dyno test the timing … up & down from 37° … and whatever timing builds most power from 4700-6300 will be your number. Make 2° changes at first, then fine tune it with 1° changes. 1° matters, especially in restricted race engines. I will definitely suggest this to them.

L. For oil, I strongly urge them to run a “blend” over full synthetic or full petroleum based oil. The “good” petroleum based oils offer better lubricity, for less wear, longer time between rebuilds & frankly more power over a longer period of time. The synthetic part of the blend offers a higher level of heat protection. Thicker viscosities add more friction. Super thin viscosities offer less protection. I’d like to see them run a 10w40 or 15w40 … depending on the rod & main bearing clearances. If you keep them .0015” - .0018” that would be my choice. Again, I will pass this along

M. Blueprinting the oil pump is strongly suggested … or simply buying it that way. Getting the rotors deburred & the clearances optimized so the pump is “low drag” is the goal here. You don’t need a ton of volume or pressure in a SBC turning 6300 rpm. Buy a quality pump, but don’t get carried away with pressure or volume. Both are HP reducers. Do you have a prefered source and or part number. They will be buying a new pump anyway, I'm sure.

O. There doesn’t seem to be a timing chain rule. At a minimum, go with the tru-roller from Cloyes with the index-able gears. If budget allows, I’ve seen better power & extended engine life with the Comp Cams belt drives. They are currently running the Cloyes Hex Adjust that was on the engine I sold them.

P. I can’t say enough about making the rotational assembly light. If the crank rule is 48#, for Pete’s sake get down right to it. Target 48.5#. I told them this already. Since they are replacing pistons, I told them this can be done if it hasn't already when they have the rotating assembly balanced

Q. Several manufacturers offer light pistons. I think JE has them around 375 grams with standard pins. Already suggested

R. An area not tech’ed is piston pins. This thing won’t build major power, so you can run thinner wall, light pins.Already suggested

S. A little out of order, but whatever cam I recommend, they’re going to want 1.65 roller rockers. I ran Comp Cams Magnum Rockers, but again in saving money, the went will aluminum rollers, not sure of brand. Do you have a preference?

T. With only 6300 rpm, they don’t need big ol’ pushrods. Here is an opportunity to go small diameter & thin wall chromoly & lighten the valvetrain. (Hardend tips.)That's what they had when they got it from me. I will make sure they replace them. You may be confused with some of this. They spun a couple bearings in the motor they got from me. I think due to a water leak, but has not been confirmed. LOL so they transferred the top end to another short block.

U. Spend the little extra for titanium valve spring retainers. They will pay for themselves plus some with extended life of the valvetrain.

V. Probably not a big issue, but make sure the valve springs are set-up close to coil bind to reduce oscillation & bounce. (Remember, the engine doesn’t make compression until the intake valve stops bouncing & actually seals. )

W. Once we land on a cam, valve spring pressure is critical. Too little & we have power loss along with durability issues.

X. Don’t cut corners on the valve guides or seals. We need it sealed with as close to zero oil contamination in the cylinder as possible. Some people justify the cylinder need lubrication, but the low tension oil rings already take care of that.

Y. If we end up on gasoline, run as cold of a plug as possible, like a 1 on an Autolite scale or a 10 on an NGK scale & dial in the jetting & timing. If we run Ethanol, run 1 step hotter … like a 2 on an Autolite scale or a 9 on an NGK scale. Stay away from the trick of week 2, 3, 4 or 987 prong spark plugs. I buy $3 race plugs so I can read them & throw them away. Buy plugs with the strap cut back or cut it back yourself. Gap them at .035" & index it so the gap opening is pointing straight down to the top of the piston or just slightly towards the intake valve.

Z. Frankly, an ignition amplifier won’t build any more power here unless the jetting is too rich. But make sure they have a top notch coil 7 new wires. Replace the wires every season. Don’t wait for them to “go bad.”

Get me answers to my few questions above & we’ll get working on cam & exhaust.


Hopefully I have given you what you need. I plan on taking the results of this discussion and putting together an outline for this engine. I will then pass it along and hope hope hope they work to it.

Later I would like to discuss this car's front end as well as another friend's I help. This car is a Dirtworks Asphalt car Bart Bates built. The other car I help with is an Ellis. I think you are familiar! But that's another topic!

The post had too many characters so I had to split it. In hind site, i should have just refereed to the letters. Next go around!
__________________
Chad
Instagram - @cctek
https://https://www.facebook.com/CCTek

68 Chevy Pickup Project
Build Thread: https://lateral-g.net/forums/showthread.php4?t=7505

THANKS TO: A&M Machine and Fabrication, CCTek (http://www.candctek.com), Hermance Design(www.hermancedesign.com), Paradise Road Rod & Custom, Harry Opfer Welding, Wegner Automotive Research, Clayton Machine Works
Reply With Quote