Hi Snowtoy,
“Not quite the same thing, dragster tires are usually filled with less than 15ps, most under 10psi, and use nitrogen since it is wont expand much/if at all under heat.”
Nitrogen is used in tires primarily to avoid the water vapor content that is in our air, which is about 79% nitrogen and 21% oxygen. With nitrogen, the fluctuation in air pressure with temperature change is reduced as well as fluctuation in nitrogen gas temperature.
“If this was happening, there should be a noticeable power loss at that speed, and your speedometer should be off more than just the % between the stock 225's(27") and your 31's.”
Yes, if my 31” tire diameter increases at 80 MPH to say 32”, then the final gear ration will also change, and it may be noticeable, mathematically it will be decrease between 80 and 90 RPMs on my tach.
"I hear ya, but there is a member on here w/a front IFS section in So.Cal, that can get you halfway.
http://board.marlincrawler.com/index.php?topic=100092.msg247122;topicseen#new"
Yeah if I were 40 years of age…… Well as I said, I’m just not into the “work-on-my-truck-every-weekend-guy” I was 15 years ago.
“True. most find 31's and 4.10's tolerable/livable, for the most part, and with the fresh rebuild it may perform just fine.”
I’m hopeful that this rebuild, 020” over bore, slight increase in compression ratio, new head with 261C cam, larger valves, rebuilt injectors, and new larger exhaust system will meet my expectations.
“If you are going to test different cams, then I would wait until you have bought the different cams you are considering, swapone in, tune/dyno, then repeat with the others, after you fond one you want, redo the HG.”
Yeah, that would be a logical way to test the camshafts. I imagine I’d want to drive the truck with each cam for a while after it’s been on the dyno. Since I have about 3 camshafts I’m mostly interested in testing, I’ll have to start a cam-kitty.
“One thing you have to remember, often theoretical power/performance gains on paper don't often transfer to the real world, which is why, as you have found, cam manufactures don't/wont state HP gains, only "x"%, nor do many post dyno runs.”
I realize that my dyno software produces projected and somewhat theoretical data, however it happens to be one of the most respected dyno software programs available.
And, yes, you can dyno an engine on a Superflow SF-902S and read gobs of data, then install that engine in a race car and the driver will experience something different. But, in the absence of any certified dyno tests on the camshafts that are advertised, I’ll just have to make some assumptions and test them myself on a local chassis dyno. Advertising and marketing claims are often more Bravo Sierra than actual facts.
“Once you get the rebuilt in, you should dyno the truck with a set of 225's and the 31's to see what the actual hp/tq loss is, it would give you a number to test your mods against.”
I stated that I have BFG’, that’s what I ran mostly in the past. Now I have a set of Michelins:
http://www.michelinman.com/US/en/tires/31/10__5/15/109/R.htmlI don’t want to run tires smaller than 31s, so there would be no point to buy or borrow a set of smaller tires just to dyno test.
Good discussion.
Gnarls.
