PTS Flowbench Forum

The many years i raced at RMR raceways I brought my stock Cuda from a horrendous 19 sec 1/4 mile run to a best of 14.18.

I tried every thing from a fresh rebuild 340, several new cams, electric water pump, electric fans, alu radiator, smaller from tires, slicks out back, alu intakes and headers, of course.

Then i got creative and made me a switch that turned off my electric fan and killed the alternators charging ability when i hit full throttle.
This amazingly took 2 ths of my time. Getting me soo close to my 13 sec. But could never get better then that.

fast forward, several years latter, playing with 1/8 mile track.
Year before last my best 1/8 mile ET was 10.10

Last year i got it down to a 9.8x ET by getting ride of my 20/50 eng oil and going to a 5w20 synthetic(Oil pressure is still plenty good)

This year i final pulled my dist and braised and file my centrifugal advance so i could get more idle advance(with faster curve springs) when i set my total advance.
With full advance at 38* i could only get 12 at idle
Now i have 20* at idle.
Idles much better, killed 60 foot times by .16 and got my best 1/8 mile ET 9.69@74.0 mph. just over a mile per hour jump in the 1/8.

I wish i had my Diesel fixed, so i could load up my car and shoot one more time for that 13 sec 1/4 miler

Gordon
What heat range spark plugs do you run in your car. I learned from an old racer who ran Mopars that they like a plug about two heat ranges colder for drag racing.

Ray

That's what i have been looking at on my plugs.

I didn't install new plugs(there a couple years old) but when i pulled then here at home, the ground strap tells me i need cooler plugs. Color all the way to the ground strap base or weld. And some of the spark plugs was just above it.

The plugs are standard heat range for a 340,.........I thing, there NGK's ......the ones that have a grove in the ground strap.

Never heard any ping noise from the eng, and no sign of it on the plug.

Most plug show over rich condition..........but i think, thats the cruise part of my carb( drove 5 miles to track and back at light throttle and 3000 rpm

This is the best UNLEADED plug reading site i could find.
http://www.angelfire.com/fl4/pontiacdud ... plugs.html
This ones Pretty good.....But........

Any body have a better one, for reading unleaded plugs?

Larry M, has a Grate one, on his site, but, its for LEADED fuel.

Thanks Ray,
Printed that out.

Got to get me a new spark plug light. left my old one, for two long, with the battery's in it.
It eat it all up

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Last year i got it down to a 9.8x ET by getting ride of my 20/50 eng oil and going to a 5w20 synthetic(Oil pressure is still plenty good)

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I am glad you pointed this out as this really is a big deal. There is a lot of "free" horsepower you can get with a little effort. Gordon, you represent what a "real" hot rodder is. You do not have to spend a lot of money to make you car substantially faster. That is one thing that disappoints me with today's "SHOProdding" when people spend a kings ransom and don't turn a wrench themselves.

Another thing to think about is a vacuum pump on you crankcase. On Larry Meaux's forum he had just stated on one engine he tested with and without the vacuum pump. In the back of my mind the vacuum pump added about 32 horsepower to the engine. Now that might be a very light tension ring motor, but I know it helps on my motors to run a vacuum of some kind on the crankcase. It is important to make the crankcase sealed very well to do this.

btw light oil has always given me better fuel economy also.

John

For every litre of capacity above the piston crown, there is another litre below the piston crown being pumped, but for no gain only loss.

John you got me curious, so, I pull out some old ET slips and did some figuring.

With the eng the same then, as it is now(No internal changes)
I when from 15.16@93mph, to 14.18@98 mph and And a HP increase of 38 HP.
Most of that ET was going from 3:91's and cheater slicks, to 4:56's and real 10" wide slicks)

38 hp is quite a lot for not bolt'n on a better set of head or a better cam, or.... Exc.

I don't have a calculator to figure HP from 1/8 ET slips but, i have basically killed .4 ths in the 1/8 mile(all thew some of it was rejecting/tuning for the Higher altitude of this 1/8 mile track.)(4400feet to 6800feet)

I would Love to be a SHOProdder.......but my lack of money, keep me pushing, for that last HP of my combination.

For every litre of capacity above the piston crown, there is another litre below the piston crown being pumped, but for no gain only loss.

jsa, I had never though about the compressor affect of the bottom side of the piston, but that is so true!

John i thought it was vary interesting when Larry was taking about loosing so much vac, from his pump, all form a leaking valve cover bolt. Probably a leak so small that, It never would have leak oil!
Yeah i read and commented on that thread.(I'm Cudafever over there )

jsa wrote:For every litre of capacity above the piston crown, there is another litre below the piston crown being pumped, but for no gain only loss.

I am going to be the devil's advocate here, so please no one take this personal. I am just trying to get some discussion going here about this subject as it really interests me. Now in a single cylinder engine the above statement may be true to an extent, but in a V8 or other multi-cylinder engine when there is one piston coming down creating pressure there is another one going up creating a void. So is the vacuum pump really helping in that aspect or more to keep the light tension rings sealed?

Now there may be some crankcase pressure created from blow by so you would want to get rid of that also with a vacuum pump. My question is how much internal pressure are we really creating with the piston going down? Are we really concentrating on ring seal?

John

Here's some number,

350cid/12/12/12=0.203125 ft³

Rotate that at 6000rpm

0.203125 * 6000 = 1218.75cfm

Someone want to throw an assembled short block (any short block) minus two pistons on a flow bench.

Put one open bore over the bench inlet. Draw air from the other open bore through the assembled crankcase and out into the bench.

Report back with cfm @ pressure drop and engine spec.

With flow and pressure drop data, some ballpark figure could be extrapolated for the running engine power loss.

John, yes I think ring seal is also part of the advantage of sump vacuum.