The filter idea is a necessary evil. No one wants his motor to eat a chunk of burnout rubber while waiting to stage. I would think a period correct scoop could be made using a newspaper type mailbox as a mold or as in my case a greer, black and prudome type scoop that are still being made
Depending on the desired shape a simple old style scoop could be fabricated of aluminum panels riveted together. That said, I used a newspaper mailbox as our scoop by making an aluminum base plate.
I wouldn't mind running without the filter but lately ma nature likes to throw quite a bit of real estate in the air around here.Also we have a Lucas series off-road course near the top end of my home track and they're running the same time as the strip occaisionaly.
Most engines'll have no trouble digesting the odd piece of matter under .050" or so without harm. That level of filtering can be accomplished with a reasonable screen, nearly anywhere in the intake, without sacrificing airflow. My own response to the problem uses ram style tubes without bells to filter the air, since even .050" stuff won't turn the corners at the open ends. They also serve to contain the standing waves from valve closure, keeping the mix inside the system at revs.
There you go. Everyone has a different idea that works for them. I use a scoop to create a positive pressure at the carb inlet which puts my motor in danger of swallowing any junk headed my way. I have been hit with rubber 1/2 inch in diameter from being stupid enough to stand behind a car during its burnout. Opinions are what make this hobby work. Otherwise, we`d all be driving pintos and pacers.
You say that like Pintos and Pacers are a bad thing. Personally, I liked them both...and Corvairs, Studebakers and International pickup trucks too. OK, so I'll admit, I am a bit off, but that's what hotrodding is all about.
I get my pressure from a mild slash cut into the wind at the tips of the stacks. At some of the strips I run, the lanes are directly behind the water boxes (with Eagle Field's dirt approach being the most hazardous, I've seen some pebbles moving pretty well there). If I were running a scoop under those conditions I think I'd go with 1/2" hardware cloth over the front for the big pieces, and window screen over that for the smaller stuff. You might also get some ideas from some of the boggers' sites.
That scoop that you see in the picture to the left was on the flow bench, the drilled chrome plate that comes with it was used and not used on the flow bench. It was a 6% loss at a 650 cfm flow. well a 500 cfm carb will not know the differance. And with only 233 cu. in. I would stick with it. That small filter that comes with it was left out. Joe
I run the bells on the S.Us on the straight six but only because they look the part, with no filters. On a similar note, but not the same (I sound like a politician), late last year I forked out for some dyno time. It was mainly to get a good ignition setting. After playing with timing and picking up 10 h.p. by fitting a distributor that the mechanical advance actually worked , we tried changing the pump fuel. I know that octane ratings used in Australia are a bit different elsewhere but I replaced the 91octane with 98 octane and immediately lost 6 h.p.. That doesn't sound too dramatic but when you only have 90 h.p. to start with, it's a good bit to lose. Changed back to 91 octane and straight away picked up the lost h.p.. We could've played with ignition settings but a bit of research shows 98 octane is designed for computer controlled ignition for slow burn, not like 'bang for your buck' low compression dinosaur engines. The Holden Grey motor came out with about 7.5:1 compression ratio and mine with minor head work is probably only 8.5:1.
I know what you are talking about Spanners. The 1934 Dodge flathead 6 we're using for our car had all of 6.5:1 compression from the factory. with luck we may be able to squeeze it up to 7.5:1 or 8.0:1. On the bright side we'll be able to use bottom grade 87 octane pump gas as our race fuel which fits my frugal budget well.
I new what you said about 98 octane being for slow burn smog engines with computer controlled ignitions. Nice to see a dyno test on a small 6 cylinder motor to show the HP difference. On a older 327 motor I ran in my altered that had 10.75 CR and would not run on 87 octane I cut my cost a little my blending 1 gal 100 octane race gas with 4 gal of 87 pump gas, worked real well and cut the cost down, good power. I know it may not be the best way to get around the problem, but it a money saver.
I agree with Bobw on the fuel discussion.Some good info and insight there, My motor is around 10.1 on the compression and not sure how to go on the fuel route as it was built more as a street engine. On a side note the truck stop across the interstate from the track sells 101 octane so I might try that and see how it goes.
Tom, you say you were able to blend your race gas with a 10-1 motor. Did you have hardened valve seats? I`m running 100 octane av gas, more because of the lead content than octane concerns. I couldn't install hard seats without busting into the water jacket and I like the extra lube for the valves.
Dan, ya had hardened valve seats and I ran 100 octane av gas at first, worked fine, you just need to stay on top of the engine oil as it contaminates oil like alcohol. I like the mix setup as it is easier on carb parts than the AG. I think your setup will be fine, just keep up on the engine oil condition. 300racer, do try some of the 101 octane from pump if it is a true 101. We had stations up in WA state when I was there that sold it, good price, we ran our antique pulling tractors on it and lots of the motors were 9-12.0 CR. wish we could get it in our area.
http://bangshift.com/general-news/v...-ford-flathead-six-with-a-homemade-turbo-setu Flathead 6 Ford Running.
Tom, now you tell me. I`ve been chasing an oil contamination issue for a month, even to the point of changing the head gasket ignoring a good leakdown. You don`t know how much good you did with that one sentence. thanks, Dan
Dan, That AV Gas is real good for the lead content and a little higher octane, but when you run it you have the same cylinder oil wash down that we had when running our past alcohol motors and the same oil contamination problems. That why we had to change oil after a days racing & it don't matter if you run 0 gap rings or not. Oil's cheap compaired to motor parts. You going to make the ANRA opener in April?
Tom, you learn something new every day. Or in my case, learning something simple like the avgas thing. keeps me from getting to arrogant. This is why I think this thread is the best one yet. I plan on attending the anra opener if I can get a test session at sac before then. watch it start raining now.
Learned from the "old school of hard nocks" after I killed a set of crank & rod bearings that had been in less than 30 passes. There is a big difference in pump gas oil for automotive and av gas oil for planes but this is to far out of my small mind area to get into so I just change oil more often. I agree about the tread, lots of good information.
Guys, I will put my two cents worth in on octane. On older engines the combustion process is impeded by combustion chamber design. Some of the low compresssion engines require more octane than would seem necessary. Just keep an eye on your plugs, and keep racin'.
I think the NHRA rule book of the times said "top, back, and sides must be covered". The logic was reversion in the intake often caused a fog of gasoline to exist above the carbs. Airflow over the carbs directed this back into the (FED or altered) drivers face such that a backfire or random spark could ignite it causing a blowtorch effect on the drivers head. Some teams just "lifted" a newspaper delivery box and used that. That's kinda what I simulated with my nostalgia racer:
Or you can just go to the newspaper office and ask for one. That worked for us. At the time we got ours we were visiting my mother-in-law in Arizona (we live in So Cal) and I went into her newspaper office and got one.
Re: Filters I've started using a piece of honeycomb laminar flow element inside my scoops after encountering damage to the top of a piston from ingesting debris. It actually straightens the airflow without restricting it. Here is a poor photo of the element in an O/T car. Many late model EFI throttle bodies use a similar device.
I drove a jr. fueler for a friend until he could get his license and on every pass peppered my face shield with fuel droplets with stack type injectors. We changed to hat type injection, dropped almost a tenth and every pass was clean with no debris on my face shield. On another subject, those of you out there running later model chevys with hydraulic cams. The book states zero lash with no preload as you would have on the v-8. What do you guys do?
Yes, three Holley 350s. Equivalent to 750 cfm of 4V flow. When I slowed the car down I took off three 500 2Vs and put the 350s on. Also changed the roller cam from a .650 lift to a .600 lift roller , again to slow it down so I wouldn't have to re-cert the chassis every three years. This on a 305 ci Ford.
Thought I would throw this out there.Had a friend call me this weekend and is planning his trip this fall.He is planning to hit the CHRR,he was tellin me that some of the Northwest folk will be coming down as well. Just wondering if maybe we could set up a group get together for the event???
Are they in for exhibition runs or not bringing their cars? If they bring their cars, they won`t get in many runs.
The Jalopy Journal
