Properly Shutting Down A Alky Engine

I Have A Question About The Proper Way To Shut Down A Alky Engine We Always Used The Fuel Shutoff To Shut Down And Not Too Use The Mag Switch Because It Would Load The Engine Up With Fuel Or At Least That Is What I Was Told Ok That All Makes Sense But After A Run And You Want To Read Spark Plugs If You Use The Fuel Shutoff Will It Not Give You A False Reading On The Plug? And I'm Still Not Sure About The Mag Switch If You Shut Down Useing The Switch Will It Or Will It Not Load Up With Fuel I'm Confused The Way I'm Looking At This Is After A Run Shut Off The Mag Switch Push In The Clutch So The Engine (fuel Pump) Is Not Turning I Was Also Told Dont Push In The Clutch Will Someone Tell Me The Truth About This There Are So Many Opinions On This And I Dont Want To Open A Can Of Worms Its A Lenco With A Pedal Clutch Just Wanted To Know The Right Way With Out Blowing Something Up Any Help? Thanks Jamie

 

I ALWAYS used to push in the clutch...just the way I did it, until last season we had Bucky Austin over looking at some things, including the computer readout. After he saw every run a fairly significant spike in engine rpm at the end of every run I was told very sternly to "please don't do that ever again". Now that I saw the grapghs in front of me, I agree, engine rpm going up that quickly could really hurt some things.

Plus, with the clutch still out you can get stopped faster, see on the computer where you actually lifted, etc.

I use the fuel shutoff to kill the car at the end- after the chutes are out, and after I have then slowed enough to push in the clutch, then the kill switch. Everyone has their own style and reasoning for it though - don't think anyone's way is wrong, they're just all different.

 

I hate to be argumentative here, but I think you should always push in the clutch as soon as possible. "Riding" down the motor on the clutch puts alot of pressure on the rod caps. In Shreveport this year, the car was loose at the top end, and our driver was late getting on the clutch, and it cracked a rod cap, which then broke in half on the warmup before the next round, ruining the block, cam, oil pump, etc. It's not a very good feeling to waste all that money sitting on the jack stands. Needless to say we should've dropped the pan after that run. Live and learn. You can see it on the bearings. The cap bearings always look nice and fairly new, even after a few runs, but if you don't dissengage the clutch, it wears them out quickly. I don't think the caps are designed to handle alot of pressure, but then I could be wrong.
As far as killing it, I think most people shut the fuel off, let it start to run out ( as the rpm's come up), and then kill the mags. It also depends on what kind of motor you have. Roots blowers will run out of fuel alot faster than a PSI, so it may not be as bad to kill them with just the fuel.

bryan brown

 

I was always taught that compression braking or de-acceleration braking was hard on the rods. After a pass the speed of the car is still driving through the clutch and the motor, with the motor acting as a compression brake.
I would like to hear some more thoughts on this.

 

A couple of ways:
The graph showing the motor and driveshaft coming down at the same rate for an extended period of time;

The cap bearings had been hammered, excessive wear, and they only had two runs. The rods don't "hit" the crank in that direction under acceleration.

I know a TAD driver who had this happen a couple of times when he first started driving.

If it cracked during the run, it would've kicked all the rods then. The car went through the lights at 9500. I guess he hit the clutch just in time to let it drop to idle before it broke completely. During warmup, it started fine, and he started going through the gears, and it must've given just enough shock to the motor that when he hit high, at idle, the cap split, and half of it got tossed.

This is my opinion, although I'd like to hear from some of the more experienced guys.

bryan

 

I can't say that we've ever experianced the rod cap failure you described pertaining to letting the car ride down on the clutch, we check bearings all the time and haven't seen excessive wear. We run the GRP billet rods with the 'V' (hard) bearings, so maybe you wouldn't be able to see it with the harder bearings.

Though now that you mention it, it doesn't sound like a really nice thing to do to your motor, but also pushing in the clutch right away and getting a pretty decent spike in rpm doesn't sound much better. So, what is the lesser of the two evils?

 

I have worked on a fuel funny car and sometimes the clutch welds together and is compression braking in the shut down. We have not had any problems with rod failure. Just my opinion but I do not think that is what broke the rod. Did you chech the rod bearings after the first pass?

 

Another thought on pushing in the clutch at the top end. The clutch should be at max load with all the centrifugal force applied. It seems that it would be putting a ton of force against the release levers and the throwout bearing. I have always let the motor slow down before I push the clutch in. Maybe we could ask Frank Hawley. I went to his school years ago but I must have slept through the shutdown lecture.

 

What purpose do the sprags have in the trans

 

exactly shut the motor off
does the motor still turn as your coasting to a stop??

 

Will Dont You Run A Lenco Drive? Doesnt That Have A Converter If So It Would Not Be The Same As With A Clutch I Understand What You're Saying About The Clutch The Weights Would Hold The Clutch Engauged Until The Rpms Came Down So Really It Wouldn't Matter If You Pushed In The Clutch Right Away Or Not. IF I'm Thinking about This Right It Has To Be Tough On The Rods And Bearings But Hell I Dont Know Thats Why I Put This Out There Just To Find Out Whats Really Going On.like I Said I Dont Want To Blow Up Stuff We Havent Even Started The New Engine Yet But Maybe Some Experienced Engine Builders Could Answer Or Like Dave Said Maybe Frank Hawley Or Someone Like That Just Looking For Answers But I Sure Didnt Mean To Open A Can Of Worms Or Step On Anybodys Toes Thats For Sure Jamie

 

I Agree There Is Lots Of Good People On Here Very Smart People Like Yourself Mike

 

Quick Question Mike If You Shut Down The Engine With The Fuel Shutoff Would That Not Give You A False Reading On The Plug? Thanks Jamie

 

Story time....

OK kids, the ol'fella has a bedtime story for ya.
Nathan: what Bucky might have meant was that he was a better tap dancer than you, meaning coordination of the feet. Right one up, left one down, only in this order. (BTW, I sat with your G'Pa at the new Fontana, also say Hi to your Dad.)
1. My pal and partner in the Lenco early days, did the reverse TWO times in a row, costing TWO blowers. In those days there was a guy called Video Bill (from Minnesota) who used to shoot from the stands at a lot of National events, and he would come by the trailer to show us because we had a TV/Video player, well we caught it instantly from the tapes.
2. When I first started to work with the Russell's, they were having lots of rod breakage problems. While disecting a pile of rubble at Columbus one year, Denny Lucas - Tom Conway- Mike Kosky and I were squating and reaching into big holes in the block lifting rod chunks out and passing them around. A lot of mumbling was going on because we all knew of a problem with one manufacter's certain forging. Nope these rods were not those. When I made the statment that aluminum rods don't like deceleration, I happened to catch a glimpse of the expression change on Darrell's face.
Later, I walked over to him and asked if he had something he needed to tell me. With a frown he said "nobody ever mentioned that to me, I've been driving it just like my S/C car." Let's just say that they almost never had a rod problem again. When I would fly in after missing a few races with them, I would always have to straighten the clutch stop. Anyone who ever saw him on the startline, would know he never bent it there! (I sure miss him)
I'm just a welder, so do your own research, but have a good look at why any form of circle- scca -TransAm- F-1- Indycar - IRL - snowmobile or lawnmower racing that is on and off the throttle do NOT use aluminum rods, then do what you gotta do.

Please don't start comparing a T/F shutdown with a welded clutch and a wallet to what we're talking here.

 

you've got to remember that when you shut it down with the fuel shut off , the blades on the injector are closed (at least they better be) so it can't show a hotter reading than during the run.

 

Thanks for the bed time story Uncle Bob......
You are way more than just a welder!!!! When I crewed on another car, I remember racing against you & Gary back in the day, you guys were tough!
Great post!!!!