No revs

Discussion about Datsun 1500, 1600, and 2000 race cars.

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Ponder
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Location: Southern Indiana

No revs

Postby Ponder » Wed Nov 02, 2005 10:33 am

I've been struggling with this for six weeks now. (I'm sure many of you know that I bought Chris's car from him in the first part of September.) The first time I took it out it wouldn't rev above 1000 rpms after I let the clutch out. It revs fine when it's not under a load. It seems like a timing issue. I've checked it and moved it to where Chris says it should be. Or at least in the ball park. I'm usually working on it alone and I dont have a remote tach, so I look at the tach in the car, try to hold the revs steady and grab the timing light.

Chris recommended a dial-back timing light which I don't have. He times the engine to 32 degrees before TDC at 3000 rpm. So I put a mark on the crank pulley where 32 degrees should be. I should re-mark that since the mark was originally made kind of sideways and has smudged a little since then. Anyway, the best I can tell is that it looks slightly too far advanced right now (maybe 38 degrees). But much less and it runs pretty rough at idle.

I've checked fuel filter, fuel pump, carbs to some extent, exhaust seems open. I replaced the coil. The spark looked a little too yellow. But that didn't help so i went back to the original coil.

I haven't checked cam timing, changed out spark plugs, found vacuum leaks.

I've not done a whole lot of this kind of thing in the past and I knew I'd be learning about new things (engine timing had always made me nervous; thought I'd screw it up and never get it to run again, but I got the timing 180 out :oops: and was able to get it back, I'll take little victories wherever I find them), but I'd hoped I wouldn't run into a wall like this so soon.

Anyway, thanks in advance. I haven't talked to Chris in a while, thinking he'd be fairly busy last month, but he's been really helpful.

Steve B.
Last edited by Ponder on Thu Nov 10, 2005 4:58 pm, edited 1 time in total.
I drank what? - Socrates

Bill Wessel
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Postby Bill Wessel » Wed Nov 02, 2005 10:52 pm

Steve,

What a bummer, as I'd of thought that Chris's car would run good right out of the box. I'm sure he's dismayed that you've had problems.

Two things come to mind when an engine won't rev up.
#1) Ignition advance: you should have about 15 degrees mechanical advance in the distributor, such that the timing around idle is ~15-20 degrees BTDC but by 3-3.5K rpm it's all in and advanced to 30-35 degrees BTDC. There are five grooves in the pulley marking 0, 5, 10, 15, and 20 degrees (plus whatever mark Chris might have put on there...it's easy with a guage to scribe marks further out). Vacuum advance runs off a small port at the bottom of the rear carb (NOT from the manifold). I doubt Chris had the vacuum advance in the distributor. It is unnecessary in a race car.
Time the engine such that you have 32-35 degrees advance at 3.5-4000 rpm where all the mechanical is in.

#2) Sticking carb piston(s). If the piston(s) in the carbs won't lift synchronously, you'll only be using half the engine and that would seriously affect your power. Rmove the air cleaner and lift the piston with your finger. It should rise easily and drop with an audible "thunk". If not, then grit or varnish has gummed it up. Clean up the sliding surfaces, inner bell wall and piston skirt. Do not scour or sand/scratch! and do not oil (oil will only attract more grit). These are polished surfaces and should remain so! Be careful not to damage the needle (don't drop it!) as you work.

As you mention, it runs rough at idle. Chris car is tweaked from stock so the idle may be around 1500 rather than 800 rpm. But if it's rough, I might suspect a dead or missing cylinder. That would certainly cut the power. Or perhaps you've got the wires misrouted (1-3-4-2, counter clockwise...it's easy to mix 2 and 3 up in the firing order)

Hope this helps...

Mike Poorboy
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Postby Mike Poorboy » Wed Nov 02, 2005 11:09 pm

Steve,
I am not sure if chris had gross jets in the carbs, but I have heard of the ball getting dislodged after a hard trip. I would be leaning toward carb/fuel issues
other then timing. You really need to invest in an adjustable timing light. I bought my 15 or more years ago when they were really expensive, but its the easiest way to check timing at different RPMS.

Try to get someone over to take a look at it. It never hurts to have that second set of eyes.

Mike

Chris Coker
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Postby Chris Coker » Thu Nov 03, 2005 7:45 am

Steve, all-

No Gross jets, so that shouldn't be a problem. Tried them once, didn't work for me.

I'd try running more advance. I think I may have run much higher than 35 degrees advance, now that I think about it. Never could quite figure out why, but it seemed to run better with more advance, with no ill effects.

It's entirely possible that I had the distributor off a tooth after pulling it out to prime the oil pump. When Steve took delivery, the car idled well at about 1200-1500 rpm, and revved well in the garage. I think Steve's issues have been when the car is under load.

It's also worth double-checking the carb floats. Take off the piston domes, pull out the pistons, and turn on the fuel pump. You should be able to see the fuel levels in the jets, and you shouldn't see any fuel running out into the carbs.

Hope this helps!

In other news, Lisa and I are starting to get settled in, and we signed a purchase agreement on a new house last weekend. We should be able to move in after the first of the year. So, lately my time is being spent keeping an eye on the construction, and helping Lisa pick out cabinets, countertops, etc. The house has the nice view that Lisa wants, and the 3 car garage that I've been dreaming about. :D I should hopefully be insulating the garage this weekend, before they drywall everything next week.
Chris C.

Ponder
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Postby Ponder » Tue Nov 08, 2005 11:05 am

Thanks everyone. Sorry this response is so late. I had one written Thursday during work. But I'd write a little bit, work a little bit and by the time I hit the Submit button, I had been logged off. That's not meant as a criticism. I had not run into that before. So a relatively long response was lost and I didn't get to the computer over the weekend.

I also didn't get to Audrey II over the weekend. (The race car. Explanation forthcoming)

The carb pistons are fairly free. The first time I took it out was at an autocross at Columbus, IN. I hadn't run it. The place where I have it stored has some room, but I never thought to run it around before trying to run it seriously. I figured I'd get some feel for it in the paddock. The Columbus autocross was meant to be a feel out event. So, after I found the problem and took the car back to the paddock to try to troubleshoot, a competitor came over and helped out quite about. Focused in on timing right away. He had run a prepared Sprite or Spitfire or something and wa familiar with the SU's. So he asked if I had oil in the dashpots. That was honestly one thing I hadn't checked. So we look and there is none. Before I could verbalize that maybe in this situation I don't want oil in the dashpots, he says, "Hell I got some 20W in the car" and proceeds to fill up the dashpots. Anyway, they have oil in them now. It didn't affect the revving problem, not that either of us expected it to. So, long answer to a short question is that the pistons aren't sticking.

One thing that seems like a clue to me is that when you cover up the air intake to one carb to kill two of the cylinders, it takes a long time for the engine to recover. Maybe 10-12 seconds. I think I did that to my road car and it recovered in maybe half that time.

Thanks again.
Steve

Chris, congratulations again. It's been a long time since I was in your shoes, but those sure were heady times. HMMMM...three car garage.

S
I drank what? - Socrates

Ponder
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Postby Ponder » Tue Nov 08, 2005 11:15 am

Okay. Audrey and Audrey II.

Audrey is the Roadster in my avatar. I bought that car from my cousin who has a car dealership adn had taken the car in on a trade in the early 90's. Love the car. Fun autocrosser. Severely limited in stock class by narrow wheels. Fun to drive. My cousin had named the car "El Toro" because it was painted like and sounded like a Toro lawn mower. While the car doesn't seem feminine in nature, I thought of the Fairlady moniker, the My Fair Lady movie tie-in named the car after Audrey Hepburn. He has a vette he's restoring named Lilly, so I thought I could get away with Audrey.

Chris sometimes referred to the race car as Elmo, seeing as how the color is the same as that of the Muppet. I liked that, but Audrey II came to mind from another movie, Little Shop of Horrors. In case you haven't seen it, Audrey II is a plant from outer space that wants to take over the planet and eat its owner. Probably all too appropriate. When I'm working on it and having little success, I'm taking to calling it the Mean Green Mother from Outer Space.

Anyway, I'm sure everone is bored to tears by now, so I'll stop.

S.
I drank what? - Socrates

Chris Coker
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Postby Chris Coker » Tue Nov 08, 2005 3:02 pm

Don't use oil in the dashpost. If my memory is correctly, I'm not sure the dashpots even have all of the hardware in place to slow down the piston even is there was oil there.

Also keep in mind that with that cam, there's not much power till you get up past about 4500 rpm. It really like to spend it's time between 5000-8000 rpm.

Chris
Chris C.

Ponder
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Postby Ponder » Tue Nov 08, 2005 3:43 pm

I was thinking that the oil wouldn't hurt, but I'll get that out of there. I haven't taken a good look at the pistons to se if there were differences with my street car.

Regarding the revs, that was why I actually took one start at the Columbus Autocross. I couldn't really so a high rev clutch dump anywhere else. I was thinking that the rear wheels wound spin and I could stay in the higher rev range. There was just no torque and the revs dropped. I did a u-turn off the course and back to the truck.

Thanks,
S.
I drank what? - Socrates

Mike Poorboy
Posts: 302
Joined: Sat May 24, 2003 2:38 pm
Location: Hayden, Idaho

Postby Mike Poorboy » Tue Nov 08, 2005 4:22 pm

Steve,
With the UC box and my 4:37's , and two liter the car will almost stall unless
I do a huge clutch dump. Lets say around 5k. Once the wheels spin and they
finally hook up the car will hesitate until I get into the cam. Then she pulls
like stink ;) . You are going to have to put 5;13's in her to get it to launch
with a road race cam. You have to remember the car was set up for a rolling
start.

If I am not on course and I am just putting around the grid area. I have to keep the RPM's high and feather the clutch a bit to get it up to speed.

Mike

Mike Poorboy
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Location: Hayden, Idaho

Postby Mike Poorboy » Tue Nov 08, 2005 4:45 pm

Steve,
I read Chris's car for sale ad info before you bought it, and it looks like he has the 4:62's in it. I still think it could be you might not be geared low enough .

Mike

Ponder
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Location: Southern Indiana

Postby Ponder » Thu Nov 10, 2005 10:57 am

I don't remember the rev level I dumped it from at Columbus. It was at least 4K. Shouldn't the rev's come up eventually even with the racing cam? The rev's max out at 1K and do nothing but oscillate between 800-1000.

MY thoughts as I pulled away from the line " Am I in the wrong gear? No. I'm in first. This UC doesn't have a stange shift pattern does it? No the speed seems about right for 1st and 1000 rpm. Oh hell, let's get off the course, I'm not going to tool around at 10 mph."

Chris told me that despite it being an Ultra close, first gear is still pretty tall. I can tell it's taller than reverse. Where did I see the ratios of the transmissions? Sharp's manual?

S
I drank what? - Socrates

Chris Coker
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Postby Chris Coker » Thu Nov 10, 2005 11:07 am

Check timing. You probably need to add a lot of advance. If the engine will idle at that low of an rpm, the timing is almost certainly off. I've run as high as 45-50 degrees total advance (above 3500 rpm) will no ill effects. Engine compression isn't too terribly high, and with high octane race gas, you shouldn't have any detonation problems.

Check the carbs, make sure you don't have a float valve stuck open.
Chris C.

Ponder
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Location: Southern Indiana

Postby Ponder » Thu Nov 10, 2005 2:57 pm

It will currently idle at around 1000 rpm.

Will check timing again tomorrow or Saturday.

Thanks.
I drank what? - Socrates

Chris Coker
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Postby Chris Coker » Thu Nov 10, 2005 3:08 pm

If it willl it will idle at 1000 rpm, I'm 99% sure you need to give the distributor a good twist and add in advance. It WILL be more finicky to start (you'll have to choke it), and it will only idle at about 1500 rpm after it's well warmed up.

Remember, it's a race motor. It's set up more for wide open running than idleing around. :)
Chris C.

Ponder
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Joined: Fri Mar 21, 2003 11:47 am
Location: Southern Indiana

Postby Ponder » Thu Nov 10, 2005 4:48 pm

Which produces the question:

How do you choke this car? You probably showed me, but I don't remember. There are no choke cables (unless I've been really blind, not saying that couldn't happen). I helped out with our Formula SAE car in college (a LONG time ago) and the guy with the most practical experience would cover the air intake briefly with his hand as the starter was cranking to dump some fuel into the engine to richen the mixture up.

I'm thinking it's going to need choking with the weather cooling down.
I drank what? - Socrates


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