crotchety old man

I posted this question elsewhere and did not get any response. Perhaps someone here can answer. I am helping a friend with a recently acquired '62 FI. The car sat for years with leaded fuel in the system. We have cleaned out all the varnish we could and I have disassembled and cleaned the injector twice now. It is clean at the moment and we have a LARGE fuel filter adapted in temporarily. It is unknown at this time what engine is under the injector but it appears that it has the 30 30 camshaft instead of the original 097 Duntov. The problem is that the idle can not be adjusted consistently. It is constantly changing with engine temp and seemingly ambient temp. I was working on these injectors when they were relatively new and built several small blocks, one with a 326 degree roller with over .500 lift and have never had this idle issue. Does anyone know if the 30 30 cam has an unstable enough engine vacuum at idle to affect the injection? I never used one in an engine but from what I read they don't start to work until about 3800-4000, and I am wondering if this could be the problem. This idle issue is starting to drive me to the point of irritation and I am now grasping at straws. Any help anyone might be able to offer would be appreciated.

rustylugnuts

Check out this site: http://www.jerrybramlett.net/tips.html#percolation

Then scroll down to: CAMSHAFT CONSIDERATIONS

rustylugnuts

BarryK

I'm not going to pretend to know anything about FI units and troubleshooting them, BUT, I doubt the 30-30 cam is the issue since it was the standard cam used in the 375hp FI motors in both '64 and '65. If there was major idle issues caused by the cam than I'm sure GM wouldn't have used it.
Not a FI motor, but my '65 L76 365hp motor, which was the other motor that used the 30-30 cam doesn't have issues with idle quality at all.
Yes, the 30-30 cam doesn't bring the power band on until around 3500rpm or so but that shouldn't affect your idle quality.

What distributor are you using? a Vacuum advance unit or a non-vacuum advance distributor? If using a vacuum advance distributor are you sure you have the correct and appropriate vacuum advance canister based on the level of vacuum the motor is producing at idle? If the VC is wrong it could be right on the borderline cutting in and out based on slight flucuations of the idle speed.

DZAUTO

If this car you are working on has a GENUINE 62 FI unit and 62 FI dist, then there are some differences between it and the 64-65 FI engines that got the 30-30 cam.
FIRST, the 62 FI dist DOES NOT HAVE a vac adv!!. The 62 FI dist was strictly a mech adv, dual point dist. GREAT for performance, but NOT for street/cruising/hiway driving-------------------unless maybe the car has a 4.11 or 4.56 gear. This dist was OK for the original 097 cam that was in the 62 engine, BUT NOT so good for the later 30-30 cam or any of the larger profile cams. Also, the 64-65 (7380 units) FI had a completely different spring in the enrichment housing. If the 62 unit you're working on has the original spring in the enrichment housing, that doesn't help things.
Also, The early FI units were kind of cantankerous to begin with (although, the 62 unit, 7360, was the BEST of all of them), and a vac adv dist (63-65 style dist) will make a world of difference in the low rpm ranges with a big cam.
Last, the early engines, ESPECIALLY the FI engines just DO NOT do well on today's ethanol gas!!!! The heat, and resulting perculation in the tiny fuel distribution lines, just plays havoc with these units (at lower rpm's).
As mentioned, look at the information on Jerry's site. Tune the engine to the finest degree possible, and then just live with it.
I have a highly modified early FI unit on the SB400 (with a big profile cam) in my 56 with a 65 dist. During cooler/moderate temperatures, it does just great at the low rpm's, but it just does not like the Okla summer heat. One of the best improvements that I've discovered is using aviation gas, and race gas is even better (YA, YA, YA, YA, YA, I know, not everyone has access to avgas or race gas).

Tom Parsons

Ironcross

with the above information from Tom and Barry....its not the camshaft but could just be the FI unit out of sinc......once correctly set up there almost trouble free....but busy fingers can quickly *** them up.....

I see nothing wrong with Av gas....worked in my T-210

63Corvette

While I wholeheartedly agree with the posts above (Esp Tom's) I would also suggest that if your FI unit has NOT been overhauled, that you will probably have a vacuum leak somewhere.....such as an old or cracked main diaphragm. Vacuum leaks will totally screw up your idle. Best of luck.

jim lockwood

Assuming you mean idle speed....

1. Is this a failure of the engine to return to idle? (Often a sign of worn throttle shaft and throttle shaft bushings)

or

2. Does the engine idle speed seem to "hunt"? (Mechanical advance starting to kick in too early, enrichment diaphragm rod not properly adjusted, inappropriate enrichment diaphragm spring for the engine cam, fuel percolation, erratic vacuum advance (if distributor so equipped))

3. Does this happen all the time or only at a certain engine and ambient temperature? If temperature related, what temperatures?

4. If, instead of idle speed, you mean idle mixture, how are you determining the mixture is wrong?

Answers to the above will make it possible to offer useful suggestions about what's happening.

Jim

crotchety old man

It is an original 62 FI. The problem is that when the car is driven, particularly in traffic, and the underhood and engine temp are elevated it begins to run extremely rich at idle. It appears that there could be a problem with the start enrichment valve bleeding vacuum into the main diaphram but I am only making an educated guess as I have never been with him when it happened. The first time I cleaned out the injector (and yes I did replace all the daphrams) the cranking signal diaphram did not close at all. I pulled the rubber hose out and plugged both lines and it idled fine, responsive adjustrment etc, just would not start cold. We sent the valve out and had it rebuilt as there seems to be no source on a new one. With the rebuilt valve in it started and ran fine. Now when the engine and underhood temp elevate it acts the same as it did with the bad start valve, but as I said I have never been in the car when it has happened so can not condemn it for sure. Has anyone ever tried using one of the solenoid controlled vacuum valves that are so common on emission devices. It seems that it could be wired into the start circuit so it only operates when the starter is active and being mechanical would not be subject to variations in manifold vacuum. Just a thought. Also had not considered the fuel perk temps, I will need to factor that into the mix. I might interject at this time that the engine, whatever it is, is tired. It does leave an oil spray on the back of the car after a hard run and I am sure that this is not helping the problem. This winter we will probably tear it down and have Valley Head Service do the hard seat thing on the heads for the unleaded fuel and at the least re ring it depending on cylinder condition. Tom Parsons mentioned the vacuum advance distributor and it occurred to me that when I used an injector on an engine with a long camshaft I would re-curve the distributor for about 16-18 degrees of initial timing and 38 degrees total with the advance not starting until about 1200 RPM but that was back in the days when I had the sun distributor machine at my disposal. When we tear this thing down I will be looking for an 097 camshaft, are the aftermarket replacements reasonably close to the original? Thanks for all the feedback, it is jogging my memory and giving me different avenues to check.

wmf62

and, unlatch/prop the hood in the summer
Bill

MikeM

I would tell your buddy to run the tank level down low and then stick in five gallons of race gas and see if the problem clears. If it does, you have a problem with fuel, not the injector.

It'd only cost s few bucks to find out.

jim lockwood

High underhood temperatures will cause fuel percolation which results in an excessive lean condition, not a rich condition.

During fuel percolation the engine will run roughly and require constant feathering of the throttle as long as it has no load. However, once the engine sees a load (i.e. start driving), it will instantly smooth out.

Yes, this is a common modification. Doing this is a good idea independent of whether or not the car is experiencing fuel percolation. I use small solenoid valves similar to those used on nitrous oxide power adder systems. They are readily available and extremely reliable.

Here's a picture of one I recently added to a '62 FI unit:



Jim

DZAUTO

I have installed the elec solenoid valves on several FI units, including mine.
Sometimes I completely replace the cranking signal valve completely, sometimes I install it inline with the cranking signal valve as Jim's picture above shows.









Tom Parsons

crotchety old man

We can try the race gas however the car starts blowing black smoke which indicates rich not lean. I am still leaning toward a cranking signal valve bleeding vacuum into the main diaphram. It does not take a lot of vacuum to screw up the calibration of a diaphram that size with almost zero resistance, but the race gas is an easy check and definately worth the effort. I have never looked for race gas but it has to be available somewhere in the Los Angeles area.

jim lockwood

It would have helped to have known this earlier.

In light of what you just posted, skip the racing gas.... won't prove or help anything for now.

Instead, using a length (10" or so) of rubber hose, replace the short piece of hose that currently connects the Cranking Signal Valve to the tube going to the main diaphragm "T". Form the 10" hose into a loop, as necessary.

Start the engine.

Drive until you start getting the black smoke.

When the black smoke appears, pinch the 10" length of hose completely shut.

Did the smoke go away?

If "yes", the Cranking Signal Valve is bad.

If "no", something else is wrong.

Jim

63Corvette

I have run the electronic enrichment valve since 1976. The reason is that the existing cranking signal valves were manufactured with leaks.....that is, eventually your existing valve would leak, and wherever you got your replacement valve, it had a very high probability of ALSO being bad at the time of installation. I just got tired of paying for CRAP, and went to the electronic version.....and have never had another problem (yeah, 36 years is pretty reliable)

rustylugnuts

If it is impossible to find racing fuel, a good alternative is if your near a private air port is aviation fuel 100LL (100 octain low lead). Personally I believe it's much better then racing fuel.

rustylugnuts

jim lockwood

For the problem as he has now described it, he needs neither racing gas nor aviation fuel.

Instead, he needs to perform the definitive test of the Cranking Signal Valve that I described.

Jim

rustylugnuts

I agree, but with addition to your suggestive modification. I’m a believer, my 1961 100% stock fuelie runs perfectly on 100LL especially when ambient temps reach 90 plus in Florida with high humidly.

rustylugnuts

crotchety old man

Correct me if I am wrong but my failing memory seems to recall that av gas is specifically formulated to burn slower because aviation engines turn slower than automotive engines to keep the propellor speed down. As I recall propellor tips must remain sub-sonic. If this is still the case then in an automotive engine with the corresponding shorter burn time the exhaust valve is opening into a still raging inferno and valve life will suffer as a result. Besides which everything, including racing fuel, is available in Los Angeles somewhere. Jim, I don't know when the weather in so cal will warm up enough to duplicate the problem as ambient temperature seems to be a factor. What if we were to loop the hose to the inside of the car so it could be pinched with a pliers without having to pull off the road and open the hood. When it screws up from what I understand it wont idle long enough to do all that. Would the additional hose length affect the operation of the unit. Again thanks to all for the feedback.

jim lockwood

I can't say the hose length would have no effect. But my mostly educated hunch is the effect would be very slight, probably even undetectable.

In any event, for the purpose of the experiment to condemn or exonerate the Cranking Signal Valve, the long hose idea is a good one and I encourage you to do it.

Jim