'65 fuel injection
My '65 fuel injected engine runs pretty well, but there are two issues. The major one is inability, most of the time, to get a reasonable idling speed. I have ignored this issue for years, but would like to try to fix it. It starts easily, stalls, and then runs fine on high idle after the second start. Once it's warmed up, it won't idle reliably under about 1100-1200 rpm. It's much worse in the summer if it idles too long, as is in a stop and go situation like a parade, but I assume that's possibly vapor lock or fuel boiling?? That aside, the motor starts to falter much below 1200 rpm, but runs fine above that. One other issue is that there is a miss at about 3300-3500 rpm, which is almost unnoticeable if you floor it and pass right through that range. I understand there is an adjustment for the air flow at idle, but haven't found any explanation of how to check that. I know there is the rich/lean adjustment on the fuel meter, but does that affect the idle? I would appreciate any advice on these issues. Thank you.
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Re: '65 fuel injection
Harold, I don't think there is an easy answer to your questions. How long has it been since the unit was rebuilt (you said you have put up with it for years)? What gas do you use? Have you went through the ignition system? I'm not an expert but believe these things would be a good start. Good luck, Don H. -
Re: '65 fuel injection
The first place I would start is with dwell angle checking with a known good working gauge. Next I would go to the timing to make sure that it had the proper timing map as has been covered here multiple times over the years. That would be after I knew that my points and spark plugs were in good to excellent condition. Most problems that people blame of the fuel injection are in the ignition system of the auto. I would start there and even check the plug wires and coil before I looked at the fuel injection. When I restore and injection it will run trouble free for 75000 or more miles and points and plugs sometimes will last less than 10000. Dwell angle should be checked every time you wind it up over 6500 rpm and it acts like it is not running as good as it did. I would discourage you from looking at the injector until you were sure of the ignition system.It's a good life!
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Re: '65 fuel injection
Harold------
Back in "days of old when knights were bold", FI cars were in their "heyday" and used as daily drivers by most that bought them, many of these systems got yanked and replaced with carburetors. The problems you describe are among those that influenced the aforementioned actions. Some owners were so frustrated with these FI systems that the units got junked (gasp!!!!) as "revenge" for the owners. In fact, I once removed one from my brother's 1964 in about 1968 for just this reason. He didn't care if he ever saw the FI again and gave me the whole system in trade for a manifold and nearly new Holley 4150 carb (then unbeknownst to me, he gave MY FI system to the new owner when he sold the car).
Many years ago I purchased a 1958 900R FI system that had been sitting on a shelf for years. To look at it, it appeared brand new (except for the dust it had accumulated sitting on the shelf). So, I figured it must have been yanked off the car very early in its life, probably for the same reasons that most other FI units got yanked. In fact, this FI unit is the ONLY part I EVER sold and I regret it now. Not that I would ever have used it, though.In Appreciation of John HinckleyComment
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Rob.
NCRS Dutch Chapter Founder & Board Member
NCRS Software Developer
C1, C2 and C3 Registry DeveloperComment
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Re: '65 fuel injection
Thank you all the comments. The fuel injection unit was restored in the early 90's. The car has been driven just over 1000 miles since then. I have a Pertronix ignition module, not the normal points/condenser. The plugs have been checked and are indexed to a uniform position. I use premium fuel, which means 10% ethanol where I live. While I could imagine the miss in mid-range is possibly ignition related, I highly doubt the irregular idle has anything to do with ignition. Sometimes, it will idle fine at a lower rpm, and it seems to be affected by something in the linkage, after you hit the pedal to release the fast idle at warmup. This is why I was asking about idle air flow, as I seem to recall there is a setting on the air meter to adjust the throttle plate opening at idle. Regarding hot weather, I have been told that it's prudent not to run in weather over 85F or in parades. In a historical parade last June, which took almost two hours in 90F weather, the engine ran rough, and would hardly run below 2000 rpm. When I got to the end, I left for home, and within a few short miles, the engine was running fine, except, of course, for the high idle.Comment
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Re: '65 fuel injection
Same thing happened to me in my 65 FI car last summer in LA. Ran rough and would not idle properly after a one hour parade. Thanks for the advice Paul.Comment
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Re: '65 fuel injection
Due to the extremely high overlap of the OE 30-30 camshaft and idiosyncrasies of the FI system it is not practical to expect a stable idle speed of less than about 1000 for the 375 HP FI engine. My recommendation is 1000-1200. The carbureted 365 HP version of the same long block usually needs no less than 900 RPM idle speed.
It's critical that the OE vacuum advance work properly. Have you checked it with a vacuum pump? Initial timing should be in the range of 10-14, and total idle timing should be 28-34, which is the sum of initial, full vacuum, and a couple of degrees centrifugal since it starts at about 700. Full centrifugal, 24 degrees, should be in by 2350.
Because the engine will not idle low enough to set initial timing before the centrifugal starts, timing should be set (VAC disconnected and plugged) with a dial back timing light at about 38 at 2500-3000 (once you've verified that the centrifugal is all in at 2350). Then with the vacuum advance connected, total idle timing should be in the above specified range.
Once the spark advance map is verified the idle speed mixture adjustment procedure is very simple. It's in the 1963 Corvette Shop Manual and the '65 Supplement, however there is a subtle but major difference between FI and carburetors. On most carburetors turning the idle mixture screws out (CCW) richens the mixture and vice versa.
FI is the opposite. The idle mixture screw does not regulate the flow of an air-fuel emulsion. It is it simply an air bypass adjustment, so turning the mixture screw IN richens the mixture and OUT leans it out. The high overlap causes major exhaust gas dilution at idle, which slows flame propagation, which is why very high total idle timing is required. Exhaust gas dilution also reduces mixture ignitibility unless the mixture is very rich. It's the nature of the beast.
Your final idle vacuum in the 1000-1200 RPM range should be 10-11" Hg, which is very low compared to typical road engines, but that's what extremely high valve overlap does. At low speed, especially when throttled, it creates a full time EGR system.
Because of the long duration, high overlap 30-30 camshaft in the 365/375 HP small blocks these engines are the most "high strung" road engines ever produced by any manufacturer (L-88 and ZL-1 excluded because they were never intended for normal road use). They have poor idle characteristics and lack low end torque, however, if set up properly both should be liveable and not stumble or stall in normal low speed use or starting from a dead stop as long as the axle ratio is not less than 3.70.
The 30-30 camshaft is a very poor choice for a road engine, which is why Chevrolet replaced it with the LT-1 camshaft circa 1970 for both production AND SERVICE. Some owners further "detune" the engine by using the L-79 camshaft.
E10 gasoline has a lower midrange boiling point than straight gasolines of yore, which causes percolation problems on vintage cars with non-pressurized fuel systems in hot weather, especially during periods of low speed driving or extensive idling.
One of the worst things you can do with an SHP/FI Corvette is run them in parades. You should leave that type of service to base engines with Powerglide.
DukeComment
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Re: '65 fuel injection
This is incorrect.
Turning the mixture screw (AKA "Idle Fuel" screw) CCW (out) richens the idle mixture on all Rochester FI units. CW rotation (in) leans the idle mixture.
Mixture enrichment happens because correct adjustment of the Idle Fuel screw permits a small amount of manifold vacuum to supplement the venturi signal which is very weak at idle speeds. CCW rotation increases the amount of supplemental manifold vacuum; CW rotation decreases it.
JimComment
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How to make a 7380 FI system idle all day at 850 rpm.
These are in no particular order because all are of equal importance.
1. Install a good spider. Most assembly line GM spiders are bad now (I think 50% were bad in 1965). About 50% of reproduction spiders are bad out of the box.
2 . Make sure you have a clean, closely matched set of nozzles. Gas pressure at the nozzles is only .25 psi at idle; any variation in nozzle orifice size will give you weak cylinders.
3. Have a tight gear pump. The only person who can re-machine gear pumps properly and supply new gears is Maxine Parsons in Ohio at (740) 344-8010.
4 . Have good plug wires, plugs, and distributor electrical parts and not any of that "properly dated" repro crap.
5. Have a "low vacuum" canister for vacuum advance such as a GM 236 or an aftermarket B28.
6. Run 12 degrees of initial advance and 36 total advance. Install a brass bushing on the pin to limit mechanical advance to 24 degrees. Install stronger advance springs to prevent mechanical advance from starting below 1,000 rpm. Check the location of the balancer TDC mark using a piston stop tool before you set your timing.
7. Run at least .030" valve lash. Sorry, but the magic tight settings you read about on the interweb will kill your idle.
8. Use only undiluted racing gasoline to prevent percolation in the spider.
9. Adjust the idle mixture screw to get the highest idle. This should be about 1/3 to 3/4 turn out from killing the engine lean. This should also be 1.5 to 2.0 turns out from seated if you have a good spider.
10. Have your unit properly calibrated on a running engine while under load. Of course, you must have a unit that can be properly calibrated with a good Antonicelli axle link, a proper .090" orifice in the PCV fitting on the front of the plenum, a good flexible main diaphragm with a noticeable hump around the magnesium wafer, no vacuum leaks anywhere (especially at the plenum bottom), a free-breathing Forward Balance Tube with no leaks, etc., etc. Properly calibrated on a warmed-up stock engine on a 70 degree day at sea level means Air / Fuel ratios of 13.5 - 14.0 to 1 at idle, 14.0 - 14.8 to 1 at steady cruising from 40 to 70 mph, and 12.8 - 13.2 to 1 under full acceleration from 3,000 to 6,000 rpm.
11. If you have one of those weak-suck bright blue repro return springs, throw it in the trash and buy one with the proper tension from John DeGregory.
12. Make sure the combined resistance of your ignition coil and ballast resister is between 2 and 3 ohms. After you do all this, you'll have a consistent 850 idle speed after your engine is warmed up. Properly tuned, a 327 with a 30-30 cam and domed pistons should make 11 to 12" of vacuum at 850 rpm. I have tried my best to split this post into paragraphs, but I am just too stooopid to get it done.
My "ENTER" key does not skip down to start a new paragraph in this program.Comment
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Re: How to make a 7380 FI system idle all day at 850 rpm.
And I definitely agree with #7! Adjust the valves to the correct .030" lash.
Also, as previously mentioned, the centrifugal advance on 64-65 solid lifter engines can cause some weird idle sped issues. It may sit at around 1000 RPM for a bit, then suddenly drop to 700-800 RPM for no apparent reason. That's because the cent advance is actually right on the edge of pulling the weights back in to rest. This is a very common issue. Again, as previously mentioned, a set of slightly stiffer springs will correct this problem.
To see if this is occurring, use your timing light. With the engine running at idle, note the position of the timing mark. If/when idle speed drops off, see if the timing has also retarded a few degrees.
You can test for this by running the engine at idle while the centrifugal weights are made inoperative. Pull the weights in fully to rest and secure with the rubber band. If the idle is stable, it mans you have found the problem.
I've owned quite a few 64-65 FI cars over the decades and I didn't have to set the idle speed to over 1000 RPM. These engines idled very well when new at 850 RPM.Comment
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Re: '65 fuel injection
Although I am not a fan of the after market point replacement electronic ignitions I would take out the dwell equations from your puzzle. I put up to 3000 miles on my 63 injector a year and try to run ethanol free gas that anyone can find on a web site called pure-gas.org , I also will run a bottle of the Chevron fuel injection cleaner through my system once or twice a year when I am on a road trip. I have built an insulation unit out of a product called second skin that is sold for insulation under carpet for the passenger compartment of automobiles. It is made out of butyl and foil and I cut it to fit on top of the adapter and sit under the spider to help insulate from heat soak. I used about 2 or three layers of the second skin material. It helps as well as I always leave my hood unlatched when it is hot out and open it when I stop and am going to restart it hot so that cooler air can get under the hood and hot air can be released easily to escape. I can't always find non ethanol fuel while on road trips and I can tell a big difference in the way the car runs because the ethanol fuel boils at a much lower temperature. I do not use aviation fuel or race fuel because of the expense but when I worked at a drag strip years ago and added some from time to time I could tell a big difference in the way it ran. I have seen where others have put insulation tubes on their fuel lines and I can see value in that and will probably do that the next time I take the lines off for some other work. Back in the eighties when I drove the 63 as a daily driver I had a piece of asbestos wrapped in tin foil under the spider. I am running a 50 year old spider and do not have a problem with it but I think that the Chevron fuel cleaner helps keep it cleaned up. Brian Futo and I took a spider apart and cleaned debris out of the needle/seat/spring area one time in the eighties and we soldered new lines one it many times as bubba had over torqued the lines at the injectors until the ferrules cut the lines. I also have run an extra fuel filter in the line back by the tank where the rubber hose connects from the tank to the steel fuel line. I have put about 100000 miles on my 63 and every one has had the injector on it. It is a good running unit and gets good mileage and is dependable and has required very little work on it to keep it in top running condition. I think that you still should scrutinize your ignition system closely and thoroughly before even touching the injection. I also think that ethanol fuel is giving a bit more trouble now than the fuel was back in the time before we all had to use it. I would be glad to answer any questions that you have if I have not touched on your areas of concern. PaulIt's a good life!
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