EFI yay or nay - Pontiac GTO Forum
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post #1 of 26 (permalink) Old 01-20-2019, 05:07 PM Thread Starter
 
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EFI yay or nay

Anyone put efi system on 400 ram air engine?
Pros,cons,...
Thanks
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post #2 of 26 (permalink) Old 01-20-2019, 06:27 PM
 
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Their are some of us old school Pontiac guys who don't think these old Pontiacs should be strapped with late model technology.

If they came with a Q-jet, I say run a Q-jet. They ran just fine when new. A correctly built & tuned Q-jet can run 9's in a Super Stock Pontiac, and a correctly built & tuned Q-jet can supply all the fuel you need for a street Pontiac, and get decent mileage, with the right combination of parts & tuning.

If you want FI, sell your GTO & buy a later model car which came with FI, IMO.

Opinions differ.

Some have the opinion "It's your money & your car, so build it like you want it".
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post #3 of 26 (permalink) Old 01-21-2019, 06:20 PM
 
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Originally Posted by rheckman View Post
Anyone put efi system on 400 ram air engine?
Pros,cons,...
Thanks
Better still, rather than ask us our opinions for the pros & cons of an EFI system, how about you fill us in with your list or reasons so we can compare?
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post #4 of 26 (permalink) Old 01-21-2019, 06:49 PM Thread Starter
 
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Main reason for want is my Quadrajet is a bitch to tune in.

Main reason i don't want to,it should have and run what it came with.
But i have the Quadrajet that only has vac advance from trans switch so only in 3rd and fourth gear.
The alternative,run vac advance all the time,or replace quadrajet with one that has ported vac.
I have tried running both ways,changing timing as needed but I'm still not sure.
Of course they tell you the efi is bolt and go pretty much,but I'm sure there are issues a well
Bob
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post #5 of 26 (permalink) Old 01-21-2019, 09:31 PM
 
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Originally Posted by rheckman View Post
Main reason for want is my Quadrajet is a bitch to tune in.

Main reason i don't want to,it should have and run what it came with.
But i have the Quadrajet that only has vac advance from trans switch so only in 3rd and fourth gear.
The alternative,run vac advance all the time,or replace quadrajet with one that has ported vac.
I have tried running both ways,changing timing as needed but I'm still not sure.
Of course they tell you the efi is bolt and go pretty much,but I'm sure there are issues a well
Bob

What year GTO again? Sounds like you have the set-up with the emissions controls maybe? Should be able to work around it I would think.
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post #6 of 26 (permalink) Old 01-21-2019, 09:49 PM Thread Starter
 
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It's a 70 ram air 3,it has the Tcs solenoid and that's where vac line goes then back to dizzy vac.
Makes sense ,because otherwise it would be constant vac as there's nothing above the blades on carb for vac port.
I wish i wasn't dealing with this setup,although timing base is true because Tcs doesn't vac until trans kicks it when timing.
I'm around 16 tdc running slightly higher 800 rpm,seems smooth
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post #7 of 26 (permalink) Old 01-22-2019, 08:30 PM
 
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Originally Posted by rheckman View Post
It's a 70 ram air 3,it has the Tcs solenoid and that's where vac line goes then back to dizzy vac.
Makes sense ,because otherwise it would be constant vac as there's nothing above the blades on carb for vac port.
I wish i wasn't dealing with this setup,although timing base is true because Tcs doesn't vac until trans kicks it when timing.
I'm around 16 tdc running slightly higher 800 rpm,seems smooth

This is going to cover 2 different subjects: The TCS System and your Timing (as I see it).


OK, I am looking at a schematic/diagram of the 1970 set-up you are talking about. I see that the vacuum source at the carb is below the throttle blades which will give you a constant supply of vacuum - just like as if you ran the vacuum line for your distributor directly to a manifold source like some do.

The TCS Solenoid is what open and closes the vacuum supply coming from the carb to the distributor. It is an electrically operated switch that opens and closes the vacuum and is controlled off of a switch on your transmission. When energized it it is closed and provides no vacuum to the distributor. When it is de-energized, it opens allowing vacuum through to advance the distributor.

The switch on the transmission is a "pressure switch" that is closed in first and second gear and opens when in third gear (this must be for a 3-speed trans. It says there is also a "double terminal" switch and must be for the 4-speed so the switch is activated in 3rd & 4th gear.) So my understanding is that there is no vacuum going to the distributor while in 1st & 2nd gear. You only get vacuum to the distributor when in 3rd or 4th gear (or Drive if automatic).

Interestingly enough in 1972 the TCS Solenoid pressure switch that was on the transmission in 1970-71 was adapted to fit on the speedometer cable and was set to activate at 35 MPH, rather then in just 3rd or 4th gear on the transmission.

Personally, I don't see a problem with this as long as it is working as it should. However, I do see a problem assuming you are using a factory RA III distributor and its specs. Because you are not using the factory spec of 9 BTDC degrees initial at the crank at idle and you have your initial at 16 degrees (Ram Air IV was actually factory set at 15 degrees BTDC), the timing may become too advanced when the TCS operates in 3rd & 4th.

16 degrees initial at idle may be fine and could be used, BUT then as the engine revs up, the mechanical advance begins to increase. RA III distrib. specs say that the centrifugal advance is 20-24 degrees at 4600 RPM's. So if you add the 16 degrees initial plus the 20-24 degree mechanical, you get 36-40 degrees total. My opinion - way too much! You are asking for trouble and will damage the engine. Total should be around 32-34 assuming you are using 100 plus octane if you have 10.75 compression.

You can run 16 degrees, but you have to now limit your total advance by limiting the mechanical advance in the distributor. You need to add a "stop" of some sort to limit the weights.

The RA III vacuum advance specs say you should have 20 degrees at 15-17 inches of vacuum. Again, if you take your total advance from above, 36-40 degrees and you add that to your vacuum advance of 20 degrees, you now have 56-60 degrees of total advance when you let off the gas with the engine above 4600 RPM's. This is engine damage territory. Total advance of initial, mechanical, and vacuum should not exceed about 52-54 degrees advance. You can get a different vacuum advance that only has 10-12 degrees of total advance and install it. This would solve this issue.

So I would keep the 16 degree initial if it runs best. Use a stop/limiter on my mechanical advance in the distributor to give me 32-34 degrees total. The swap out my vacuum advance canister with one known to have only 10 degrees total advance to give you the 52-54 total degrees of advance when you let off the gas.

Now if this was me and I wanted to do a work around on the TCS system:

Option#1 might be to find a 1972 speedometer activated switch to energize the TCS Solenoid. My guess is this may be pretty tough to find if at all.

Option #2 would be to use a "pressure switch" like a brake/stop light switch, and adapt it with a bracket that would be used on the carburetor much like the factory idle stop solenoid. You would want the switch to be open, 12Volts, when the carb is closed in the idle position. This would energize the TCS solenoid to provide vacuum to the distributor at idle and advance your timing. When you open the carb, the switch (12 volts) is shut off, the TCS Solenoid closes, and vacuum is disconnected from the distributor in the same way it would be when you open up the throttle blades. When you let off the gas pedal, the carb returns to its idle position and the switch is again energized causing the TCS switch to open and provide vacuum to the distributor again.

You will get vacuum to the distributor when you let off the gas and this is what advances the timing during deceleration to provide better gas mileage and engine cooling.

Your options are that you can run the engine without a vacuum advance, use direct manifold vacuum via the carb port you presently have. Which ever way you go, you then have to bring in the correct initial timing at the balancer and then match the distributor timing curve to your initial timing. The way I see it now is that you have too much total advance and may do damage to the engine.

BTW, you don't even want to see what they did in 1973! TCS and EGR valves are tied in along with thermal and time delay vacuum switches.
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post #8 of 26 (permalink) Old 01-23-2019, 03:06 PM Thread Starter
 
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Thanks Jim,

The 16 degrees is at 850 rpm.
i have tried around 12 degrees and lower rpm but it seems to bog,while trying to set idle mixture screws as well.

I am running petronix with flame thrower coil, per their website timing shouldn't change but I don't know.
Assuming the tcs is working correctly,its a 4 speed m21,I would like to be close as possible to timing specs.
Which is why efi looks attractive.
Im going to have to go out and try again,or maybe replace the carb.

Timing this car is easy and there is no jumping around from the timing chain.

Getting the carb in line is another.
I did replace pump piston,needle and seat as well as new gaskets as it was leaking at the pump on the carb,tested the vac is good and no more fuel leak.
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post #9 of 26 (permalink) Old 01-23-2019, 03:28 PM
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Nay. If your Quadrajet is a bitch to tune, you need it gone through by an expert, such as Cliff Ruggles. The Q-jet on my '67 has over 253,000 miles on it, has been overhauled twice by me in 36 years of use, and operates as seamlessly as fuel injection. Great mileage, fast start up, tons of power opened up. The engineers knew what they were doing. The Bubba Backyarders in the past 50 years of tinkering with a car? Probably not so much. From what I've seen in the past few years, the trend is "if I don't understand it, I'll just replace it". It ought to be "Since I don't understand it, I'm going to learn how it works". Just my 2 cents, probably worth less.....
BTW, I also run stock ignition points and coil. I prefer their reliability over Pertronix and aftermarket coils. There is absolutely no power or performance gain with electronic ignition. Only the luxury of avoiding points and condenser service every 15,000 miles.....which is an epic task.
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post #10 of 26 (permalink) Old 01-23-2019, 07:28 PM
 
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Originally Posted by rheckman View Post
Thanks Jim,

The 16 degrees is at 850 rpm.
i have tried around 12 degrees and lower rpm but it seems to bog,while trying to set idle mixture screws as well.

I am running petronix with flame thrower coil, per their website timing shouldn't change but I don't know.
Assuming the tcs is working correctly,its a 4 speed m21,I would like to be close as possible to timing specs.
Which is why efi looks attractive.
Im going to have to go out and try again,or maybe replace the carb.

Timing this car is easy and there is no jumping around from the timing chain.

Getting the carb in line is another.
I did replace pump piston,needle and seat as well as new gaskets as it was leaking at the pump on the carb,tested the vac is good and no more fuel leak.

How would EFI make your timing better?
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