Looking for 425 tune up info.
November 4th, 2012, 04:33 PM
#1
Registered User
Thread Starter
Join Date: Sep 2012
Posts: 11
Looking for 425 tune up info.
We have a '65 Starfire with 425 and rochester 4 jet. Went through an ordeal getting carb rebuilt but it's done and car runs pretty good now. Heck it might get 10 mpg now! Anyway I don't know how long since this gem had a tune up and I'd like to do plugs, wires cap rotor points etc. so I know it's all new. I'd appreciate any input on what plugs to use, best place to get stuff and also timing info. I tried to set the timing to factory specs and the car ran pretty bad. It seems to need to be retarded quite a bit to get good performance. It does seem to run pretty good now. I just want everything as good as it can be.
Thanks
ROUNDSY
Thanks
ROUNDSY
November 5th, 2012, 07:04 AM
#4
Registered User
Join Date: Jun 2009
Location: southeastern Michigan
Posts: 14,436
I have a '67 Delta 88 with a 425, and I bought all tune-up parts (condenser, rotor, points, distributor cap, plugs, wires) at Autozone. I did this after I rebuilt the carburetor. Set dwell, idle speed, etc. according to the chassis service manual, and the car runs like a top.
November 5th, 2012, 07:57 AM
#5
CH3NO2 LEARN IT BURN IT
Join Date: Jul 2010
Location: Land of Taxes
Posts: 5,014
Don,
The tune-up specs from yesteryear won’t work well for today’s fuel. This goes for carb settings as well as tune-up settings. The float level may need to be increased or decreased from the original spec, generally decreased. Other settings in the carb will/may need modern spec updates hopefully your carb shop is up on this. Hopefully they installed a high quality pump cup designed for today’s crap fuel?
The basic tools you’ll need are a setback timing light, vacuum/PSI gage, Tac/dwell meter, maybe a volt/Ohm meter.
Verify you don’t have any vacuum leaks and your plugs, wires and coil are good. Check the primary (smaller) wires feeding the coil and dist. I like 8mm Taylor spiral core plug wires, but regular Packard’s work well too. Measure the resistance on the coil windings and plug wires if you’re in doubt.
Get a high quality point set and condenser. (Echlin (NAPA) Hi-Po... Vette/L79/Z28 Camaro spec). The points settings will stay the same .019”open gap or 30* dwell. Make sure the breaker plate, breaker cam and all connections are clean, tight and move freely. Lightly grease the cam with special cam grease where the points bumper rides. Check that grease every 3-5K miles. Inspect the mechanical weights and springs for freedom of movement, lightly lubricate etc…Make sure there isn’t any side to side play in the distributor shaft. Up down is normal but no side to side. Invest in a high quality cap & rotor (Echlin, Mallory, Accel etc...Brass towers)
The plugs I like are Autolites. Cheap and last. You could file back the ground wire some to expose the electrode… that’s the L shaped tab that you bend to adjust the gap. Old racers trick. (Google it).
Now it’s time to “super tune”. This involves customizing the 3 timing events in the distributor. But first use your vacuum gage hooked to an intake manifold vacuum source to obtain the highest vacuum reading possible. Do this by adjusting the carbs air/fuel mixture screws. The engine needs to be at the proper curb idle RPM and warm. You will need to go back-n-forth with each change you make to keep the vac reading the highest throughout the tuning procedure.
Now set your base timing (with the vac advance disconnected and its vacuum source plugged so there’s no vacuum leak). Start at 10-12* BTDC at curb idle with the engine warm.
Once the base is set now go at the vacuum advance. Get yourself an adjustable travel (not rate) vacuum advance canister (Jegs ,Summit). Set it to bring in another 10-12* of advance at idle. So now this adds up to 20-24* of timing at idle. If the exhaust “pops” back it down until it stops. Readjust air/fuel with vac gage.
Using your RPM meter and set back timing light, start increasing your RPMs and see where the mechanical timing starts coming in and at what RPM its “all” in, This is your total engine timing. You want the mechanical to be completely “all in” by 2500-2800 some say as high as 3000 RPM on a sane street driven car. Use different springs on the weights to obtain this. You can mix-n-match springs to get the desired rate. Your total should be about 36* at 25-2800 RPMS. So the mechanical brings in another 10-14* of timing. Readjust the air/fuel mix using the vac gage. This is just a starting point. Test drive it and see how it feels. It might like more base timing and less vac etc. I try to get my cars to run as much base timing as possible without spark knock. If the exhaust “pops” at idle I'll back the vacuum advance and base down. If I get spark knock at high RPMs I'll back off on the base and mechanical etc… Take your time and do one small change at a time keeping track of each change. It’s all how the engine reacts to your driving habits and available fuel. Once you tune for a certian fuel you should try to keep using that fuel. If you follow the initial basic recipe you will get it close. From there you can teach yourself what the car likes and optimize and tweak as you like.
If all this sounds like too much you have other options. One is to send the distributor in for a re-curve. Your carb shop will know who still does this. Or stab a new HEI in there with a customized curve. Or several distributor makers now have small cap “new school” distributors where the vac and mechanical settings are adjusted via turning a small Pot on the side of the dist.(cats buttocks).
With this level of super tuning you will extract the best fuel economy and performance possible provided everything else is up to par…engine internals, plug wires, good grounds throughout the car etc…Let us know if this was at all helpful. Sorry for long read but I had the time to explain.
The tune-up specs from yesteryear won’t work well for today’s fuel. This goes for carb settings as well as tune-up settings. The float level may need to be increased or decreased from the original spec, generally decreased. Other settings in the carb will/may need modern spec updates hopefully your carb shop is up on this. Hopefully they installed a high quality pump cup designed for today’s crap fuel?
The basic tools you’ll need are a setback timing light, vacuum/PSI gage, Tac/dwell meter, maybe a volt/Ohm meter.
Verify you don’t have any vacuum leaks and your plugs, wires and coil are good. Check the primary (smaller) wires feeding the coil and dist. I like 8mm Taylor spiral core plug wires, but regular Packard’s work well too. Measure the resistance on the coil windings and plug wires if you’re in doubt.
Get a high quality point set and condenser. (Echlin (NAPA) Hi-Po... Vette/L79/Z28 Camaro spec). The points settings will stay the same .019”open gap or 30* dwell. Make sure the breaker plate, breaker cam and all connections are clean, tight and move freely. Lightly grease the cam with special cam grease where the points bumper rides. Check that grease every 3-5K miles. Inspect the mechanical weights and springs for freedom of movement, lightly lubricate etc…Make sure there isn’t any side to side play in the distributor shaft. Up down is normal but no side to side. Invest in a high quality cap & rotor (Echlin, Mallory, Accel etc...Brass towers)
The plugs I like are Autolites. Cheap and last. You could file back the ground wire some to expose the electrode… that’s the L shaped tab that you bend to adjust the gap. Old racers trick. (Google it).
Now it’s time to “super tune”. This involves customizing the 3 timing events in the distributor. But first use your vacuum gage hooked to an intake manifold vacuum source to obtain the highest vacuum reading possible. Do this by adjusting the carbs air/fuel mixture screws. The engine needs to be at the proper curb idle RPM and warm. You will need to go back-n-forth with each change you make to keep the vac reading the highest throughout the tuning procedure.
Now set your base timing (with the vac advance disconnected and its vacuum source plugged so there’s no vacuum leak). Start at 10-12* BTDC at curb idle with the engine warm.
Once the base is set now go at the vacuum advance. Get yourself an adjustable travel (not rate) vacuum advance canister (Jegs ,Summit). Set it to bring in another 10-12* of advance at idle. So now this adds up to 20-24* of timing at idle. If the exhaust “pops” back it down until it stops. Readjust air/fuel with vac gage.
Using your RPM meter and set back timing light, start increasing your RPMs and see where the mechanical timing starts coming in and at what RPM its “all” in, This is your total engine timing. You want the mechanical to be completely “all in” by 2500-2800 some say as high as 3000 RPM on a sane street driven car. Use different springs on the weights to obtain this. You can mix-n-match springs to get the desired rate. Your total should be about 36* at 25-2800 RPMS. So the mechanical brings in another 10-14* of timing. Readjust the air/fuel mix using the vac gage. This is just a starting point. Test drive it and see how it feels. It might like more base timing and less vac etc. I try to get my cars to run as much base timing as possible without spark knock. If the exhaust “pops” at idle I'll back the vacuum advance and base down. If I get spark knock at high RPMs I'll back off on the base and mechanical etc… Take your time and do one small change at a time keeping track of each change. It’s all how the engine reacts to your driving habits and available fuel. Once you tune for a certian fuel you should try to keep using that fuel. If you follow the initial basic recipe you will get it close. From there you can teach yourself what the car likes and optimize and tweak as you like.
If all this sounds like too much you have other options. One is to send the distributor in for a re-curve. Your carb shop will know who still does this. Or stab a new HEI in there with a customized curve. Or several distributor makers now have small cap “new school” distributors where the vac and mechanical settings are adjusted via turning a small Pot on the side of the dist.(cats buttocks).
With this level of super tuning you will extract the best fuel economy and performance possible provided everything else is up to par…engine internals, plug wires, good grounds throughout the car etc…Let us know if this was at all helpful. Sorry for long read but I had the time to explain.
Last edited by droldsmorland; November 6th, 2012 at 07:57 AM.
November 6th, 2012, 06:10 AM
#6
Registered User
Thread Starter
Join Date: Sep 2012
Posts: 11
Thanks DROLDS,
This may be a little to involved for my limited skill set but I'll do what I can with all your info. I have to admit the car runs pretty good now so a little tweaking and tuning can only make it more fun. Iwas especially interested in the suggestions for parts. I know this stuff is readily available but I wanted to know what others are using.
Thanks to All that have replied. I need all the help I can get!
This may be a little to involved for my limited skill set but I'll do what I can with all your info. I have to admit the car runs pretty good now so a little tweaking and tuning can only make it more fun. Iwas especially interested in the suggestions for parts. I know this stuff is readily available but I wanted to know what others are using.
Thanks to All that have replied. I need all the help I can get!
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