Joined
·
3,884 Posts
my cousin has a 305. he is putting headers an intake and a carb on it. he is looking to bump up the timing a few degrees too. anyone with any experience on how much total advance a motor like this would be able to handle?
bolt on 305 ignition timing
1 - 10 of 10 Posts
Joined
·
18,121 Posts
depends..
what year 305? which 305- LG4? L69? TBI? TPI? vortec?
what year 305? which 305- LG4? L69? TBI? TPI? vortec?
Joined
·
3,884 Posts
i believe LG4. carbureted 1986 monte carlo. ss clone.
Joined
·
2,739 Posts
Look for 36° ± 2° "total" (static + centrifugal) at 3500 RPM, with the vac adv disconnected
Probably work better to get a distributor with less range of centrifugal adv, say, 18°, and set the static to 18°, to get the 36° "total". As opposed to the usual stock arrangement, which is something like 6° static, plus 28° centrifugal, or the like (too little "static", too much centrifugal).
Except that if it still has the computer controls, you have to re-program the chip to change the relationship between "static" and "final" timing.
Doesn't matter if it's a LG4, L69, LM1; 305, 350, 400, 151, or any other CID; TPI, carb, TBI, or any other induction. It's mostly a property of how gasoline burns. As long as it's an internal combustion engine running gasoline, it's not going to vary very much from that.
Probably work better to get a distributor with less range of centrifugal adv, say, 18°, and set the static to 18°, to get the 36° "total". As opposed to the usual stock arrangement, which is something like 6° static, plus 28° centrifugal, or the like (too little "static", too much centrifugal).
Except that if it still has the computer controls, you have to re-program the chip to change the relationship between "static" and "final" timing.
Doesn't matter if it's a LG4, L69, LM1; 305, 350, 400, 151, or any other CID; TPI, carb, TBI, or any other induction. It's mostly a property of how gasoline burns. As long as it's an internal combustion engine running gasoline, it's not going to vary very much from that.
Joined
·
3,884 Posts
Look for 36° ± 2° "total" (static + centrifugal) at 3500 RPM, with the vac adv disconnected
Probably work better to get a distributor with less range of centrifugal adv, say, 18°, and set the static to 18°, to get the 36° "total". As opposed to the usual stock arrangement, which is something like 6° static, plus 28° centrifugal, or the like (too little "static", too much centrifugal).
Except that if it still has the computer controls, you have to re-program the chip to change the relationship between "static" and "final" timing.
Doesn't matter if it's a LG4, L69, LM1; 305, 350, 400, 151, or any other CID; TPI, carb, TBI, or any other induction. It's mostly a property of how gasoline burns. As long as it's an internal combustion engine running gasoline, it's not going to vary very much from that.
o wow so even a stock motor likes 36 degrees? any tips on pulling the computer stuff in exchange for a regular HEI? i have an HEI i could give him if he needs it.
Joined
·
2,739 Posts
If you remove the computer controls, you have to change out the carb and distributor; and also make some kind of provision for the TCC.
If he's changing out the carb, he pretty much HAS TO replace the dist and do away with the computer.
Personally, I don't think it's a real good idea, most of the time; and almost never, on a stock, or near-stock, engine. It ends up being a HUGE expense with relatively little benefit. The system as a whole, when working right, is highly effective, and reasonably adaptable to larger engines and other mods, as long as the cam isn't too radical. Repairing the Q-Jet and getting the electronic stuff all working right usually costs less up front, and uses AHELLUVALOT less gas and therefore costs less in the long run, than just hacking some other carb onto it.
Talk him out of swapping the carb, and instead, PREOPERLY RESTORE the stock system to fully correct operation. It's not that hard, will cost MUCH less, and he'll be far happier with the finished product. There's lots of good intakes that he can use, such as the ZZ4 one or a Performer (with EGR). Have him do that, and snarf a chip out of a car with the L69. That will make a NOTICEABLE difference. Gives a more aggressive timing and fuel curve than the grocery-cart setup in the LG4 programming. Then set the timing for about 36-38° at 3500 RPM with the MAP sensor disconnected. Raise the RPMs, disconnect the tube from the sensor, and set the timing QUICKLY without letting it go back to idle, so that it doesn't see an "error" condition (high RPMs, low throttle angle, and high MAP which is a set of conditions that CANNOT possibly exist and will set a code and send the thing into limp-home mode); or on an engine dyno with the RPMs at 3500 or above and the vacuum below about 6" (fairly heavy load). It'll probably end up about 8-10° of static timing.
Be aware that on that engine, you have to also disconnect the Weatherpak connector that hooks the dist up to the ECM; it's a big flat thing with about 4 or 5 wires, on a harness that comes out the opposite side of the dist from the harness that goes up to the cap. It usually hangs down into the trans tunnel and hides real good, so it's a pain to find if you don't already know where it is.
If he's changing out the carb, he pretty much HAS TO replace the dist and do away with the computer.
Personally, I don't think it's a real good idea, most of the time; and almost never, on a stock, or near-stock, engine. It ends up being a HUGE expense with relatively little benefit. The system as a whole, when working right, is highly effective, and reasonably adaptable to larger engines and other mods, as long as the cam isn't too radical. Repairing the Q-Jet and getting the electronic stuff all working right usually costs less up front, and uses AHELLUVALOT less gas and therefore costs less in the long run, than just hacking some other carb onto it.
Talk him out of swapping the carb, and instead, PREOPERLY RESTORE the stock system to fully correct operation. It's not that hard, will cost MUCH less, and he'll be far happier with the finished product. There's lots of good intakes that he can use, such as the ZZ4 one or a Performer (with EGR). Have him do that, and snarf a chip out of a car with the L69. That will make a NOTICEABLE difference. Gives a more aggressive timing and fuel curve than the grocery-cart setup in the LG4 programming. Then set the timing for about 36-38° at 3500 RPM with the MAP sensor disconnected. Raise the RPMs, disconnect the tube from the sensor, and set the timing QUICKLY without letting it go back to idle, so that it doesn't see an "error" condition (high RPMs, low throttle angle, and high MAP which is a set of conditions that CANNOT possibly exist and will set a code and send the thing into limp-home mode); or on an engine dyno with the RPMs at 3500 or above and the vacuum below about 6" (fairly heavy load). It'll probably end up about 8-10° of static timing.
Be aware that on that engine, you have to also disconnect the Weatherpak connector that hooks the dist up to the ECM; it's a big flat thing with about 4 or 5 wires, on a harness that comes out the opposite side of the dist from the harness that goes up to the cap. It usually hangs down into the trans tunnel and hides real good, so it's a pain to find if you don't already know where it is.
Well said, I agree, You can get away with 10 degrees initial.
Joined
·
3,884 Posts
well he is swapping in a 327 or 350 later on. for now he is only doing bolt ons that he can transfer onto a larger small block. he already has the intake and carb. he already removed all the egr from his car too. as far as the lockup, hes going to have to get the stand alone lockup kit then huh? i have it with my 2004R and its not hard to hook up, but any way we could keep from touching the tcc stuff?
0°
You have a EST control and the distributer must be set at 0° as it is loked out and the EST takes care of advance if it still has all the Fuel Injection and all, if so 0° with the EST dis-connected
You have a EST control and the distributer must be set at 0° as it is loked out and the EST takes care of advance if it still has all the Fuel Injection and all, if so 0° with the EST dis-connected
Joined
·
2,739 Posts
The LG4 doesn't have fuel injection; it's the base-model low-output computer-controlled carb system. We're working with a computer-controlled Q-Jet system here.
On the LG4, if you set the static timing to its spec (0°) it will most likely have only about 28° of "total" timing measured the same way you'd check a mechanically controlled distributor.... the "spec" is influenced by emissions levels, not just as the engine's "ideal" "best power" requirements or even "best economy". Just because you can look up in "the book" and find a "spec", does not necessarily mean that it's the "best possible" setting; the factory has too many other purposes that the "spec" serves, not all of which are the same as yours. Instead of slaving yourself to "the spec", give the engine what it wants.
As stated, in the electronic system, the distributor itself is totally fixed at one point, with no physical advance occurring either due to RPM or vacuum. Rather, the ECM examines the engine's operating conditions (throttle position, RPM, MAP/vacuum, coolant temp, O2 sensor indication, etc. etc. etc.) and looks up in a table of values programmed into it, what the "correct" advance should be, for that specific set of conditions; and applies it electronically. You can't easily change those values in that old crude Stone Age computer, not like you can with the newer ones; which is why the easiest thing to do to improve its performance is to set the static timing to the point at which the "total" timing, checked under the same set of conditions you'd check a mech dist under, is where it needs to be (36-38° or so). As also previously stated, more than likely that will produce a static timing setting of around 8-10°, with the factory LG4 programming.
The computer controls the TCC. It requires a list of inputs to do that accurately; throttle position, vacuum/MAP, vehicle speed, coolant temp, brake status, and so forth. Clearly, if the ECM is removed, it can no longer control anything; and if any of those inputs are missing (particularly throttle position, which is a part of the carb), then it can't do it either. The "kits" that you can buy are pretty crude and brute-force. About all they do is make it to where you can tell yourself "yeah the TCC comes on sometimes". It's FAR FROM as sophisticated as the computer, even as basic and minimal as that computer system is.
If there's no good reason to hack the ECM system off, resist the temptation. Like I said, on a stock or near-stock motor, NO OTHER carb and dist is going to really make much difference as far as making more power, because that's not what limits that motor's potential. As we all know, the way to make a car go faster, is NOT to just un-bolt and re-bolt the big shiny things that sit up on top, out in the open where everybody can see; the only way that doing that will make the car faster, is by weight reduction, with all reductions applied exclusively to the driver's wallet.
The CORRECT mental approach to modding a car is to look at THE CAR (not just the "engine"), and find the ONE THING that's most slowing it down, and apply a properly chosen, compatible modification to THAT THING. That will then expose some other thing as the next ONE THING that most slows the car down, and you then do the same to that thing. In the LG4, those things are, in order of importance, the exhaust first (which you're dealing with), then the programming (which the L69 version is MUCH better and is very easy to get and install), then the cam, then the gears, then the torque converter, then the compression, then the heads. Somewhere along the line it needs a better air cleaner too, preferably NOT an open element, in spite of the gratifying additional noise it makes which does nothing at all for power but merely recalibrates the driver's "butt dyno" (usually in fact leaves power on the table, because it picks up hot thin air instead of cold dense air).
Then and only then, MAYBE, after ALL that other stuff is changed, a carb swap will do something productive. Until then, you'll get FAR MORE bang for the buck, by repairing, tuning and working WITH the stuff that's there, rather than just indiscriminately hacking it all off, like illiterate newbies do in the name of "cleaning up the engine bay" or "what emissions crap do I not need". Make an effort to understand how the computer works, and use it to your advantage. In particular, it's good for around 20%, or more, of fuel economy, compared to a typical Edelbrock (Carter) carb or the like. Add that expense in to whatever cost calculations the owner is making, and suddenly all that hacking isn't near as attractive-looking. Personally I'll take a few hoses and wires snaking around on an engine that nobody ever sees, in exchange for a constant and permanent cash flow burden of $10 or $15 or $40 or whatever per week, in increased fuel cost.
Also as stated before, the whole computer system will work fine on a 327 or 350 with almost no modification whatsoever, IF the cam is chosen accordingly. If the car's owner isn't looking to race the car, that's still not a reason to hack the factory stuff off. Use it to his advantage.
On the LG4, if you set the static timing to its spec (0°) it will most likely have only about 28° of "total" timing measured the same way you'd check a mechanically controlled distributor.... the "spec" is influenced by emissions levels, not just as the engine's "ideal" "best power" requirements or even "best economy". Just because you can look up in "the book" and find a "spec", does not necessarily mean that it's the "best possible" setting; the factory has too many other purposes that the "spec" serves, not all of which are the same as yours. Instead of slaving yourself to "the spec", give the engine what it wants.
As stated, in the electronic system, the distributor itself is totally fixed at one point, with no physical advance occurring either due to RPM or vacuum. Rather, the ECM examines the engine's operating conditions (throttle position, RPM, MAP/vacuum, coolant temp, O2 sensor indication, etc. etc. etc.) and looks up in a table of values programmed into it, what the "correct" advance should be, for that specific set of conditions; and applies it electronically. You can't easily change those values in that old crude Stone Age computer, not like you can with the newer ones; which is why the easiest thing to do to improve its performance is to set the static timing to the point at which the "total" timing, checked under the same set of conditions you'd check a mech dist under, is where it needs to be (36-38° or so). As also previously stated, more than likely that will produce a static timing setting of around 8-10°, with the factory LG4 programming.
The computer controls the TCC. It requires a list of inputs to do that accurately; throttle position, vacuum/MAP, vehicle speed, coolant temp, brake status, and so forth. Clearly, if the ECM is removed, it can no longer control anything; and if any of those inputs are missing (particularly throttle position, which is a part of the carb), then it can't do it either. The "kits" that you can buy are pretty crude and brute-force. About all they do is make it to where you can tell yourself "yeah the TCC comes on sometimes". It's FAR FROM as sophisticated as the computer, even as basic and minimal as that computer system is.
If there's no good reason to hack the ECM system off, resist the temptation. Like I said, on a stock or near-stock motor, NO OTHER carb and dist is going to really make much difference as far as making more power, because that's not what limits that motor's potential. As we all know, the way to make a car go faster, is NOT to just un-bolt and re-bolt the big shiny things that sit up on top, out in the open where everybody can see; the only way that doing that will make the car faster, is by weight reduction, with all reductions applied exclusively to the driver's wallet.
The CORRECT mental approach to modding a car is to look at THE CAR (not just the "engine"), and find the ONE THING that's most slowing it down, and apply a properly chosen, compatible modification to THAT THING. That will then expose some other thing as the next ONE THING that most slows the car down, and you then do the same to that thing. In the LG4, those things are, in order of importance, the exhaust first (which you're dealing with), then the programming (which the L69 version is MUCH better and is very easy to get and install), then the cam, then the gears, then the torque converter, then the compression, then the heads. Somewhere along the line it needs a better air cleaner too, preferably NOT an open element, in spite of the gratifying additional noise it makes which does nothing at all for power but merely recalibrates the driver's "butt dyno" (usually in fact leaves power on the table, because it picks up hot thin air instead of cold dense air).
Then and only then, MAYBE, after ALL that other stuff is changed, a carb swap will do something productive. Until then, you'll get FAR MORE bang for the buck, by repairing, tuning and working WITH the stuff that's there, rather than just indiscriminately hacking it all off, like illiterate newbies do in the name of "cleaning up the engine bay" or "what emissions crap do I not need". Make an effort to understand how the computer works, and use it to your advantage. In particular, it's good for around 20%, or more, of fuel economy, compared to a typical Edelbrock (Carter) carb or the like. Add that expense in to whatever cost calculations the owner is making, and suddenly all that hacking isn't near as attractive-looking. Personally I'll take a few hoses and wires snaking around on an engine that nobody ever sees, in exchange for a constant and permanent cash flow burden of $10 or $15 or $40 or whatever per week, in increased fuel cost.
Also as stated before, the whole computer system will work fine on a 327 or 350 with almost no modification whatsoever, IF the cam is chosen accordingly. If the car's owner isn't looking to race the car, that's still not a reason to hack the factory stuff off. Use it to his advantage.
1 - 10 of 10 Posts
- This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Team Chevelle
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
Top Contributors this Month
View All
shovelrick
250 Replies
Ripper/Wrench
240 Replies
mrpaticular
173 Replies
Recommended Communities
Join now to ask and comment!
