I have an '84 Monte SS that still has the original 305HO engine in it. I've installed the Edelbrock tubular exhaust headers for this application that connect to the original high flow cat, then had a 2 1/2" cat back exhaust system installed with Walker Dynomax mufflers. On the intake side, I replaced the original intake manifold with an Edelbrock Performer intake that would retain all of the O.E. emissions equipment, and I kept the original feedback carb. I upgraded the ignition system with an Accel supercoil for the O.E. HEI system, with Taylor wires, and upgraded AC spark plugs. I had a friend built a dual snorkel air cleaner for me. I replaced the stock water pump with an Edelbrock high flow pump. Now I know that the engine/trans combination isn't exactly the same as what you have, but it did make a noticeable improvement in the performance of the car, while retaining the original 305 engine. I believe that this is about as good as it gets with a pretty much stock 305 long block in the car. I don't think that its realistic to expect to get an extra 40-50HP from a stock LG4 305 engine with external bolt-on parts, while staying smog legal. Like most of the other guys here are saying, you best bet for a substantial improvement in the performance of the car is to swap out the 305 for a 350. I also have an '86 Grand Prix which is going to be a long-term project. It has the LG4 305, and the 200R4 trans. I don't intend to keep the 305 in the car. When I get around to it, I'll be pulling the 305, and putting in either a 350, or a 383 small block. Keep in mind that all small block engines from 262 right up to 400 have the same external dimensions, so your engine bay won't look any different, unless you decide to change any external engine accessories, or dress up the engine bay. Hope this helps.
1986 GP V8 305 _help with making this engine faster!
- Thread starter elcolombiano
- Start date
- Status
I have an '84 Monte SS that still has the original 305HO engine in it. I've installed the Edelbrock tubular exhaust headers for this application that connect to the original high flow cat, then had a 2 1/2" cat back exhaust system installed with Walker Dynomax mufflers. On the intake side, I replaced the original intake manifold with an Edelbrock Performer intake that would retain all of the O.E. emissions equipment, and I kept the original feedback carb. I upgraded the ignition system with an Accel supercoil for the O.E. HEI system, with Taylor wires, and upgraded AC spark plugs. I had a friend built a dual snorkel air cleaner for me. I replaced the stock water pump with an Edelbrock high flow pump. Now I know that the engine/trans combination isn't exactly the same as what you have, but it did make a noticeable improvement in the performance of the car, while retaining the original 305 engine. I believe that this is about as good as it gets with a pretty much stock 305 long block in the car. I don't think that its realistic to expect to get an extra 40-50HP from a stock LG4 305 engine with external bolt-on parts, while staying smog legal. Like most of the other guys here are saying, you best bet for a substantial improvement in the performance of the car is to swap out the 305 for a 350. I also have an '86 Grand Prix which is going to be a long-term project. It has the LG4 305, and the 200R4 trans. I don't intend to keep the 305 in the car. When I get around to it, I'll be pulling the 305, and putting in either a 350, or a 383 small block. Keep in mind that all small block engines from 262 right up to 400 have the same external dimensions, so your engine bay won't look any different, unless you decide to change any external engine accessories, or dress up the engine bay. Hope this helps.
Gears, headers, cat back simplest and normally biggest bang for buck and they carry forward to a 350/383/400. The cheapest most idiot proof way to the gears is have your local salvage yard do a computer search to locate you a whole rear drum to drum out of a MCSS. Its a bolt up with simple tools that you can do in a few hours. Jack & jack stands. Cost around here is usually around $225/250. They come with 3.42 or 3.73 depending on the year. A lot of times you get the rear sway bar with it which your car does not have unless it came equiped with optional f-41 handling package. The front sway bar off that MCSS would be thicker than the one on your GP also so grab it if you can. The Edelbrock headers and a cheap Summit/Jegs generic dual exhaust to go with it. Car will be measurably quicker sound better with relatively minimal investment that carrys forward whether you cam up the 305 or upgrade to a bigger sbc. Wait on the intake etc untill after you have done these mods.
The 305 LG4 in your car usually came with anemic highway 2.41:1 rear gears so a switch to 3.23-3.73:1 would be a good start. Applying the Monte SS H/O treatment to your engine would be straight forward and Compcams offers a good selection of cams for the 305. Vortec heads also added a lot of power to this engine in the truck line in 1996 but those aren't cheap. A better intake and headers will do there part also. I do vividly remember a guy that worked at a local Chevy dealer take a 1980 Grand Prix and hop up a Vortec 305 with better cam, intake etc and that car really performed. You just have to ask yourself how much $$ do you want to spend and how stock you want it to look. The cheapest and easiest mods that will keep stock appearance would be to swap in 305 H/O parts, upgrade the rear gears and add a cat back dual exhaust. I performed these same basic mods to a 1983 Cutlass 307 and the results were well worth it. That Cutlass went from a whimpy 12.5 second 0-60 car to a tire screaching 7.5 second car for less than $600.00 and I was able to keep my stock carb with richer secondaries and quicker opening rate and I got a good deal on a Comp cam 252H. The 3.73:1 rear end came from a local junk yard from a wrecked 85 442 for a measly $75.00! This of course was years ago so things are going to be more expensive now.
ponchoman49 said:
Thanks, this sound very good. I Like how descriptive you were. Often people leave suggestions but forget to state which parts and the manufactures. I don't want to spend more than $700, so it seems like the rear swap for a Monte SS or Grand National or 442 and headers and catback system might be my way to go.
I have another question for you guys. If I remove all the emission equipment from my car, would it perform better or worst and would the check engine light come on. I live in Florida and we don't have yearly emissions. Apart from that, I would like to remove all the extra hoses and canisters that come with the emissions equipment. I think the engine would look cleaner without it, so I was curious if anyone has done it and what were the outcomes.
Thanks
If you remove emissions equipment from your car then you will have to go all the way so to speak. The carb and distributer would have to be changed over to pre 1981 with vacuum advance. If you do this you will also lose your lockup torque converter which helps mileage. If you unplug any single emissions device such as the blue or black connectors to the carb which are the throttle position sensor and mixture control solonoid then you will get a resulting check engine light. There is also the VSS(vehicle speed sensor located up in the speedometer), Map sensor, barometric sensor both located in the engine bay, oxygen sensor which is located on the passenger side of the exhaust manifold and a 4-way connector going to the distributer. In essence it is a more primitive version of todays much more powerful computer controlled emissions systems. If it were my car I would leave it all connected and instead make sure everything is in tip top shape with no vacuum leaks, timing is set correctly, carb is in good proper working order with correctly adjusted float and two good shots of fuel from a new accelerator pump diaphram. It would be a good idea also to aquire a GM service manual for your year car. The purpose of the C4 emissions system was to reach that magical 14.7:1 stoichiometric ratio at low to part throttle driving conditions to reduce pollution and improve fuel economy while maintaining reasonable levels of driveability and performance. The added benefit of having this system is differing elevations, weather conditions, temperature and fuel quality. Vehicles using oxygen sensors enable the air-fuel ratio to be monitored by means of an air fuel ratio meter thus enabling your engine to run well in a variety of differing conditions. But keep in mind that this system only remians in closed loop(under computer control) under low to part throttle conditions. The secondaries are not under computer control and thus when you mash your foot down on the go pedal you are in WOT condition(wide open throttle) or full fuel enrichment mode. With this in mind there is some things you can do even on the feedback carb in your car on the secondary side. Making the secondaries open further and quicker are but a pair of pliers, allen wrench and flat tipped screwdriver away. You will also want to aquire some thinner/richer secondary metering rods to compliment the extra flow and a freer flowing exhaust is a must when performing this hop up. There is a good performance 307 Olds site that describes this with pics. As for whether a feedback C4 car vs an older non C4 equipped car is better or faster is really subjective. Power isn't really lost by having the C4 system connected. Out of tune carbs, worn ignitions wires, bad plugs, incorrect timing, bad Oxygen sensors etc can cause poor performance and mileage. Just as an example the 85 on up LG4 305 4BBL V8 put out 165 HP and 245 torque with the C4 system in the Monte Carlo and El Camino. A 1979 Olds Cutlass with the same LG4 305 4BBL put out 160 HP and 245 torque at similar RPM's with no computer controls. This is purely stock of course and more power can be had with the older 79 setup from distributer recurves and carb tweaks but the difference won't be dramatic and mileage will be worse on the older car. A lot of the untapped power in these engines comes from better breathing intakes, secondary carb tweaking, exhaust, cam upgrades and timing. Also don't forget the TV cable for that 200R4 transmission. It must be set correctly too and that will contribute to crisper faster shifts and better off the line movement.
^^ you mentioned highway gearing and this brought me to this question: I understand that overdrive makes highway driving easier on the car's engine, but does anyone know how these G-body 305 perform on the highway with stock transmissions?
If you want to upgrade your engine it makes no sense to leave any emissions and vacuum crap on there, unless you need to have it inspected. Headers and a new carb/manifold etc won't give you enough power to play with unless you allow the engine to use those 'breathing' upgrades by removing the emissions junk. It's not as involved as it seems, especially when you change the manifold and carb to an older style without the vacuum/electric q-jet
The transmission question - the overdrive gear simply lowers the engine's power output to the wheels so you 1)save gas, 2)can reach higher rpms for a longer period of time = a higher top speed
The transmission question - the overdrive gear simply lowers the engine's power output to the wheels so you 1)save gas, 2)can reach higher rpms for a longer period of time = a higher top speed
- Status
Similar threads
