318 carb questions
With a stock longblock, unless the tires spin, the 4bbl will not do much until much later in the game. It really depends on your stall and gears.
If you have one available, yes, bolt it on . But I sure wouldn't fork over big bucks for new stuff, in your situation.
The secondaries usually do not or can not open until the engine vacuum is sufficient to pull them open . Furthermore, the power might only peak at say 15 hp on a stock longblock 318, and it doesn't arrive until maybe 4000rpm. And it doesn't start until whatever rpm your current carb gets to be too small, which might not be until ~3300rpm.
If you have a A904, stock stall, 27" tires;
and 2.73 gears; this might not be until maybe 30mph. But if you have
3.55s and the tires don't spin, then maybe 23mph, but if you have
4.30s and the tires spin, then the secondaries might open just a few feet off the line.
But if you have a 2800stall, then it don't matter what gear you have, the secondaries are gonna jump open. However, just cuz they are open doesn't mean the engine is making power yet .....it just means the engine is ready to make power.
It can't make more power than the current combo,until the rpm starts to rise past whatever the choke point is, with the current carb.
If the engine can only inhale 300cfm at a particular rpm, then it don't matter if it is does with 2bbls, or 4, or 8, it will only inhale 300. And if the engine can only inhale 400cfm no matter what, installing an 850 will not make any more power.
The stock 318 Carter 2bbl, IIRC is rated as a IDK 280cfm or something, on the 2bbl rating, which, doing the math is 198cfm using the 4-bbl rating, which is supposed to go 2150rpm@100% VE..... but your stock engine will never make 100%. If it makes 65%, a stretch, then the 2bbl is good to 3300rpm . In Second gear for passing, with 2.73s, 3300 is about 58mph, so in this situation, the 4bbl is just starting to make power, over the 2bbl.
If you wanna make significantly more power; your engine has to be able to inhale more air, and that usually takes more rpm. The usual way to do this is to extend the rpm with a longer period cam, ...... then the 4 bbl will start to earn it's keep. But along with a bigger cam, might come a requirement for a higher stall convertor, and/or bigger number rear gears, and/or better heads.
If you want the power at low rpm; it usually means more pressure, or a bigger engine. But a short-period solid-lifter cam can help maintain pressure.
If you want the power at a lower roadspeed; this usually means a lower rear gear, a lower first gear, a higher stall TC, or a bigger engine.
I hope that helps.
PS; if you decide to take the plunge, do some time trials with the current combo tuned, and again after the swap. Do not make any other changes between the two tests; just the intake and carb. Then you will know if it was worth it.
IMO; the best bang for the buck at this stage is a higher than stock stall convertor, if you don't already have one. Below, is a curve that can help you see the difference from a stock TC that might stall at 2000rpm, versus say 2800. The power difference on this graph is from ~105 to ~155, so 50hp on the starting line. Realize that this is on a higher-compression 5.2M, which also has better heads. But the end result to you will be a similar result when measured as a percentage. For example, in this engine, 155/105=47.6% increase. If your engine makes 80hp at 2000, you might expect 80x1.476=118, which is plus 38hp; the 4bbl cannot touch this at 2800rpm, on a stock longblock; it will NEVER happen.
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With a stock longblock, unless the tires spin, the 4bbl will not do much until much later in the game. It really depends on your stall and gears.
If you have one available, yes, bolt it on . But I sure wouldn't fork over big bucks for new stuff, in your situation.
The secondaries usually do not or can not open until the engine vacuum is sufficient to pull them open . Furthermore, the power might only peak at say 15 hp on a stock longblock 318, and it doesn't arrive until maybe 4000rpm. And it doesn't start until whatever rpm your current carb gets to be too small, which might not be until ~3300rpm.
If you have a A904, stock stall, 27" tires;
and 2.73 gears; this might not be until maybe 30mph. But if you have
3.55s and the tires don't spin, then maybe 23mph, but if you have
4.30s and the tires spin, then the secondaries might open just a few feet off the line.
But if you have a 2800stall, then it don't matter what gear you have, the secondaries are gonna jump open. However, just cuz they are open doesn't mean the engine is making power yet .....it just means the engine is ready to make power.
It can't make more power than the current combo,until the rpm starts to rise past whatever the choke point is, with the current carb.
If the engine can only inhale 300cfm at a particular rpm, then it don't matter if it is does with 2bbls, or 4, or 8, it will only inhale 300. And if the engine can only inhale 400cfm no matter what, installing an 850 will not make any more power.
The stock 318 Carter 2bbl, IIRC is rated as a IDK 280cfm or something, on the 2bbl rating, which, doing the math is 198cfm using the 4-bbl rating, which is supposed to go 2150rpm@100% VE..... but your stock engine will never make 100%. If it makes 65%, a stretch, then the 2bbl is good to 3300rpm . In Second gear for passing, with 2.73s, 3300 is about 58mph, so in this situation, the 4bbl is just starting to make power, over the 2bbl.
If you wanna make significantly more power; your engine has to be able to inhale more air, and that usually takes more rpm. The usual way to do this is to extend the rpm with a longer period cam, ...... then the 4 bbl will start to earn it's keep. But along with a bigger cam, might come a requirement for a higher stall convertor, and/or bigger number rear gears, and/or better heads.
If you want the power at low rpm; it usually means more pressure, or a bigger engine. But a short-period solid-lifter cam can help maintain pressure.
If you want the power at a lower roadspeed; this usually means a lower rear gear, a lower first gear, a higher stall TC, or a bigger engine.
I hope that helps.
PS; if you decide to take the plunge, do some time trials with the current combo tuned, and again after the swap. Do not make any other changes between the two tests; just the intake and carb. Then you will know if it was worth it.
IMO; the best bang for the buck at this stage is a higher than stock stall convertor, if you don't already have one. Below, is a curve that can help you see the difference from a stock TC that might stall at 2000rpm, versus say 2800. The power difference on this graph is from ~105 to ~155, so 50hp on the starting line. Realize that this is on a higher-compression 5.2M, which also has better heads. But the end result to you will be a similar result when measured as a percentage. For example, in this engine, 155/105=47.6% increase. If your engine makes 80hp at 2000, you might expect 80x1.476=118, which is plus 38hp; the 4bbl cannot touch this at 2800rpm, on a stock longblock; it will NEVER happen.
