318 camshaft swap 260 duration

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nm9stheham said:
I would ask you next about what you like (or would like) to do with this car.
- Do you like just cruising down the road to the car show?
- Do you wanna take it to the drag strip some, a lot, or never?
- Do you like to race around in the mountains?
- Auto trans?
Click to expand...
Yeah I would take it drag racing once a month, daily drive it as well yes auto trans with a trans go shift kit
 

Don't know if this works.If so it's kinda crappy.You sure can hear the wind blowing.
Running in park and also in gear. Again, I'm not much of a movie maker....
 
It has a nice slow idle and lope. Like what everybody wants. Nice!
 
Darter6 said:

Don't know if this works.If so it's kinda crappy.You sure can hear the wind blowing.
Running in park and also in gear. Again, I'm not much of a movie maker....
Click to expand...


Sounds good. I think the 114* C/L makes it sound smoother. Those specs on a 110* C/L would be choppier.
 
Slantsix64 said:
Yeah I would take it drag racing once a month, daily drive it as well yes auto trans with a trans go shift kit
Click to expand...
OK, well that makes it more of a compromise as most daily driver use drives you to a lower cam duration (better low RPM torque) and most drag racers want higher cam duration (more peak HP). Understand that I don't drag race but like a road race/rally type of engine which emphasizes a wide torque band over raw peak HP. So I tend to go lower on duration and wider on LSA to preserve low RPM torque, and it colors my opinions a certain way. I care very little about 'sound' as a 2-1/2" dual exhaust will makes it sound good IMHO with even a mild cam.

Maybe here are a couple things to think about while you decide that may help you zero in on something:
LSA - Lobe separation angle will typically be in the 110-114 degree range for smaller cams like this. A smaller LSA will tend promote higher RPM HP and have a rougher idle, but at the expense of fuel economy and low RPM performance. So smaller tends to make it better for drag racing and higher for cruising and daily driving.
Ramp rate - Fast moderate or slow are ways to look at that. You can get a good idea on ramp rates by subtracting the .050" lift duration number from the advertised duration number. In the range of the mid 40's is a fast ramp; around 50-ish is moderate; high 50's and more would be slow. Fast ramps (Comp XE and Lunati Voodoo are examples) get the valve open faster and allow better cylinder filling; that tends to help mid-range and upper RPM's the most. Fast ramps can also make a shorter duration cam act like a bigger duration cam but without as much adverse effect on low end torque, so that is nice for a mixed use situation like yours. The downside is that fast ramps put more pressure/stress on all parts of the valve train from the lifter-cam lobe interface to the valve. So will tend to be more prone to break-in failures or long term wear.
- Engine compression - Even with your rebuild you likely have the classic low CR 318. The issue there with too much cam duration will be to make the engine 'doggy' at low RPM's. You have that 3.55 rear gear so that will help make up some for that, but it sounds like you have the stock torque converter, which will tend to make the engine bog more and more at low RPM's if the cam duration is too long. (And you will know this problem when you feel it... with full throttle, the engine will just 'think about' revving up for a bit, and then 'BAM', when you hit a certain RPM, it will blast off.) So that is why the cautions against going too long on cam duration; for example, going from an RV cam to a 268 cam is 2-3 'steps' up in duration and that will be a big change and you may well be disappointed in the low RPM performance.

As a reference: If you indeed have an RV cam now, then it will likely have a 112-114 LSA and advertised duration in the 240-250 range. Lift will typically be lower too; so just going up 10 degrees in duration to the 250-260 range will get you at least .020" more valve lift, which will help performance all over.

I personally would go with the Crane H-260-2 cam which is danged similar to the Comp CL20-416-3 Dual Energy one recommended in post #8. I would consider either of those to be 1 step down from the cam you originally suggested and have slower ramps for less vavletrain stress. Your initial cam selection's fast ramps would have a rougher idle and higher peak HP but be lower on low RPM torque.

FWIW....
 
nm9stheham said:
OK, well that makes it more of a compromise as most daily driver use drives you to a lower cam duration (better low RPM torque) and most drag racers want higher cam duration (more peak HP). Understand that I don't drag race but like a road race/rally type of engine which emphasizes a wide torque band over raw peak HP. So I tend to go lower on duration and wider on LSA to preserve low RPM torque, and it colors my opinions a certain way. I care very little about 'sound' as a 2-1/2" dual exhaust will makes it sound good IMHO with even a mild cam.

Maybe here are a couple things to think about while you decide that may help you zero in on something:
LSA - Lobe separation angle will typically be in the 110-114 degree range for smaller cams like this. A smaller LSA will tend promote higher RPM HP and have a rougher idle, but at the expense of fuel economy and low RPM performance. So smaller tends to make it better for drag racing and higher for cruising and daily driving.
Ramp rate - Fast moderate or slow are ways to look at that. You can get a good idea on ramp rates by subtracting the .050" lift duration number from the advertised duration number. In the range of the mid 40's is a fast ramp; around 50-ish is moderate; high 50's and more would be slow. Fast ramps (Comp XE and Lunati Voodoo are examples) get the valve open faster and allow better cylinder filling; that tends to help mid-range and upper RPM's the most. Fast ramps can also make a shorter duration cam act like a bigger duration cam but without as much adverse effect on low end torque, so that is nice for a mixed use situation like yours. The downside is that fast ramps put more pressure/stress on all parts of the valve train from the lifter-cam lobe interface to the valve. So will tend to be more prone to break-in failures or long term wear.
- Engine compression - Even with your rebuild you likely have the classic low CR 318. The issue there with too much cam duration will be to make the engine 'doggy' at low RPM's. You have that 3.55 rear gear so that will help make up some for that, but it sounds like you have the stock torque converter, which will tend to make the engine bog more and more at low RPM's if the cam duration is too long. (And you will know this problem when you feel it... with full throttle, the engine will just 'think about' revving up for a bit, and then 'BAM', when you hit a certain RPM, it will blast off.) So that is why the cautions against going too long on cam duration; for example, going from an RV cam to a 268 cam is 2-3 'steps' up in duration and that will be a big change and you may well be disappointed in the low RPM performance.

As a reference: If you indeed have an RV cam now, then it will likely have a 112-114 LSA and advertised duration in the 240-250 range. Lift will typically be lower too; so just going up 10 degrees in duration to the 250-260 range will get you at least .020" more valve lift, which will help performance all over.

I personally would go with the Crane H-260-2 cam which is danged similar to the Comp CL20-416-3 Dual Energy one recommended in post #8. I would consider either of those to be 1 step down from the cam you originally suggested and have slower ramps for less vavletrain stress. Your initial cam selection's fast ramps would have a rougher idle and higher peak HP but be lower on low RPM torque.

FWIW....
Click to expand...
I have a 1986 360 four barrel camshaft I pulled out would this be a good upgrade?
 
Yes,
Hang on, I read 360 and missed the 4bbl
The 360-2bbl cam, yes; 252/260/112
The factory 318 cam was 240/248/112
The earlier 360-4bbls had the 340 cam in them and you don't want that one. IDK about 1986s.
So that is a big enough step that the drop in cylinder pressure will be very noticeable, especially with a stock TC. Keep in mind, that without changing the compression ratio,and all other things remaining unchanged; installing a bigger cam will always trade away low-rpm power to get higher rpm power. The difference in the above two cams is about 7psi in cylinder pressure,5% loss, and almost 10% loss in low-rpm performance from stall to 3000/3400(guessing). To make up for that you might need to upgrade your rearend to the next higher perf gear. Or get a new TC that stalls at a higher rpm where the torque is increased that same %.
 
Last edited:
Check out the 265DEH Comp. Those grinds have a similar affect as the Thumpr without the extra money attached. They sound nastier than they are, because of the split and they run very well. Sorta like the old Crower Hydraulic Hauler series.
 
AJ/FormS said:
Yes,
Hang on, I read 360 and missed the 4bbl
The 360-2bbl cam, yes; 252/260/112
The factory 318 cam was 240/248/112
The earlier 360-4bbls had the 340 cam in them and you don't want that one. IDK about 86s
So that is a big enough step that the drop in cylinder pressure will be very noticeable, especially with a stock TC. Keep in mind, that without changing the compression ratio,and all other things remaining unchanged; installing a bigger cam will always trade away low-rpm power to get higher rpm power. The difference in the above two cams is about 7psi in cylinder pressure,5% loss, and almost 10% loss in low-rpm performance from stall to 3000/3400(guessing). To make up for that you might need to upgrade your rearend to the next higher perf gear. Or get a new TC that stalls at a higher rpm where the torque is increased that same %.
Click to expand...


Think your overstating the facts here. Yes hopefully the OP is at least building some CR into his build 8.8-9:1 would nice but if not I still think he'll happy with a mild cam over stock.
 
You may be right;
Per post #1, the engine is already built, and no compression stated. Since it wasn't important enough to brag on, I assumed it's still sub 8/1. But if the Scr at the 69 spec , then you are right.
 
AJ/FormS said:
You may be right;
Per post #1, the engine is already built, and no compression stated. Since it wasn't important enough to brag on, I assumed it's still sub 8/1. But if the Scr at the 69 spec , then you are right.
Click to expand...
273 said:
Think your overstating the facts here. Yes hopefully the OP is at least building some CR into his build 8.8-9:1 would nice but if not I still think he'll happy with a mild cam over stock.
Click to expand...
Yes compression is 8.1
 
RustyRatRod said:
Check out the 265DEH Comp. Those grinds have a similar affect as the Thumpr without the extra money attached. They sound nastier than they are, because of the split and they run very well. Sorta like the old Crower Hydraulic Hauler series.
Click to expand...
 
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