need advice on cam selection
07-09-2018, 11:56 AM
#61
Understand the shortcomings of that motor.
My point is and has been that if you go 383 and are not making over 475+Gross HP/475-480+ Gross TQ in a streetable RPM range, you are not really getting the benefit of a 383 over a strong 355. Again, just having a 383 does NOT mean that you will make more power over lesser cube motors. The 383 will only make more power than an identically prepped 355 if built to maximize the few additional 28 cubes..It's not an automatic given just because it is a 383. There are literally dozens of examples going back to the 50's and even today where lesser cube/liter motors handily will out power and perform bigger cube engines with more liters...has always been that way.
My point is and has been that if you go 383 and are not making over 475+Gross HP/475-480+ Gross TQ in a streetable RPM range, you are not really getting the benefit of a 383 over a strong 355. Again, just having a 383 does NOT mean that you will make more power over lesser cube motors. The 383 will only make more power than an identically prepped 355 if built to maximize the few additional 28 cubes..It's not an automatic given just because it is a 383. There are literally dozens of examples going back to the 50's and even today where lesser cube/liter motors handily will out power and perform bigger cube engines with more liters...has always been that way.
If the goal is to make as much power as possible on a budget (which it must be said IS the case here because if there wasn't a budget and you were deciding between a 350 and a 383, you would obviously go with the 383) then you have to analyze your particular situation and budget.
Have a decent bottom end 350 that is in good shape and doesn't need a rebuild? You can probably get to about 400 hp with just a head/cam/intake swap.
Have a bottom end that has excessive blow by or low compression on a cylinder or two? You are going to rebuild it anyway, so it is very little extra cost to go to a 383 and have the extra cubes and power.
The other situation to consider is future power. What is your eventual goal? If you are wanting a 500 hp motor, you are better off with a 383 than a 350. The 383 will make that power easier and at a lower RPM. And most likely with less expensive porting work. Getting a 350 to make 400-450 hp isn't all that difficult with off the shelf parts. Getting a 350 to make over 500 hp you are looking at expensive porting work from a professional, or CNC ported heads and custom cam, as well as higher compression pistons.
In your case JB, you are obviously happy with your 350 in your car. And it is a healthy built street motor. Extracting any more power from that package starts to cost a pretty penny, and most would argue is not worth it for the marginal gain. So if the power your motor makes is what you are happy with, then more power to you! Could you make more power with a longer stroke crank? Absolutely! Would it be worth it? Sounds like not at all to you since you are very happy with how smooth and even the torque and power curve is in your motor, as well as the overall power.
07-09-2018, 12:02 PM
#62
Le Mans Master
I see where you are coming from, and it definitely depends on the individual persons situation. A 383 can be more "forgiving" because of the extra cubes, in that someone could make 450 hp with a 383 and some decent flowing heads that cost half of what the AFR heads cost. This is due both to the larger displacement pumping more air, and the larger displacement allowing for the use of a bigger camshaft (both of these have been discussed). I think you already agree, but obviously in an apples to apples comparison (both engines with near-optimal parts) there is no comparison: the 383 will always make more power.
If the goal is to make as much power as possible on a budget (which it must be said IS the case here because if there wasn't a budget and you were deciding between a 350 and a 383, you would obviously go with the 383) then you have to analyze your particular situation and budget.
Have a decent bottom end 350 that is in good shape and doesn't need a rebuild? You can probably get to about 400 hp with just a head/cam/intake swap.
Have a bottom end that has excessive blow by or low compression on a cylinder or two? You are going to rebuild it anyway, so it is very little extra cost to go to a 383 and have the extra cubes and power.
The other situation to consider is future power. What is your eventual goal? If you are wanting a 500 hp motor, you are better off with a 383 than a 350. The 383 will make that power easier and at a lower RPM. And most likely with less expensive porting work. Getting a 350 to make 400-450 hp isn't all that difficult with off the shelf parts. Getting a 350 to make over 500 hp you are looking at expensive porting work from a professional, or CNC ported heads and custom cam, as well as higher compression pistons.
In your case JB, you are obviously happy with your 350 in your car. And it is a healthy built street motor. Extracting any more power from that package starts to cost a pretty penny, and most would argue is not worth it for the marginal gain. So if the power your motor makes is what you are happy with, then more power to you! Could you make more power with a longer stroke crank? Absolutely! Would it be worth it? Sounds like not at all to you since you are very happy with how smooth and even the torque and power curve is in your motor, as well as the overall power.
If the goal is to make as much power as possible on a budget (which it must be said IS the case here because if there wasn't a budget and you were deciding between a 350 and a 383, you would obviously go with the 383) then you have to analyze your particular situation and budget.
Have a decent bottom end 350 that is in good shape and doesn't need a rebuild? You can probably get to about 400 hp with just a head/cam/intake swap.
Have a bottom end that has excessive blow by or low compression on a cylinder or two? You are going to rebuild it anyway, so it is very little extra cost to go to a 383 and have the extra cubes and power.
The other situation to consider is future power. What is your eventual goal? If you are wanting a 500 hp motor, you are better off with a 383 than a 350. The 383 will make that power easier and at a lower RPM. And most likely with less expensive porting work. Getting a 350 to make 400-450 hp isn't all that difficult with off the shelf parts. Getting a 350 to make over 500 hp you are looking at expensive porting work from a professional, or CNC ported heads and custom cam, as well as higher compression pistons.
In your case JB, you are obviously happy with your 350 in your car. And it is a healthy built street motor. Extracting any more power from that package starts to cost a pretty penny, and most would argue is not worth it for the marginal gain. So if the power your motor makes is what you are happy with, then more power to you! Could you make more power with a longer stroke crank? Absolutely! Would it be worth it? Sounds like not at all to you since you are very happy with how smooth and even the torque and power curve is in your motor, as well as the overall power.
You make some good points and support some of mine as well:
1. Build a 383 if you need a crank, rods, and/or pistons in the current 350
2. A 383 is easier to make power (in the upper 400's Gross HP) with lesser quality components. BUT if your are planning to be in the 400-430 Gross HP range, a 355 will make that power very easily today as well, in my opinion
3. Build a 383 if you are looking for 475+ Gross hp/Tq
4. Build a 383 if you intend to upgrade the HP in the future
I still think that one should not build a 383 just to say its a 383...the majority of them out there, especially crate 383's will get smoked by a strong 355.
Don't build a 383 if you think its only an additional $500 for the parts needed and labor to do the conversion...not a chance it's that cheap unless you can provide the free labor and then just a maybe. There is no free ride and the 383 conversion is included in that phrase, despite what many say about the 383 conversion..it will cost money and substantially more for the conversion with good quality parts for the crankshaft and rods to handle close to 500 Gross HP/TQ reliably....
Last edited by jb78L-82; 07-09-2018 at 01:07 PM.
07-09-2018, 01:41 PM
#63
Le Mans Master
Understand the shortcomings of that motor.
My point is and has been that if you go 383 and are not making over 475+Gross HP/475-480+ Gross TQ in a streetable RPM range, you are not really getting the benefit of a 383 over a strong 355. Again, just having a 383 does NOT mean that you will make more power over lesser cube motors. The 383 will only make more power than an identically prepped 355 if built to maximize the few additional 28 cubes..It's not an automatic given just because it is a 383. There are literally dozens of examples going back to the 50's and even today where lesser cube/liter motors handily will out power and perform bigger cube engines with more liters...has always been that way.
My point is and has been that if you go 383 and are not making over 475+Gross HP/475-480+ Gross TQ in a streetable RPM range, you are not really getting the benefit of a 383 over a strong 355. Again, just having a 383 does NOT mean that you will make more power over lesser cube motors. The 383 will only make more power than an identically prepped 355 if built to maximize the few additional 28 cubes..It's not an automatic given just because it is a 383. There are literally dozens of examples going back to the 50's and even today where lesser cube/liter motors handily will out power and perform bigger cube engines with more liters...has always been that way.
Sure more cubes does not automatically mean more power if the large cube is poorly built and the small cube is well built.
its just that going on and on about a 355 that can beat some 383s and the “benefits” of said 355 does not means that a 383 is not worthy of consideration, particularly on an L-48 since it needs most of it’s components changed in any case. Built with the same attention to detail it will handily outperform a 355 in torque ,acceleration and HP every single time. If that’s what a person is looking for then that is a viable and logical route vs the 355.
my 350 will beat a poorly built 383 as well, simply because I optimized to the best of my ability all the components during the build, additionally I exceeded just assembling the engine and took the time to modify some components to optimize their performance as well. In addition high stall torque converter, shift kit, 3.55 rear diff, cold air intake, performance carb tune,all these help out the 350, crutch it really to make its lesser torque perform better vs just having a higher torque engine. Take all that away and drop in your standard crate 383 and the results would be disappointing I’m sure.
I would use the same attention to detail for a 383 built by me and it would without a doubt outperform my 350 everywhere except in fuel economy. I had an eye to fuel economy (effenciency really) as well when I built my 350, as I need to drive long distances to get anywhere from my house and would prefer to not have to stop for fuel every 150 miles.
I’m sure you did the same with your 355 and it is performing very well. Until you get up to a $10,000 crate 383 you’re not going to do better than one built with the same care as one built by you.
The desktop Dyno data is interesting on a comparison basis and is good for comparison based on the parameters of the software, but it cannot account for all variables in a running engine. So I would only take that data with a grain of salt as there are many unaccountable variables.
One engine built identically to another can even vary to some degree, but that at least is an absolute known quantity vs desktop dyno data. Even that is dyno data and the dyno set up will vary from the installed set up, so even that is not exactly what is going to be seen once installed.
chassis dyno are probably the most valid on a comparison basis for performance changes with an installed configuration.
Last edited by REELAV8R; 07-09-2018 at 01:51 PM.
07-09-2018, 02:11 PM
#64
Le Mans Master
Yup agree, a chassis dyno is the most accurate indicator of what a particular engine will produce for power but as stated earlier by me and others, known components on a certain size engine will reliable produce a given range of HP/TQ UNLESS the builder screws up something pretty major.
You mentioned you built your 350 versus a 383 because you wanted better fuel mileage? I would have thought the 383 with more TQ at a lower RPM could handily beat a 350 for fuel efficiency since the easiest and most reliable method for beter fuel economy on any motor is to drastically drop the cruising RPM's to the lowest level without lugging the motor which a 383 should be able to do better than a 350. My 10 C6Z06 427 LS7 with 505 NET Hp gets 28 MPG at 80 mph mostly because it turns 1,800 RPM at 80 in 6th gear. Talk to C3 guys with 355/383's and a 5/6 speed tranny and they can get in the mid 20's for fuel economy with a carb. Most of the MPG gain is from lower revs which the 383 should be able to achieve slightly better than a 355.
You mentioned you built your 350 versus a 383 because you wanted better fuel mileage? I would have thought the 383 with more TQ at a lower RPM could handily beat a 350 for fuel efficiency since the easiest and most reliable method for beter fuel economy on any motor is to drastically drop the cruising RPM's to the lowest level without lugging the motor which a 383 should be able to do better than a 350. My 10 C6Z06 427 LS7 with 505 NET Hp gets 28 MPG at 80 mph mostly because it turns 1,800 RPM at 80 in 6th gear. Talk to C3 guys with 355/383's and a 5/6 speed tranny and they can get in the mid 20's for fuel economy with a carb. Most of the MPG gain is from lower revs which the 383 should be able to achieve slightly better than a 355.
07-09-2018, 03:32 PM
#65
Melting Slicks
You mentioned you built your 350 versus a 383 because you wanted better fuel mileage? I would have thought the 383 with more TQ at a lower RPM could handily beat a 350 for fuel efficiency since the easiest and most reliable method for beter fuel economy on any motor is to drastically drop the cruising RPM's to the lowest level without lugging the motor which a 383 should be able to do better than a 350. My 10 C6Z06 427 LS7 with 505 NET Hp gets 28 MPG at 80 mph mostly because it turns 1,800 RPM at 80 in 6th gear. Talk to C3 guys with 355/383's and a 5/6 speed tranny and they can get in the mid 20's for fuel economy with a carb. Most of the MPG gain is from lower revs which the 383 should be able to achieve slightly better than a 355.
-I had a good percentage decrease in fuel economy quote for a 383s from Vizard or BigJoe that I've now lost and can't find.
Now if you combined that 383 with a higher rear end gear (numerically lower) to take advantage of having more low-end torque you might be able to increase your fuel economy or match it, along with the increase in power.
I think the C7 Vettes do a great job balancing the two: go with a really low ratio rear gear for the automatics (2.56 or 2.73 for the Z51 package); then use a transmission with tons of gears- some super low gears to provide plenty of-off-the-line torque and then some really high OD gears to get engine speeds down to a minimum; to make sure you can go fast you need a trans that can shift fast. If you did the same thing with an old TPI C4 with tons of torque down low, you'd see some pretty fantastic fuel economy, too. (That broad spread in gear ratios from a trans with lots of gears is a great thing.)
An EFI SBC in an old Vette is capable of getting GREAT fuel economy with lower numeric rear end gears and a modern 7 speed transmission... I'd love to see one; haven't heard of any.
Adam
Last edited by NewbVetteGuy; 07-09-2018 at 03:38 PM.
07-09-2018, 05:25 PM
#66
Le Mans Master
Nope. On average, 383's LOSE fuel economy vs. 350s. More displacement means more air and requires more fuel. Ring friction is the #1 source of friction in an engine, by far; increase in stroke means an increase in friction- although I'm not sure you can even buy stroker pistons with 3/16" rings so you'll get thinner rings with less tension and friction vs. old pistons.
-I had a good percentage decrease in fuel economy quote for a 383s from Vizard or BigJoe that I've now lost and can't find.
Now if you combined that 383 with a higher rear end gear (numerically lower) to take advantage of having more low-end torque you might be able to increase your fuel economy or match it, along with the increase in power.
I think the C7 Vettes do a great job balancing the two: go with a really low ratio rear gear for the automatics (2.56 or 2.73 for the Z51 package); then use a transmission with tons of gears- some super low gears to provide plenty of-off-the-line torque and then some really high OD gears to get engine speeds down to a minimum; to make sure you can go fast you need a trans that can shift fast. If you did the same thing with an old TPI C4 with tons of torque down low, you'd see some pretty fantastic fuel economy, too. (That broad spread in gear ratios from a trans with lots of gears is a great thing.)
An EFI SBC in an old Vette is capable of getting GREAT fuel economy with lower numeric rear end gears and a modern 7 speed transmission... I'd love to see one; haven't heard of any.
Adam
-I had a good percentage decrease in fuel economy quote for a 383s from Vizard or BigJoe that I've now lost and can't find.
Now if you combined that 383 with a higher rear end gear (numerically lower) to take advantage of having more low-end torque you might be able to increase your fuel economy or match it, along with the increase in power.
I think the C7 Vettes do a great job balancing the two: go with a really low ratio rear gear for the automatics (2.56 or 2.73 for the Z51 package); then use a transmission with tons of gears- some super low gears to provide plenty of-off-the-line torque and then some really high OD gears to get engine speeds down to a minimum; to make sure you can go fast you need a trans that can shift fast. If you did the same thing with an old TPI C4 with tons of torque down low, you'd see some pretty fantastic fuel economy, too. (That broad spread in gear ratios from a trans with lots of gears is a great thing.)
An EFI SBC in an old Vette is capable of getting GREAT fuel economy with lower numeric rear end gears and a modern 7 speed transmission... I'd love to see one; haven't heard of any.
Adam
There have been many forum members with 5 speed OD's that report on this forum a dramatic jump in MPG just with the OD swap with SBC and BB's with hefty HP. The biggest contributor to all modern cars efficiency is the reduction in RPM's on the highway. Low friction pistons and such of course help but the biggest impact on any motor is just reducing revs, regardless of motor size.
Last edited by jb78L-82; 07-09-2018 at 05:47 PM.
07-09-2018, 05:54 PM
#68
Dr. Detroit
Member Since: Mar 2012
Location: New Braunfels Texas
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The mild Lunati grinds on the first page are not bad choices.......team them up with an Elgin "Z-28" 1.250 spring kit from E-Bay or Alex's Parts.
The Elgin stuff is close to stock in installed height for you to set up at home and get some Umbrella style seals.
Jebby
The Elgin stuff is close to stock in installed height for you to set up at home and get some Umbrella style seals.
Jebby
07-09-2018, 08:28 PM
#69
Melting Slicks
Starting with a 350 and replacing the bottom-end with a 383 rotating assembly will decrease your fuel economy from what it was as a 350.
I think what you were saying was the increase in torque with a 383 would let you cruise at a lower RPM than the 350 because there's more torque and the lower RPM will off-set the extra displacement. I think that's a pretty rare situation; it just basically means you went with too short of a rear gear numerically for your cam duration. If you go with a Tremec 6 speed your 2nd OD is 0.64. With the stock 355 rear gear of an auto L82 and 27" tires the engine speed @ 65 MPH is 1,838 RPM. If you had a 350 with a cam that didn't have enough torque to spin at @1,838 RPM -you probably went with a cam that recommended at least a 3.73 gear in the first place. (I started lookup cams that claim to not go "cam on" until after 1,800 RPM and generally those cams state that you should have at least a .373 rear gear (which would've brought the engine speed @ 65mph up to the RPM where the cam has enough torque to cruise).
You'd have to have a cam that's just slightly too big for your rear gear, compression ratio, and 350 cubic inches such that it couldn't cruise with even a 0.64 transmission ratio @ 65 MPH. But in that case, the 383 would allow it to operate in the lower OD gear and maybe save more fuel on the highway. (A Lunati "Bare bones" 290/300 old-school grind might put a 350 into that situation.)
It's a very rare and specific situation in which a 350 wouldn't have enough torque to cruise and adding 30ish cubic inches is going to make the difference and result in a potential increase in fuel economy; it requires a lot of mental gymnastics to find a situation in which an otherwise identical 383 gets better fuel economy than the same motor with 350 cubic inches. Most people are going to see LESS fuel economy with a 383 vs. a 350 as the general rule. The friction improvements from a thin ring pack or an improved CR as a part of the move to a 383 are the only thing the 383 has going for it in terms of fuel economy vs the 350.
Adam
Last edited by NewbVetteGuy; 07-09-2018 at 08:30 PM.