Minimum Cross Sectional Area: Question

[Orr89rocz]

The combo is a 383, vortec heads flowing 260, RPM A/G, headers, 230-240 cam...... and you’re looking for peak power between 5500-6000?

You’re done...... put it together.

X2, or maybe put a vic jr on it. Thats the best you can do here. Short of going superstock type cam lobe and tons of gear to make it as fast as possible lol but no street life

[skinny z]

The combo is a 383, vortec heads flowing 260, RPM A/G, headers, 230-240 cam...... and you’re looking for peak power between 5500-6000?

You’re done...... put it together.

Almost. Have to make a decision on the RPM limit (as in 5500 or 6000 or right in the middle) and then dial in the cam spec.
The Torque Master program makes easy work of moving peak HP RPM around. A little experimenting with that and I'll learn what it would take to get the peak more towards the higher end of that range.

[skinny z]

The combo is a 383, vortec heads flowing 260, RPM A/G, headers, 230-240 cam...... and you’re looking for peak power between 5500-6000?

You’re done...... put it together.

X2, or maybe put a vic jr on it. Thats the best you can do here. Short of going superstock type cam lobe and tons of gear to make it as fast as possible lol but no street life

The Vic Jr may be a follow up item.

[mt-engines]

The combo is a 383, vortec heads flowing 260, RPM A/G, headers, 230-240 cam...... and you’re looking for peak power between 5500-6000?

You’re done...... put it together.

X2, or maybe put a vic jr on it. Thats the best you can do here. Short of going superstock type cam lobe and tons of gear to make it as fast as possible lol but no street life

The Vic Jr may be a follow up item.

Only if you add more duration, and open those heads up. A regular performer RPM is good to 6000. Your combo will be down power at 6000 because of the port size.

Hence the tow truck comment. A 5.7 Vortec is about what 175cc? They put those in tow trucks. Heck a 6.0 LS has what 2.3" CSA and those are in 1 tons and tow trucks.

If you want to make power. Man up and make them bigger, add 15 degrees of Cam and spin her up to 6500.

Or just bolt it together.

People have been building that very combo for decades. There is no need for any computer simulation. You will be out of head. Open them up, slow em down.

[skinny z]

[quote=mt-engines post_id=847365 time=1580934021 user_id=31879]
Only if you add more duration, and open those heads up. A regular performer RPM is good to 6000. Your combo will be down power at 6000 because of the port size.
Hence the tow truck comment. A 5.7 Vortec is about what 175cc? They put those in tow trucks. Heck a 6.0 LS has what 2.3" CSA and those are in 1 tons and tow trucks.
If you want to make power. Man up and make them bigger, add 15 degrees of Cam and spin her up to 6500.
Or just bolt it together.
People have been building that very combo for decades. There is no need for any computer simulation. You will be out of head. Open them up, slow em down.
[/quote]

I'd get a better cylinder head (and something lighter at that) before I dig into these any further. Yeah, Vortec's are advertised at 170cc with about 235cfm at .500". These are somewhat better but certainly still small. But they are what they are and I'm going to run with it.
Interestingly, DV did a little experimenting with a 383 and Edelbrocks 170cc Performer RPM head. That's what caught my attention and kind of added the fuel to try and do something similar. Seeing as I need a shortblock anyway, it seems reasonable to connect the dots, so to speak. The turn that makes this build a little different was over-camming and a lower compression ratio. Cam specs for that were 240/244 on a 106 LCA. Pretty steep compared to the traditional route. What's been suggested here and elsewhere? In or around 230? The small heads and increased velocity were to make up for the lazy result you would get otherwise. And such was the case.
I may follow that approach or as you mention, build the same combo that's been copied for decades.
What the computer simulations do is let me enjoy the sport whereas otherwise, I'd be doing nothing. So I indulge myself that way. DynoSim, PipeMax and now Torque Master. Hours of fun without leaving my desk.

[FC-Pilot]

I indulge myself that way. DynoSim, PipeMax and now Torque Master. Hours of fun without leaving my desk.

Or spending a dime. I understand that many of us don’t build a bunch of engines so we lean on the shoulders of others that do. If only we all had unlimited funds and a dyno to experiment with. Heck, we have a dyno and I still don’t get to play with things to learn real world relationships the way I would like. (Darn that need for a job and having to earn money to keep a roof over my families head and food on the table). LOL

I tend to push the boundary on staying on the small side of the MCSA when I build most of my engines. My thought process is that an engine that might be lazy down low has a more noticeable feel than one that runs out of steam 500RPM’s early. That is just me, and the last batch of engines I have build lately are for trucks or daily drivers. The trucks will probably never be run to their peak HP of 5500, so trading power down low and part throttle drivability for another 500 or 1000 RPM’s is not worth it for me.

Anyway, do what you think is best for you. But what ever you do, enjoy it.

Paul

[Orr89rocz]

Define lazy down low?

What is low? 2500? Off idle? 4000?

Gear and converter to match and there is no down low to worry about so why the worry with velocity so much? Unless stick car.

[FC-Pilot]

Define lazy down low?

What is low? 2500? Off idle? 4000?

Gear and converter to match and there is no down low to worry about so why the worry with velocity so much? Unless stick car.

For a play car I would agree that gear and converter should match what your peak performance goal. As I stated, this is my “personal” take on the subject when dealing with a “daily driver”. I live in Phoenix AZ where heat is dealt with a little different than other parts of the country. When the interior of your car Is 140* the idea of not having AC in your car makes it almost unusable. Now the idea of a daily driver “FOR ME” cruising at 2800 rpm’s through forty minutes of commute each way is not appealing. I have already done that. Then I geared it to be more realistic for daily driving, and the heat produced from the stall converter baked the trans fluid even with what was considered and oversized trans cooler. So a lower stall was used. At that point throttle input was sluggish in the cruising rpm regardless of ignition and carb tuning. (EFI might have prevented that issue, but many of us still use and tune carbs). So in selecting heads better suited for the realistic application throttle response was improved as was fuel mileage (which did not break my heart). I bet if I had been able to dyno before and after I would have lost power over 5500. But what was gained was clearly an advantage of general drivability (which is not often talked about here) and a noticeable power increase up to 3500 RPM’s which is where 90% or more of my driving took place. So those are my thoughts in response to your question.

As I stated in my first post, this was my personal choice (to clearly make a point as not being “the end all”). This theory was stated for “daily drivers and trucks”. Now my race motors I do not choke with undersized runners. I never said anyone else was wrong, just stating what I have done and why. I did not even say the OP should ascribe to my thinking. I was just giving a little food for though and my $.02 just like everyone else.

So not trying to be a jerk, but for a daily driver, what would you consider a pleasant cruise RPM? What would you do to optimize it for use in its predominantly used RPM range? I love hearing others ideas and thoughts as open thinking and dialogue lifts the whole group.

Paul

[skinny z]

Let's see if I can address these replies without all the quotes.
First off Paul, thanks for the "do what I think is best and enjoy it" props. This is all part of it and I enjoy this too.
Now for some clarity.
Orr has been watching me go back and forth on this build for some time. In the time it's taken to get this far many have gone racing. Or cruised across the country. Or commuted everyday. But I'm in no hurry and really like hearing and engaging with all that contribute.
So I'll put down a specification of sorts. This is an engine. No chassis. No prerequisite to being able to use it as a daily driver, cross country cruiser or dedicated race car. Really what I'm doing here is building an engine with parts that I have. Heads (the key component here), an intake and a general platform that being Gen 1 SBC. I have several examples from which to draw. It was pointed out that this has been done for decades. But there's always a twist. And the twist is what has peaked my interest.
If I build in the direction I'm thinking, I may exclude myself from having that daily driver or driving 2500 miles in one go. That part I'm unsure of, but given my experiences, I can make something somewhat untenable into something less so. But I may get something I haven't had in a while and that's a track performer. But that's so easy now. Put a single turbo on your 5.3 and have your cake and eat it too (right Orr?) But I'm stuck in the old school for a least one more go around. So NA it is.
So here's the deal. Make the best engine package out of the parts I have and the future shortblock. By best I'm taking about a dyno engine. Use the heads to their fullest, compliment with the right cam and go.
But I've found that there is more than one approach and this is really what I'm working through. Build to an RPM the heads will support and cam it to suit the CR and that RPM. That's the traditional method. Or use the benefit of the small head's characteristics (as in mid-lift, lower RPM capabilities) and make something more aggressive with more cam than you might think. One particular example of that has stood out and I'm pursuing that possibility
I'd say that even the most intense version of this wouldn't be something unreasonable on the street. Cams I'm looking at are in the low 70 to upper mid 70's overlap. I've worked with that before in a 355 inch. Even got decent fuel consumption out of it. So I'm confident I can make it work with larger cubes too. Lazy down low is subjective but I think a general definition might be one that says leaving a stoplight under normal acceleration leaves something to be desired. I can say that the stall converter I have now gets me into the mid-range fairly quickly so my "dyno engine" shouldn't suffer in that regard.
The more common version is what you'd expect. All around good street engine.
Now I know that's dragging the chassis into it but it's been brought up in conversation here so I can address it in context.
So, in a nutshell, I've got those two choices. Build a bomb that's more suited to the track and adapt it accordingly to something other than that. Or do like I've done in the past and build something that has nice manners, decent and respectable (or at least what used to be respectable because there's always that turbo guy now ready to kick ass) but just misses the mark performance-wise because of the compromise.
Anyway, that was a long one. Maybe not part of the thread's title but then again it's my thread...
Thanks and keep it coming.
By the way, I'll be doing computer simulations on all of this. With more cam recommendations than I can count.

[Old School]

My 383 combo I ran last year
Dart 178cc cast iron heads 1.81" pinch
SFT comp oval cam 235-242 @ 0.050"
500" lift 106 ICL 106 LSA
10.6 compression
Stock airgap
950 hp holley
1.94"Intake valve
1.5" Exhaust valve
261 cfm @ 550"
3650 pound streeter 11.71 @ 114.51 mph
1.57 in the 60ft radial tyre.
Ran best et and mph with as cast Vic jnr
2 tenths and 2 mph slower with airgap.
Shift points 6000rpm
Finish line 6300 rpm
After 12 months on track testing, cam timing, lash loops, timing curves and high speed retard and advance testing, 3 x different carbs, different headers and exhaust system, different shift points 5800-7000 rpm, I came to the conclusion that the pushrod pinch was holding it back, also tested 2 x different converters 8" 5600 stall was better than 9"4000stall
The best gain was changing to single plane intake also tried different spacers 1",2" tapered, 4 hole tappered.
What heads are you going to use as in size, what valve combination, what application??
If I was doing this type of combination again I would work for average CSA of 2" and around 185-190cc, run a single plane intake that is complemented with the heads meaning entire intake tract sizing and if using a 230ish cam look at getting as much valve lift as possible, are you porting heads and intake manifold yourself??
How would you approach the sizing of the intake tract from plenum /runner entry down to throat size for your application??
Alot of questions if you want a lot of answers

Just curious as to the results of some of your tests. For example how much difference in et did you find moving the cam around, the different headers, etc. Thanks Billy

[raynorshine]

Let's see if I can address these replies without all the quotes.
First off Paul, thanks for the "do what I think is best and enjoy it" props. This is all part of it and I enjoy this too.
Now for some clarity.
Orr has been watching me go back and forth on this build for some time. In the time it's taken to get this far many have gone racing. Or cruised across the country. Or commuted everyday. But I'm in no hurry and really like hearing and engaging with all that contribute.
So I'll put down a specification of sorts. This is an engine. No chassis. No prerequisite to being able to use it as a daily driver, cross country cruiser or dedicated race car. Really what I'm doing here is building an engine with parts that I have. Heads (the key component here), an intake and a general platform that being Gen 1 SBC. I have several examples from which to draw. It was pointed out that this has been done for decades. But there's always a twist. And the twist is what has peaked my interest.
If I build in the direction I'm thinking, I may exclude myself from having that daily driver or driving 2500 miles in one go. That part I'm unsure of, but given my experiences, I can make something somewhat untenable into something less so. But I may get something I haven't had in a while and that's a track performer. But that's so easy now. Put a single turbo on your 5.3 and have your cake and eat it too (right Orr?) But I'm stuck in the old school for a least one more go around. So NA it is.
So here's the deal. Make the best engine package out of the parts I have and the future shortblock. By best I'm taking about a dyno engine. Use the heads to their fullest, compliment with the right cam and go.
But I've found that there is more than one approach and this is really what I'm working through. Build to an RPM the heads will support and cam it to suit the CR and that RPM. That's the traditional method. Or use the benefit of the small head's characteristics (as in mid-lift, lower RPM capabilities) and make something more aggressive with more cam than you might think. One particular example of that has stood out and I'm pursuing that possibility
I'd say that even the most intense version of this wouldn't be something unreasonable on the street. Cams I'm looking at are in the low 70 to upper mid 70's overlap. I've worked with that before in a 355 inch. Even got decent fuel consumption out of it. So I'm confident I can make it work with larger cubes too. Lazy down low is subjective but I think a general definition might be one that says leaving a stoplight under normal acceleration leaves something to be desired. I can say that the stall converter I have now gets me into the mid-range fairly quickly so my "dyno engine" shouldn't suffer in that regard.
The more common version is what you'd expect. All around good street engine.
Now I know that's dragging the chassis into it but it's been brought up in conversation here so I can address it in context.
So, in a nutshell, I've got those two choices. Build a bomb that's more suited to the track and adapt it accordingly to something other than that. Or do like I've done in the past and build something that has nice manners, decent and respectable (or at least what used to be respectable because there's always that turbo guy now ready to kick ass) but just misses the mark performance-wise because of the compromise.
Anyway, that was a long one. Maybe not part of the thread's title but then again it's my thread...
Thanks and keep it coming.
By the way, I'll be doing computer simulations on all of this. With more cam recommendations than I can count.

Skinny: what do your computer sims recommend for duration at .050"...6000 RPM redline...3.75" stroke...? (intake specifically)

-i feel 240 degrees is excessive not many small-block tow-trucks have 240 intake degrees duration..

[steve cowan]

My 383 combo I ran last year
Dart 178cc cast iron heads 1.81" pinch
SFT comp oval cam 235-242 @ 0.050"
500" lift 106 ICL 106 LSA
10.6 compression
Stock airgap
950 hp holley
1.94"Intake valve
1.5" Exhaust valve
261 cfm @ 550"
3650 pound streeter 11.71 @ 114.51 mph
1.57 in the 60ft radial tyre.
Ran best et and mph with as cast Vic jnr
2 tenths and 2 mph slower with airgap.
Shift points 6000rpm
Finish line 6300 rpm
After 12 months on track testing, cam timing, lash loops, timing curves and high speed retard and advance testing, 3 x different carbs, different headers and exhaust system, different shift points 5800-7000 rpm, I came to the conclusion that the pushrod pinch was holding it back, also tested 2 x different converters 8" 5600 stall was better than 9"4000stall
The best gain was changing to single plane intake also tried different spacers 1",2" tapered, 4 hole tappered.
What heads are you going to use as in size, what valve combination, what application??
If I was doing this type of combination again I would work for average CSA of 2" and around 185-190cc, run a single plane intake that is complemented with the heads meaning entire intake tract sizing and if using a 230ish cam look at getting as much valve lift as possible, are you porting heads and intake manifold yourself??
How would you approach the sizing of the intake tract from plenum /runner entry down to throat size for your application??
Alot of questions if you want a lot of answers

Just curious as to the results of some of your tests. For example how much difference in et did you find moving the cam around, the different headers, etc. Thanks Billy

Billy,
This is the point I was sort of trying to make that all that track testing netted next to zero, I collect weather data as well from my
Weather stations (2) to try and get some sort of trend, and because of track and different weather conditions as the year moved on its difficult, I would look at mph mainly and over 12 months picked up 3 x mph.if the Port shape and size are not set up correctly for the application you are sort of governed to a limit, 6000 rpm was it and the car stopped accelerating even if I turned to 7000 rpm on 2-3 gearshift, if the intake tract from plenum to throat is set for cubic inchs, rpm etc, I think engine would see better responses for better or worse.
This is why I am jealous of guys who have access to dyno and understand how to use it to there advantage.
Basically I am saying I don't have a proper answer for you unfortunately but I learned a couple of things for myself that I had been told about by a couple of smart people but had to learn for myself, that's why I posted what I would do differently if I chose that combination again , apologies for long post.

[Old School]

My 383 combo I ran last year
Dart 178cc cast iron heads 1.81" pinch
SFT comp oval cam 235-242 @ 0.050"
500" lift 106 ICL 106 LSA
10.6 compression
Stock airgap
950 hp holley
1.94"Intake valve
1.5" Exhaust valve
261 cfm @ 550"
3650 pound streeter 11.71 @ 114.51 mph
1.57 in the 60ft radial tyre.
Ran best et and mph with as cast Vic jnr
2 tenths and 2 mph slower with airgap.
Shift points 6000rpm
Finish line 6300 rpm
After 12 months on track testing, cam timing, lash loops, timing curves and high speed retard and advance testing, 3 x different carbs, different headers and exhaust system, different shift points 5800-7000 rpm, I came to the conclusion that the pushrod pinch was holding it back, also tested 2 x different converters 8" 5600 stall was better than 9"4000stall
The best gain was changing to single plane intake also tried different spacers 1",2" tapered, 4 hole tappered.
What heads are you going to use as in size, what valve combination, what application??
If I was doing this type of combination again I would work for average CSA of 2" and around 185-190cc, run a single plane intake that is complemented with the heads meaning entire intake tract sizing and if using a 230ish cam look at getting as much valve lift as possible, are you porting heads and intake manifold yourself??
How would you approach the sizing of the intake tract from plenum /runner entry down to throat size for your application??
Alot of questions if you want a lot of answers

Just curious as to the results of some of your tests. For example how much difference in et did you find moving the cam around, the different headers, etc. Thanks Billy

Billy,
This is the point I was sort of trying to make that all that track testing netted next to zero, I collect weather data as well from my
Weather stations (2) to try and get some sort of trend, and because of track and different weather conditions as the year moved on its difficult, I would look at mph mainly and over 12 months picked up 3 x mph.if the Port shape and size are not set up correctly for the application you are sort of governed to a limit, 6000 rpm was it and the car stopped accelerating even if I turned to 7000 rpm on 2-3 gearshift, if the intake tract from plenum to throat is set for cubic inchs, rpm etc, I think engine would see better responses for better or worse.
This is why I am jealous of guys who have access to dyno and understand how to use it to there advantage.
Basically I am saying I don't have a proper answer for you unfortunately but I learned a couple of things for myself that I had been told about by a couple of smart people but had to learn for myself, that's why I posted what I would do differently if I chose that combination again , apologies for long post.

Thanks for the reply and apologizes to sort of taking the original thread hostage. I did everything you did forty years ago and I got the same results. Once a combination is sorted out with somewhat matching parts it is very hard to find very much et. I think your combination ran very good and was a good choice of parts, much like what the original poster was wanting to do. Again, sorry to derail the thread.

[steve cowan]

Just curious as to the results of some of your tests. For example how much difference in et did you find moving the cam around, the different headers, etc. Thanks Billy

Billy,
This is the point I was sort of trying to make that all that track testing netted next to zero, I collect weather data as well from my
Weather stations (2) to try and get some sort of trend, and because of track and different weather conditions as the year moved on its difficult, I would look at mph mainly and over 12 months picked up 3 x mph.if the Port shape and size are not set up correctly for the application you are sort of governed to a limit, 6000 rpm was it and the car stopped accelerating even if I turned to 7000 rpm on 2-3 gearshift, if the intake tract from plenum to throat is set for cubic inchs, rpm etc, I think engine would see better responses for better or worse.
This is why I am jealous of guys who have access to dyno and understand how to use it to there advantage.
Basically I am saying I don't have a proper answer for you unfortunately but I learned a couple of things for myself that I had been told about by a couple of smart people but had to learn for myself, that's why I posted what I would do differently if I chose that combination again , apologies for long post.

Thanks for the reply and apologizes to sort of taking the original thread hostage. I did everything you did forty years ago and I got the same results. Once a combination is sorted out with somewhat matching parts it is very hard to find very much et. I think your combination ran very good and was a good choice of parts, much like what the original poster was wanting to do. Again, sorry to derail the thread.

I don't think op will mind to much as we are all trying to learn,
Damn Billy,wish I did what I am doing now 40 years ago, I might be a bit smarter lol
But I would of only being 9 years old,just reaching gas pedal with toes so to speak

[randy331]

But I would of only being 9 years old,just reaching gas pedal with toes so to speak

That would add some more variables to the testing ! LOL

Randy