question on delta stage 2 cam

[lostforawhile]

I was wondering if anyone is running a delta stage 2 cam? I talked to a representative from Delta today and he thinks with my dual Su's.long intake runners, ignition, long tube headers and 2 inch exhaust, that a stage 2 would be better suited to my needs, I believe he was thinking that a stage one wouldn't be able to take full advantage of the modifications, I was wondering about torque loss and power band, He said the power band started at 1800 to 2000 rpm, which isn't too bad, I had looked up information about them on line and I was impressed with the work they put into these cams. He quoted me about 54 bucks with core, which I already have. I'm also going to run an adjustable gear, any base setting with this cam from someone who has run one? I would assume with the stage 2 I would need the bisi springs? This car is finally starting to come together, my wife is trying to budget in the cost of getting the carbs overhauled.

[ecogabriel]

Where are you going to overhaul the carbs?

I am glad you are getting closer to fire her up.

[lostforawhile]

Where are you going to overhaul the carbs?

I am glad you are getting closer to fire her up.

I'm going to send them to Z therapy, I'm waiting on a quote, there is still a lot to do, but I think once I sink the money into the carbs, it will get me going again. I have to budget this in,they are rare carbs and very expensive to overhaul.

[ecogabriel]

I'm going to send them to Z therapy, I'm waiting on a quote, there is still a lot to do, but I think once I sink the money into the carbs, it will get me going again. I have to budget this in,they are rare carbs and very expensive to overhaul.

I recently cleaned up two bike carbs (Keihin) same as the SU. I just disassembled the bare minimum to get them cleaned. Bike fired right up ... my wife's friend could not believe it... well... women!

I do not fear those carbs, but calibration may be a bitch if they cannot be adjusted from the outside
The Stromberg I used to work with had a main jet adjustment right at the bottom so it was quite easy to get it running properly. Do they have external adjustment for the main jet, or you have to be careful on how you install the needle?

[lostforawhile]

I recently cleaned up two bike carbs (Keihin) same as the SU. I just disassembled the bare minimum to get them cleaned. Bike fired right up ... my wife's friend could not believe it... well... women!

I do not fear those carbs, but calibration may be a bitch if they cannot be adjusted from the outside
The Stromberg I used to work with had a main jet adjustment right at the bottom so it was quite easy to get it running properly. Do they have external adjustment for the main jet, or you have to be careful on how you install the needle?

they have no jets, the main reason I'm sending them off is Z therapy installs roller throttle bearings,and that fixes the vacuum leak issue, they also fix the sticking choke issue common to these. well if you can call it a choke. They are one of the few people who sell parts for these or work on them, there are some age issues that are hard to fix at home, they don't just throw some parts in, they recondition them back to factory new condition, once they have been overhauled they will run for decades with very little work,which can be done at home.

[ecogabriel]

Got the throttle bearings modification they do; they probably have to do some machining. or at least modified throttle shafts.

I called it "jet" because I do not know the name of the part where the needle works to provide a variable flow of gas according to throttle opening

I saw the place; they look quite knowing of what they do. The SUs in the main page remind me of the carburettors in early 1960s Morris (well, only one of them in those)
http://www.youtube.com/watch?v=ntUSsIJzUuE

[lostforawhile]

The big difference is the sealed bearings are proprietary parts, if I could find them I would do it myself,but if they screw up a carb body, they can grab another

[cygnus x-1]

I was wondering if anyone is running a delta stage 2 cam? I talked to a representative from Delta today and he thinks with my dual Su's.long intake runners, ignition, long tube headers and 2 inch exhaust, that a stage 2 would be better suited to my needs, I believe he was thinking that a stage one wouldn't be able to take full advantage of the modifications, I was wondering about torque loss and power band, He said the power band started at 1800 to 2000 rpm, which isn't too bad, I had looked up information about them on line and I was impressed with the work they put into these cams. He quoted me about 54 bucks with core, which I already have. I'm also going to run an adjustable gear, any base setting with this cam from someone who has run one? I would assume with the stage 2 I would need the bisi springs? This car is finally starting to come together, my wife is trying to budget in the cost of getting the carbs overhauled.

Which one is the stage 2? Is that the 272? Lots of people have used that cam and it seems to have a good reputation. However, the line about the power band starting at 2000RPM seems suspect for a stage 2 cam, at least compared to the other brands (Colt, Web, Bisi). The stage 2s generally don't start until about 3000RPM. I would also mention that I've done some simulations (yes I know, they're only simulations) comparing different cams (that I have actual measurements for) and the Delta 272 did not come out very well for low end torque. As I recall it did about the same as the Web stage 1. The stage 1 Colt triflow came out significantly better for low end torque than the Web and Delta. The Web and Delta did better at higher RPM ranges than the Colt though. I don't remember the numbers now, I would have to run the simulations again. What I do know, is that the lobes on the Colt are more aggressive in opening the valves (open at a faster rate) than the other two, which means that the Colt has less overlap. That I think is what makes it better at the low end than the others.

I can run the simulations again and graph the 3 cams against each other if you like. Is your head all stock or have you done any work to it? Still running the S&S header? How long is your intake setup from head ports to carb trumpet ends? Any idea what the flow rate on the carbs is or can you tell me the butterfly diameter?


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[lostforawhile]

Which one is the stage 2? Is that the 272? Lots of people have used that cam and it seems to have a good reputation. However, the line about the power band starting at 2000RPM seems suspect for a stage 2 cam, at least compared to the other brands (Colt, Web, Bisi). The stage 2s generally don't start until about 3000RPM. I would also mention that I've done some simulations (yes I know, they're only simulations) comparing different cams (that I have actual measurements for) and the Delta 272 did not come out very well for low end torque. As I recall it did about the same as the Web stage 1. The stage 1 Colt triflow came out significantly better for low end torque than the Web and Delta. The Web and Delta did better at higher RPM ranges than the Colt though. I don't remember the numbers now, I would have to run the simulations again. What I do know, is that the lobes on the Colt are more aggressive in opening the valves (open at a faster rate) than the other two, which means that the Colt has less overlap. That I think is what makes it better at the low end than the others.

I can run the simulations again and graph the 3 cams against each other if you like. Is your head all stock or have you done any work to it? Still running the S&S header? How long is your intake setup from head ports to carb trumpet ends? Any idea what the flow rate on the carbs is or can you tell me the butterfly diameter?


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if you can guestimate the intake runners the carb openings are about 6 inches from the firewall, with aircleaners, the carb butterflys are 38 mm, I'm running the S@S header, the head is stock now, but I may do some work to it, the exhaust has no cat and it's all mandrel bend from the headers back, and the muffler is a straight through design, I have pictures of the muffler in the header thread if you haven't seen it yet. , you might want to estimate the exhaust as 2 1/2 or 2 1/4 as there are no restrictions at all,as far as bends. I believe a standard crimped system is worth a 1/2 less in pipe diameter or something like that. It depends on if your program asks. the intake should be pretty unrestricted, it looks like it has some odd areas if you look at it from the outside, but I blended the intake passages pretty good on the inside.

[cygnus x-1]

if you can guestimate the intake runners the carb openings are about 6 inches from the firewall, with aircleaners, the carb butterflys are 38 mm, I'm running the S@S header, the head is stock now, but I may do some work to it, the exhaust has no cat and it's all mandrel bend from the headers back, and the muffler is a straight through design, I have pictures of the muffler in the header thread if you haven't seen it yet. , you might want to estimate the exhaust as 2 1/2 or 2 1/4 as there are no restrictions at all,as far as bends. I believe a standard crimped system is worth a 1/2 less in pipe diameter or something like that. It depends on if your program asks. the intake should be pretty unrestricted, it looks like it has some odd areas if you look at it from the outside, but I blended the intake passages pretty good on the inside.

The exhaust system (behind the header) really doesn't factor into the model much at all. As long as it has enough flow capacity it really has very little effect, other than to send the exhaust gas to the back of the car and cut the noise. The intake runner length is actually far more important so if you can get a measurement for that it would make the numbers more accurate. On my Prelude the distance from head port to firewall is 16 inches, so 6 inches back from there would be 10 inches from carb inlet to head port. That would put the total intake tract length at 12.5 inches. I guess that's probably close enough to get an idea of how the cams compare to each other.

Alright, let me run the numbers and I'll post up the graphs later tonight.


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[cygnus x-1]

Before I post the graph I want to make it clear that this is only a simulation based on a crap ton of parameters about the A20A1 engine. Because it's just a simulation the actual numbers are not necessarily accurate, and will likely not match what you would get on a dyno. However it does illustrate the difference between the 3 camshafts with the same engine.

So here's what we came up with:






Overall the Colt pretty handily beats the other two for torque. Up to about 4000RPM the Delts kills the Web, but from there on up the Web has a slight edge. Notice though that after 5000RPM they all drop like a stone. This says that this particular engine is limited by air flow, specifically the carbs. The estimated air flow for two 38mm throttle plates is around 310CFM (calculated by the software), which as I recall is about what the Weber 38/38 is rated at. This is not necessarily a bad thing. If you don't plan to rev beyond 5000RPM very often then it doesn't really matter. But if you want to pretend you're engine is a B16 (and rev the crap out of it), then you really need some bigger carbs.

Just for the sake of comparison I upped the flow rate to what you would get with two 45mm throttle plates, like if you had a bigger 2 barrel carb (e.g. single Weber DCOE, or similar) rated at 420CFM. And then I tried with a twin Weber DCOE45 individual runner setup at 820CFM. Here is the Delta 272 with the three different intake types.






Notice how the original and the 420CFM are almost identical until 4000RPM, and then they diverge. That's the extra 100CFM kicking in. It's also interesting to look at the 820CFM individual runner setup. It has better low end torque than the others, falls a little in the midrange, but then stays really strong up to 6000RPM. The high end is due to the extra CFM, but the extra low end torque I think is due to tuning effects. This was with the "typical" settings for an individual runner setup though so I don't know what it's assuming for runner sizes.


This last one is all three cams with the twin DCOE45 individual runner setup (because IR setups are kind of the holy grail of intake systems).







Again, the Colt totally romps on the other two. Which I have to say I found really surprising when I started doing these simulations. I always considered the stage 1 Colt to be pretty conservative, but these results do match up to what I've observed on my own engine. It has really strong low end torque but then after about 5000RPM is kinda dies. I was really expecting the Web to be better, but clearly it's designed for mid to high RPM power. The Delta does have a pretty flat torque curve but it still loses to the Colt in terms of performance. What the Delta does have however is a competitive price. The Web is $240 and last I remember the Colt was damn near $200, maybe higher now (I think partly due to the weak US dollar against the Canadian back bacon).


Something else I should mention is that the program I'm using doesn't take into account the staggered lobes on the Colt. It only allows for one intake valve profile so I used the shorter one, which is 260* advertised duration, where the bigger lobe is 270*. I know Delta does have a 260 cam, which raises the question of whether or not that cam might be competitive with the Colt. I couldn't say without some direct measurements from a cam.


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[lostforawhile]

thanks for all the great info, I would say these carbs are closer to the webber 45s then to the 38s the design of the carbs allows much more airflow then a standard type of carb throat, no choke plate,jets etc in the way, when the piston lifts during full acceleration it's basically straight through with the needle in the middle, I wonder if anyone makes a program to simulate these, as the SU is a design all on it's own, remember the carb constantly adjusts itself depending on engine demand, it actually acts as a bigger or smaller carb, I will be glad to get this thing done and on a dyno just to see what it does.

[cygnus x-1]

thanks for all the great info, I would say these carbs are closer to the webber 45s then to the 38s the design of the carbs allows much more airflow then a standard type of carb throat, no choke plate,jets etc in the way, when the piston lifts during full acceleration it's basically straight through with the needle in the middle, I wonder if anyone makes a program to simulate these, as the SU is a design all on it's own, remember the carb constantly adjusts itself depending on engine demand, it actually acts as a bigger or smaller carb, I will be glad to get this thing done and on a dyno just to see what it does.

Actually that's true that a single 38mm SU would flow better than a 38mm Weber bore, because of the lack of a venturi. However, I calculated the flow rate based on a 38mm bore using the "slide valve" setting, which means that it assumes a venturi-less design, like your SU's. I also looked up the flow rate online and found this page:

http://www.mgbmga.com/tech/mgb19.htm

Down around the the middle is lists flow rates for the HS4 (38mm) and HS6 (44mm). The HS4 is listed at 142, so double that is 284. The software calculated the flow rate at 310CFM, which is pretty close so I used that.


Having said that, I do think these simulations run a bit on the low side for reported HP. There are a huge number of variables and some of them have to be estimated because there is no easy way to measure them. One big one is head flow. I tried to find some flow numbers for an A20 head but the only thing I could find is a *really* old 3geez post from "Sean" that claimed a flow rate of 190CFM. That might have included some head work too, it was hard to tell exactly. I do have plans to someday build a flow bench so I can test out some theories while I'm building my big valve head (that I've been working on forever). No idea when I'll actually get to it though. Lack of funding has been a serious problem lately, as I know you can relate.


Anyway, for the price it's pretty hard to beat the Delta. I wonder if they could do a custom grind to provided specs? My guess is they would need to make a new master profile, which could be expensive. I should look at the Colt more carefully and try to figure out exactly what makes it do so well in the simulations.

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[lostforawhile]

Actually that's true that a single 38mm SU would flow better than a 38mm Weber bore, because of the lack of a venturi. However, I calculated the flow rate based on a 38mm bore using the "slide valve" setting, which means that it assumes a venturi-less design, like your SU's. I also looked up the flow rate online and found this page:

http://www.mgbmga.com/tech/mgb19.htm

Down around the the middle is lists flow rates for the HS4 (38mm) and HS6 (44mm). The HS4 is listed at 142, so double that is 284. The software calculated the flow rate at 310CFM, which is pretty close so I used that.


Having said that, I do think these simulations run a bit on the low side for reported HP. There are a huge number of variables and some of them have to be estimated because there is no easy way to measure them. One big one is head flow. I tried to find some flow numbers for an A20 head but the only thing I could find is a *really* old 3geez post from "Sean" that claimed a flow rate of 190CFM. That might have included some head work too, it was hard to tell exactly. I do have plans to someday build a flow bench so I can test out some theories while I'm building my big valve head (that I've been working on forever). No idea when I'll actually get to it though. Lack of funding has been a serious problem lately, as I know you can relate.


Anyway, for the price it's pretty hard to beat the Delta. I wonder if they could do a custom grind to provided specs? My guess is they would need to make a new master profile, which could be expensive. I should look at the Colt more carefully and try to figure out exactly what makes it do so well in the simulations.

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all of their grinding is cnc, so I would assume they punch the numbers in the computer and it grinds the cam

[cygnus x-1]

all of their grinding is cnc, so I would assume they punch the numbers in the computer and it grinds the cam

Is it? That's not what the videos on their website show.

http://deltacam.com/camshaftgrinding.php?p=3

The video here shows them grinding a cam based on a master pattern. If they've upgraded their capabilities they should update their website too.

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[cygnus x-1]

And the fun continues. I found some measurements on the Delta 260 cam from a Preludepower user awhile back, and also dug up some measurements from a stock A20 carb cam. The results are quite interesting.







This is a little bit cluttered but I wanted to get all of them in one graph. First of all these are all assuming an induction system flow rate of 310 CFM, based on Lost's SU carbs. A Weber 38/38 would be similar with a bit of a drop at the upper RPMs. Same for a Weber 32/36 but with a bit more drop at upper RPMs.

Again looking at just the torque curves. The medium blue line is for the stock cam. It's pretty flat, which is good for a stock cam. Nice wide even power band. The light blue line is the Delta 260. Not really sure what the deal is with that one. Clearly it sucks. Hard. I've only ever heard of one person trying it, and maybe this is why. The others are the same as before but now you can see them next to the stock cam.

Overall the Colt still wins. The Delta 272 is a respectable second though. Fairly wide and smooth power band, and a significant improvement from the stock cam across the board. It loses a bit to the Web in the mid to high RPMs but hardly enough to matter. And it has better low end than the Web.

So for a budget cam upgrade I would say go with the Delta 272. Or if you're willing to save your pennies for awhile, go for the Colt.


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[lostforawhile]

And the fun continues. I found some measurements on the Delta 260 cam from a Preludepower user awhile back, and also dug up some measurements from a stock A20 carb cam. The results are quite interesting.







This is a little bit cluttered but I wanted to get all of them in one graph. First of all these are all assuming an induction system flow rate of 310 CFM, based on Lost's SU carbs. A Weber 38/38 would be similar with a bit of a drop at the upper RPMs. Same for a Weber 32/36 but with a bit more drop at upper RPMs.

Again looking at just the torque curves. The medium blue line is for the stock cam. It's pretty flat, which is good for a stock cam. Nice wide even power band. The light blue line is the Delta 260. Not really sure what the deal is with that one. Clearly it sucks. Hard. I've only ever heard of one person trying it, and maybe this is why. The others are the same as before but now you can see them next to the stock cam.

Overall the Colt still wins. The Delta 272 is a respectable second though. Fairly wide and smooth power band, and a significant improvement from the stock cam across the board. It loses a bit to the Web in the mid to high RPMs but hardly enough to matter. And it has better low end than the Web.

So for a budget cam upgrade I would say go with the Delta 272. Or if you're willing to save your pennies for awhile, go for the Colt.


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ok dumb question but the 272 is the stage 2 right? sorry lack of sleep all this week

[cygnus x-1]

I'm also going to run an adjustable gear, any base setting with this cam from someone who has run one? I would assume with the stage 2 I would need the bisi springs? This car is finally starting to come together, my wife is trying to budget in the cost of getting the carbs overhauled.

The adjustable cam pulley I would say is mostly optional. The only effect it will have is to shift the power band slightly, towards lower RPMs by advancing the cam, and towards higher RPMs by retarding it. I've tried adjusting this as well in simulations and it doesn't make a big difference. You can pick up a couple lb-ft at the low end by advancing the cam and lose almost nothing at the top, but that's about it. The adjustable pulley is more useful if you've milled the head and need to correct the cam timing because of it.

You don't really need the Bisi springs either unless you plan to rev it beyond the stock red line. Stock springs are fine.

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[lostforawhile]

The adjustable cam pulley I would say is mostly optional. The only effect it will have is to shift the power band slightly, towards lower RPMs by advancing the cam, and towards higher RPMs by retarding it. I've tried adjusting this as well in simulations and it doesn't make a big difference. You can pick up a couple lb-ft at the low end by advancing the cam and lose almost nothing at the top, but that's about it. The adjustable pulley is more useful if you've milled the head and need to correct the cam timing because of it.

You don't really need the Bisi springs either unless you plan to rev it beyond the stock red line. Stock springs are fine.

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I have the chance to buy one of the gears for 50 bucks from someone on here,so the price wasn't too bad.

[cygnus x-1]

ok dumb question but the 272 is the stage 2 right? sorry lack of sleep all this week

I would assume so, but that would be something to ask Delta. I've always heard it called the 272 (the advertised duration) so I'm sticking with that.

I have the chance to buy one of the gears for 50 bucks from someone on here,so the price wasn't too bad.

That's a pretty good deal. Worth getting I think. This would allow you to advance the cam and try to eek out some more torque.

I've been studying the cam profiles some more, and it looks like (and this is somewhat speculative) the Colt does better than the Delta272 (and the others) because it closes the intake valve sooner and faster than the Delta. This would increase the dynamic compression ratio, meaning you retain more charge in the cylinder during compression. The Colt also starts opening the intake valve fairly early and really slams it open quickly, which I think is good considering these engines have a short rod/stroke ratio, meaning the intake suction starts very soon after TDC and is very strong. Slamming the valve open takes advantage of this. The Delta opens the intake quickly as well but starts a little later so it loses a bit. I think shifting the lobe separation 2 degrees closer on the Delta272 would make up for the late closing and take more advantage of the early cylinder filling.

That's my theory anyway.

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[Tdurr]

You know too much.

Lol I'm loving this thread tho.

[lostforawhile]

this thread ought to be a sticky this is really great info with the charts

[cygnus x-1]

You know too much.

Lol I'm loving this thread tho.

I spend WAY too much time researching this stuff. It's fun to learn about it though so I keep doing it. I just wish had the money to do real dyno testing to back up the simulations. Models and simulations are nice to get you going in the right direction but they're no substitute for real world testing.

It's weird though, the more you get into this stuff, the more you find out you don't really know what you thought you did. When I read stuff by guys like Larry Widmer of Endyn and David Vizard, it blows me away how much information those guys have stored in their brains.

this thread ought to be a sticky this is really great info with the charts

I like graphs. They make comparing things so much easier. I also like making sense out of things that don't make sense. Choosing cams always seems like black magic, and that bugs me.

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