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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
OK. Here we go. Target for this is before the racing season ends here in the fall of 2020.
Nothing particularly special about the short block. .030" over Gen1, forged crank and rods (6"), 15cc D-dish forged piston. 9.8:1 CR with a .040" piston to head clearance. The heads are unusual in that they're small for a 383 at about 175cc port volume, 255 CFM @ max lift of ~ .550". They're relatively fresh from the porting shop. Sadly they're iron but I have them and that's that.
The hydraulic roller cam is the deal here.
Plenty of information out there about what typically works best for this size of engine. A 195cc port is standard stuff. Higher RPM engines move up in volume.
This lump will be limited to about a 6000-6200 shift point and will work towards making peak HP at or just below 6000.
The requirement of this cam is to produce the most torque possible at the RPMs it'll operate in. That would be, given the current platform it'll drop into is 3500-6000 for drag racing. That'll tighten up closer to 4500-6000 but that's still a better converter spec away. Open road events would also fall within that RPM range. As for cruising on the highway, converter locked at 75 MPH will see around 2500. I'm not too concerned about idle quality as I've managed to tune around some difficult combinations so I'm trusting that I can continue in that regard.
I've solicited recommendations from Mike Jones and Bullet Cams. I've also gone through various builds through the likes of Vizard (no surprise there from some reading this) and the results are all over the map. Different LSAs, ICLs. Overlap is similarly spread out between 70 to just north of 80 degrees. One thing that did stand out was the resulting DCR from the spec 9.8 static compression ratio. All within half a point with the exception of one cam too small and another oddball I threw in the mix (because I have that cam on the shelf).
The following is a spread sheet I've compiled.
If you've anything to share or built something similar and have cam specs I'll expand on the list. At some point, I intend to run a pile of simulations to see how the curves vary with respect to changes in cam profiles.
I'm open to discussion.
Assuming 2.02 valve, 6000-6200 shift point should only need a 278/280 advertised, 226/227 at .050, .363/.353 lobes, .572/.555 with 1.6 rockers. 107 icl 111 ecl 109 lsa
vizzards cams are super aggressive by those advertised vs .050 numbers but the lobe lift is low. Small cam seems better, large is way wrong
bullet im surprised would be that large for a small head
Jones as well, thats a pretty large duration for that motor goals and rpm, buts it closer to the cam i had in my 383 with afr 195’s. But it peaked 6300 and pulled to 6800
its true a restricted head would need more duration to get more out of it power wise.
out of all of them, i like the custom xfi 224/230 on a 106-109 lsa. 4 deg adv. cant go wrong there
Pump gas or racing fuel?
Based mostly on your DCR, #1 choice is the Custom XFI, #2 is Vizard LG. Is there a Vizard MEDIUM?
There is nothing wrong with your 175cc heads because they can flow the amount needed.
Just my opinion.
Too bad Rhoads does not offer a V-MAX retro-fit hydraulic roller lifter.
The Wallace Calculator for figuring the cross sectional area of intake ports with no choke point from RPM says:
Your RPM of 6200 and Bore of 4.030 and Stroke of 3.75 is a Cross Sectional Area of 2.17 Square Inches. http://wallaceracing.com/chokepoint-rpm.php
Last edited by NoEmissions84TA; 12-27-2019 at 05:25 PM.
2.02 and 1.6. Exhaust flowed 176 @ .500 and 180 at .600
Assuming 2.02 valve, 6000-6200 shift point should only need a 278/280 advertised, 226/227 at .050, .363/.353 lobes, .572/.555 with 1.6 rockers. 107 icl 111 ecl 109 lsa
vizzards cams are super aggressive by those advertised vs .050 numbers but the lobe lift is low. Small cam seems better, large is way wrong
In all fairness to Vizards specs, he chose a flat tappet for his tests. But I find his profiles to be slow. His 288/244 while the XR288HR is 288/236.
bullet im surprised would be that large for a small head
Bullet liked the XR288 as they requested what the current build was. Suggested that if I add more gear, there suggestion might be better suited. Onterestingly, in one of the small headed 383 tests, the 288 was a cam selected and gave promising results.
Jones as well, thats a pretty large duration for that motor goals and rpm, buts it closer to the cam i had in my 383 with afr 195’s. But it peaked 6300 and pulled to 6800
Jones' cam confused me the most. He's a guy that I believe likes to spec a tighter LSA but then this 110 comes along. I'm sure with greater detail, that spec would change.
its true a restricted head would need more duration to get more out of it power wise.
I'm kind of working on that premise. The small heads help cylinder filling at lower RPMs and gain back what would be lost with the lower compression and larger cam. Or so say the dyno results anyway.
out of all of them, i like the custom xfi 224/230 on a 106-109 lsa. 4 deg adv. cant go wrong there
That's interesting.
Originally Posted by NoEmissions84TA
Pump gas or racing fuel?
Pump gas and while 94 is available here, I'm a little weary of being on the detonation edge. Hence the dialed back SCR.
Based mostly on your DCR, #1 choice is the Custom XFI, #2 is Vizard LG. Is there a Vizard MEDIUM?
Going back to the pump gas, I've run 8:1 DCR (and more) with some success. A Vizard medium would probably be less on the LSA while keeping the overlap where I'm comfortable. That would be mid to low 70's.
There is nothing wrong with your 175cc heads because they can flow the amount needed. Just my opinion.
They'e just somewhat outside the norm for the cubes involved although at my rpm limit, I think too that they're capable.
Too bad Rhoads does not offer a V-MAX retro-fit hydraulic roller lifter.
Too outside the box for me.
Not sure if the above format works or not. I may have to edit all of this later.
What intake manifold? Of the cams listed, I'd lean toward either the small vizard, or the xfi to achieve your goal. If there was something similar to the vizard, with a bit more lift to go with your heads, that may be the way to go.
Of the cams listed, I'd lean toward either the small vizard, or the xfi to achieve your goal.
I can see where this is going. That's another vote for a cam that's giving back some of the lost compression. I can't say I disagree.
If there was something similar to the vizard, with a bit more lift to go with your heads, that may be the way to go.
And that's where this is going. I'm building a spec and I've always been short on duration but large on lift. It's just hard on parts. It's why a roller cam is superior to a flat tappet in my view. Part of the spec includes plenty of highway driving. But I'm sure what comes out of this will be a blend of what's on display here.
I'll sort through the suggestions. And find a couple more examples from what works with this combination.
I think overall the Vizard listed cams are taking direct aim at the small port volume. In the text that accompanies the testing the thinking is that the small head has better velocity than a large port with the same flow values. Makes sense. Less space. Gotta move faster for the same volume/time. The greater velocity aids in cylinder filling at the targeted low lift and low RPMs. Then, as suggested by Orr, the bigger cam ( lift and duration) helps the top end fill until it simply runs out of breath. Hence my ~6000 top end speed.
As for a couple of the larger cams, seems to me they're trying to keep the valve open as long as possible to make up for the lack of flow (not taking velocity in consideration) when compared to something like the AFR 195s.
The Wallace Calculator for figuring the cross sectional area of intake ports with no choke point from RPM says:
Your RPM of 6200 and Bore of 4.030 and Stroke of 3.75 is a Cross Sectional Area of 2.17 Square Inches. http://wallaceracing.com/chokepoint-rpm.php
Wish there was an easy way for me to get that cross section value. I had hoped that my shortblock would be ready and cam in hand without having the car in pieces and immobile for any length of time. Rather, it's looking like pulling it apart first might be the order of the day.
Here's a few more to check out.
I've added Orr's 383 cam, took the Custom XFI and tightened up the LSA to 106 and added a hybrid. It's probably plain to see I'm looking hard at the tighter LSA.
Looking at it, maybe relaxing the spread on the XFI would be of some benefit. I feel the DCR of 8.22 might be a little aggressive for everyday driving and pump gas.
EDIT: An LSA of 108 on the XFI puts the overlap to 62 and the DCR to 8.11.
Not enough overlap is my thinking here.
Take a look at the Howards 110525. It’s 280/286 adv and 227/233 @.050” with 0.373” lobe lift on the intake and exhaust. I’m using it in my 383 with AFR 195s and an RPM Air Gap, and the specs are similar to what you’re looking at with a little more lift. Mine is 110/106, but a 106/104 may get you where you want to be with overlap while still keeping DCR around 8.
The engine is still being built, or I could give you some better feedback on it.
Wish there was an easy way for me to get that cross section value. I had hoped that my shortblock would be ready and cam in hand without having the car in pieces and immobile for any length of time. Rather, it's looking like pulling it apart first might be the order of the day.
You just need to measure the intake port(s) at the pushrod pinch point (L x W) and hope you have at least 2.17 sq/in.
Here's a few more to check out.
I've added Orr's 383 cam, took the Custom XFI and tightened up the LSA to 106 and added a hybrid. It's probably plain to see I'm looking hard at the tighter LSA.
Looking at it, maybe relaxing the spread on the XFI would be of some benefit. I feel the DCR of 8.22 might be a little aggressive for everyday driving and pump gas.
EDIT: An LSA of 108 on the XFI puts the overlap to 62 and the DCR to 8.11.
Not enough overlap is my thinking here.
Why do you think you need overlap? I agree with the rest you said. Shoot for 8.0:1 DCR.
Take a look at the Howards 110525. It’s 280/286 adv and 227/233 @.050” with 0.373” lobe lift on the intake and exhaust. I’m using it in my 383 with AFR 195s and an RPM Air Gap, and the specs are similar to what you’re looking at with a little more lift. Mine is 110/106, but a 106/104 may get you where you want to be with overlap while still keeping DCR around 8.
I had totally forgotten about Howard's. I remember them as having some interesting grinds. Thanks. I'll check that out.
Originally Posted by NoEmissions84TA
You just need to measure the intake port(s) at the pushrod pinch point (L x W) and hope you have at least 2.17 sq/in.
Well, I guess that's just an intake manifold away. That said, if it's coming off, I really owe it to myself to check these heads. While they're kind of fresh, I'd be pissed if I planned a build around them and then find out they need servicing. I've WAY too much invested in these things and they're not going to get another life. Not from me anyway. I'll go straight to some aluminium replacements and cut my losses.
given the exhaust flow numbers
i suggest a 278/290, 226/234. .363/.353 lobe. .572/.555 with 1.6 rocker. 109 lsa 107 icl
advanced induction had a cam like this for their lt1 builds.
i think of this like those lt1’s. Guys add big duration to stock heads and make few extra ponies up top, but hold onto those ponies longer, and suffer abit of bottom end and drivability. The medium duration cams do not hurt bottom as much and dont give up Much to the bigger cams up top. Win win
xfi lobes in the 226/232 or 226/234 or even 226/236 wouldnt be to far off. Given a 5800 peak, hold few hundred rpm for shift
6000 rpm peak, add 5-6 degs to both. Jones cam makes sense here at 232/240 or so
The “best” cam will typically be the one with the tightest lobe spread, fastest rate of rise, least duration, and most lift that meets the end user’s particular application and desired goals. The combination of those will vary GREATLY to meet the needs and intended use of a particular engine AND car combination.
To arrive at “the best” there are factors to consider for any given build and desired result. You’ve given a number of the parameters needed but other critical parameters needed are:
Weight of car
Rear gear ratio
Transmission (to determine ratios and recovery rpm for best power under the curve)
Stall speed of converter
Header primary diameter and length
Collector length and diameter
Exhaust system: Y-pipe diameter into single diameter or dual diameter, brand and size of muffler (part number if known)
Desired vacuum - you said you didn't really care about the idle and could manage, but giving a number in inches or a combo you ran before that was marginal would be helpful
In general, a really good flowing exhaust system is needed to prevent lower rpm peaks and nulls with the tight lobe spreads – seen it numerous times. Tight lobe spreads with any decent overlap are more sensitive to the primary header length also.
Even if you have a killer exhaust system as small as your heads are I can tell you 106 is probably going to be too tight. Generally speaking if the heads are on the small size for the desired results (best average power for a 383 between 3500-6000) and you haven’t already taking that into consideration, you’re going to need to increase duration and widen the lobe spread from whatever optimal you’re considering.
Why do you think you need overlap? I agree with the rest you said. Shoot for 8.0:1 DCR.
Of the many parameters to consider when doing what I'm trying to do, selecting the overlap, I've learned, is at the top of the list. Followed by the LSA, advance/retard setting, lift and finally duration. Interestingly most people back into the overlap by virtue of choosing duration and an LSA they think is correct.
So, as far as overlap is concerned, for my application, (and I can't stress the my part enough because this is where the input from others doesn't necessarily agree with my objective), I want enough to be able to take advantage of the exhaust scavenging that comes along with it. I can't give away "street manners" entirely however so I'm looking for that balance. I've learned that an overlap of 70° is very tuneable and given the right exhaust, is in that range where scavenging becomes possible. My serious racing efforts will be through open headers. Street-wise, the effect won't be as pronounced with the full exhaust but that won't be much different than what I've experienced in the past.
So, overlap first.
The majority of the cams listed have overlap in the 70's. But adding 4° is more than just increasing the duration because along with it comes increased lift so the effect is amplified. Overlap also determines, given a certain CID and cylinder head, how far into the rev range an engine starts to perform. Or rather, at which point down in the rev range, that an engine doesn't. Witness the engine with with a far too big a cam. Bets are, along with those big duration numbers, is also a large overlap. And that's where the driveability goes down the toilet.
I'm going to work around the 70° mark and progress from there.
given the exhaust flow numbers
i suggest a 278/290, 226/234. .363/.353 lobe. .572/.555 with 1.6 rocker. 109 lsa 107 icl
advanced induction had a cam like this for their lt1 builds.
i think of this like those lt1’s. Guys add big duration to stock heads and make few extra ponies up top, but hold onto those ponies longer, and suffer abit of bottom end and drivability. The medium duration cams do not hurt bottom as much and dont give up Much to the bigger cams up top. Win win
xfi lobes in the 226/232 or 226/234 or even 226/236 wouldnt be to far off. Given a 5800 peak, hold few hundred rpm for shift
6000 rpm peak, add 5-6 degs to both. Jones cam makes sense here at 232/240 or so
There's a pattern emerging here. I'll going to compile another short list of the latest proposals and amendments. I do have a few parameters that I'm going to keep at the front of the selection process, namely overlap and LSA, but the overall spec is starting to take shape..
The “best” cam will typically be the one with the tightest lobe spread, fastest rate of rise, least duration, and most lift that meets the end user’s particular application and desired goals. The combination of those will vary GREATLY to meet the needs and intended use of a particular engine AND car combination.
I agree. And I can't stress enough the importance of the particular engine part.
To arrive at “the best” there are factors to consider for any given build and desired result. You’ve given a number of the parameters needed but other critical parameters needed are:
Weight of car
Rear gear ratio
Transmission (to determine ratios and recovery rpm for best power under the curve)
Stall speed of converter
Header primary diameter and length
Collector length and diameter
Exhaust system: Y-pipe diameter into single diameter or dual diameter, brand and size of muffler (part number if known)
This is a good time to point that this isn't an all out drag racing effort. If it were, I'd be doing something different altogether. This is more of an exercise in spec'ing a cam that suits my target. Drag racing is just a part of it. So is driving across the country. And there's an open road event or two I'd like to try my hand at. At one time, I had my complete vehicle spec listed in my signature but I've since dropped the sig as it appeared to get posted "ad nauseam" and was too wordy for that.
In the meantime I'm more or less looking for the most torque at a given RPM. The rest will play out.
FWIW, if this 383 performs as I expect it to, it'll play into the chassis combination and become better sorted with respect to gearing and stall from the increased power output alone.
Desired vacuum - you said you didn't really care about the idle and could manage, but giving a number in inches or a combo you ran before that was marginal would be helpful
As for the desired vacuum, 71° overlap with the XR288HR (on a 102 ICL) in a very tired and worn out 355, produced around 10.5" of idle vacuum at 850 RPM. That was with nearly 30° of idle advance as well. That was on the edge of power brake assist. I can work with that going forward. A fresh shortblock is going to do wonders for the idle quality and the increased displacement is going to eat up some of that overlap as well. Idle is bound to improve with just the addition of the fresh parts.
In general, a really good flowing exhaust system is needed to prevent lower rpm peaks and nulls with the tight lobe spreads – seen it numerous times. Tight lobe spreads with any decent overlap are more sensitive to the primary header length also.
Serious track days will see the headers uncorked.
Even if you have a killer exhaust system as small as your heads are I can tell you 106 is probably going to be too tight. Generally speaking if the heads are on the small size for the desired results (best average power for a 383 between 3500-6000) and you haven’t already taking that into consideration, you’re going to need to increase duration and widen the lobe spread from whatever optimal you’re considering.
I'm targeting overlap first. That'll determine where the engine will start to perform or perhaps better stated, the point below which it doesn't. This doesn't include the idle RPMs or the highway cruise. 3500-6000 is right and what worked for the 350 will be small in comparison to a 383. The bigger engine needs more flow through area. I'm looking at the cams with 70-75°.
The LSA, which is what I'm hunting down next, is based on the cubes and port flow. Particularly flow just off the seat. (A big valve helps here). What I am including in this choice is the empirical data collected and seeing what works best when compared to something similar to what I'm putting together. 106 seems to be the number. With really goods heads (and maybe a 2.05 valve vs the 2.02), and you can open that up a little.
Then will come the ICL and related valve events.
All the lift I can manage.
Duration then, will have been determined.
When I started this, I approached a couple of cam suppliers and gave the car specs and such. Because of that, I think their choices are a little skewed thinking that I need something based on that car info rather than just giving the cam that best suits the engine's needs. The car will come later if it has to catch up.
This is Ai's 225/235 on a 110 lsa cam card as an example. I ran it on a 350. They advertise their lobes as being very valvetrain friendly. Their 230/238 on maybe a 108, would fit your needs perfectly, imo.
I’ve swapped numerous cams and tuned carbs in hundreds of cars over the years and have been using simulation software for close to 30yrs of that time. I played around a little with the simulation, plugging in my best guess on unknown factors. For what it’s worth, assuming you have 986 Comp valve springs with an installed height of at least 1.72”, I ended up thinking that a custom XFI grind on a 110 spread with a 106 ICL would be a good choice. Aside from the more aggressive lobe profile this is close to Mike Jone’s recommendation, which I believe is at the top of his profession based on recommendations I’ve seen him make on SpeedTalk.
That’s not a lot different from your current HR288 3316 – 288 – 236 – 157 - .347 .089 .075 .521 3317 – 294 – 242 – 164 - .360 .101 .086 .540
In fact, the simulation estimated peak TQ would only be down 3lb/ft and the average (from 3500 – 6008) TQ down 2. The peak HP would be the same and average HP would only be down 2. That’s not significant and probably wouldn’t be worth the money since you already have the XR288. The custom grind would give slightly better vacuum and off idle response but if you were OK with the XR288 in the 355, then you should be more than happy with it in the 383.
What simulation software do you have? If it’s decent, you should be able to run these cams through it and have a pretty good idea what will work and what won’t for you (like that XFI 224/230 - 106).
I'll look into that. I also have a current edition of COMPs Master Lobe Index. Very insightful in that you can compare and old school Magnum profile to an Xtreme Energy to an XFI. Interesting stuff.
Originally Posted by GTA matt
This is Ai's 225/235 on a 110 lsa cam card as an example. I ran it on a 350. They advertise their lobes as being very valvetrain friendly. Their 230/238 on maybe a 108, would fit your needs perfectly, imo.
I'll try and work out the advertised specs for that. AI says valvetrain friendly so that'll be a good reference when compared to some of the other profiles. As an example, I'm not sure the XFI lobes can be described as such. That cam was the noisiest of the lot I've pushed through the old 350.
Originally Posted by BadSS
I ended up thinking that a custom XFI grind on a 110 spread with a 106 ICL would be a good choice. Aside from the more aggressive lobe profile this is close to Mike Jone’s recommendation, which I believe is at the top of his profession based on recommendations I’ve seen him make on SpeedTalk.
What simulation software do you have? If it’s decent, you should be able to run these cams through it and have a pretty good idea what will work and what won’t for you (like that XFI 224/230 - 106).
The reason I contacted Jones is because of that reputation. His offering stands out among the others but I'm not so sure that's it's in a good way for my purposes. I've participated in the Speed Talk forums many times over the years. One thing I can say, is that there always seems to be that one guy that turns the thread into a pissing match and it kind of ruins the whole thing. I tend more to observe that interact these days.
I've an old DynoSim (and DragSim) program that I've worked with for a decade or so (maybe 20 years!). I find that the results are often difficult to accept in that they seem to go against the science. One thing that I'll do is to try an establish a proven baseline. Take a validated dyno graph from a similar build and try and recreate it in DynoSim. There are so many variables to move the curves that it's sometimes difficult to arrive at a reasonable output. The exhaust in particular plays a significant role in the results. Camshafts and cylinder head specs seems a little easier as they're back and white as far as input values are concerned.
That said, I've several profiles to push through now and I'll post results. But it might take a while.
My motor is similar to your with the exception of the cylinder heads. I have Brodix RR200’s. I custom spec’d a Comp XFI for mine. 218/224@.050 109 lsa with 107 icl.
My goal was to design a cam that worked in the operating range of my intake which is a TPI design but modified. I was pleasantly surprised by the power and throttle response. I’m a big fan of tight lobe separation. It makes for a lively cam.
With that said, I personally like the XFI profile with 109 lsa.
You will need aggressive valve springs. I use Crower with 150 lbs close 420 lbs open.
My motor is similar to your with the exception of the cylinder heads. I have Brodix RR200’s. I custom spec’d a Comp XFI for mine. 218/224@.050 109 lsa with 107 icl.
My goal was to design a cam that worked in the operating range of my intake which is a TPI design but modified. I was pleasantly surprised by the power and throttle response. I’m a big fan of tight lobe separation. It makes for a lively cam.
With that said, I personally like the XFI profile with 109 lsa.
You will need aggressive valve springs. I use Crower with 150 lbs close 420 lbs open.
Therein lies the rub HiTech. If I were to build from a clean slate, I'd move up to a large port head like your 200's. As it is, I'm using a worked over pair of RHS Pro Torkers, which are an aftermarket version of GM's Vortecs. They started out at 170cc and may have gained some with the porting but that said, they're still small for a 383. My understanding is that the cam spec would be a little different than it would be normally. That's not really bearing out in the recommendations I've received however I'll be assessing and running simulations on the lot of them and we'll see what sticks.
The XFI lobes concern me a little in that of the lot of the various domestic profiles available, they're aggressive. Or at least the XFI custom cam I spec'd years ago seemed so.
Follow up to the Mike Jones cam recommendation.
I approached Mike a 2nd time but this go around I asked that he exclude the car specs from the engine specs. I asked for the most torque and horsepower in the RPM range specified. I'd often thought that those that spec a cam do so with a specific platform in mind. I asked that my platform be an engine dyno.
His initial design was:
There would be very little difference in those designs on the dyno or on the street. It seems you are looking for confirmation on a spec that you had in your head already so i would go for it. Pick one you like the best
As this thread progresses, I'm finding that my preconceived spec is changing. With new information and insights from the contributors here seems the world is not all necessarily what I've read or been involved in.
Next step is to run some simulations. It's only for comparisons sake as we all know the results won't necessarily reflect actual output but they should at least be representative of each other.
My best guess is that the tight LSA of 106 (which I've obviously been pursuing) isn't going to be the magic formula for a super engine. I'll work with what's been offered up here and see where that goes.
There's been a pause in the action during this busy time of year. I've started putting together a list and have fired up the old DynoSim program but it might be a bit before I can post up the findings. It should, I hope, make for some interesting discussion. Sadly, as far as the car stuff goes, this is about all I've got to keep me occupied. It's full on winter here and with my house move (twice in 5 years), I've no shop or garage. But that'll come. In the meantime I'm theorizing.
Thanks for the input to this point.
If you havent done so, engine analZyer pro was available for free download and a 7 day trial period before its deactivated. But if you never close the program and dont turn off the computer it seems to last longer than 7 days . Its well worth the trial to play with some numbers but you need alot of information and accurate information at that to get meaningful results
I see too Orr that he's answered one of questions.
While I haven't had the opportunity to read the entire thread, I soon will and undoubtedly will have a question or two of my own to ask.
But I don't believe DV will back down on a 106 LSA for my particular engine spec: 383, 10:1 CR, 23 degree SBC head with a 2.02 intake valve.
We'll see.
I see too Orr that he's answered one of questions.
While I haven't had the opportunity to read the entire thread, I soon will and undoubtedly will have a question or two of my own to ask.
But I don't believe DV will back down on a 106 LSA for my particular engine spec: 383, 10:1 CR, 23 degree SBC head with a 2.02 intake valve.
We'll see.
I would back down about 2° on the LSA unless you have an exhaust system that scavenges really well. I could not be happier with the 108 LSA Bootlegger cam in my ~210cc headed 11:1 383. With the cutouts open it might have made a few more ft/lbs with the 106 LSA cam but with the exhaust flowing into my somewhat restrictive muffler the 108 seems to work great. Especially with the Rhoads lifters bleeding off about 20° at 0.050 in the lower rpms. My converter flashes to about 2,800 rpm and with 5.13 gears the 6,200 lbs van feels really lively!
Even at half throttle on the primary butterflys of the 1,200 cfm 4bbl throttle body it feels very lively. When the secondary butterflies open it pulls extremely hard.
The 128 topic was discussed many times over so not sure why he made another post about it but for a specific set if parameters it does seem to work
but as he says its wot performance oriented and there are factors to consider to shift lsa around from the base spec if your engine parts go outside those parameters or goals for performance go outside of pure wot
get the durations right and i bet you wont feel much of a difference between any cam between 106 and 110 lsa
I would back down about 2° on the LSA unless you have an exhaust system that scavenges really well. I could not be happier with the 108 LSA Bootlegger cam in my ~210cc headed 11:1 383. With the cutouts open it might have made a few more ft/lbs with the 106 LSA cam but with the exhaust flowing into my somewhat restrictive muffler the 108 seems to work great. Especially with the Rhoads lifters bleeding off about 20° at 0.050 in the lower rpms. My converter flashes to about 2,800 rpm and with 5.13 gears the 6,200 lbs van feels really lively!
Even at half throttle on the primary butterflys of the 1,200 cfm 4bbl throttle body it feels very lively. When the secondary butterflies open it pulls extremely hard.
which bootlegger? Thought you were doing a 215 deg high lift comp deal?
I've been playing around with the engine analyzer for the past few days on my own combo, using cams I've been interested in, ran in the past, currently running, and what I thought may be ideal. What I have found is that there is no clear cut winner that would make it worth the time and money to do a cam swap if you already have something decent. My setup is a 10.92:1 383, street port AFR 195 eliminators, miniram intake and xfi292 cam, installed 2 degrees advanced. Being primarily a street car, I chose to advance the cam slightly, willing to trade off just a bit up top, for a bit more low end. It's a manual trans car, which is why I chose the 292 over the 280 that I had in mind. The results of both 292 cams and the 280 cam show exactly what I anticipated, and I'm happy with my choice. The new player is the Tick LT1 'hold my beer' cam 241/245 LSA111+4 (.609"/.615" ) that I've been eyeballing. Its results are also as expected, but the bottom end loss is more then I would want for a street car. The big surprise was when I plugged in the AI cam I had in my 350, giving the most torque, and nearly as much hp as the big tick. Note that all the cams had a VERY similar midrange. Pick one and run, they would probably all ET very similar. Tha AI would have an edge, but cylinder pressure and my compression ratio, plus pump gas, wouldn't make it the ideal cam for me personally.
Maybe bigger is not better in regards to heads that may be a little on the small side, and if so, a cam in that same 220-230 range on a 108-110 may be ideal for the OP. His dual plane will increase torque over the mini ram, and drop peak hp rpm by a good bit, giving him what he needs. I don't get too much into the LSA argument, I know that the tighter LSA's seem to drop off very quickly after peak hp, and I played around quite a bit with the numbers, with a pretty consistent tradeoff between tq and hp, as would be expected. I'll also note that the peak numbers given seem maybe 15-20hp higher then I anticipated for my build, so I'm taking that with a grain of salt, but the comparison of different cams remains the same. I spent a good amount of time trying to make sure my cylinder head data was correct.
I would back down about 2° on the LSA unless you have an exhaust system that scavenges really well. I could not be happier with the 108 LSA Bootlegger cam in my ~210cc headed 11:1 383. With the cutouts open it might have made a few more ft/lbs with the 106 LSA cam but with the exhaust flowing into my somewhat restrictive muffler the 108 seems to work great. .
That's just it. The exhaust and how it all ties into to the overall spec. And this is where the distinction of my spec lies. I've got this and I've got that. So with all of that there are a lot of viable suggestions.
What I'm doing is focusing in what going to be the best result from a dyno sheet point of view. How it relates to my "street car" is something I'll have to manage. I'd much rather have an engine with a given "character" and make the car suit it than the other way around.
To address the exhaust, this will be an open header deal when at the strip. If there's something to be gained with the effect of exhaust scavenging then I want to be take advantage of it. That I have to bottle things up with a full exhaust when I'm on the street and suffer some, then so be it. I'm not a street racer. At least not any more.
This is what makes drag racing somewhat easier to design a engine around. WOT till you lift. While I'm not building a car around a drag racing spec, until I'm thinking otherwise, I'll build the WOT engine and will work the rest of the chassis to suit. It's always been about the "street" side of the car that's kept me realizing the true performance, quarter mile-wise, of anything I've put together in the past. So this time around, I may give up on some of that street stuff so I can lay down a decent time slip. How this will parlay into open road racing is different matter although I suspect that if I start off with the best engine output, the rest can be built to suit.
Originally Posted by Orr89RocZ
The 128 topic was discussed many times over so not sure why he made another post about it but for a specific set if parameters it does seem to work but as he says its wot performance oriented and there are factors to consider to shift lsa around from the base spec if your engine parts go outside those parameters or goals for performance go outside of pure wot
get the durations right and i bet you wont feel much of a difference between any cam between 106 and 110 lsa
I've been following his work quite closely over the years. The reason 128 has come up again is fairly evident in the SpeedTalk posts. Folks have no reading comprehension. They drag BBC's, variable valve timing and even F1 engines into the mix when it's clearly stated what the parameters are. It's a specific target but somehow that's not grasped by the folks who reply. SBC with 23 degree heads with a typical discharge coefficient and 10.5 CR. I've got all that. The variable here (for me) is the smallish head on that CID. This is something I will try to address specifically in the ST thread.
I've been playing around with the engine analyzer for the past few days on my own combo, using cams I've been interested in, ran in the past, currently running, and what I thought may be ideal. What I have found is that there is no clear cut winner that would make it worth the time and money to do a cam swap if you already have something decent. My setup is a 10.92:1 383, street port AFR 195 eliminators, miniram intake and xfi292 cam, installed 2 degrees advanced. Being primarily a street car, I chose to advance the cam slightly, willing to trade off just a bit up top, for a bit more low end. It's a manual trans car, which is why I chose the 292 over the 280 that I had in mind. The results of both 292 cams and the 280 cam show exactly what I anticipated, and I'm happy with my choice. The new player is the Tick LT1 'hold my beer' cam 241/245 LSA111+4 (.609"/.615" ) that I've been eyeballing. Its results are also as expected, but the bottom end loss is more then I would want for a street car. The big surprise was when I plugged in the AI cam I had in my 350, giving the most torque, and nearly as much hp as the big tick. Note that all the cams had a VERY similar midrange. Pick one and run, they would probably all ET very similar. Tha AI would have an edge, but cylinder pressure and my compression ratio, plus pump gas, wouldn't make it the ideal cam for me personally.
Maybe bigger is not better in regards to heads that may be a little on the small side, and if so, a cam in that same 220-230 range on a 108-110 may be ideal for the OP. His dual plane will increase torque over the mini ram, and drop peak hp rpm by a good bit, giving him what he needs. I don't get too much into the LSA argument, I know that the tighter LSA's seem to drop off very quickly after peak hp, and I played around quite a bit with the numbers, with a pretty consistent tradeoff between tq and hp, as would be expected. I'll also note that the peak numbers given seem maybe 15-20hp higher then I anticipated for my build, so I'm taking that with a grain of salt, but the comparison of different cams remains the same. I spent a good amount of time trying to make sure my cylinder head data was correct.
This one I need time to digest. I haven't the ability at the moment to analyze the graph and the conclusions.
But I will.
I can't say I disagree. Hell, I may be able to refresh the existing short and drop on some high zoot heads and go fast but...
However this is what I've got and dammit, I've got to give it go.
I'm about this far from packing in the whole Gen 1 thing and getting the crate LS3 with the cam upgrade. But it's probably four times the cost to pull that off all things considered so this is where I'm at. 5k for a 383 shortblock and I have all of the supporting parts or 10k+ for the LS3 and controller plus all of the swap bits. The bits and pieces could run up another 10k by my latest estimation. (All prices in CDN $).
which bootlegger? Thought you were doing a 215 deg high lift comp deal?
I started out with the 215/224 high lift with 1.7s. After I got it running, I wanted more power. The heads and 11:1 compression ratio were begging for more cam. Swapped the Bootlegger 232/244 into it. Powerband is about the same but it pulls much harder in the mid-upper rpm band with little sacrifice down low. With Rhoads lifters that 215/224 idled like a stock Vortec cam. I wanted some idle thump with the cutouts open.
FWIW with those GMPP plastic lifter guides the cam swap on a SBC goes as easily as any LS save for having to adjust the valves rather the the LS torque and go on the rocker arms. The distributor has to come out and get the CMR set after but in the van that was the easy part. Especially since I only use it for cam position and it lacks plug wires coming off it.
I've been playing around with the engine analyzer for the past few days on my own combo, using cams I've been interested in, ran in the past, currently running, and what I thought may be ideal. What I have found is that there is no clear cut winner that would make it worth the time and money to do a cam swap if you already have something decent. My setup is a 10.92:1 383, street port AFR 195 eliminators, miniram intake and xfi292 cam, installed 2 degrees advanced. Being primarily a street car, I chose to advance the cam slightly, willing to trade off just a bit up top, for a bit more low end. It's a manual trans car, which is why I chose the 292 over the 280 that I had in mind. The results of both 292 cams and the 280 cam show exactly what I anticipated, and I'm happy with my choice. The new player is the Tick LT1 'hold my beer' cam 241/245 LSA111+4 (.609"/.615" ) that I've been eyeballing. Its results are also as expected, but the bottom end loss is more then I would want for a street car. The big surprise was when I plugged in the AI cam I had in my 350, giving the most torque, and nearly as much hp as the big tick. Note that all the cams had a VERY similar midrange. Pick one and run, they would probably all ET very similar. Tha AI would have an edge, but cylinder pressure and my compression ratio, plus pump gas, wouldn't make it the ideal cam for me personally.
Maybe bigger is not better in regards to heads that may be a little on the small side, and if so, a cam in that same 220-230 range on a 108-110 may be ideal for the OP. His dual plane will increase torque over the mini ram, and drop peak hp rpm by a good bit, giving him what he needs. I don't get too much into the LSA argument, I know that the tighter LSA's seem to drop off very quickly after peak hp, and I played around quite a bit with the numbers, with a pretty consistent tradeoff between tq and hp, as would be expected. I'll also note that the peak numbers given seem maybe 15-20hp higher then I anticipated for my build, so I'm taking that with a grain of salt, but the comparison of different cams remains the same. I spent a good amount of time trying to make sure my cylinder head data was correct.
Plug the bootlegger cam into it. I think the torque under peak in the curve would suprise you as would peak HP. It pulls like a freight train from the moment it flash stalls the converter ~3,000 rpm all the way to the 6,200 fuel kill. I am running it with a 1.7 rocker for 0.628" lift.
wow thats way bigger than i thought. And closer to what i would have run in the first place
my old 383 cam was 286/306. 230/245 109 lsa 108 icl and .603/.613 with 1.6’s. But it turned 6800 rpm. Not sure why yours is done early is it the intake?
bootleggers get a bad reputation since they are kind of like comp thumpers, designed somewhat around sound but they seem to work well enough
Plug the bootlegger cam into it. I think the torque under peak in the curve would suprise you as would peak HP. It pulls like a freight train from the moment it flash stalls the converter ~3,000 rpm all the way to the 6,200 fuel kill. I am running it with a 1.7 rocker for 0.628" lift.
I'll run that through later tonight, in a few different iterations of lift and ICL. I plugged 1.7 rockers in on a couple of my tests, and in each one, I lost power compared to 1.6's. Maybe someone smarter then myself could answer why (smallish heads, port velocity, etc.). The only cam that made more power with over .600 lift was the tick. I also never ran a cam with that much exhaust duration, the xfi292 with 292/300 was the largest duration cam I tested. In any case, I'm curious about the results. Another thing that is important to my personal needs is a good, smooth torque curve, with hp carrying as far past the peak as possible since I autocross the car and just leave it in one gear. Rpm can range from 2500 to my 6700 rpm limiter, and a peaky torque curve can upset the balance of the car if it comes in suddenly. I don't want to get too far off the OP's topic, but at the same time, I find it interesting what does and does not work.
wow thats way bigger than i thought. And closer to what i would have run in the first place
my old 383 cam was 286/306. 230/245 109 lsa 108 icl and .603/.613 with 1.6’s. But it turned 6800 rpm. Not sure why yours is done early is it the intake?
bootleggers get a bad reputation since they are kind of like comp thumpers, designed somewhat around sound but they seem to work well enough
It ends early because that is where I chose to rev-limit the engine. It has H-beam rods and a cast crank. It also has some chinese 4-bolt caps that I am not overly happy about Summit using on their blocks. Would have been happier with a factory 4-bolt cap. I want the engine to be somewhat reliable. It looks like the MAF is still climbing when it rev-limits and I kinda doubt it has reached peak HP at 6,200. Maybe someday I will hit the dyno with it and see.
My ~210cc 2.02/1.60 heads outflow Lloyd Elliots LE2s he does for LT1s by a healthy margin. Flow is still increasing at .600 and increases even at .700.
I think the Bootleggers get a bad rap because of the Thumpers. But in the few tests I have seen they seem to create a nice flat torque curve and make great power all through the rpm band.
Ah makes sense now. I was gonna say that thing should go well above 6000
Another thing that is important to my personal needs is a good, smooth torque curve, with hp carrying as far past the peak as possible since I autocross the car and just leave it in one gear.
usually get a longer power curve after peak hp rpm with extra exhaust duration and aggressive timing curve.
12-27-2019, 12:19 PM
. Its well worth the trial to play with some numbers but you need alot of information and accurate information at that to get meaningful results 
