Comp cams xe268h for 318

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nm9stheham said:
I want to hear what others have experienced, but here is what I have found when having low DCR with a low stall TC (or too high gear with a manual):
  • When 'off the curve', you can push the throttle 1/4 of the way and then all the way down and it makes hardly ANY difference; it accelerates slowing at the same pace regardless of throttle positions of 1/4 or 100%. In other words, throttle response is non-existent. Have you ever driven a loaded truck and picked too high a gear, and put the throttle to the floor and the acceleration did not change? It's just like that.
  • When you get 'up on the curve', the thing takes off. You end up with a light switch-like behavior: off, then on. If you ever have ridden 2 stroke motorcycles, you will know how this feels: get the RPM too low and the thing just falls on it's face. My overcammed low CR Opel was (seriously) like a light switch. You have more cubes to weight, and not as bad a DCR if in the low 6's but it will still have an off-on character. That on-off character, plus the non-responsive throttle at low RPM's, tends to suck when trying to accelerate out of corners on back roads.
  • As far as 0-60 times... I can't say a number with total confidence. But several seconds improvement would not surprise me with the cam change you mention. The guy with a 7.4 DCR and the XE256/262 valve lift of .447"/.462"will be far ahead of the guy with a 6.7 DCR and the .421" lift of the present cam. And with the added lift, the advantage will continue past 60 MPH; the performance will be better past the mid RPM's 'til the heads' flow stall out.
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My truck is like that. Stock 2001 5.2 5 speed except mine is like that In the middle range. Like it is pretty strong in first sec then when you get to third nothing you can hold it to the floor it makes no difference. Then as you get up in speed more the top end has pretty good throttle response. If I'm going 60 to 70 I can hit 90 quick but 45-65 takes forever no throttle response at all
 
nm9stheham said:
I want to hear what others have experienced, but here is what I have found when having low DCR with a low stall TC (or too high gear with a manual):
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I agree on the first two points and not enough experience to comment on the third point. I have way too much power, and way to stiff a suspension, to 60ft well on the street. But it survives jumps well, if a lil nose-heavy,lol..And it slides predictably on the bump-stops.
 
dartfreak75 said:
My truck is like that. Stock 2001 5.2 5 speed except mine is like that In the middle range. Like it is pretty strong in first sec then when you get to third nothing you can hold it to the floor it makes no difference. Then as you get up in speed more the top end has pretty good throttle response. If I'm going 60 to 70 I can hit 90 quick but 45-65 takes forever no throttle response at all
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I'm gonna guess that your '01 truck has a locking TC in top gear, and your drivetrain is simulating a manual trans when you go to top gear (probably an OD gear): i.e., the locked TC won't allow the engine to rev to a better place on the torque curve. You 'fall off the torque curve' a bit, and coupled with the top gear's gearing, it is 'flat' in that 45-65 mph range. (And that is with a 5.2 Magnum engine that has a static CR that is 0.5 to 0.75 points higher than the '83 LA 318 engine and a roller cam with a profile that I'll bet is much more like the shorter duration Voodoo's or XE's than the Summit 6900.)

Just translate that into moving off from a stoplight in 1st gear with too low of a DCR. Do it again in 2nd gear unless you revved it in 1st to 4k RPM, and manually upshifted. To fix, you raise the DCR or put in a higher stall TC. The higher stall TC hurts fuel mileage, adds wear & tear, and you get tired of manually 'optimizing' the shift points in everyday driving. It is a lot easier and nicer to drive when the low DCR is fixed instead, fuel mileage is a good bit better (I computed it out and the $137 for a Voodoo is paid for in around 5k miles), etc., etc., etc.

Sorry to go on so much LOL
 
Wyrmrider said:
We used the term "come up on the cam"
makes a big deal in sports cars where you can get below the curve and maybe have to shift down where with a little more torque you would not
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Exactly where I was with that overcammed, low DCR Opel engine, Wyrm, and the tall 2-3 upshift.. it was miserable, and on some rally stages, I dropped 5-10 places on the timesheets over what a smaller cam, higher DCR set-up would have done. I just kept rebuilding the motor that way; if I had learned sooner, it would have been better.
 
nm9stheham said:
I'm gonna guess that your '01 truck has a locking TC in top gear, and your drivetrain is simulating a manual trans when you go to top gear (probably an OD gear): i.e., the locked TC won't allow the engine to rev to a better place on the torque curve. You 'fall off the torque curve' a bit, and coupled with the top gear's gearing, it is 'flat' in that 45-65 mph range. (And that is with a 5.2 Magnum engine that has a static CR that is 0.5 to 0.75 points higher than the '83 LA 318 engine and a roller cam with a profile that I'll bet is much more like the shorter duration Voodoo's or XE's than the Summit 6900.)

Just translate that into moving off from a stoplight in 1st gear with too low of a DCR. Do it again in 2nd gear unless you revved it in 1st to 4k RPM, and manually upshifted. To fix, you raise the DCR or put in a higher stall TC. The higher stall TC hurts fuel mileage, adds wear & tear, and you get tired of manually 'optimizing' the shift points in everyday driving. It is a lot easier and nicer to drive when the low DCR is fixed instead, fuel mileage is a good bit better (I computed it out and the $137 for a Voodoo is paid for in around 5k miles), etc., etc., etc.

Sorry to go on so much LOL
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It's a 5 speed manual.
 
I actually just ran into some extra money (sold a gun) so I'm looking at cam shafts again lol I know I'm back and forth flip flopping. I apologize. I have to buy my paint for my car and I just bought that cam bearing tool that is coming of this money but after the paint and a few other things I have to get if I have enough left over I'm probably gonna get a cam. I will post the finalist.
 
What I have found is that a lotta EFI cars do not have linear opening TBs. That is to say, the first 50% of the pedal travel actually opens the TB closer to or something like 70%. So the last 30% is only a small cfm change.
I think they do this to make those little tiny engines feel bigger than they really are, in the lowest gear or two. I had an 07Honda Pilot 3.5liter heavy Cross-over SUV, like that. To take off, I always had to ride the brake and feather it out, else my wife complained about my jack-rabbit starts. I was not sad when I hit a deer last month and wrote it off. I've had several EFI SUVs like that.The only thing I liked about that engine was the VVT system, and the 6500 redline. That VVT was hilarious. It came on at 4000, like clockwork, and felt like afterburners,lol. Just a solid top-end 3.5l charge. I mean CHARGE!
 
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This thread is an interesting one but no different than any of the other 318/cam threads. 09 pages,207 replies, and 2500 views and still no definite answer. There is none! Just guidelines about how big "not to go" with a certain combination. No magic bullet here.
 
AJ/FormS said:
What I have found is that a lotta EFI cars do not have linear opening TBs. That is to say, the first 50% of the pedal travel actually opens the TB closer to or something like 70%. So the last 30% is only a small cfm change.
I think they do this to make those little tiny engines feel bigger than they really are, in the lowest gear or two. I had an 07Honda Pilot 3.5liter heavy Cross-over SUV like that. To take off, I always had to ride the brake and feather it out, else my wife complained about my jack-rabbit starts. I was not sad when I hit a deer last month and wrote it off. I've has several EFI SUVs like that.
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My mountaineer is like that it has that stupid electronic gas pedal system the pedal activates a sensor and the sensor controls the tb the first 1/2 inch of pedal will jerk your neck you have to feather the crap out of it. We have had it for 7 years and to this day my wife takes off like a drag racer lol it's not her fault it's just how the Pedal is.
 
toolmanmike said:
This thread is an interesting one but no different than any of the other 318/cam threads. 09 pages,207 replies, and 2500 views and still no definite answer. There is none! Just guidelines about how big not to go with a certain combination. No magic bullet here.
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Haha I agree this thread was not intended to be another 318 build thread I found a new previously owned xe268h cam on Ebay for 89 bucks it was such a great deal I couldn't pass it up but I wanted the pros (you guys) opinion on it before I wasted more money. I was worried it was to large of a cam. I started this thread to be a quick yes or no before I bought the cam. And it turned out to be a great thread. I have learned so much from this one. I have made new friends and started conversations with very knowledgeable people that gave me a better understanding on cams and what the numbers actually mean. So that just goes to show there are no dumb questions. I started the budget 318 build thread with (what I know now) very little knowledge and understanding. I have a better understanding and feel alot more confident in choosing the right cam when the time comes.
 
Here are the cams I'm between leaning towards the larger one just because I know eventually I'm gonna have lower gears 3.73.

Screenshot_20181002-214410_Samsung Internet.jpg


Screenshot_20181002-214141_Samsung Internet.jpg


Screenshot_20181002-214501_Samsung Internet.jpg
 
dartfreak75 said:
Haha I agree this thread was not intended to be another 318 build thread I found a new previously owned xe268h cam on Ebay for 89 bucks it was such a great deal I couldn't pass it up but I wanted the pros (you guys) opinion on it before I wasted more money. I was worried it was to large of a cam. I started this thread to be a quick yes or no before I bought the cam. And it turned out to be a great thread. I have learned so much from this one. I have made new friends and started conversations with very knowledgeable people that gave me a better understanding on cams and what the numbers actually mean. So that just goes to show there are no dumb questions. I started the budget 318 build thread with (what I know now) very little knowledge and understanding. I have a better understanding and feel alot more confident in choosing the right cam when the time comes.
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And you know which cam bearing goes where. (another thread I know) :poke::lol:
 
  1. How's about get those heads off this weekend, look at what you have for pistons (no eyebrows or ??), and VERY precisely get a piston to TDC and measure how for down in the hole they are?
  2. Carefully cc the 302 chambers so that is know, unless you already have).
  3. Decide if you will mill the heads and how much.
Then the picture of what SCR you really have will be known, and then the cam situation can be better looked at. If you really have flat tops, down .075" in the hole, and mill the heads to 60 cc's or a tad less and use .028" head gaskets, then even the 262 is looking pretty decent: DCR around 7.5. (Less a few 10th's due to your elevation.)
 
nm9stheham said:
  1. How's about get those heads off this weekend, look at what you have for pistons (no eyebrows or ??), and VERY precisely get a piston to TDC and measure how for down in the hole they are?
  2. Carefully cc the 302 chambers so that is know, unless you already have).
  3. Decide if you will mill the heads and how much.
Then the picture of what SCR you really have will be known, and then the cam situation can be better looked at. If you really have flat tops, down .075" in the hole, and mill the heads to 60 cc's or a tad less and use .028" head gaskets, then even the 262 is looking pretty decent: DCR around 7.5. (Less a few 10th's due to your elevation.)
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Working on it I will try to get it done in the next day or two. How do you get the dcr number ? What info do you use?
 
I have learned one thing on off the shelf cams.
When you think you have found the perfect one, order the next size smaller.
It will make for a better driver.
 
sireland67 said:
I have learned one thing on off the shelf cams.
When you think you have found the perfect one, order the next size smaller.
It will make for a better driver.
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That is great advice that is kinda the way I'm leaning also lol
 
dartfreak75 said:
How do you get the dcr number ? What info do you use?
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Bore, stroke, rod length,Scr, Ica, and elevation
then go here,
Wallace Racing: Dynamic Compression Ratio Calculator
and pay close attention to the V/P, which you can read about that here
V/P Index Calculation

to get a picture of where you are starting from , plug 7.8 in for Scr and 50* for the Ica,These are the specs for a stocker with a 240/248/112 cam, in at 110....
plus the basics; 3.91x3.315, 6.123rods, and your local elevation; 300ft IIRC. I get 132psi@109VP, and you already know what that feels like.
I took the liberty to max out your compression for this cam, with a bore job and hi-compression pistons and retarded the FACTORY cam to a Ica of 53* so you can rev it a bit. This is about the max you could run on pumpgas. I get
Scr of 9.25 @161psi @132VP @7.97Dcr.
This would make a real stump puller, with fabulous first gear performance. and tons of grunt in second at say 30 to 45 mph just where you need it.
With 2.76s and the 2800TC, you won't get any better, to somewhere between 45 and 50 mph.
As a comparison this 132VP is more VP than a factory 340(128)calculates to , more than a factory 360(121)calculates to,and even a 440Magnum calculates to just (136) with the 4bbl cam.
And we haven't even talked about the fuel mileage improvement,or what the 4bbl and headers are gonna do for you. These V/P numbers are most valuable to know, from a factory stall to in the range of 3000 to 3500, after that the combo better be making power elsewhere cuz the VP advantage has diminished to nothing. That factory 240 cam is done pulling around 4500rpm. That doesn't mean you have to shift it there, in fact with the standard TF ratios, the 1-2 split is 59.2%, so for low-ET this combo might need to be revved yet higher, perhaps 5000 or a bit more.

And for anyone reading this that has a manual trans, you know how much time you spend from 1600 or so to 2800 or so. For you guys VP is really really important. If your combo is doggy in there, I know you ain't happy. And nothing sounds worse than a Mopar impersonating an old Mustang, having to slip the clutch out so it don't stall, and then rev it to near 4000 to find some torque in second; Man, I would be so embarrassed . With VP like this, and typical street gears,and street flywheel,you can just dump it and go. I'm not kidding. As a comparison my 367 calculates to 156VP and spins 295s/325s to waaaaay past the speed limit. I have to lift at 65,lol. Actually I have to cuz that is 6900 with my gearing,lol. Oh! we're not talking about high rpm in this chat,sorry,lol.
Ok so with my 10.97 starter gear, it really is a blip the throttle and slip it out, without any gas pedal, deal. It was pretty similar with a 9.44 starter gear. But with 3.23x2.66 it needed a bit of gas-pedal, and/or easy on the clutch pedal. This is where big VP pays off;throttle response and low-rpm driveability and the ease of initiating tirespin without racegears. 156 is a lotta,lotta VP. 132, as you can see, is quite a bit.
 
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dartfreak75 said:
Working on it I will try to get it done in the next day or two. How do you get the dcr number ? What info do you use?
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Here is the calculator I use; go to the bottom of this page and install the tool on you computer:
Dynamic CR

Select "DCR Calculator with VB6 Runtime Files". It is for most up-to-date Windows operating systems. It's free. (VB6 is Visual Basic version 6, which is a Microsoft program.)

This is a nice tool because it does SCR and DCR and figures out intake closure angles for you all in one place. Let me know if you want to use this, and I'll see if I can figure out how to post some pix of filled-in data and the resulting output so you can see what to put in.

BASIC USE OF THIS PROGRAM
The program has 3 tabs, and is used in 4 steps.
  1. Enter engine/head data on tab 3 and hit "Calculate" to get SCR in the bottom box. (If you want just SCR, then use this tab only.)
  2. Enter 4 pieces of cam data in the top half of tab 2 and hit "Calculate". Note that the duration you use is the cam's "advertised duration", NOT the .050" lift duration. (There are some mods to the data entries with some cams (like mechanical cams) but that is not needed for hydraulic cams.)
  3. Then go to tab 1, enter stroke and rod length and hit "Calculate"
  4. Finally, go back to tab 3 and check the box on the 'stroke' line and hit "Calculate" again and the DCR will appear in the bottom box
There is one clunky aspect of this tool: If you change any cam data on tab 2, then you have to:
  • hit "Calculate" again on tab 2
  • hit "Calculate" again on tab 1
  • uncheck the box on tab 3 and hit "Calculate" to go back to SCR
  • then re-check the box on tab 3 and hit "Calculate" to get the new DCR
It takes a bit of work to dig out the data to know what to put in, but once you know it, you can run a combination in a minute.

A NEXT STEP IN DCR DATA (if you want more info)
This tool does not tell you 'effective DCR' with elevation, or cranking pressure. For that, I go to the results on tab 2 and pull out the 'intake close ABDC' number (the ICA, or intake closing angle), and the SCR data on tab 3. Then put that info into the Wallace Racing Dynamic Compression Ratio Calculator (you can google search for that), and put in the other data, including your elevation above sea level, wiht 0 boost for a carbed engine. That simpler tool will put out the 'effective DCR' (which will be lower above sea level) at your elevation, AND expected cranking pressure.

Why bother with 'effective DCR'? It shows what will happen to the cylinder filling process at elevation; the air pressure is just plain lower and so for a carbed engine, it will simply get less fuel-air mixture pushed in each cycle, and will have less torque/HP. The less the 'effective DCR', then the less cylinder pressure and torque you will have.
 
AJ/FormS said:
Bore, stroke, rod length,Scr, Ica, and elevation
then go here,
Wallace Racing: Dynamic Compression Ratio Calculator
and pay close attention to the V/P, which you can read about that here
V/P Index Calculation

to get a picture of where you are starting from , plug 7.8 in for Scr and 50* for the Ica,These are the specs for a stocker with a 240/248/112 cam, in at 110....
plus the basics; 3.91x3.315, 6.123rods, and your local elevation; 300ft IIRC. I get 132psi@109VP, and you already know what that feels like.
Click to expand...
I was just over there checking things out. My dyno program lists "intake valve closes" at advertised duration or at .050 duration. What specs should I use?
 
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