Comp Cams XR280r thoughts to given combo

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DC Dart

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I am wondering how the comp cams xr 280r would respond in following car engine configuration. The engine is a 451 with Edelbrock performer rpm heads, 10.23 compression, 440 source crank, rods, pistons, comp cams rockers, Edelbrock performer RPM intake, TTI 1 3/4 headers and going with a Holley Sniper.
xtreme energy solid roller
242/248 @.050 lift
intake lift .570 exhaust .576
lobe separation 110
The car is 68 Dart, TKX 5 speed trans, 3:55 gears 25.6 inch tire stock rear tubs.
The car is going to be mostly street with very occasional strip.
At what rpm would peak horsepower and torque be?
Would this be an easy cam on valve train?
Any advantage of running the comp cams sportsman lifters over the endure x? Other lifter recommendations?
Any input, thoughts, recommendations would be highly appreciated. Thanks
 
I'm not given to guessing what different combinations will make but I can speak from experience.

My combination was....
451
9.5:1 compression
"452" iron heads that flowed equal to or better than RPM heads
XR292R roller cam
950 4150 Quick Fuel DP
M1 single plane
588 lb-ft @ 4,600 rpm
621 hp @ 6100 rpm

It was easy to drive on the street with 4.89 gears.
 
DC Dart said:
The car is 68 Dart, TKX 5 speed trans, 3:55 gears 25.6 inch tire stock rear tubs.
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DC Dart said:
The car is going to be mostly street with very occasional strip.
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Nice trans choice.

That cam may power-peak around 5400, but the curve will be fairly wide and so you might want to shift it at say 6000.
You didn't specify which TKX you bought; the 3.27 low or the 2.87low box.
Since you are using 3.55s;
my guess is the 3.27 low.
in which case 6000 will be ~39mph in First, 65 in Second..... with tires spinning all the way.
But if the 2.87 box then; 6000 will be 45/68... and tires still spinning all the way.
So since traction will be your number one problem, I'll guess it won't much matter what cam you put into it. Just make sure that it is big enough so that the Ica is late enough, so that your pressure is low enough to NOT put your engine into detonation ...... which with alloy heads at 10.23 Scr, should be easy enough to do,
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On the flipside; You could install a smaller cam, to drive the pressure up even higher, to maximize your low-rpm torque, so that you can roast the tires yet further, which at your very low cruise rpm in overdrive, means fantastic fuel-economy.
Depending on which box you have, the overdrive ratios available are; .68/.72/.81..
Your cruise rpms at 65mph are expected to be; 2060/2181/2454 (depending on the ratio).
That XR 280R will not like to rev too slow on the hiway.
Why?
Cuz of the large amount of overlap, the very short power-extraction duration, and your possibly less than ideal EFFECTIVE DCR of 7.84 (at 1000ft elevation).
But, I don't think fuel economy was on your mind when you built a 451, lol.
Furthermore, I don't think you want a smaller cam with more pressure, cuz your pressure is already more than adequate.
I think the 280, for me, would be a pretty good choice. As for me; If I had the .68overdrive;
I would install that 280 at 2* advanced instead of the usual 4*. That would trade away 2* of compression duration which the 451 doesn't need in street trim, to get 2 extra degrees of power-extraction, which would work better in overdrive. In first and second gear, I doubt you would notice the ~3.5psi pressure loss.
In all likelihood, this combo will make better fuel mileage at 2400 than at 2100. Some combos are like that.......
 
Thank you for the replies. My trans is the close ratio 2.87,1.89,1.28,1,.68.
I bought the XR 280r and was wondering if the XR 274r would have been better. AJ/FormS explained the pros and cons to that well. Power peak at around 5400 would be great.
The XR292 made awesome power and at reasonable RPM. Nice to know it drove nice on the street too. IQ52s hp and torque numbers would likely put me spinning in 3rd too. LOL. most the time on the freeway will be 70 MPH plus so that may help get my rpms up in 5th gear.
 
I ported some RPM heads for a customer who is running that cam in his Dart. I can’t recall if the motor is a 470 or 451, but I think it’s a 470.
Pump gas, street friendly 3.55 gears, all steel, full interior, etc.
It’s gone 10’s regularly at the track.

I have another customer who is running one in an RB 446, owner ported stage V heads and SD manifold.
it made 558.6hp@5900, 548.6tq@4700.
Still making 544.6hp@6500.
This one is in a 70 Charger with a 4 speed.
 
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DC Dart said:
At what rpm would peak horsepower and torque be?
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With unported RPMs, the RPM intake and that cam my bet is 5600-5700ish neighborhood provided the springs are right. 1-3/4" headers will work for you but they're a little on the small side.

DC Dart said:
Would this be an easy cam on valve train?
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Easy compared to what? It's a solid roller cam and from the 'Xtreme Energy' series at that......in other words probably not.
So shoot for an idle speed on the higher side and keep an eye on things.

DC Dart said:
Any input, thoughts, recommendations would be highly appreciated. Thanks
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I'd just add, don't even think about running Cooper/BFG/street radials...get some M/T or Nitto drag radials at a minimum. Good tires made a big difference with my 505" B-body.
Being able to spin the tires at any speed sounds good on the internet, (and the kids love it:D) but it's pretty lame, getting beat off the stoplights by every other car on the road because of lack of traction...and sometimes just plain dangerous.

Now, despite my negative nancy attitude I think that will be a heckuva fun beast on the street in a Dart, with your gearing/tire combo... I like the cam choice for a nice street 451. That's gonna be a rocket!
 
The XR lobes are pretty easy on the valvetrain and don’t require really high spring loads in most applications.
 
I have the XR 280R in my 470" street toy. 69 B'cuda. 833, 3:73 rear with 255 tires. 10.2:1 with stock Eddy heads. I run the Comp roller lifters that were recommended,Comp, springs(200ish closed,500ish open) Comp rockers, Smith Bros pushrods, Eddy RPM intake/800 Holley DP
It idles nicely at 900 with about 10-12 inches of vacuum. Makes good low end and pulls hard through the middle.
Made 425 at the wheel on a chassis dyno at 5500rpm.....would pull easily to 6500. Made 500ft lb all the way up there.
I always say....RPMs like a chainsaw and pulls like a freight train!
Great cam......been real easy on components. Mine's always street driven......check lash every so often...all good!
 
Dcuda69 said:
I have the XR 280R in my 470" street toy. 69 B'cuda. 833, 3:73 rear with 255 tires. 10.2:1 with stock Eddy heads. I run the Comp roller lifters that were recommended,Comp, springs(200ish closed,500ish open) Comp rockers, Smith Bros pushrods, Eddy RPM intake/800 Holley DP
It idles nicely at 900 with about 10-12 inches of vacuum. Makes good low end and pulls hard through the middle.
Made 425 at the wheel on a chassis dyno at 5500rpm.....would pull easily to 6500. Made 500ft lb all the way up there.
I always say....RPMs like a chainsaw and pulls like a freight train!
Great cam......been real easy on components. Mine's always street driven......check lash every so often...all good!
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very nice :thumbsup: one thing I will say, you need more tire !
 
fishmens67 said:
very nice :thumbsup: one thing I will say, you need more tire !
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LOL....Had 245s on it for a bit......1st and 2nd gear were useless. 255s aren't a ton better but......point it straight and have fun!!
 
I appreciate all the feedback. Dcuda69s car sounds similar to the direction I am heading. The power curve should be awesome with a manual transmission. The vacuum and idle characteristics should hopefully work good with Holley sniper. My head's came with the hydraulic roller springs. I will likely change to heavier as they are on the light side. Debating on the sportsman lifters still.
Summer time and busy with other things so this project is going slow. Engine is on stand ready for cam install. TKX and Quick time bell on floor waiting to be mocked up to start modifications to floor. Similar to TKO.
Car will be prepped for cornering as well as take off so may not Excell at either? Will be asking alot from my tires.
 
I think you need a good bit more tire and a suspension to help hook. That’s a small tire on there.
 
Yeah the 340 had no issues turning the tires. Should be a bit more hp and torque with the 451.LOL
Have a Hotchkis front sway bar going bigger torsion bars tubular upper control arms etc. All the stuff to make it lay flat and corner.
Will try to figure things to help it move forward later. Tires likely won't last long and will be changed early on.
May need to start a pro touring mini tub thread.
 
Sounds good but put at least a 2" header on it.
 
A body. Mostly street. Went 1 3/4 TTIs. Went with more room versus slight power increase.
 
DC Dart said:
A body. Mostly street. Went 1 3/4 TTIs. Went with more room versus slight power increase.
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WHAT?! That's like rentin a workin gal and not even usin her.
 
I had planned to use the XR280R, but ended up using a XR274R in a 10 to 1 compression, 499 RB. Heavily ported 452's with pushrod holes filled in and the short side walls pushed way out running .450" offset rockers, and a seriously ported Victor intake. I have it in a 74 Duster with the battery in the trunk and it will eat the tires off forever. Most people will say that this is counterproductive, but I added another 100 pounds in rear bumper to help with traction. The BB weighs more than your previous engine, so the front to rear bias now will just make it even easier to spin the tires. Adding some weight isn't a bad thing if you want to really enjoy the power.

Tom
 
With the milder cam, extra cubes and higher flowing heads I would think your combo is less tire friendly than mine. LOL
I plan on having the battery in the trunk. I am doing the American auto wire kit and the whole car will be re wired anyway.
My progress is very slow as time has not been on my side lately. The Edelbrock Performer RPM is not available til like August or something and not holding my progress up.
I think I am going to order the AR engineering timing cover, ATI stock pulley balancer, timing set and lifters soon.
Been debating the Torrington bearings on the timing set or not and BAM lifters or the 829s or? I've read the 829s are happy in stock lifter bores? Some of the more expensive can be loose? Experiences and people's lifter bores seem to vary on this one.
 
DC Dart said:
With the milder cam, extra cubes and higher flowing heads I would think your combo is less tire friendly than mine. LOL
I plan on having the battery in the trunk. I am doing the American auto wire kit and the whole car will be re wired anyway.
My progress is very slow as time has not been on my side lately. The Edelbrock Performer RPM is not available til like August or something and not holding my progress up.
I think I am going to order the AR engineering timing cover, ATI stock pulley balancer, timing set and lifters soon.
Been debating the Torrington bearings on the timing set or not and BAM lifters or the 829s or? I've read the 829s are happy in stock lifter bores? Some of the more expensive can be loose? Experiences and people's lifter bores seem to vary on this one.
Click to expand...

For what it's worth I have stock size 3/8" OEM Mopar valves in my heads. Aluminum heads only save about 40 pounds over iron and lose heat (power) compared to iron. The real issue I have with aluminum heads is they all have larger valves in them than they actually need. Air speed is power and big valves slow air speed down. A port like the mine can use a 2.08" intake valve and move a lot of air. Air speed and holding the heat in makes for great power production.

I have a Cloyes Race Billet(9-3625TX9) timing set with the bearing in mine, but it's honestly not a needed item. I just wanted it and a factory double roller would have worked just as well. I plan to buy a Jesel belt drive for the next engine for the main reason of harmonic reduction. I have the Comp 829 lifters and have used many sets over the years. I just couldn't justify the cost of the Isky lifters for cams/ springs I've used. If I was running cams over .700" lift I would most likely be using Isky lifters.

Here's a Performer RPM I spent about 40-hrs. smoothing out before the engine grew larger and never used it. I also did the same thing to the Victor I am running on the 499.

440-Performer-RPM-Reworked.jpg


20210120-211142.jpg



Tom
 
I wondered about the need for the bearings on the timing set. Whether beneficial or not.
The 829s seem readily available and a decent choice of milder builds. Still pondering.
Not sure I will be doing any port work this time around. Maybe nicer valve job when valve springs are swapped out. My heads came with the hydraulic roller springs that may be on the light side for mechanical.
 
I am running the last set of K-Motion K800 springs I had. Those have a 471# spring rate. Have already looked into what I would use if I need to replace them later. Next go around I'll use Comp Cams 7256 Conical springs that are 486# rate and change out the valves to 11/32".

Tom
 
PROSTOCKTOM said:
I had planned to use the XR280R, but ended up using a XR274R in a 10 to 1 compression, 499 RB. Heavily ported 452's with pushrod holes filled in and the short side walls pushed way out running .450" offset rockers, and a seriously ported Victor intake. I have it in a 74 Duster with the battery in the trunk and it will eat the tires off forever. Most people will say that this is counterproductive, but I added another 100 pounds in rear bumper to help with traction. The BB weighs more than your previous engine, so the front to rear bias now will just make it even easier to spin the tires. Adding some weight isn't a bad thing if you want to really enjoy the power.

Tom
Click to expand...
Is that 10-1 499/ 452’s a pump gas engine ?
 
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