FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: JamesonRacing on February 04, 2013, 04:01:06 PM
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Assembling an engine for my 66 F250 that will be used for towing and some cruising, no racing. Block is a std bore 427 with a 4.25 crank setup, for about 480 cubes. Compression ratio is right at 10:1. Block isn't drilled for hydraulic lifters, so I'm trying to spec a solid cam.
All the cam recommendations seem to be for 390-428 size engines, with durations starting at 224, 230, 236, 240...., with LSAs at 110 for the smaller cams and 108 for 240 on up.
How much more duration should the cam have to account for the additional size? I'd be looking at the 224 duration if it was a 390, but the extra ninety cubes should make a difference.
Thanks for your input and discussion.
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Big cubes will eat up camshaft duration. If you are running 20% more displacement, you probably need 20% more "area under the curve" of the cam lobe, so to speak, to get 20% more power. One thing I've done in the past is map the intake valve operation with a given cam lobe, for lift and duration. Here's a comparison I did between two cams a while back, where I just stuck each cam into a set of V blocks and checked the lobe lift every 10 crank degrees. You will get a curve like the ones shown below:
(http://fepower.net/Photos/Posts/camlobe.jpg)
If you have a preferred cam that would work on a 400" engine, what you would be looking for in the stroker would be a cam where the area under that curve is about 20% bigger. From a practical standpoint, I'd guess that would be in the range of an additional 12-15 degrees of duration, and maybe .050" - .075" lift at the valve. But if you had a couple of cams you were considering, you could run them in the V-blocks and get a better idea...
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Thanks for the info Jay. Makes a lot of sense. Eager to see how much torque this one will make. Think I'll be filling the tank with premium with the 10:1 CR and towing a trailer. Will be good to be able to tow the race trailer with some style and power this Summer.
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Wonder whre I heard this before? 12-15 degrees more duration ;D I know this much that truck is you lol and that engine builder needs to get back to work he is fired.
Wasn't that Van Halen that said "COME ON Dave" @ 2:30 one change coming up, good music man I miss that.
http://www.youtube.com/watch?v=maQjttazW6Q
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Yeah, heard that somewhere before recently!
Hope the blocks arrived in Green Bay okay. Engine's on the stand, looking for a little warmer weather to get wrenching.
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I can wait to see it go down the digs a few times :o
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For peak hp numbers, I agree that you need to feed the beast, and the 12-15 degrees seems pretty close
However, remember that you are also changing overlap, advertised valve timing, and the engine has a different piston dwell time and cylinder fill capability, etc. To go from a 224 degree 390 to a 236 degree 445 with the added overlap, I think you'd have a little rowdier engine than you expected, not radical, but a little more choppy idle.
If you use the 12-15 degree increase, I think I'd spread the centers to maintain the same overlap and keep the intake lobe timing early. That way you wouldn't lose part throttle low rpm behavior, but you'd get the cylinder fill.
What I think is more important as you go up in displacement is intake and cylinder head selection. You'll go far by making a deep breather using heads and intake, then camming for where you plan to use it the most
BTW, I used a 270H in my 445, rolled it back to 110 ICL and wonder sometimes if I should have went 112, but mostly because I had a tough time getting to the DCR I wanted.
With that being said, I did it because I was being cheap and I had a good cam and lifters matched to the block I used, already broken in. We'll see how it does, the heads flow 280 and the RPM intake was worked and balanced. Hopefully the heads and intake will hold on at the upper end of the curve
No doubt it would make more power with more cam, but in a 4x4 with 3.50 gears and 33 inch tall rubber, we'll see how it does when I get the body back together. It sounds REAL strong, but the story will be told when the tach hits 5K LOL
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You made this statement;
"If you use the 12-15 degree increase, I think I'd spread the centers to maintain the same overlap and keep the intake lobe timing early. That way you wouldn't lose part throttle low rpm behavior, but you'd get the cylinder fill."
then later you mention rolling the ICL back. These are not the same thing and I just want to confirm that what you meant was you would have a cam ground on more LSA (like 112 instead of 110 or 108) if you were trying to take advantage of the extra cubes without ending up with a rough idle. Yes?
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Two different situations, sorry I wasn't clear
For his motor, assuming he is buying a cam anyway, I would add duration and lobe seperation, spread the centers to reduce overlap, but keep an early intake lobe.
In my 445, I DIDNT do that, I ran the small cam, made some up with the head and intake, and then retarded the cam a bit because I couldn't control DCR otherwise, plus I wanted it to hang in a little longer.
Thats why I made the point that I was being cheap, and that I was hoping the heads and intake would make up the difference.
If I didn't have the 270H, I probably would have added duration, kept overlap low with LSA, and then kept an intake valve closing point similar to where I am now.
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Well this is what I got for my 445 any advice on which timing gear key to use?
(http://i1304.photobucket.com/albums/s524/1966FEComet/IMG_20130206_153724_242_zps5b231790.jpg)
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How much spring do you have to run with that cam? Wondering what was the reason for choosing an LS1 intake lobe and a lift rule aggressive race only exhaust lobe?
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Well I failed to mansion it is a hydraulic roller so the profiles look a little odd. I wanted a big breather up to 6500 that would still be somewhat streetable. I am running a stick so idle is not a big deal either. The lift I did not go too crazy as it will rarely see 7000 rpm but will do it on the lifters, I just want to stay in the safe zone. Seat pressure is 350 psi into/ exh to hold the heavy rollers down. I would have liked a stabilizer kit for more rpm but could not find a compatible one and I would have to get a main girdle too. I may do that anyhow for extra cap support, it is your basic 390 block so nothing special.
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Boy that's a lot of seat pressure! :o What's your open pressure? Didn't know they make hydraulic roller lifters that can handle that much.
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Going with a Comp Cams 282S, 236/236, 0.571/0.571, so about 12 degrees more duration than what I would have picked for a 390. Using an iron CJ intake manifold, and a set of nicely ported D2 heads with CJ valves. For the RPM range I'm planning on using the engine, I think the combo should good low and mid-range torque, idle okay, and still rip when I need it to. If it doesn't, I still have my two Fairlanes to go play with!
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I have had many 390 powered pickups they all would leave wrinkles in the asphalt so I think you will be surprised LOL
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Looking good Dave, I would set the chain/cam advance 4* also if you can yet. But man that looks really nice now that its all painted. I think for a "TOW" truck that thing is going to rip off some time slips, and you could run some grudge/cash races ;D With all that detuned Iron look you will have going on. Would make most Bow tie boys go to sleep when looking in the engine bay.
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Boy that's a lot of seat pressure! :o What's your open pressure? Didn't know they make hydraulic roller lifters that can handle that much.
I think Jon may be talking about the open pressure, not seat pressure. Maybe he can confirm...
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7k rpm with a hydro roller? That's a lot of mass flying around. I know mine won't do it without floating.
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There are folks who run hydraulic roller setups that high, but the valves are floating and they are kind of playing with fire after 6000 RPM. I did a lot of work on making a hydraulic roller cam work at higher engine speeds back in 2005 and 2006, and the most I ever got out of one before valve float set in was 6300 RPM. What I found was you needed a lot of seat pressure, like over 200 pounds, but open pressure had to be limited to around 425 or so. The interesting thing was that the engine still sounded good for a few hundred RPM over the point where valve float occurred, but you could tell by the horsepower curve from the dyno data that the valves were floating; the curve got very choppy and power started dropping off.
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No that was seat I am not sure of open @ 590 lift? The Beehive spring came either 330 close ( too light ) or 350, kinda heavy but all comp cams makes. Spec on the spring was 340 open but at my installed height it worked out to 349 or something like that. Barry said with that setup and the light weight race lifters I have it will start to float around
6800 on the dyno. I gotta say all that was not your usual 2000 dollar kit, more like 4500 bucks in can and valve train without rockers.
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Are you sure about that? I've never seen a beehive spring with that much seat pressure. I assume this is a Comp cams spring? What part number?
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Therese are it
http://m.summitracing.com/parts/cca-26981-16
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Check out where you can buy those springs:
http://www.sears.com/comp-cams-competition-cams-26981-16-beehivevalve-spring/p-SPM7503546011?prdNo=14
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Here they are installed
(http://i1304.photobucket.com/albums/s524/1966FEComet/IMG_20130207_130610_838_zps37957355.jpg)
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Ha Ha buy em at Sears in the tire department.
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Now that I look at it again I went with those.because they are strait rater with no compressed rate.progression, 347 all the way through the stroke.
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Here are the specs
http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=26981-16&Category_Code=
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You might hit coil bind with those springs. At an installed height of 1.7", you could probably safely run about .535" or so lift since coil bind is supposed to be at 1.115". I would measure actual coil bind to be safe. Your seat pressure is pretty low too for such a radical hydraulic roller.
Is that rust on your springs? I would check them closely to make sure there's no pitting. If you break a spring, it might be pretty serious since beehives are single springs.
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No that is condensation I believe I mentioned it is terrible here in another post. I sprayed then down and brought them inside after that pic was taken they are always stored in a plastic tub with silicate beads , as soon as you remove them on a cool rainy day that is what you get. The spring specs are what comp cams said to use, 347 and they gave me the part numbers of what was recommended so I went to the higher rate spring in that range. Barry did all the setup on the head design with that camshaft already shelved for me so I would trust he checked that. We built the heads with 600 lift in mind. I just basically told him what I wanted and Survival did the make happen magic.
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Those springs are a 347 pound per inch spring rate, not 347 pounds on the seat. The Comp catalog says they are 110 pounds on the seat with an installed height of 1.700", and 292 pounds open at a spring height of 1.175". I think you will need a lot more spring with that cam if you want to run past 5000 RPM, and I too would be concerned about hitting coil bind, unless you increase the installed height.
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Eh I guess I will have to call Barry then I thought he had that covered?
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If those are the springs that Barry recommended then I wouldn't be too concerned; he has done a whole bunch of hydraulic roller motors, and he certainly knows more than I do on that topic. Did he also give you the cam grind?
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Talked to Barry whoops me dummy, he used these and explained the characteristics of the spring and said you cannot bind a beehive more or less.
http://m.summitracing.com/parts/cca-26055-16
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Yeah, that one makes more sense.
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Per the original question. A respected engine builder once said:
For a given engine combo if I have a known good cam profile I add 8 degrees of duration @ .050" lift for each additional 50 cubic inches. I also like to tighten the LSA 1 to 2 degrees for each additional 50 inches.
Both combos will HP peak in the same RPM window and have similar idle characteristics...
He was talking about building a similar but larger engine from the same engine family with the same or similar parts. Just a displacement increase.
I assumed he tightened the LSA because the larger displacement motor can tolerate more overlap (in addition to the increased overlap from more duation) and still have similar idle and low rpm characteristics. And also because the larger displacement motor needs even more overlap to help breathing at high rpm, given that it has the same or similar induction system trying to feed more cubes. I'm not sure, but that's what I assumed.
The 8 degrees per 50 cubes would yield 14.4 more degrees for a 90 cube increase which seems to be in line with the other replies.
The big variable not addressed by this, which Ross mentioned, is the rest of the induction system. I would think if the heads, intake, etc. were marginal on the small cube motor, then the large cube motor would need even more cam duration added to keep a similar rpm range, and the results would not be very good. If the heads, intake, etc. were replaced with higher flowing pieces on the bigger motor then you might need less cam duration increase than the formula calls for. The rpm range is determined by displacement and the flow characteristics of the entire induction system. The cam is just one part of that. That's the thing with rules of thumb. They by intention oversimplify the situation. They can still be useful though.
JMO,
paulie
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It would seem relevant that if comparing say a 352 two barrel engine to a 428 CJ the parts on the induction side would be different anyhow. The two barrel head would be useless from the get go.
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Absolutely. I was just trying to make the point that the cam is only one part of the equation. Also when people put a stroker kit in their motor, they often reuse the induction system they had on the motor before adding the stroker kit. It may or may not be a good choice for the increased displacement. It's something that should be considered.
JMO,
paulie
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Thanks for that info Paulie, I've never seen that particular rule of thumb before. Makes sense though, and is in line with my own experience...
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de nada, enchilada! (ya sure ya betcha!) ;D
paulie
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Sorry I was out of town (was at Blair Patrick's FE house of wonder) But in Daves defense he does have a nice set of CJ valved and worked D2 heads with a good CJ intake. And is going in a truck to pull his race car so it may not be a total induction package for racing but should provide a nice package to tow and snap for going down the track. I think it will catch a few chevy guys off guard thinking it's a garden 390 in a truck till it drives by at the digs on the big end ;D And that would be worth getting on you tube 8)