FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: darren121671 on February 25, 2015, 10:10:49 AM
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I'm building a 390 for my 1970f-100. I need help picking a cam. The engine is a 4.080x3.780 with stock rods with ARP rod bolts. Speed pro flat top 4 eyebrow pistons 10-10.5 compression . Heads are 428 CJ with stock valve size. Blue thunder LR intake. And a 735 CJ carb. I have read that I need to keep the duration @.050 under 221 for power brakes. What is limit with enough vacuum and duration? Can I get into 230-240 range?
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I personally think power brakes are over rated.
Along with heated seats.
It is more about how you drive than anything.
Be honest and you will have a great driving vehicle.
240* in a 10 to 1 396 ci is a bit of a pain at slow speed in traffic.
Out on the highway with room to run it's great.
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I think you could get away with 228 or 230 and still have enough vacuum; 236 is too much, based on at least one cam that I ran. Alternatively you can always get one of those add-on electric vacuum pumps if you guess a little too high on duration.
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I personally think power brakes are over rated.
Along with heated seats.
It is more about how you drive than anything.
Be honest and you will have a great driving vehicle.
240* in a 10 to 1 396 ci is a bit of a pain at slow speed in traffic.
Out on the highway with room to run it's great.
Hey, heated seats are great, just like my heated steering wheel, in my new Kia Optima! Can't wait to get my Stangs out once this stupidly cold winter ends but in the meantime, those heaters rock! ;D
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Thanks guys. Theses are the cams I'm looking at. Lunati 219/227@.050, lift .540/.552 LSA/ICA 112/108, 227/233@.050 Lift .552/.564 LSA/ICL 110/106. Comp cams 218/224@.050 lift .513/.520 LSA/ICA 110/106, Howard's 213/223@.050 lift.525/.525 LSA/ICL 112/108. I know all of these cam are very similar, but which one would you choose for my combination. My goal for this engine is 375- 400 hp. And still be able to drive it to California on pump gas with power brakes. I know I might be dreaming but tell me what you think.
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I think I'd stay around the 220 mark, and 112-ish on the lobe separation. A truck used like a truck is easily over-cammed if you are not careful. As far as the power brakes go, you can operate brakes at 230 on a 390, as long as you keep the lobes spread to 112, but it will start to be sluggish off-idle and up to around 1500 if you go too far. I'd go .500 lift, 220 @ .050, and 112. If you go hydraulic roller, add about 4 degrees to it, since the quicker ramps will restore some of the off-idle response. Might want to think about a smaller manifold for a 390.........maybe even an iron CJ intake if in a truck, or a PI or Streetmaster. JMO.
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Less cam than you want, but for comparison purposes a Comp XE 256 (212 @ .050 on the intake / 219 @ .050 on the exhaust, 110 lobe separation, just a hair under .500 lift) on a +30 390 sustains 17-in vacuum at idle and 20-in+ above 1500 rpm. This engine has a set of cleaned-up iron GT heads w/3-angle valve job, 10:1 compression, aluminum PI intake and a 650 cfm Holley on a 1-in spacer. Not a screamer but very smooth and steps out with authority above 2000 rpm.
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So which cam out of the 4 would you guys pick? I haven't contacted all 4 cam manufactors but lunati recommend the the 219/227 lift .540/.552 for this set up. I'm just worried about having enough vacuum for power brakes.
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Not a truck but might as well be.
64 galaxie with 3.00 gears.......
the XE262H from comp
Hydraulic Flat Tappet, Advertised Duration 262/270, Lift .513/.520
Has done this ol thing very well. Power brakes work really well and I used to drive this thing 160 miles every weekend to come home from shool. Then it was my daily driver for a few years. Cruised great, pushed that thing pretty darn well.
390, 9.5:1, FPA headers, C8ae-h heads with bigger valves and mild port work, edelbrock RPM intake and 650 carb.
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I would say any of the cams listed will work fine. Remember, when you need good brakes you are on deceleration, lots of vacuum. When you are at idle speed (low vacuum) you are going slow enough you don't need power brakes. I will also say, none of those cams will get you 400hp on pump gas. I have found with heavy trucks, the FE is prone to detonation with small cams and performance ignition timing on regular gas. So to get by, I used cold plugs, reduced ignition timing and poor performing truck but it would live. Disclaimer: I am not a cam guru at all ;D
Nick
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A little off track, but... do the requirements for vacuum change as you go up in cubic inches as it relates to duration and lobe separation?
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Also off track, but all the cams on your list are split duration and I wonder what others would say about perhaps a Comp 268H or 270H instead?
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I think Blair is close.
I've been running a Crane solid cam in my 6000lb '68 F250 4wd for 20 years and it has been perfect. 227@.050, 112LSA, low 5s on lift. C4 heads with an iron S intake and 750 Holley vacuum secondary. It's a fantastic combo, roughly 380-390hp and will pull/haul anything I want to. Enough vacuum for PB, although mine are not power. About 10:1 compression and no detonation with 89 octane and 38* timing. With an MSD Blaster ignition, it starts instantly in any temp or weather.
I can't say enough good things about this cam for an all-around good street cam for a 390 in a car or truck. It pulls strong and smooth from idle to 5500, but most of its power is done by 5000. I've pulled loads over 7500lbs with ease on countless occasions. At those loads, a good hill will make me drop to 3rd, but that's a result of cubic inches. At lesser loads, hills are not an issue.
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Not a truck but might as well be.
64 galaxie with 3.00 gears.......
the XE262H from comp
Hydraulic Flat Tappet, Advertised Duration 262/270, Lift .513/.520
Has done this ol thing very well. Power brakes work really well and I used to drive this thing 160 miles every weekend to come home from shool. Then it was my daily driver for a few years. Cruised great, pushed that thing pretty darn well.
390, 9.5:1, FPA headers, C8ae-h heads with bigger valves and mild port work, edelbrock RPM intake and 650 carb.
The cam I should have selected (but which the Comp rep, incidentally, advised against ::) ).
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Darren, of those choices, I'd go with the Lunati. The Howards is a bit small, IMO, and I'd stay away from the others with 110 LSA's if you actually want to use it as a truck. A wider LSA will give you a much friendlier and useable power band. But I think you can still go a bit more than the Lunati and it won't feel so "stockish" in terms of power. The heads and intake would be overkill with such a mild cam. I'm assuming by your posts that your set on a hydraulic?
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Yes, I would like to stick with a hydraulic. Maybe even a hydraulic roller if you guys think I could run one with head and intake combo.The intake is not set in stone yet. I'm leaning towards the Lunati cam also. Thanks for everyone's input.
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I'd go hydraulic roller and never look back. It's more torque and more reliable than a flat lifter cam. I use a .524 lift, 224/224 on a 112 custom grind pretty often for what you descibe. We put it in heavy cars, 1-tons, etc. It is my favorite for an engine that needs to be there right off idle. The cam is a little more, and you'd have to buy lifters, but much better in the long run, and no worn lobes when you least expect it.
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Thanks guys for all of your input. I think I will go with the Lunati 219/227@.050, lift .540/.552 LSA/ICA 112/108 or .524 lift, 224/224 on a 112 custom grind roller if I can scrape up the dough for the roller. CaptCobrajet who makes that grind for you anyway?
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I'd pm Blair and see if he could order you the correct set up as he's a vendor. He might not want to give up one of his secrets ;). Also he would give you a better cam selection than the techs at lunati or comp IMHO.
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I'd go hydraulic roller and never look back. It's more torque and more reliable than a flat lifter cam.
Blair, your hatred for flat tappet cams is well known. I know there are occasional lobe failures on flat tappet cams, but I've never had one. I've got solids that have been running for over 25 years that require no lash adjustments. I know of plenty of others that have been used for well over 35 years, in multiple engines. So when people can show me rollers that have gone over 100k miles and last 25+ years of daily use IN AN FE (not in a new engine), then I'll believe that rollers COULD be as reliable as a solid flat tappet.
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I'd go hydraulic roller and never look back. It's more torque and more reliable than a flat lifter cam.
Blair, your hatred for flat tappet cams is well known. I know there are occasional lobe failures on flat tappet cams, but I've never had one. I've got solids that have been running for over 25 years that require no lash adjustments. I know of plenty of others that have been used for well over 35 years, in multiple engines. So when people can show me rollers that have gone over 100k miles and last 25+ years of daily use IN AN FE (not in a new engine), then I'll believe that rollers COULD be as reliable as a solid flat tappet.
Not sure I'd call it a hatred for flat tappets. I actually like solid flat tappets. We get them well into the 9's with .500 lift in racing apps, BUT the problem for me comes when I build an engine for a customer, and neither the customer or myself does anything "wrong". No wrong spring pressures, no wrong parts, no wrong break-in, and no wrong treatment after the customers gets it...................and then.................for no reason..........it wears a lobe off after a short time period. Now, if I send that engine to, let's say, California, from Tennessee..... if that customer wants me to fix it, think of the cost to me. I would have to have two more successful builds to recover from the loss on that one. I don't like to build street/strippers for customers with flat lifters because of the potential for it to cost me an arm and a leg "if" it happens to kill a lobe............which is possible. I admit, I have never had that happen, but I know the cost if it did. I have just made a decision to not build aggressive flat tappets for street use. A low rpm, 100 seat, 280 open, 5000 rpm truck engine............fairly safe, and I will do that, but a 160/400 sprung, 7500 rpm flat lifter that sits in a garage for three months at a time.......not me. In that case, it is a cocked gun, just waiting to fail. I would rather do a solid roller and tell a guy he has 10,000 safe miles before a lifter change. Just a business decision more than a "hatred". The oils we use do not have the same "guts" that oils used to have. There is a reason the OEMs went away from flat lifters, and I have grown to prefer the hydraulic rollers on the street. They have been cycle tested at 400 open pressure, and proven reliable, and I am on that program.
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All good and valid points from a business perspective. I won't use hydraulic flat tappets in anything. I just don't see any advantage from them, only negatives. And I admit, I'm always nervous the first 500 miles on a solid cam build. But so far I have either been lucky, or just take the right steps to avoid any problems. Still, I'll always be of the mind that, on older engines at least, a solid flat tappet is the most reliable cam/lifter set-up out there. Rollers will need replaced, hydraulics (even OEM) WILL fail eventually, but a good solid cam will last for generations without problems. I've got some 60+ year old flathead performance cams that I would not hesitate to use again, and again.
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Huuummmm.... I'm a Roller type of guy myself. Normally solid rollers. But I will be building a Hydraulic flat tappet for my back yard 390 build. Using a Comp XE274H cam. Should be about perfect for what I want to build.
As for the 4x4.... Take a look at the XE264H.... It would be about perfect for what your looking for. JMHO
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I have had better luck with lunati then comp but that is just my opinion