Roller Cam or Flat Tappet in a 400 - Pontiac GTO Forum
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post #1 of 27 (permalink) Old 01-16-2015, 09:16 AM Thread Starter
 
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Roller Cam or Flat Tappet in a 400

I'd like a camshaft recommendation.

This is for a 64 Lemans convertible, it will be a street only cruiser, driven to work a few days a week on the interstate, local cruises/car shows. 2.93 posi, M20, Pypes 2.5, R/A manifolds, 65 Tri-power, power brakes, full roller rockers (ratio depends on what you recommend, I have 1.5s now). I want the engine to be all done by 5500 RPM and run on 89. We have 91 octane here now but...

I just bought a fresh never fired 75 400. +.040 TRW, XE262, recon stock rods w/ARP bolts, balanced, pistons are .015 in the hole (I've only measured one so far). It has fresh 6X-8 with no port work, stainless valves 1.77 exh.

I plan to ditch the 6X-8 and use my other fresh 6X-4's, they have some heavy bowl work done and are gasket matched. I plan to disassemble the engine and have the block decked and squared to about .005 down in the hole. I plan to mill the heads to achieve 9:1 static.

I was leaning towards a XE268 cam or a voodoo 60902,
Part Number: 10510702
•Advertised Duration (Int/Exh): 262/268
•Duration @ .050 (Int/Exh): 219/227
•Gross Valve Lift (Int/Exh): .468/.489
•LSA/ICL: 112/108
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1300-5500

Seems many folks don't like the XE because they slam the valve down vs voodoo that lets the valve down easier. I started looking hard a Sandoval Performance's website and reading more about hydraulic roller cams. Now I'm torn, confused and tired of thinking about it.

I was looking at his L/C2 206/[email protected] 110 LSA or L/C3 214/[email protected] 108 LSA rollers or "the daily driver" 224/[email protected] on 108LSA

I see VooDoo makes a similar roller to their 60902 HFT.
Part Number: 20510710
•Advertised Duration (Int/Exh): 262/270
•Duration @ .050 (Int/Exh): 211/219
•Gross Valve Lift (Int/Exh): .507/.515
•LSA/ICL: 112/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 1400-5400
•Includes: Cam Only
Previous Part Number: 60910

It seems that there are only positives with a HR, more torque, less wear, decent idle. Are there any draw backs to having a roller cam with the tri power? Will I see a big drop off in fuel economy with a high lift roller? I'd like to get at least 17 MPG if possible.

So what would you do? Is there a good HR that will fit the bill for what I'm trying to do? Or will the roller kill my MPG, (the reason I chose 2.93 axle). Am I better with one of the HFT? Which one?

I do not want a max effort, squeeze every hp out engine.

I've kind of steered away from the OEM grinds because of the low 9:1 compression. Should I just stick a 068 in and be done? I have a crower 60916 on the shelf but I don't think I have enough compression for it either. I've heard the Crower 60240 HFT works pretty good in a 9:1 400.

Thanks for any recommendations and advice to help un-confuse me.

Dean
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post #2 of 27 (permalink) Old 01-16-2015, 09:29 AM
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IMO that roller cam is too large for what you want. With the 2.93 gear and low compression she will be lazy down low where you drive 99% of the time. You say you want it to be all done by 5000 rpm but if you go with the large cam you are moving the powerband up in the rpm range so you are effectively narrowing the powerband.

If you had more cubes I could see running something larger but with the 400 and 9:1 compression I'd stay with something on par with the 068. Use that famous Pontiac torque to move that freeway geared, low compression convertible.
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post #3 of 27 (permalink) Old 01-16-2015, 07:11 PM
 
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Personal Opinion.

I think a roller cam/lifters are a bit pricey for an average street build. Neat to say you have it, but I feel really not needed. And what if you don't like the cam? Expensive guess.

Flat tappet cams are great for the street, but you will read all the fears about a cam lobe going flat, the cam being soft, or poor quality. Get a cam/lifters from a reputable manufacturer. If they were all that bad, it would not take long for "that" company to get a black eye and be out of business. Sometimes I doubt these claims per say, because there are many dealers/sellers who want you to buy their cam brand - so they blog about xxx cam that went bad and they would never buy another and once they bought xxx cam, they had no problems. Bad press is a great marketing tool. And with a flat tappet cam, you must use an oil with zinc in it or use a zinc additive to prevent cam /lifter wear. Roller cams are not as sensitive -so this is a positive for rollers.

Hydraulic cams are the best for no hassle adjustment -install cam/lifters, correctly lash them, and your done. Solid cams require a periodic check/adjustment of the valve lash. Us hardcore motorheads don't mind the periodic adjustments because they have a unique "clatter" sound that implies "race car." I selected a solid for my build. The solid also gives you a more aggressive cam for the same hydraulic grind. The ramps on the cam are ground differently to open the valve up faster. Slamming the valve open and closed? Isn't that what a cam does? I personally don't feel this is a problem unless you get into some big spring pressures, but then you would not be really using this for a street car, and then you would go roller.

Once you know your actual compression, then you can look around for a cam grind -there are 100 different ones. The things to consider are indeed your compression. Then the RPM range you want to spin the engine and where you want your power band to be. Next is your rear gear ratio, transmission/torque converter stall, and even the weight of the car.

Pontiac knew what to do when they built their engines. They did not build them for high revs. They were built for broad torque and provided a good vacuum to run power brakes. The RPM range was aimed at daily drivers.

You do not have to do a lot of modifications to get a great running street car & still get reasonable gas mileage. I personally don't think the XE cams on a 110 LSA are good for 9 to 1 and up compressions, although no doubt they are used. I feel they are best suited for under 9 to 1 as they build a higher dynamic compression to work with the under 9 to 1 compressions. Use this on 9 and over and you may have an engine that pings/spark knocks unless you use top grade gas or an additive. These cams seem to have a narrower power band, and drop off on power like a stone at whatever peak RPM they are intended for. But they do pull like a freight train with lower compressions.

The cam you see advertised needing higher compression, higher stall converters/4-speeds, 3.55 gears or better are those typically having 114 LSA or more. Why? Because they have more intake/exhaust opening/closing overlap and bleed off some of that higher compression at lower RPM's, but gain it right back at the mid to upper RPM's. You would not want to bleed off any compression on an engine with 9 to 1 or lower. These cams can also be a little "sluggish" on the bottom end so on the street, you might not be too impressed with the lack of get-up-and-go at lower RPM's. Mid-range and up they would however rip your head off -thus you need the slightly higher stall converter and taller gearing to get your engine up the usable RPM range of the cam. This is basically what Pontiac used on the GTO's. These also give a broader torque/HP range and good vacuum.

So, my opinion, the 112LSA cam is just right for 9 to 1 compression if you go aftermarket.(I went with a Crower with the 112LSA) Then you want to select a cam duration number to match your RPM range. Very easy to get caught up in "bragging rights" and over cam on these numbers. Duration wise, probably 260-270 intake, 270-280 exhaust for street manners. Factory Pontiac lift on the valves were .406" with several grinds getting only .374" on the intake and .406" on the exhaust. Pontiac heads flow good at lower lifts, so I would not get too crazy for the street and put it somewhere around .450" max. Now here you could play around with lift. A .406" lift uses 1.5 rockers. Install a 1.65 rocker and you now get .446" lift. The 1.65's will also open the valve quicker which will act like a few more degrees of duration. If the engine responds to the 1.65's then keep them. If it doesn't seem as good, go back to the 1.5's - not all engines will respond favorably to more lift. The use of 1.65's sometimes require a little grinding on the head where the pushrod goes through -you open it up a little so the pushrod does not hit the head. It should not be a problem for under .500" lift, but while at the machinist, I'd have it done just to be safe.

The 1965 factory cam was the 066. 273 In duration, 282 Ex duration, .406" lift, 55 degrees of cam overlap. The 067 cam was 273 In/289 Ex, .406" lift, 54 degrees overlap. The 068 cam was 288 In/302 Ex, .406" lift, 63 degrees overlap. Lift stays the same, exhaust gets more duration to compensate for the restricted exhaust flow. With these 3 factory cams, I think the 068 cam would be the biggest factory cam I would go with, but gas mileage will be down. It may be too much for the 9.0 compression and be a dog at lower RPM's. I like the 067 cam as a better choice & it is going to be smoother with its lowered overlap -should get good gas mileage too. (Had a '67 GTO with this cam: lots of power & upwards of 20 MPG @ 55MPH back then with 4sp & 3.08's) And of course the 066 is good as well.

Invest your money in a good 3 angle valve job & a good dual exhaust system. -this is where you will get big improvements with a Pontiac engine.

There is no "one fits all" cam. Sometimes it is trial and error. There are "safe" cams and others that may not quite work as intended. Many of the cam grinders and/or Pontiac engine builders have a cam data sheet you can fill out with your car's info and they will recommend a cam for you. They know what they are doing. You can also ask them a question on a cam you think would work and they will let you know as well.

That's my opinion ('cause I'm no expert) and I'm sticking to it.

I think geeteeohguy has the 068 in his lowered compression GTO, so maybe he has some input here as well.
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post #4 of 27 (permalink) Old 01-17-2015, 10:49 PM
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Ok, I'll play
Advantages of a (carefully chosen) roller:
Less worry about wiped cam lobes due to no/insufficient ZDDP in the oil and/or improper break in.
Steeper opening/closing ramps mean that you can get the benefits of longer duration without the drawbacks of significantly increased overlap.
Solid roller cams have higher rpm potential.
Less parasitic loss due to friction.

Advantages of a (carefully chosen) flat tappet cam.
Less expensive.
No chance of a roller coming apart and taking the engine with it.

Disadvantages of a roller.
More expensive.
Hydraulic roller lifters are usually heavier (more valve train mass)
Risk of "bad things" happening if a roller fails.

Disadvantages of a flat tappet.
Break in procedure and proper oil (ZDDP) very critical.
Getting harder and harder to find high quality parts.
Longer duration means more overlap (negative effect on idle and vacuum)
More parasitic loss due to friction.

In short, it's possible to build a stout Pontiac using either and there are advantages and disadvantages to both.

I chose to build my engine with a solid roller system MAINLY because it allowed me to get the valve timings I wanted without having to suffer the effects of significantly increased overlap. My car idles with some attitude but it's not overly obnoxious, and it still makes 13-14 inches of idle vacuum. I bought good parts and did the job right, including putting in oiling restrictors in the lifter bore oil passages. I also went with good springs, titanium spring retainers, and full roller rockers. It was expensive, but it was what I wanted and I understood why I was doing what I did.

It'd be a lie if I said that my way "was the only way to build an engine", because it's certainly not.

To pick a cam, start with how and where you plan to use the car, how it's geared, what kind of transmission it has and honestly where it's going to be spending most of its time, RPM-wise. Pick a cam that has duration, lift, and lobe separation specs that are optimum for those conditions. (Having some sort of engine modeling software is very helpful here. I used Performance Trends Engine Analyzer Plus). When you're running the simulations, pay attention to the effect that lobe separation and type (roller or flat) both have on rpm range and idle vacuum. You should start to see "patterns" emerge that tend to steer you towards what's right for you.

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post #5 of 27 (permalink) Old 01-19-2015, 08:37 PM
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I am running a 9.3:1 original 400 in my '67 GTO convertible. Original distributor and carb. Using a Melling 068 spec cam (it's been in there over 20 years). With a very lazy 2.56 rear gear and a TH400, the car does fine. Good power from idle to 5200 rpm, but I never rev it that high. It's a great cam for a street driven car, and good on fuel mileage, too. Roller rockers are nice, and come recommended for a high performance (450 HP on up) engine, but are overkill for a basically stock street driven car. I've put about 70,000 trouble free miles on the 068 cam since I installed it.
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post #6 of 27 (permalink) Old 01-22-2015, 09:02 PM Thread Starter
 
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Thanks for all the advice. I appreciate it. I just found out today, the machinist I was hoping to use is retiring. I've been waiting a few months to bring him my parts and start/finish this build. I was hoping he could help me sort this all out. He recommended XE274 but ground on a 112. I think this may be a little big for my combo, he didn't know my rear gear ratio (2.93), when we were talking.

Anyhow. I think we've narrowed it down to a 112 LSA.

I have a used cam (maybe 10k miles on it) out of my 350, it's a melling 214/224 442 465 on 112, this is real close to a summit 2801, and similar to the 068 212/225 but with more lift. This may work.

I keep going back to the voodoo 60902 219/227 .468/.489 on 112. Lunati recommends it as their Tri-Power cam.

or the voodoo roller 60910 211/219 .507/.515 on 112

Other folks have recommended the Crower HFT 60240 210/221 422/446 on 112

This is going a 9:1, +.040, 400, with 87cc ish 6X-4's, R/A manifolds and 2.5 Pypes fed by a Tri-Power. 4 speed power brakes.

Is there a free engine simulator software package I can down load? I've been playing with CamQuest, but they only have their comp cams to choose from, and the engine parameters mainly revolve around SBC specs.

The roller may just be a waste of money at this point. Nice to say I have it, but 90% of folks won't even know what it is.

Thanks again for the help.

Are any of the cams above jumping out at you? For this combo? Most of these cams are all similar in specs, designed for higher compression. The asymmetric lobes of the voodoo should help with my 9:1 SCR.
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post #7 of 27 (permalink) Old 01-23-2015, 09:09 AM
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With your 2.93 rear and a stick, you want to make power right off idle and in the low end. Your camshaft choice should reflect that. (mild or close to stock). A big cam that ups the power in the high end will make your car a poor performer with those rear gears. A stock cam, it will run pretty well, though a bit soft out of the hole. (3.08 is as low as Pontiac went with stick cars for this reason).
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post #8 of 27 (permalink) Old 01-23-2015, 06:44 PM
 
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I feel the 2.93 posi may be a stumbling block. You are going to have to run short tires, ie stock 26" diameter. If you go larger, you effectively lower the 2.93's even more. You may have a problem if you select a cam that requires a higher than stock idle because you won't be able to pull the car down below 10 MPH without having to push in the clutch because the car is "bucking". I had this experience with my car as I went with tall tires, I think I figured them to be 3.23's, and had a higher idle -so be aware of this in your cam selections.

Stock Pontiac heads are said not to produce much extra benefits go too big on the lift. You did some bowl work/port match which should allow you more flow numbers at higher lifts. Did the same with my heads but, I too was not sure what cam to use because each cam is truly car/engine build specific and what may work well for one guy might be a dog in another's. Some of these guys select a cam and then fine tune that by swapping a ton of parts from carb to gears to get it dialed in -then they say it is the greatest cam ever. Was it the cam, or all the parts matching?

For that reason, I still feel a roller is not the best first choice until you get a cam that you feel is best for your car. You can try a flat tappet cam, not care for it, and later try another grind. Little bit cheaper. Find one you like, then go roller if you feel you want to add one.

I feel the 112 LSA is still a good choice for 9 to 1 compression. Now looking at your cam choice, because you have it, I would honestly try the Melling cam first. Is it a little small? Not necessarily. Smaller cams build more torque. Torque is exactly what you want with those 2.93 gears. Your heads will do the extra flowing without the need for a bigger cam.

But, here is what I see as an advantage and what I too am doing in my cam choice with my 455CI 9 to 1 compression engine, 112 LSA, 284/288 duration. Got a solid cam that will give me a very modest .455" net lift at the intake valve. Not very big by Chevy standards or anyone else's that you read about, right?. The lift is based on 1.5 ratio rockers, and so is your Melling cam. Your Melling cam gives you .442" In & .465" Ex. using the 1.5 rockers. If you switch up and go with the 1.65 Pontiac rockers, you now get .486" In & .511" Ex. The 1.65's also open the valves quicker which effectively gives you about an additional 3 degrees more duration. So you can experiment here with lift and see how it changes the engine characteristics. You can also experiment with advancing or retarding the cam to slightly change the powerband -making sure you have valve to piston clearance which you should do anyway for your engine build.

If you try the 1.65's, you want to make sure you elongate the pushrod holes in the head so the pushrod does not hit it at full up travel. Make sure you have springs & retainers to match the .511" lift and that the valve spring does not go into coil bind. I set my heads up to handle a good .550" or so lift and did the pushrod hole elongation. Also know I have the valve to piston clearances.

As another option you could also try the Rhoads lifters which will effectively reduce lift and duration below their lifter pump up of 2,500-3000 RPM (depending on oil weight). Click on this link to go to their site: Rhoads Lifters. This allows you to use a bigger cam, ie more duration and lift over the Melling cam (like the XE 274 on 112LSA), but the lifters make the cam act more like a stocker cam until it gets up in RPM's and the lifters pump up and the cam comes on at full lift/duration. Improves engine vacuum as well. I used these on my brother's 360 build and they do do their job. It is said they clatter a little like solid lifters, but if they do, I could not really hear it over the exhaust tone.

Cam selection can be perplexing. No one cam does it all. You want the best cam for your engine, but what is it? Honestly, I can't say, even in my pick of cam for my engine. Believe me, I read a ton of blogs, forums, "how-to's", books, cam technology, head flow, and everything in between. Does it mean I picked the "best" cam. Nope. I may have a dud on my hands, who knows. It simply boiled down to just picking a cam I felt OK with and bought it. I'll know more once it hits the road.
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post #9 of 27 (permalink) Old 01-24-2015, 11:46 AM
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What Jim said, and what I tried to say. Selecting a cam is dependent on what 'combo' you are running. With a stickshift, aggressive high lift, long duration cams work well with stiff gears (3.55-.433) and headers. With a stickshift and a lazy rear gear (2.93-3.23) you want a much more mild cam, one that will produce the low end torque to let the car move out without surging, bucking, or lugging. You need an engine to run strong and smooth at low to mid rpms, not a high strung, low torque, high revving engine. With your 2.93 rear gear, an 068 grind and stock 1.5 rockers would be the most streetable choice. If you want to run a bigger, badder camshaft, you need to swap rears for at least a 3.36 ratio. BTDT................
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post #10 of 27 (permalink) Old 01-24-2015, 12:05 PM
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Originally Posted by ALKYGTO View Post
IMO that roller cam is too large for what you want. With the 2.93 gear and low compression she will be lazy down low where you drive 99% of the time. You say you want it to be all done by 5000 rpm but if you go with the large cam you are moving the powerband up in the rpm range so you are effectively narrowing the powerband.

If you had more cubes I could see running something larger but with the 400 and 9:1 compression I'd stay with something on par with the 068. Use that famous Pontiac torque to move that freeway geared, low compression convertible.
And, after aaaaaallllll that, exactly what the "Chevy guy" said in the first response. Sorry guys, I had too.
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