Another Camshaft Question
06-03-2006, 11:06 AM
#21
Registered
iTrader: (1)
Re: Another Camshaft Question
Liberator21 -
I believe RM was commenting only between the XE268 and XM270. #'s vs #'s - nothing else.
Post what you have for:
Intake Manifold
Compression
Cyl heads - and if any work to them // also spring type/man with installed seat psi, open psi, ret to guide clearance, etc,etc
Exactly what your wants/needs out of this motor is, including octane available, dependability of valve train, etc,etc,etc
Are we aware of possible cam wear issues ? Any possiblity of going roller ?
I believe RM was commenting only between the XE268 and XM270. #'s vs #'s - nothing else.
Post what you have for:
Intake Manifold
Compression
Cyl heads - and if any work to them // also spring type/man with installed seat psi, open psi, ret to guide clearance, etc,etc
Exactly what your wants/needs out of this motor is, including octane available, dependability of valve train, etc,etc,etc
Are we aware of possible cam wear issues ? Any possiblity of going roller ?
06-03-2006, 12:03 PM
#22
Registered
Thread Starter
Join Date: Jan 2004
Location: Long Island NY.
Posts: 450
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
SB:
I know RM was comparing the camshafts, but his comments seemed to elude to the XM270 being better suited to my application (given the two cams). Of course the final decision will be mine.
The engine is a 383, using a Scat stroker kit with 6" rods, and forged pistons. The heads are GMPP 300HP crate engine heads with some porting.
64cc chambers with the small valves (should have went for the Dart Heads). Compression ratio is a little over 9.5:1 The valve springs I'm using, are the Comp springs recommended for the XM270 cam. Installed height, and spring pressures are all at the manufacturer's required specs.
The setup will easily handle the 270's valve lift. I also clearanced the inside of the cast rocker covers for the roller tip rockers. The intake manifold is the GMPP cast iron high rise intake (dual plane). It's the cast iron version of the Z28 manifold. It came stock on the OMC 270hp cobra setups. Internally it looks just like an Edelbrock performer. The manifold's internals have been "massaged" by my porting guy. The carb is a Q-jet with quite a bit of work done to it. Fuel is not an issue in my area. My wants/needs for the engine? Reliability of course, which I don't think the 270 will sacrifice, good cruising performance with the ability to open this thing up occasionaly, and have it go. With the current setup, I pretty much have everything I want with the exception of the top end performance. The engine pulls like crazy till about 4600 ~ 4700 rpm, then just stops. I've been through the fuel and ignition systems, and a half dozen different props, and the engine won't go above that rpm range. I've come to the conclusion that it's the cam based on many things. The first being a cam swap we did in a 350 chevy I/O. We went from a mild crane cam to the comp XM262, and the boat picked up mid range pull, but it used to max out at 5100 rpm at full throttle, and after the cam change, it stops at 4700rpm. Strange huh? What's even stranger is a year or so ago, I posted my "problem" on this site, and someone responded with the same issue. I have since spoken to someone else who had the same results. So I like to think I'm not crazy (about this anyway).
As far as going roller, I'd love to, but it's not in the budget anytime soon.
I figure I'll swap out the cam while I have the engine out, and see what that does. Cam wear issues? I'm fully aware of what's going on with that, and I'm extra careful when breaking in my cams. I don't claim to be an expert (I'm not), but I have built quite a few engines since about 1979.
I've learned a lot over that time working with novices, and pros, and I'm always learning more. That's why I'm here. Sorry for the long post, but I hope I gave you enough info (maybe too much
).
Paul
I know RM was comparing the camshafts, but his comments seemed to elude to the XM270 being better suited to my application (given the two cams). Of course the final decision will be mine.
The engine is a 383, using a Scat stroker kit with 6" rods, and forged pistons. The heads are GMPP 300HP crate engine heads with some porting.
64cc chambers with the small valves (should have went for the Dart Heads). Compression ratio is a little over 9.5:1 The valve springs I'm using, are the Comp springs recommended for the XM270 cam. Installed height, and spring pressures are all at the manufacturer's required specs.
The setup will easily handle the 270's valve lift. I also clearanced the inside of the cast rocker covers for the roller tip rockers. The intake manifold is the GMPP cast iron high rise intake (dual plane). It's the cast iron version of the Z28 manifold. It came stock on the OMC 270hp cobra setups. Internally it looks just like an Edelbrock performer. The manifold's internals have been "massaged" by my porting guy. The carb is a Q-jet with quite a bit of work done to it. Fuel is not an issue in my area. My wants/needs for the engine? Reliability of course, which I don't think the 270 will sacrifice, good cruising performance with the ability to open this thing up occasionaly, and have it go. With the current setup, I pretty much have everything I want with the exception of the top end performance. The engine pulls like crazy till about 4600 ~ 4700 rpm, then just stops. I've been through the fuel and ignition systems, and a half dozen different props, and the engine won't go above that rpm range. I've come to the conclusion that it's the cam based on many things. The first being a cam swap we did in a 350 chevy I/O. We went from a mild crane cam to the comp XM262, and the boat picked up mid range pull, but it used to max out at 5100 rpm at full throttle, and after the cam change, it stops at 4700rpm. Strange huh? What's even stranger is a year or so ago, I posted my "problem" on this site, and someone responded with the same issue. I have since spoken to someone else who had the same results. So I like to think I'm not crazy (about this anyway).
As far as going roller, I'd love to, but it's not in the budget anytime soon.
I figure I'll swap out the cam while I have the engine out, and see what that does. Cam wear issues? I'm fully aware of what's going on with that, and I'm extra careful when breaking in my cams. I don't claim to be an expert (I'm not), but I have built quite a few engines since about 1979.
I've learned a lot over that time working with novices, and pros, and I'm always learning more. That's why I'm here. Sorry for the long post, but I hope I gave you enough info (maybe too much
).Paul
Last edited by Liberator21; 10-30-2006 at 10:14 PM.
06-06-2006, 07:02 AM
#23
Registered
iTrader: (1)
Re: Another Camshaft Question
The Bowtie cast iron intake is an excellent piece. Use them all the time.
I'm not familiar with the 300hp head. Does it have the 1.94 / 1.50 valves ? I assume intake runners are 160ish ?
Anyway, what I'm getting at, a 383 with mediocre heads and small cam can run out of steam real soon. Short valve open times + runners that don't want air to move through freely can be a major choke, especially as CID's increase. A longer duration cam can give the tracts more time to get more air in there.
As you probably know, judging by your knowledge, effecient cylinder heads will usually let you use less 'cam' to make desired power thru intended rpm range.
You say the engine stops pulling around 2800rpm ? Are we sure something else isn't off kelter ? Are we sure carb is calibrated/working correctly ? Never assume, you know where that get's us.
I'm not familiar with the 300hp head. Does it have the 1.94 / 1.50 valves ? I assume intake runners are 160ish ?
Anyway, what I'm getting at, a 383 with mediocre heads and small cam can run out of steam real soon. Short valve open times + runners that don't want air to move through freely can be a major choke, especially as CID's increase. A longer duration cam can give the tracts more time to get more air in there.
As you probably know, judging by your knowledge, effecient cylinder heads will usually let you use less 'cam' to make desired power thru intended rpm range.
You say the engine stops pulling around 2800rpm ? Are we sure something else isn't off kelter ? Are we sure carb is calibrated/working correctly ? Never assume, you know where that get's us.
06-07-2006, 01:42 AM
#24
Registered
Join Date: Jul 2005
Location: Napa, CA
Posts: 158
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
cheapest price on the comp xm270 (12-240) cam is summit racing. its $119.00 and they have free shipping. Plus they are open 24/7 I feel like i own stock i shop there so much. Plus if you find the cam cheaper in a magazine they will beat the price. 800-230-3030 Has anyone looked at the lunati voodoo cams. there is one very similar to the 270 only with a larger advertised power band, tighter LSA and more lift. costs more money though. part # LUN 60103 this is the add cut and pasted.
Basic Operating RPM Range: 1,800-6,200 RPM
Intake Duration at 050 inch Lift: 227
Exhaust Duration at 050 inch Lift: 233
Duration at 050 inch Lift: 227 int./233 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 276
Advertised Duration: 268 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.489 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.504 in.
Valve Lift with Factory Rocker Arm Ratio: 0.489 int./0.504 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Quantity:
on a seperate note before you buy the comp I heard from my builder that he has had 2 comp cams flaten in the last 6 months. The machine shop he uses has had the same problem only recently though. The cam companies are blaming the oil, something is different in the formulation. may be worth checkin into.
Basic Operating RPM Range: 1,800-6,200 RPM
Intake Duration at 050 inch Lift: 227
Exhaust Duration at 050 inch Lift: 233
Duration at 050 inch Lift: 227 int./233 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 276
Advertised Duration: 268 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.489 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.504 in.
Valve Lift with Factory Rocker Arm Ratio: 0.489 int./0.504 exh. lift
Lobe Separation (degrees): 110
Intake Valve Lash: 0.000 in.
Exhaust Valve Lash: 0.000 in.
Computer Controlled Compatible: No
Quantity:
on a seperate note before you buy the comp I heard from my builder that he has had 2 comp cams flaten in the last 6 months. The machine shop he uses has had the same problem only recently though. The cam companies are blaming the oil, something is different in the formulation. may be worth checkin into.
06-07-2006, 02:00 PM
#25
Registered
Thread Starter
Join Date: Jan 2004
Location: Long Island NY.
Posts: 450
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
SB:
I found the info on the heads: GM Performance Parts Cyl. Heads #10125377. Like I said, these heads had some port work done to them.
As far as anything being off with the carb or ignition, I don't think that's the case. A lot of work was done on the carb, and two different carbs were tried with the same results. The original ignition was points, then I went to a Pertronics Flame Thrower II Billet Marine Distributor. No difference.
Also, I used this cam in two different engines with the same results.
I also spoke to two other people who had the same results as me.
Flatout:
I was looking at the Voodo cams, and have heard some good things, but I'm just not familiar with them. As far as lobes wearing out, I am fully aware of the oil issue (thanks to this board), and I have been taking extra steps to try and avoid wasting a cam. So far I've been lucky.
Paul
I found the info on the heads: GM Performance Parts Cyl. Heads #10125377. Like I said, these heads had some port work done to them.
As far as anything being off with the carb or ignition, I don't think that's the case. A lot of work was done on the carb, and two different carbs were tried with the same results. The original ignition was points, then I went to a Pertronics Flame Thrower II Billet Marine Distributor. No difference.
Also, I used this cam in two different engines with the same results.
I also spoke to two other people who had the same results as me.
Flatout:
I was looking at the Voodo cams, and have heard some good things, but I'm just not familiar with them. As far as lobes wearing out, I am fully aware of the oil issue (thanks to this board), and I have been taking extra steps to try and avoid wasting a cam. So far I've been lucky.
Paul
10-25-2006, 11:28 PM
#26
Registered
Join Date: Oct 2006
Location: Vt
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
Liberator21,
I am running the XE268h(.477/.480,224/230 at 50, 114lsa, hyd. flat tappet) on my 383 with Vortec heads, RPM air gap, and 9.75 c/r. I have a 21ft Checkmate Enchanter. It runs too 4400rpm with a 25p Mirage, 66mph on gps. With a 21p Mirage it hits 5000rpm at 64mph gps. I has tons of grunt, and really charges hard to 4400rpm or 5k then just stops spinning any faster. I really notice no difference in holeshot with the 2 props. I would even say holeshot seems better with the 25p, but I have an alpha and don't really hammer till up on plane. I would like to be able to spin to 5500 with the 25p, so I am looking for more cam. I was thinking of maybe going to a Comp Cams Nitrous Cam, because I am lookiing for more top end. I called Cam help, and they recomended against it, due to soft low end power, but it is supposedly a 2000-6000rpm cam, where as the cam I have now is a 1800-5800rpm cam.
This is the cam I am thinking of:
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,000-6,000 RPM
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 236
Duration at 050 inch Lift: 224 int./236 exh.
Advertised Intake Duration: 276
Advertised Exhaust Duration: 288
Advertised Duration: 276 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.502 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.520 in.
Valve Lift with Factory Rocker Arm Ratio: 0.502 int./0.520 exh. lift
Lobe Separation (degrees): 113
What do you all think?
I am running the XE268h(.477/.480,224/230 at 50, 114lsa, hyd. flat tappet) on my 383 with Vortec heads, RPM air gap, and 9.75 c/r. I have a 21ft Checkmate Enchanter. It runs too 4400rpm with a 25p Mirage, 66mph on gps. With a 21p Mirage it hits 5000rpm at 64mph gps. I has tons of grunt, and really charges hard to 4400rpm or 5k then just stops spinning any faster. I really notice no difference in holeshot with the 2 props. I would even say holeshot seems better with the 25p, but I have an alpha and don't really hammer till up on plane. I would like to be able to spin to 5500 with the 25p, so I am looking for more cam. I was thinking of maybe going to a Comp Cams Nitrous Cam, because I am lookiing for more top end. I called Cam help, and they recomended against it, due to soft low end power, but it is supposedly a 2000-6000rpm cam, where as the cam I have now is a 1800-5800rpm cam.
This is the cam I am thinking of:
Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 2,000-6,000 RPM
Intake Duration at 050 inch Lift: 224
Exhaust Duration at 050 inch Lift: 236
Duration at 050 inch Lift: 224 int./236 exh.
Advertised Intake Duration: 276
Advertised Exhaust Duration: 288
Advertised Duration: 276 int./288 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.502 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.520 in.
Valve Lift with Factory Rocker Arm Ratio: 0.502 int./0.520 exh. lift
Lobe Separation (degrees): 113
What do you all think?
10-26-2006, 02:58 AM
#27
Registered
iTrader: (1)
Join Date: Jul 2004
Location: Tacoma,wa
Posts: 79
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
azk4536,I .would check your tach,unless I am missing something, you are running at 3% slip.highly unlikely.cam is pretty close to the xm270.in my boat(stated in an earlier post) push's a 23p mirage plus @4800 at 61.2 mph gps with great accel.
10-26-2006, 07:07 AM
#28
Registered
iTrader: (1)
Re: Another Camshaft Question
azk4536 -
I haven't seen positive results using Comps Nitrous cams on NA motors yet. Pretty lackluster to say the least. They get funky with the valve events in which NA doesnt seem to like.
Max Comp Cam that I would use for your 383cid set-up would be the XM276HR (276,282--224,230--112)since this would put you at the max hp for mostly stock Vortec heads at 405-415hp. Anymore cam then this will just raise your powerband without raising actual torque/hp #'s. Again, it's the heads at this level that become the issue.
Just my 02.
I haven't seen positive results using Comps Nitrous cams on NA motors yet. Pretty lackluster to say the least. They get funky with the valve events in which NA doesnt seem to like.
Max Comp Cam that I would use for your 383cid set-up would be the XM276HR (276,282--224,230--112)since this would put you at the max hp for mostly stock Vortec heads at 405-415hp. Anymore cam then this will just raise your powerband without raising actual torque/hp #'s. Again, it's the heads at this level that become the issue.
Just my 02.
10-27-2006, 08:13 PM
#29
Registered
Join Date: Oct 2006
Location: Vt
Posts: 56
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
What should I do to check my tach? Is it possible my alpha has a weird ratio? I have been told in the past the my prop slip numbers are at an unlikely number, so maybe you are on to something with the tach. I would be willing to trade a little grunt for some more top end, but I don't want to make it a dog gettign on plane, would the xm276 give me a little more top end in your opinion? Thanks much!!
10-28-2006, 09:38 AM
#30
Registered
Thread Starter
Join Date: Jan 2004
Location: Long Island NY.
Posts: 450
Likes: 0
Received 0 Likes
on
0 Posts
Re: Another Camshaft Question
Just an update guys,
I went with the XM270H cam, and replaced my exhaust manifolds with a set of GLM center rise OMC style. The old setup was XM262H, and Aquapower Mercruiser style center rise manifolds. I didn't get a chance to take the boat out yet (Back problems all summer), but I plan on getting it out before the first snow! The engine has a definite different sound to it. It's much throatier sounding, and has a nice little lope. I have video of the engine running with both cams, and you can really hear the difference. I'll post that soon. I just can't wait to see how it performs!
azk4536, the easiest way to check your tach is to substitute a known good one. I would also check your drive ratio. Isn't the XM276 a bit much? (depending on your engine setup). What type of exhaust do you have?
Your best bet is probably going roller.
I went with the XM270H cam, and replaced my exhaust manifolds with a set of GLM center rise OMC style. The old setup was XM262H, and Aquapower Mercruiser style center rise manifolds. I didn't get a chance to take the boat out yet (Back problems all summer), but I plan on getting it out before the first snow! The engine has a definite different sound to it. It's much throatier sounding, and has a nice little lope. I have video of the engine running with both cams, and you can really hear the difference. I'll post that soon. I just can't wait to see how it performs!
azk4536, the easiest way to check your tach is to substitute a known good one. I would also check your drive ratio. Isn't the XM276 a bit much? (depending on your engine setup). What type of exhaust do you have?
Your best bet is probably going roller.
