Quote:
except for 390 carb is too small
But it is still a Holley no matter what you do.
Ducking now! 
Rick
| Slant Six Forum https://slantsix.org/forum/ |
|
| Uncloaking Mystery camshaft.. Now I have Numbers! https://slantsix.org/forum/viewtopic.php?t=43251 |
Page 4 of 5 |
| Author: | Aggressive Ted [ Wed Jan 26, 2011 9:36 am ] |
| Post subject: | |
Frank, Due you have any low end, say 1200 to 2000 rpm? What is the vacuum at 2500 cruise? Thanks, |
|
| Author: | wjajr [ Wed Jan 26, 2011 7:02 pm ] |
| Post subject: | |
Frank, What I’m gleaning from this discussion is: one, my cam has too much overlap for low rpm grunt; two, compression is too low for larger cam; three, perhaps a milder cam such as that 280/270 that you run would be a bit more street friendly with better vacuum signal; and could be my Holley 390 carburetor is too small. |
|
| Author: | Dart270 [ Thu Jan 27, 2011 7:24 am ] |
| Post subject: | |
I agree with all of that, except for 390 carb is too small. You can easily pull 6000 RPM and 250+ HP with that carb, properly tuned. Lou |
|
| Author: | wjajr [ Thu Jan 27, 2011 11:30 am ] |
| Post subject: | |
[quote]I agree with all of that, except for 390 carb is too small. You can easily pull 6000 RPM and 250+ HP with that carb, properly tuned.[/quote] Lou, That engine will crank 6000 rpm in its current tune, and may have hit it once in gear. I have called 5500 rpm as a tentative redline which the engine eagerly and smoothly revs to. I plan of installing an O2 sensor to dial in that cussed Holley. If you say it will get the job done, than I shall make it work. I’m tempted to keep this cam in place, bump up compression 0.4 more with a head gasket change. A few years ago the head got a 0.075 shave yielding 9.5:1 CR. A steel gasket produces calculated 9.9:1 static compression ratio. Did I read some where here that 0.006†reduction in head thickness equals 1cc reduction? If so, an additional cut of 0.024†garners a 10.4:1 compression ratio. I’m hesitant to shave additional material from head because of possible push rod length problems. That 250 hp number, is that actual rear wheel or flywheel dyno measured, or track time computer generated? Would a 280/270 cam generate that 250 hp number, and what would I need to do to the existing build to achieve that level of performance? I may spring for a dynamometer pull this spring with existing 9.5:1 Cr to establish a base line. Than change head gasket, make another pull or calculate what 0.4 increase in compression will give, and go from there. My cheapness is exposed. Bill |
|
| Author: | sandy in BC [ Thu Jan 27, 2011 2:29 pm ] |
| Post subject: | |
The cheapest , most sensible route would be to change to a more suitable cam. Id leave the carb and CR right where they are. The cost of a cam and lifters installed is right around $300...it doesn t get cheaper than that. |
|
| Author: | Dart270 [ Thu Jan 27, 2011 3:09 pm ] |
| Post subject: | |
250 HP from dragstrip numbers. That's high 14s in your car. 280/270 cam has been used to make over 250 HP (madmax/6), but was with a really well ported head and 11+:1 comp. 9.5:1 to 9.9:1 will give some difference, but not a huge amt - 5-10 HP if everything else is tuned up right? If you are down to degreeing the cam already (gaskets and such), then you are looking at <$200 for the Erson or <$150 for an Oregon cam w/lifters and shipping. THE ONLY way you should continue to run that cam and be happy with it is to get a true 3000+ RPM stall converter, and FORGET about good vacuum at idle. OR, go to MP-EFI and tune away (big $$$)... 99 deg is the perfect centerline for that cam, and nothing you can do will give you drastically more low end. 96 deg would get you a litte, and 9.9:1 will get you a little, but these will likely not get you where you want to be. Once you are here, why not fix the problem right? If it were me, I'd slip a $150 234/228 106 LSA, 0.480" Oregon cam in there, degree at 100, and call it a motor... If you want a really smooth idle, just get the Erson cam. With all the carb messing around and such, I really don't think you'll be happy with this 250 deg cam. Lou |
|
| Author: | Rick Covalt [ Thu Jan 27, 2011 4:36 pm ] |
| Post subject: | A Holley! |
Quote: except for 390 carb is too small But it is still a Holley no matter what you do. Ducking now! Rick |
|
| Author: | wjajr [ Fri Jan 28, 2011 8:44 am ] |
| Post subject: | |
[quote]Once you are here, why not fix the problem right? If it were me, I'd slip a $150 234/228 106 LSA, 0.480" Oregon cam in there, degree at 100, and call it a motor... If you want a really smooth idle, just get the Erson cam[/quote]. Lou you lost me there. I’m a little confused. Seams the more I learn, the less I know. First, in general, just what are these numbers such as 280/270 I see describing a cam; duration at 0.050†lift, or 0.006â€, or what? Your saying; pass on a 280/270 cam because 9.9:1 compression is not enough for it to make an appreciable performance difference over my present cam & porting? And or, is this 280/270 cam a close cousin to what I all ready have and still a bit on the big side? Is a ‘234/228 106 LSA’, 0.480†Oregon Cam close to Doc’s RV 15 cam, or is it a bit bigger and more lumpy. Will it perform well at 9.5:1, and better at 9.9:1 compression? I’m getting confused with all the numbers. Is 0.480†lift at valve not considering lash? If so, it is close to what my present cam provides. What makes Erson smoother, a little less overlap? [quote]With all the carb messing around and such, I really don't think you'll be happy with this 250 deg cam.[/quote] Which 250 deg. cam are you referring to, my present cam? I now think I have a handle on tuning the old Holley. I suspect it would be easer to dial in with higher steady idle vacuum using a different cam. Bill |
|
| Author: | wjajr [ Fri Jan 28, 2011 9:00 am ] |
| Post subject: | |
Quote: But it is still a Holley no matter what you do. Ducking now!
Rick, with a steady higher idle vacuum, I got to believe tuning this Halley will be much easer.Rick Presently I have a pulsating vacuum needle when in gear idling at 700 rpm that sends the power valve into convolutions. This pulse of fuel causes back spin of engine at shut-down, and difficulty adjusting idle circuit. Solution for that condition was to drop to a 1, or 2.5 inch Hg. rated power valve, which did not help much with cruse conditions as it would not open soon enough to enrich the mixture under light to moderate acceleration. At WOT it worked fine. So I either tuned for idle & shut-down, or cruse as there was no real good trade off between the two. Bill |
|
| Author: | Joshie225 [ Fri Jan 28, 2011 9:09 am ] |
| Post subject: | |
Bill, The Erson cams are listed by advertised duration. In this case 280° on the intake and 270° on the exhaust. To get a good idea of how much shorter the duration is than your current cam you have to compare the duration at .050" lifter rise. Your current cam is 250° duration at .050" lift while the Erson is 230/220°. The Oregon cam is in between at 234/228° at .050" lifter rise. The Oregon cam Lou suggests will have a little rougher idle than the Erson as the duration is longer and the intake-to-exhaust lobe centerline angle is narrower further increasing the overlap. It's still a big decrease in duration and overlap from what you have now. If the car were mine I'd do the Oregon cam and steel shim head gasket to bump the compression a little higher. If I were doing this for you or any other customer I'd do something a little milder so I wouldn't have to keep messing with the car and keep everyone happy. 
|
|
| Author: | Dart270 [ Fri Jan 28, 2011 11:00 am ] |
| Post subject: | |
Bill, I am very sorry if I confused you. I think Josh sorted everything out. I was under the impression you wanted to stay with your present 250 @ 0.050" cam, but I guess I was wrong about that. I do not think that would be a prudent choice, given your past experience and accumulated knowledge. That was the basis of my last post. Josh has summed up the 234/226 Oregon cam course of action, which is what I would do. As he said, the more conservative 280/270 (or 230/220 @ 0.050") Erson cam would be "safer" for the average Joe. Lou |
|
| Author: | wjajr [ Fri Jan 28, 2011 2:33 pm ] |
| Post subject: | |
Lou, think nothing of it. Sometimes I get something stuck in my head, and can’t displace it for the correct thought. Hey that’s what 2x4’s are for I guess… Thanks Josh for the explanation. I’m not adverse to a lope, as long as I can get good “in gear†idle vacuum, and another round of Holley tuning. I have reexamined my valve event graph after reading both you & Josh’s reply. I may have been disseminating faulty information with my hand generated visual aid, my 3’s look like 5’s. The intake @ .050†is 235*, lift of .321â€, and exhaust @ 234*, lift of 324â€, and overlap of 23* at .050â€. At 0.006†lift gives 314* and 315* overlap is 101*. Sorry about that. My cam is close to, but more aggressive than the Oregon’s 234/226. Its roughness of idle and low vacuum is attributed to its longer overlap than Oregon & Erson’s, right? Is there a valve event graph of the Oregon, Erson, and Doc’s RV15 cams that can be viewed for comparison. Can one change out a slant six cam with its engine in the engine bay with a bit of jacking, and grill & bumper removal? Can existing cam bearings be used, or do these have to be changed as well, and could that task be done with engine in place as well? I’m currently engine pulling equipment deficent… Bill |
|
| Author: | Dart270 [ Mon Jan 31, 2011 5:45 am ] |
| Post subject: | |
OK, if these new duration numbers are right, then you should use the Erson 280/270 cam for sure. I have changed many slant 6 cams in the car, with jacking and bumper removal as you said. I have never changed a set of cam bearings except when overhauling the bottom end, and never had a problem. My '68 Dart motor has had maybe 6-8 cam swaps over 140k miles and no bearing problems. Lou |
|
| Author: | 66aCUDA [ Mon Jan 31, 2011 7:12 pm ] |
| Post subject: | |
Sorry Im kinda out of the loop right now. Im having kid problems. I run an Eddy 1405 500cfm carb. I dont know what my vac signals are I never measured. Im with Lou though its hard to beat this cam. Frank PS PM me if you need me |
|
| Author: | wjajr [ Wed Apr 27, 2011 10:38 am ] |
| Post subject: | |
Resurrection of mystery cam saga: I'm close to firing up the engine after a long winter of disassembly. Currently I have my lash adjusted as follows: intake = 0.025â€; and exhaust = 0.026â€. I did not change out head gasket to stock steel, and continue to have 9.5:1 compression. Based on camshaft specs generated last winter, does anyone have a suggested lash setting that may improve idle vacuum & low end torque? How loose can I safely run lash settings? Bill |
|
| Page 4 of 5 | All times are UTC-08:00 |
| Powered by phpBB® Forum Software © phpBB Limited https://www.phpbb.com/ |
|