Re: torque engine build
[Re: goldmember]
#1069622
09/05/11 02:00 PM
09/05/11 02:00 PM
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Joined: Jan 2003
Posts: 75,103 A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,103
A Banana Republic near you.
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Quote:
If you want more idle vac I'd try a 2 plane performer RPM intake,that should really boost lower rpm performance without digging into the engine. Proper ignition and carb tuning will also go a long way to clean it up down low. With your compression I would not go to a cam as small as the comp 260H. I wouldn't use Campquest to make a cam choice. If you feel you must change the camshaft just call Tim @ bullet cams. I have given up giving cam suggestions,just too many guru's on the interweb.
What he said, it seems you have a large mismatch of parts so it's not surprising that drivability is less than stellar.
You can also call Dwayne Porter , fast68plymouth , he is very well versed in cams for large engines using stock exhaust manifolds .
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Re: torque engine build
[Re: rbstroker]
#1069627
09/06/11 11:07 PM
09/06/11 11:07 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
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Quote:
I wonder what simply changing the intake centerline from the recomended 106* to about 111* would do.
Advancing the cam will help low end. If you do decide to change cams I agree with calling "Dwayne Porter". He speced my cam for my 493 and it works great. Its big enough to make good power but still idles nice enough and sounds great with just enough rump rump. My cam is 264 and 270 at .050 with .634 and .630 lift with 1.6 rockers. I only run 10.6 comp but I use a very fast advance and it has nice low end. I also use the Indy dual plane intake. With standard 906 ports the Performer RPM would work good for you. Ron
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Re: torque engine build
[Re: rbstroker]
#1069630
09/07/11 09:59 PM
09/07/11 09:59 PM
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Joined: Jan 2007
Posts: 7,664 IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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I'm no expert on cams either Since I run a roughly similar combo I feel somewhat qualified to comment though. Mine's an Ed headed 496, 243@.050 .55" lift cam, 108 cl, manual transmission, MP single plane intake, 3.23 rear and 25" tire. It's a little tender launching but does fine with practice. It will accelerate cleanly in high gear from 1200 RPM with part throttle but still may buck a little if I try to run it steady at say 1500. In that situation, I just pull the next gear. With a 30" tire it would possibly be too "tender". With 10:1 (true measured) compression you may be limited in reducing cam duration much as you can run into detonation problems. You are doing well not to have problems now. Also, I think there is a good chance you can get it smoothed out without a cam change or at least without a lower duration cam with the suggestions posted above and one or two more. If you do change cams a wider LSA with about the same duration would be in the right direction. Advancing is worth a try; a lot of the rest is tuning so if you are going to advance it, start with that first. Surging at low RPM may be the result of a lean mixture, excessive advance and/or a big tight CL cam. A dual plane intake should help. Getting it to behave in the 1200-2000 range also takes a lot of tuning. I'm a little surprised reducing spark advance to 5 degrees helped... most moderatly performance cammed strokers like 15-20 initial. It makes me wonder if the rest of the timing curve is off somehow. I'd suggest an initial timing of 15 degrees and a slow advance to 34 degrees at 2800-3000 RPM. Add or re-connect the vacuum advance after you get it smoothed out without vacuum. Vacuum advance will help the engine burn clean and improve fuel economy if you can get it sorted out. The carb likley will need tuning and I'm not a carb guy, mine's EFI and has taken a lot of fiddling to get it to behave reasonably well at low RPM. 750 is a bit small for a 500" engine but may be ideal for your application to help response and low RPM drivability. A vacuum secondary carb is usually considered more street friendly than a DP. It would be worth looking for somebody in your area that's good at tuning carbs. If all of that helps, but doesn't quite get there, a step or two up in rear gear will help. 3.55 isn't much of a change so 3.7x may be the best bet with 30" tires. Good luck!
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Re: torque engine build
[Re: rbstroker]
#1069631
09/07/11 10:15 PM
09/07/11 10:15 PM
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Joined: Aug 2011
Posts: 297 Oklahoma
TinCuda
enthusiast
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enthusiast
Joined: Aug 2011
Posts: 297
Oklahoma
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Lunati voodoo cam p/n 60303 and Rhoads lifters p/n 2018. Just throwing it out there if you want to look at it.
.,
(O O {]{]{]||[}[}[} O O)
1971 Plymouth 'Cuda 440-6
{||O||}
2000 Yamaha V-Max
(O O [========= SRT] O O)
2011 Dodge Challenger SRT 392
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Making as big as a carbon footprint as I can!!!
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Re: torque engine build
[Re: ahy]
#1069633
09/08/11 12:19 AM
09/08/11 12:19 AM
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Joined: Aug 2011
Posts: 297 Oklahoma
TinCuda
enthusiast
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enthusiast
Joined: Aug 2011
Posts: 297
Oklahoma
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If you are using a big cam, look into Rhoads lifters to calm down your idle and still get all the low end torque and all the power at higher RPMs.
I copied this from thier web site.
Orginal Rhoads Lifters reduce lift and duration at idle by approximately .010" to .020". Duration is reduced by approximately 10 to 15 degrees. Total lift and duration are restored at approximately 3500 rpm. Typical vacuum increases range between 1 to 3 inches.
I am a big fan and use them in my 512 stroker 440.
.,
Last edited by TinCuda; 09/08/11 12:26 AM.
(O O {]{]{]||[}[}[} O O)
1971 Plymouth 'Cuda 440-6
{||O||}
2000 Yamaha V-Max
(O O [========= SRT] O O)
2011 Dodge Challenger SRT 392
.
Making as big as a carbon footprint as I can!!!
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Re: torque engine build
[Re: TinCuda]
#1069634
09/08/11 12:55 AM
09/08/11 12:55 AM
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Joined: Feb 2003
Posts: 10,234 Someplace you aren't
SomeCarGuy
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 10,234
Someplace you aren't
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Scott Brown spec'd a cam for mine that tore the tires off. We camed for use with a small convertor and 3.23 gear. I remember 234 at 50 and .555 lift. Guy I sold it to ran more gear, can't remember but I think it was 3.91. Said the torque was killer for him, but not enough top end charge. Had an Eddy RPM intake and Eddy heads. 10.25 comp.
Just depends on what you want to do with it. Undercam for mostly street is a good route. Really all the way around going small is better for a car thtat is street used a lot.
I want my fair share
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Re: torque engine build
[Re: rbstroker]
#1069640
09/20/11 02:15 PM
09/20/11 02:15 PM
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Joined: Feb 2003
Posts: 1,665 Milwaukee, WI
Prince_Valiant
top fuel
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top fuel
Joined: Feb 2003
Posts: 1,665
Milwaukee, WI
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Honestly, spec a cam ~ 228 @ .050 duration with a wider lsa of 112-114. This will give you peak torque in the ~-2500-3000rpm range, probably on the order of 550-ish ft-lbs.
1979 Dodge Lil' Red Express - 360 rwhp, 13.2 @ 103mph 1968 Coronet: 318, 2.76, 15.2 @ 92mph! (SOLD) 1976 Valiant: 360, 3.90, 12.90 @ 106 (SOLD) 1989 Shelby CSX #500/500
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Re: torque engine build
[Re: rbstroker]
#1069641
09/20/11 06:39 PM
09/20/11 06:39 PM
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Joined: Jan 2007
Posts: 7,664 IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
The math for the compression ratio turned out to be exactly 9.9:1. Everything was exactly cc'd. I do have a mild pinging issue if I roll into the gas a bit too hard in high gear at lower RPM. I use pump premium without ethanol. I also have the proper amounts of sta-bil and Marvel Mystery Oil in the tank. I believe that the MMO helps lubricate the valves without leaded gas. This morning, I decided to replace my early 60's timing light, that I bought new about 1963, with a digital type so I can get some exact numbers. I am able to set my idle at 800 RPM. My initial was 8.4* and stayed that way through 1000RPM. At 1500 it went to 18.2* and maxxed out at 25* at 2000RPM. With the vacuum advance hooked up, I read 9.1* at 800RPM and I had 10# vacuum. At 1000RPM I had 20.5* and 15# vacuum. At 1500 the total was 38.3* and 18# vacuum. Per suggestions, I set the initial at 18* at 950RPM. I watched as the mechanical advance maxxed out at 1880RPM. I read a total of 34.9* at 2000 RPM without any vacuum advance. If the streets dry up a bit, I'll try this initial setting and then try with the vacuum advance hooked up. Thanks again, I will keep you posted.
![](/ubbthreads/images/graemlins/thumbs.gif)
If you can slow the mechanical advance so it is all in around 3000 RPM instead of 2000 you may reduce the pinging problem and smooth out operation below 2000 RPM. Marvel Mystery oil is a great lubricant but it does drop the octane a bit.
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Re: torque engine build
[Re: rbstroker]
#1069643
09/21/11 01:34 PM
09/21/11 01:34 PM
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Joined: Jan 2003
Posts: 16,123 Grand Haven, MI
patrick
I Live Here
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I Live Here
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Posts: 16,123
Grand Haven, MI
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Quote:
I wonder what simply changing the intake centerline from the recomended 106* to about 111* would do.
I'd definitely swap the intake to an eddie RPM...
you'd want to go the other way-- move from 106 to say 102, to get the intake closing point earlier.
for a cam, I'd probably drop to a Lunati voodoo 60303 (IIRC, 268 adv, 226@.050 and about .5" lift), should still work reasonably well with your compression.
or maybe even a 60302 (~262 adv ~220.050, ~.475" lift)
add long tube headers, even 1 3/4" cheapies...should be an easy 20 lb-ft of torque throughout the rev range.
the wider LSA of the lunati cams (IIRC both are 112 degrees) will reduce overlap and smooth out the idle at the cost of peak midrange torque (torque curve will be flatter, but with a slightly lower peak)....the wider LSA also helps carry torque higher up in the rev range, offsetting the duration loss to help with upper RPM HP production
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: torque engine build
[Re: ahy]
#1069644
10/03/11 12:23 PM
10/03/11 12:23 PM
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Joined: Sep 2006
Posts: 1,139 West Tennessee
rbstroker
OP
super stock
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OP
super stock
Joined: Sep 2006
Posts: 1,139
West Tennessee
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Quote:
The extra cubes will lower the RPM range with that cam and boost peak torque. All in the direction you want to go.
The only thing I wonder about is pinging/detonation. I believe you posted you have 10:1 with iron heads. Is the 10:1 calculated with everything cc'd or based on the piston manufactures estimate? Piston manufacturers estimate high just like MOPAR did. If it is true 10:1 your current cam's higher duration may be keeping detonation at bay. Less duration may cause a problem but may not. The wider LSA actually helps prevent detonation (per comp's guidance) so it may be a wash.
Bottom line, I think the cam is a good fit. The 6 pack is also... its dual plane for good response at light loads running on a single 2 bbl. May be a little trickey to set up but good for what you want to do, a great runner and lots of fun.
It sounded like your current distributor was advancing too fast as well. I would get it checked out and adjusted. About 15 degrees initial advance and 19 mechanical advance (34 total mechanical) all in by 2800-3000 RPM should about right. This is a gentle advance curve for a heavy car and high pump gas compression ratio. An additional 15-20 degrees vacuum advance can be added on top for cruising.
I received and installed a set of distributor springs and an advance limiter from 4 seconds flat this past weekend. Per advice given here, I set up my old tach drive distributor (no vacuum advance can) with the heaviest of the springs and a 20* mechanical limit. Installed everything with about 15* initial and a total of about 34* at full advance (over 3000rpm). No other changes. Drastically decreased the "surging" and I can now let out the clutch at a stoplight without having to bring the revs way up. Pinging seems to be minimized if not gone completely. A lot more driveable all in all. I think that I'll do a bit more tweeking and once satisfied, re-install the six pack. I find that the folks on this site are pretty darn knowledgeable and willing to help.
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