Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642715
04/08/19 12:31 PM
04/08/19 12:31 PM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
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I have found that some dyno results, peak HP and peak torque, aren't what the car will want for stall on the converter and shift points My message is on shift RPM is to take it to the track and test different shift RPM, start with the RPM the dyno said was peak HP and then go down 500 RPM and if the car goes quicker try another 500 RPM lower, if it goes slower on the peak RPM shift points than shifting it at or above 500 RPM above peak keep testing to find the best RPM. Once you have it narrowed down between two five hundred RPM shift points try 200 RPM higher or lower to get to the best shift RPM, test, test and test some more
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642718
04/08/19 12:38 PM
04/08/19 12:38 PM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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That’s a really small cam for a 12.5:1 505.
Shift point is dependent on a lot of variables....... but I’d say with an appropriate gear and converter....... somewhere in the low 6000’s. Just experiment and see what goes quickest.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Hp guess & where would shift point be ?
[Re: fast68plymouth]
#2642741
04/08/19 01:34 PM
04/08/19 01:34 PM
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sam64
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That’s a really small cam for a 12.5:1 505.
Shift point is dependent on a lot of variables....... but I’d say with an appropriate gear and converter....... somewhere in the low 6000’s. Just experiment and see what goes quickest. What would you recommend ? It is a 3300lb bracket racer,2" Headman Hustler headers,4.30 dana 60,727 rmvb,4800 Dynamic foot brake conv.9x29.5x15 m/t slicks.I like to stage at 2100 rpm.
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642789
04/08/19 03:04 PM
04/08/19 03:04 PM
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Joined: Jan 2003
Posts: 31,077 Oregon
AndyF
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That’s a really small cam for a 12.5:1 505.
Shift point is dependent on a lot of variables....... but I’d say with an appropriate gear and converter....... somewhere in the low 6000’s. Just experiment and see what goes quickest. What would you recommend ? It is a 3300lb bracket racer,2" Headman Hustler headers,4.30 dana 60,727 rmvb,4800 Dynamic foot brake conv.9x29.5x15 m/t slicks.I like to stage at 2100 rpm. Is the car running now? If so how fast does it go? 650 hp will put you right at 10.0 and 135 mph. With your tires and gear you would be going thru the lights at 7000 rpm if you run 135 mph. So I think you have too much gear in the car for your engine combination since your cam is too small to pull to 7000 rpm. How fast do you want to go? Once you know how fast you want to go then you can figure out where the engine should peak at and then you can pick the cam.
Last edited by AndyF; 04/08/19 03:04 PM.
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Re: Hp guess & where would shift point be ?
[Re: AndyF]
#2642872
04/08/19 05:36 PM
04/08/19 05:36 PM
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Joined: Dec 2008
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sam64
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That’s a really small cam for a 12.5:1 505.
Shift point is dependent on a lot of variables....... but I’d say with an appropriate gear and converter....... somewhere in the low 6000’s. Just experiment and see what goes quickest. What would you recommend ? It is a 3300lb bracket racer,2" Headman Hustler headers,4.30 dana 60,727 rmvb,4800 Dynamic foot brake conv.9x29.5x15 m/t slicks.I like to stage at 2100 rpm. Is the car running now? If so how fast does it go? 650 hp will put you right at 10.0 and 135 mph. With your tires and gear you would be going thru the lights at 7000 rpm if you run 135 mph. So I think you have too much gear in the car for your engine combination since your cam is too small to pull to 7000 rpm. How fast do you want to go? Once you know how fast you want to go then you can figure out where the engine should peak at and then you can pick the cam. I took the car to the track for the first time with this motor and 6.73 @ 101.37 shifted @ 6500, same as the 11.1 SR headed 499,.580 solid ft. I pulled out .I was hoping for 6.40 with the 505 as setup.seems like I am missing about 75 hp.
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642873
04/08/19 05:38 PM
04/08/19 05:38 PM
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Joined: Aug 2003
Posts: 43,303 Bend,OR USA
Cab_Burge
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Take the car to the track and get it so it repeats times from one weekend to the next and then try tightening up the valve lash from .004 to .008 to see if the motor wants a bigger cam or not. If it goes quicker and faster with tighter lash the motor and car combination wants more camshaft You could also increase the rocker arm ratio to accomplish making the motor think it has more lift and duration with the higher ratio rockers with the same camshaft Me thinks your cam will work fine until you want to go faster than you can make it go with the parts you have now
Last edited by Cab_Burge; 04/08/19 05:39 PM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642971
04/08/19 09:13 PM
04/08/19 09:13 PM
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Joined: Jan 2003
Posts: 31,077 Oregon
AndyF
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I took the car to the track for the first time with this motor and 6.73 @ 101.37 shifted @ 6500, same as the 11.1 SR headed 499,.580 solid ft. I pulled out .I was hoping for 6.40 with the 505 as setup.seems like I am missing about 75 hp. Okay, that is some useful information that you probably should've included in your first post. I'm not so sure that if I had both engines on the dyno I'd expect a huge difference between them. The SR head is pretty good and a 580 solid flat tappet can do just as well as a small roller cam in the right engine. There are a lot of other things that influence the power level so if you're using the same headers and same carbs on both engines that could have something to do with the result. Also, are you sure the car didn't change between runs or the weather? You could also have a converter mis-match. Maybe the converter you have really liked the 499's torque curve but doesn't like the 505 as well. Testing engines in a car rather than on a dyno just opens up a big can of worms since now you're dealing with track conditions, converter, weather, tires, suspension settings, etc. If it was my engine and it wasn't performing how I thought it should I'd put it on the dyno and see what happened. That way you can look at the EGTs, the air fuel ratio, see what the torque curve looks like, try a different carb, try some different valve lash settings or ignition timing or whatever you want. You can do all of that in the car too but it takes time.........
Last edited by AndyF; 04/08/19 09:14 PM.
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642973
04/08/19 09:19 PM
04/08/19 09:19 PM
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Joined: Jan 2003
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AndyF
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Wallace says 6.73 @ 101 with a 3300 lb car is 535 hp. So I agree that you are 75 to 100 hp less than I would expect from that engine. I can't tell you where the missing hp is but you should be able to figure it out with common tuning tools. Run the lash, pull the plugs, do a compression test, check the timing, etc. If the engine is in perfect shape then you have a big mismatch with your parts. That cam is too small for a race engine but it should still be making closer to 600 hp than 500 so I'm guessing that you have a mechanical problem of some sort. Or it could be bad gas. I've seen engines lose 100 hp on the dyno with old gas. The engines run fine, they just don't make good power. You can tell by the exhaust note if you listen close but other than that they seem to run fine. It freaked me out the first time it happened but after running into it a few times we started to get better at figuring it out. So get a new pail of fuel and try it again if you don't find anything else wrong in your inspection.
Last edited by AndyF; 04/08/19 09:22 PM.
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Re: Hp guess & where would shift point be ?
[Re: AndyF]
#2642985
04/08/19 09:40 PM
04/08/19 09:40 PM
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Joined: Dec 2008
Posts: 1,285 okla.
sam64
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Wallace says 6.73 @ 101 with a 3300 lb car is 535 hp. So I agree that you are 75 to 100 hp less than I would expect from that engine. I can't tell you where the missing hp is but you should be able to figure it out with common tuning tools. Run the lash, pull the plugs, do a compression test, check the timing, etc. If the engine is in perfect shape then you have a big mismatch with your parts. That cam is too small for a race engine but it should still be making closer to 600 hp than 500 so I'm guessing that you have a mechanical problem of some sort. Or it could be bad gas. I've seen engines lose 100 hp on the dyno with old gas. The engines run fine, they just don't make good power. You can tell by the exhaust note if you listen close but other than that they seem to run fine. It freaked me out the first time it happened but after running into it a few times we started to get better at figuring it out. So get a new pail of fuel and try it again if you don't find anything else wrong in your inspection. Thanks to all that replied, I have to look at a few things that were recomended.My new job is so unpredictable as to when I am home it makes it tough to do testing at the track let alone trying to schedule dyno time. Thanks again !!
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2642998
04/08/19 10:14 PM
04/08/19 10:14 PM
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Joined: Jan 2008
Posts: 2,363 Cotati, CA
Dave Hall
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It needs a dominator size carb. Some guys made good poop running an adaptor on a good 4150 manifold though I personally have no experience with adapters. A 1.80 first gear or a second gear TB will make the shift point more presentable. As in, it will actually make a big difference. The 727 was not my friend in this area and shift points had very little effect. I think peak power was about 6,200 or so. Generally, with my dyno tuned 493 with a flowed BG 1050, ported Edelbrock RPM heads and a .660 solid roller the car would run quicker shifted at or below 6,000. I've seen 7,400-7,600 at the stripe with a 4.29 gear and 32"-33" tires. Converter went to 5,900 on the stand. The car went 1.24 60 and 9.24@145 with this 727 setup at 2,600lbs in sea level, high barometer conditions.
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Re: Hp guess & where would shift point be ?
[Re: Dave Hall]
#2643014
04/08/19 10:40 PM
04/08/19 10:40 PM
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Joined: Mar 2009
Posts: 2,475 Sydney,Australia
tex013
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here's my Cam is probably too small . I know direct comparison SFT to roller are difficult , my 505 has a 272@050 SFT . Carb size - I went from 4150 (HP1000 Prosystem) to 4500 (1050) was only a quite small gain . Definitely not what I expected or everyone suggested . I tried adapter and then bought a Super Victor , adapter did not work for me . Cylinder head is the elephant in the room . I know you have moved to TF240 from Indy (?) . I had CNC stealths car went 10.50 but that seemed close to the end of what was there . Split the intake ports on 1 head , stepped over to TF270's . Picked up a solid 0.25 seconds and about 3MPH . NO other change . I had a Super Victor I opened it up to match the TF270 . Picked up a little more MPH with a 30"tyre but lost a little ET . I ran a 5000 stall when footbraking , now has a 5800 - behind my 440 . Was 56-800 behind the Stealth headed 505 . With the TF270 the stall went higher . I was shifting @ 6000 it never fell back . Probably needs to go out towards 6300 shift when new 505 goes back in . I chose 6000 shift because it was happy and I didn't want to spin the stock block too high on shift . It trapped just under/on 7000 @ 131MPH . Plus I hit my ET goals . Unfortunately the block gave up the ghost at this time . Around 675HP . Good luck , but I have been down that road of change but no gain Tex
Last edited by tex013; 04/08/19 10:41 PM.
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2643135
04/09/19 09:47 AM
04/09/19 09:47 AM
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Joined: Jan 2003
Posts: 17,912 S.E. Michigan
ZIPPY
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505 RB 12.5 comp.,Trick Flow 240 heads,Trick Flow intake,1000 cfm 4150 carb,.660 solid roller .252 .263 @ .050 108 ICL Personally I would try shifting at only 5800. If it does not run any better than 6500 and no issues are found, enjoy the low rpm and long life. If you want to know why I say this and the experts say 6500...well, first...I don't consider myself an expert. In fact some may think I am a fool/good for them/I don't care... but my gut feeling is your combination is set up to make huge midrange torque and that's going to be what it does best.
Rich H.
Esse Quam Videri
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Re: Hp guess & where would shift point be ?
[Re: sam64]
#2643152
04/09/19 10:15 AM
04/09/19 10:15 AM
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Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
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Imo, if you set out that build a 505” 12.5:1 “bracket race motor”, to run in the 10.00 range....... you built the wrong combo I’m not saying you can’t get there, but you didn’t hit the “easy button” with the combo you built.
It should have been done with MW heads and intake manifold, 4500 carb, bigger cam, and more stall.
The std port heads will tolerate way more cam than you have now, but you’ll likely need to run more stall to really take advantage of it. If you’re racing through mufflers that needs to be taken into account for cam selection. I can’t see the motor picking up 75hp with a cam swap.
Bigger cam first, then a stall adjustment if necessary.........and in the mean time I’d try and pick up a 337 intake manifold. Get the manifold port matched to the full MW size and open the heads up to that as well.
The best shift point is usually dictated by the interaction of the motor and converter....... so some experimentation is normally req’d to determine what the best shift rpm is. Off the top of my head, I’d say somewhere in the 6000-6200 range.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Hp guess & where would shift point be ?
[Re: fast68plymouth]
#2643397
04/09/19 08:14 PM
04/09/19 08:14 PM
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Joined: Mar 2009
Posts: 2,475 Sydney,Australia
tex013
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Imo, if you set out that build a 505” 12.5:1 “bracket race motor”, to run in the 10.00 range....... you built the wrong combo I’m not saying you can’t get there, but you didn’t hit the “easy button” with the combo you built.
It should have been done with MW heads and intake manifold, 4500 carb, bigger cam, and more stall.
The std port heads will tolerate way more cam than you have now, but you’ll likely need to run more stall to really take advantage of it. If you’re racing through mufflers that needs to be taken into account for cam selection. I can’t see the motor picking up 75hp with a cam swap.
Bigger cam first, then a stall adjustment if necessary.........and in the mean time I’d try and pick up a 337 intake manifold. Get the manifold port matched to the full MW size and open the heads up as to that as well.. If you are going to max wedge you might as well sell off your 240s and buy the 270 - with a raised intake as a bonus But I do agree look at cam first to get RPM and power , allowing the 505 will swallow a lot of cam . Tex
New best ET 10.259@129.65 . New best MPH 130.32 Finally fitted a solid cam, stepped it up a bit more 3690lbs through the mufflers New World block 3780lbs 10.278@130.80 . Wowser 10.253@130.24 footbraking from 1500rpm Power by Tex's Automotive
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