Quote:
I would expect it to idle somewaht milder at 9.5. 
Quote:
Lower compression long duration cam engines tend to idle worse than with a higher compression ratio.
So which is it?
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| Author: | Bren67Cuda904 [ Fri Aug 03, 2007 3:09 pm ] |
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Quote:
I would expect it to idle somewaht milder at 9.5.
Quote:
Lower compression long duration cam engines tend to idle worse than with a higher compression ratio.
So which is it?
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| Author: | Sam Powell [ Fri Aug 03, 2007 5:35 pm ] |
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It depends on the cam you have. Milder cams idle better, but need low compression. I think 12:1 is too high, but 10:1 is not. Why not shoot for 10:1? You must run a bigger cam with high compression, and usually the vacuum is low, and the idle is rough. What vacuum are you pulling now? The cam you now have seems better than what you have taken out, even for 10:1. Sam |
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| Author: | LUCKY13 [ Fri Aug 03, 2007 5:40 pm ] |
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Geez, like you said, you need to go lay down & sleep. Start fresh, go threw the lash, retune, and see where it goes. You can experiment with lash and change things alot also. But dont go jumping to changes so quick, the power can fool you anyway when it comes to topend. But you just made a major change, and you will have to retune to even begin to take advantage of it. One thing I will have to agree on, and that is your exhaust mannies are not going to help top end power, the intake I dont think is going to hurt you any. But as far as the exhaust, I think it is hurting you on bottom end & top end ( I didnt realize you had this setup until today looking threw your pics on your web site). Not taking anything away from the DD manny setup, but with the extra cubes you have I have to believe they are to restrictive for you. Plus having tuned headers will change things on top & bottom with a build like this. Anyway, step back and take a deep breath & get some rest. Your loooking for instant WOW and it just doesnt work that way. Give it a chance & look at the big picture with a fresh mind. As always, take small steps, and read them plugs. Jess |
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| Author: | Bren67Cuda904 [ Fri Aug 03, 2007 6:39 pm ] |
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Quote: I forgot to mention that there is a hint of detonation at high RPM with 25* total timing and a splash of race fuel. (80/20%)    I really don't think so. As doc has said "I need to add CC's" I thought for a moment that a cam cam just might solve the detonation with a little compermize in other areas like idle quality. But after still having a hint of detonation on the top end and still on race fuel. Its way past time to just fix the orignal problem. Doug you can say "I told you so" if you'd like. I think that a lot was learn here and not just on my part. In the future we can quote this page and say without doubt that a 12:1 motor doesn't run on 93 octane with success.
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| Author: | Doctor Dodge [ Fri Aug 03, 2007 7:04 pm ] |
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Quote: ... without doubt... a 12:1 motor doesn't run on 93 octane with success...
I wish it would but it does not.205 psi cranking compression is still too much for pump gas. I learned years ago that I can get better performance out of a lower compression engine with more timing then I can get out of a higher compression engine with less timing. Fuel quality is the variable that I am always chasing. Here in CA, the BEST pump gas is 91 R/M. DD |
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| Author: | Bren67Cuda904 [ Fri Aug 03, 2007 7:22 pm ] |
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Do you think an 83cc camber will run on 91-93 octane? (page 5 to find your chart) I liked the quality of the idle and the way it ran with the 240@50 cam. Do you think the idle will be the same better or worse? Also do you think the cam should be installed back to the 5.5* advanced (19.5*-I) or straightup (14*-I)? It was advanced before. Never tried it straight up except to check cranking pressure, which dropped 20psi from the advance setting. My feeling is to advance it. |
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| Author: | Doctor Dodge [ Fri Aug 03, 2007 7:53 pm ] |
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If the head comes off Eileen, you need to take some careful measurements and do all the math to get an accurate final total chamber volume. ( we know the sweep volume) I never had a clear indication on the size of the dish in the piston... you (and you engine builder) need to know that. A stroker or long rod SL6 will need a large dish in the piston to keep the compression ratio in "pump gas" range. You saw the pistons, are they flat tops with valve reliefs or do they have a big dish like the ones I am building into Twiggy? Truth is a "64cc head chamber" is also somewhat odd, usually I see SL6 combustion chambers in the 58 to 60 cc range without any head milling. Please double-check all the numbers As everyone keeps saying, you have a bunch of good parts and the engine has "lived" thru it's "infant mortality" stage, you should be able to adjust the compression ratio into the 9.5 range and have a sweet running pump gas SL6. As for the cam, degree it at 2 degrees advance and tell us where the... 1) Intake valve opens (= 1/2 overlap) 2) where the exhaust valve closes ( the other 1/2 of overlap) 3) where the exhaust valve opens ( blow down event) All these "numbers" will tell us a lot about how the engine will run. DD |
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| Author: | Mag00 [ Fri Aug 03, 2007 8:00 pm ] |
| Post subject: | Why not keep that head... |
and use it on a later project , or sell it to someone that can take advantage of the higher ratio? looking at the chamber in the slant head it seems it would do well to support over 9-9.5 c/r with anything resembling a streetable profile... VERY few engine will support ratios like that on pump... check out Engine masters ... they are scienced out ragged edge pump gas motors... iron heads and old combustion chamber tech are far from EFI, aluminum headed modern chamber shaped engines ... 185 190 psi is about the max a streeable engine can handle... And that is under ideal conditions... air temp,. humiditdy, time of year, (fuel availabilty, it's not the same blend year 'round) and a hundred other factors affect octane/power/torque/ compression eqation... before you send the head out you might try 2 or three other options weber tripples, a dished piston to retain your squish / quench as best as possible and last EFI ... a proper setup on a stroker with webers or EFI would be a thing to behold....!!! |
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| Author: | Mag00 [ Fri Aug 03, 2007 8:07 pm ] |
| Post subject: | One more observation... |
taking intake air from under hood versus a cooler outside source CAN and oft time does make the difference in aleaviating incipet ping.. The factor , iIRC is something on the order of a tenth point c/r or octane rating per 10 degrees... Don't quote me... so losing 70-100 degrees or more can redcuce octane requirements substantaly... Best of luck! really wanna see you succeed !!! dr |
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| Author: | DusterIdiot [ Fri Aug 03, 2007 9:11 pm ] |
| Post subject: | The odd head... |
Quote: Truth is a "64cc head chamber" is also somewhat odd
I've seen a couple now, but these only came off of 1963 and a 1965 Dodge Truck slant six with the ping prone chamber...(I still cant imagine a Forestry Truck with 7:1 compression and a set of 3.91's with the NP435...but that's been a standard package in Oregon's Past)So that wouldn't help things too much... -D.Idiot |
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| Author: | Bren67Cuda904 [ Sat Aug 04, 2007 1:47 am ] |
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We made the 64cc's by cutting open the camber to match the big bore. The pistons are these as pictured. http://www.renaissanceracing.com/images ... iston1.JPG http://www.renaissanceracing.com/images ... iston3.JPG http://www.renaissanceracing.com/images ... iston4.JPG How does one measure the cc's of the valve reliefs with them still in the block? For take matter, how are they measured even if there not in the block? Where in this next picture would you recommend cutting in an extra 18cc's? If thats what we decide to do. http://www.renaissanceracing.com/images ... orting.JPG |
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| Author: | Bren67Cuda904 [ Sat Aug 04, 2007 1:55 am ] |
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This cam cam shows the numbers for staight up installation for my old cam, the 240@50. http://www.renaissanceracing.com/images/CamCard2A.JPG |
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| Author: | terrylittlejohn [ Sat Aug 04, 2007 5:46 am ] |
| Post subject: | measure relieves |
to measure the piston relieves move the piston .500in down the bore seal the piston to the cylinder wall with petrolem jell and clean excess, then fill the bore with minerial oil, that is measure so you know the amount that you pored in ,then do the math( volume off a cylinder/3.14xradius squaredx.500ins)then subtract the amount you measured when you pured in the oil and the differents is the relieve volume. 
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| Author: | Bren67Cuda904 [ Sat Aug 04, 2007 9:01 am ] |
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There is a spot on my cam that I plan to reinstall (240@50) that concerns me. I don't think its too much to worry about but then again with cams liking to go flat, maybe. All lobes look perfect except this one right on the tip. There is some material missing. Maybe an air pocket that was ground into? General area picture. http://tinyurl.com/37cclf Closer picture. http://tinyurl.com/2tallj Very close http://tinyurl.com/33vag7 Anything to worry about? |
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| Author: | argentina-slantsixer [ Sat Aug 04, 2007 9:34 am ] |
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don't know if my answer is going to make you more or less worrysome, but I do think that looks like a base material flaw. (as in not produced by lobe/lifter contact) |
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