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The good news to me is that the good flowing heads will make power at low boost, and lots of power at higher boost. Like T2 said, good flowing heads actually need less cam to do the same flowing. I don't know how forgiving that head's chambers are with detonation. Have to ease up onto the tune with timing IMO. Will be cool to see how it runs.
 

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You have obviously spent a lot of time and money to be competitive. I don't see any other solution other a cam change. If it was a big tire, +10,000rpm clutch/Bruno/Quickdrive car it might have a chance. I would knock the lift down to .850-.875 range and trim 8* - 10* of duration off both lobes as well. That would still be around where I'm at and definitely considered a max effort cam. Mine is 55mm roller bearing core with 2/3 and 4/7 swap(LS order) cam core. I run .937" lifters and steel T&D rockers. I would have gone 60mm roller bearing cam if it was an option. My SB cam height is BBC +.400" raised cam which is why I couldn't get the 60mm roller bearing option.
 

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Discussion Starter #63
You have obviously spent a lot of time and money to be competitive. I don't see any other solution other a cam change. If it was a big tire, +10,000rpm clutch/Bruno/Quickdrive car it might have a chance. I would knock the lift down to .850-.875 range and trim 8* - 10* of duration off both lobes as well. That would still be around where I'm at and definitely considered a max effort cam. Mine is 55mm roller bearing core with 2/3 and 4/7 swap(LS order) cam core. I run .937" lifters and steel T&D rockers. I would have gone 60mm roller bearing cam if it was an option. My SB cam height is BBC +.400" raised cam which is why I couldn't get the 60mm roller bearing option.
I got cam from bullet and talked to them yesterday and they said it was a lil big on duration he said he wanted me to advance it 4*and see what it does if that helps go 2 more so I'm a try that just to see won't take long to do it but said he could take a lil off this one. Yea this is a 60mm and it's got lifters moved and angled so not a cheap cam so I'm a try what they said just for heck of it . If it would just make a lil more boost I'd be fine so I guess we will see .
 

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I got cam from bullet and talked to them yesterday and they said it was a lil big on duration he said he wanted me to advance it 4*and see what it does if that helps go 2 more so I'm a try that just to see won't take long to do it but said he could take a lil off this one. Yea this is a 60mm and it's got lifters moved and angled so not a cheap cam so I'm a try what they said just for heck of it . If it would just make a lil more boost I'd be fine so I guess we will see .
im sure you know this but check PTV when you adv it
 

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Discussion Starter #65
im sure you know this but check PTV when you adv it
Yea it has plenty of clearance just have to check after done not sure how much 4* will close up the clearance. I'm just wondering if that will make more boost or just make it spool faster .
 

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It will be closest to the piston about 10* BTDC on split overlap. This can vary a few degrees either way but it will get you in the neighborhood and you can adjust from there.
 

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Discussion Starter #68
It will be closest to the piston about 10* BTDC on split overlap. This can vary a few degrees either way but it will get you in the neighborhood and you can adjust from there.
I'm just wondering if that will help it make more boost?
 

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Generally it does more to get up on the converter but in all fairness it does open the exhaust valve earlier. However it is still going to have a ton of overlap and there's no getting around that other than cam change.
 

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You need to remember that with a cam swap you will not need to change anything with the valve train other than the pushrods if the cam has a different size base circle. The shimming of the rocker shafts/stands has to do with valve length and lash caps etc. not the camshaft itself.
 

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Ya ,i have a sbc 401 with gt55 94mm 1.24ar. And mine doesnt build boost to like 5k+ i. Looked into a new stator but i was told that was fine (17-45) then asked about the cam was told that was fine. (Steve morris cam) so it has to be in the tune. So i am in same boat to get this new build worked out.
 

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The more timing you can safely have in the engine the faster and harder it will accelerate, therefore, build more boost and at a faster rate. Try and keep the full engine timing, whatever that may be probably somewhere between 30-40 degrees depending on the engine, until your max starting line boost pressure is achieved at a minimum.
 

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You need to remember that with a cam swap you will not need to change anything with the valve train other than the pushrods if the cam has a different size base circle. The shimming of the rocker shafts/stands has to do with valve length and lash caps etc. not the camshaft itself.
Well, almost. the valve spring installed height MIGHT be ok if you don't work backwards from bind. But it might not be too.

I agree with the post about timing. More will accelerate the engine more quickly. Where you have problems with timing is when the engine is more heavily loaded, not accelerating quickly, and at or near peak torque. That's a danger area.
 

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But valve spring installed height has nothing to do with rocker geometry. You change the installed height by adding or removing shims under the spring. Valve length is what determines rocker geometry. Not spring installed height.
 

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I think temp was pointing out that if the valve springs were setup to .0XX" from bind at .980 lift, the a lower lift cam would leave spring setup up too far from bind (likely unstable). Side note, reducing lift with same base circle cam (and reusing push rod) is going to put rocker arm not parallel with retainer at mid lift point. Push rod will be short about .040" from ideal with 1.6 rocker with .850 lift cam compared to .980" lift. Test - open valve to .425" with current cam and note rocker geometry. I would expect it to have not yet reached the parallel point If it was setup correctly.
 

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Looking back I do now see where he said it had .980 lift. I missed that somehow. I have changed camshafts lifts within .050 or a little less with no ill effect on geometry, I see where some were suggesting well over .100 less lift In that respect I have to agree that stand height will more than likely need to be changed some to accommodate that.

I think even though at first it may be somewhat expensive and maybe time consuming, but I think a cam change will be well worth it in the end.
 

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You could probably shim the springs correctly from bind but it will add a lot of seat pressure. Open pressure will be the same as now if shimmed to the same distance from bind.(typically .060") It depends on what that equals on the seat as to whether or not I would run them at that installed height.
 

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Ya ,i have a sbc 401 with gt55 94mm 1.24ar. And mine doesnt build boost to like 5k+ i. Looked into a new stator but i was told that was fine (17-45) then asked about the cam was told that was fine. (Steve morris cam) so it has to be in the tune. So i am in same boat to get this new build worked out.
Is this a 9.5" PTC Converter?? If so give some power and combo specs. I started with a 16-45 that they said was good and I'm all the way to a 12-45 that spools fine but still slips 10 - 11% at 8100rpm on just medium tuneup. I probably needed a 10" but the average SB cant run a 10". I guess that makes me special, LOL
 

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You could probably shim the springs correctly from bind but it will add a lot of seat pressure. Open pressure will be the same as now if shimmed to the same distance from bind.(typically .060") It depends on what that equals on the seat as to whether or not I would run them at that installed height.
I have run big springs at correct pressure but too far from bind. I have had some that had no problems, and some that really seemed to be hard on the guides and the valve job overall. Never broke one. The spring manufacturers claim that running them close to bind prevents spring surge, and that the pressure alone will not do that. I don't have a spintron so I guess I can't say for sure. I try to always set up from coil bind now.
 
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