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Its time to degree the cam. Its not the one i would have picked but its the one i have. It came with the engine. Bullet, 309/316, @.050 276/284, gross lift .731/.731, 110*, lash .026/.028 . Lunati link bar lifters. Comp pushrods, rockers, springs and girdle. Speed-Pro pistons L2307AF .100 over. Crankshaft Specialist crank. Steel LS 6 rods 6.135 . Dart Pro-1 heads. Block has been decked and piston is at 0 deck. Had to have heads shaved .020 to clear indentions because of previously ran copper head gaskets. Will install Fel-Pro 1027`s @ .039 . Will run two 850`s or one 1150. Mantra Performer medium weight hull. Berkeley "B". Droop snoot and place dirverter. It`ll be a lake boat. I`ve been told to degree it @ 108 to give me more on the bottom end. 108* is 30* BTDC. Maybe i should retard it 2* and gain on the big end? Or maybe straight up and have the both of two worlds? Is there really a measureable difference? Thoughts, opinions and advise welcome and thanks in advance. Richard
 

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That is a badass cam you got right there. I would love to hear it when you get it all together. I currently have almost the same cam in my setup right now, except that it is ground on a 108* lobe centerline and is ground with 5* advance, placing the intake centerline at 103*. You didn’t mention if your cam has advance ground into it or not. I can not comment on the piston-to-valve clearance because my pistons, which sit in the hole .025 and have almost an 8cc dish including the unaltered valve relief notches . No other machine work was done to resolve any clearance issues here. Zero-decking your block with those dome pistons and milling the heads .020 will definitely be tight and advancing the cam will aggravate that intake opening clearance situation further while increasing the exhaust clearance.

With that being said, while playing around with Engine Analyzer indicates that advancing the cam shows positive gains across the board, however this could be the result of hastening late intake valve closure creating a higher dynamic compression ratio in my blower application with maybe too much overlap. One of my winter upgrade projects is changing to a cam drive that incorporates a vernier timing adjustment which will allow quick timing changes in +/- 1* increments. I want to feel first-hand what these changes do.

I don’t know if you like to “test” and you didn’t mention what cam drive you are intending (if it lends itself to easy adjustment), but I would check the timing and piston-to-valve clearance at all settings, just in case you decide to play with the cam timing at the water. While you are set up to time the cam, it takes just a few minutes longer to check your clearance at your full advance/retard settings.

I look forward to hearing from Cstraub and Steelcomp on the topic. I hope that they will take time to share their knowledge on the topic. Good luck with your project.

Cheers,

Joe

P.S. Larry Shepard of Mopar Performance stated that changing cam timing only 1 degree is a waste of time.
 

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That is a badass cam you got right there. I would love to hear it when you get it all together. I currently have almost the same cam in my setup right now, except that it is ground on a 108* lobe centerline and is ground with 5* advance, placing the intake centerline at 103*. You didn’t mention if your cam has advance ground into it or not. I can not comment on the piston-to-valve clearance because my pistons, which sit in the hole .025 and have almost an 8cc dish including the unaltered valve relief notches . No other machine work was done to resolve any clearance issues here. Zero-decking your block with those dome pistons and milling the heads .020 will definitely be tight and advancing the cam will aggravate that intake opening clearance situation further while increasing the exhaust clearance.

With that being said, while playing around with Engine Analyzer indicates that advancing the cam shows positive gains across the board, however this could be the result of hastening late intake valve closure creating a higher dynamic compression ratio in my blower application with maybe too much overlap. One of my winter upgrade projects is changing to a cam drive that incorporates a vernier timing adjustment which will allow quick timing changes in +/- 1* increments. I want to feel first-hand what these changes do.

I don’t know if you like to “test” and you didn’t mention what cam drive you are intending (if it lends itself to easy adjustment), but I would check the timing and piston-to-valve clearance at all settings, just in case you decide to play with the cam timing at the water. While you are set up to time the cam, it takes just a few minutes longer to check your clearance at your full advance/retard settings.

I look forward to hearing from Cstraub and Steelcomp on the topic. I hope that they will take time to share their knowledge on the topic. Good luck with your project.

Cheers,

Joe

P.S. Larry Shepard of Mopar Performance stated that changing cam timing only 1 degree is a waste of time.

I assume boosted vs na would be a difference in if advancing cam makes more useable power...does what works on a na for cam timing differ from a boosted?
 

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Yes, cam timing for NA vs. supercharged vs. turbocharged are quite different.

What I now see that I forgot to put in my previous post is that I would suggest that Richard contact Bullet Cams if he doesn’t have the cam card for that cam to see what they recommend. That should be his first step. I think that he has part number 515005, but that is purely speculation and I can not find detailed information on that cam. Regardless, I would bet that his cam has advance already designed into it.

Bullet and formerly Ultradyne have a reputation for grinding hard running cams. If I was just going to set it and forget it, I would install it per their recommendations and be done with it.

They can also tell him at what crank angle he needs to cut the pistons for valve clearance so that he doesn’t lose too much static compression.

Merry Christmas,

Joe
 

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Discussion Starter #6
515005 is the correct part number. I called Bullet and was advised to degree to 108 and preferably to 107 ??? At 108 the events are; Intake open 30, close 66 . Exhaust open 74, close 30 . The engine originally had two 1050`s and a comp belt drive showing 2* advance. I robbed the carbs and belt drive for the 496 Texas Tunnel. I`m useing a World Products billit gears and chain with a Cloyes timing cover that was robbed from the 496. Late tonight i`ll use the modeling clay see what my clearences are. Aren`t i supposed to have a minimum of .060 ?
 

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515005 is the correct part number. I called Bullet and was advised to degree to 108 and preferably to 107 ??? At 108 the events are; Intake open 30, close 66 . Exhaust open 74, close 30 . The engine originally had two 1050`s and a comp belt drive showing 2* advance. I robbed the carbs and belt drive for the 496 Texas Tunnel. I`m useing a World Products billit gears and chain with a Cloyes timing cover that was robbed from the 496. Late tonight i`ll use the modeling clay see what my clearences are. Aren`t i supposed to have a minimum of .060 ?
You better be shooting for more like .100 minimum if not .125 on the exhaust. You can get away with .060 on the intake.



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You better be shooting for more like .100 minimum if not .125 on the exhaust. You can get away with .060 on the intake.
X2

The intake valve is chasing the piston down and you can get away with tighter P/V clearances but, the exhaust valve is being chased up by the piston. The ex valve is nowhere to be playing with tight clearances, unless you like pulling the motor apart again and repairing carnage.
 

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No disrespect and not to be argumentative but that cam starts opening the intake valve 30* BTDC. It has a pretty aggressive opening rate. Until the piston reaches TDC, the piston and the intake valve are headed for a head-on collision. Then, ATDC, “the intake valve is chasing the piston down.” IMHO, based on my humble experience, it is this window from about 16* BTDC to slightly ATDC that has caused problems for me. I would NEVER say, “Don’t check the exhaust.” I think checking everything helps develop your skills as an engine builder, builds confidence in the quality of your assembly, and you develop a certain Zen oneness with your ride.

Exhaust valve to piston clearance of .100 is safe and .125 is even more conservative for “a lake boat” with a timing chain. Intake valve to piston clearance of .060 in a race engine, living on the edge, where you are concerned about reducing compression by cutting valve reliefs in the pistons is acceptable, but a clearance of .080+ would be safer.

The only time I would consider tightening up the piston-to-valve clearance would be to minimize compression loss from fly cutting huge reliefs in the pistons. This doesn’t sound like an all-out effort, so better to error on the safe side. Losing a few grams off of those pistons wont hurt throttle response any.

Good luck and Merry Christmas,

Joe
 

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Let us know what the numbers look like.
 

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No disrespect and not to be argumentative but that cam starts opening the intake valve 30* BTDC. It has a pretty aggressive opening rate. Until the piston reaches TDC, the piston and the intake valve are headed for a head-on collision. Then, ATDC, “the intake valve is chasing the piston down.” IMHO, based on my humble experience, it is this window from about 16* BTDC to slightly ATDC that has caused problems for me. I would NEVER say, “Don’t check the exhaust.” I think checking everything helps develop your skills as an engine builder, builds confidence in the quality of your assembly, and you develop a certain Zen oneness with your ride.

Exhaust valve to piston clearance of .100 is safe and .125 is even more conservative for “a lake boat” with a timing chain. Intake valve to piston clearance of .060 in a race engine, living on the edge, where you are concerned about reducing compression by cutting valve reliefs in the pistons is acceptable, but a clearance of .080+ would be safer.

The only time I would consider tightening up the piston-to-valve clearance would be to minimize compression loss from fly cutting huge reliefs in the pistons. This doesn’t sound like an all-out effort, so better to error on the safe side. Losing a few grams off of those pistons wont hurt throttle response any.

Good luck and Merry Christmas,

Joe
I have ran intakes as tight as .040 in a race deal. Tell me how a intake valve gets closer to the piston, without the piston hitting the head first if the closest thing to the piston is the head? The valve can only open as fast as the cam allows. If its .060 away on assembly, the only way for it to get closer is for the rod/piston assembly to stretch under the RPM. In that event, any PV more than .040(or the head gasket thickness) will put the piston in the head before the valve and piston meet up. .020 more than the head gasket is plenty.

Its a mute topic. It won't clear.



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^ We need more details. Which Dart Pro1's? What's the bore & stroke? What rpm are you intending to run and how much power do you expect to make?
If I have .070-.080 ex p/v I'm happy. It's never as much in a running engine as it is on the engine stand, especially if you're using checking springs. Difference between checking springs and running springs with a solid roller can be as much as .070". On the intake, in 99.9% of cases, a miss is as good as a mile...but there are circumstances where there needs to be some xtra intake p/v clearance...but that's an entirely different discussion. ;)
 

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^ We need more details. Which Dart Pro1's? What's the bore & stroke? What rpm are you intending to run and how much power do you expect to make?
If I have .070-.080 ex p/v I'm happy. It's never as much in a running engine as it is on the engine stand, especially if you're using checking springs. Difference between checking springs and running springs with a solid roller can be as much as .070". On the intake, in 99.9% of cases, a miss is as good as a mile...but there are circumstances where there needs to be some xtra intake p/v clearance...but that's an entirely different discussion. ;)
:thumb:
I like alittle more on the exhaust, but then I am a chicken. I can live with .100 no problem. I tell others .125 because I never trust their spring choice, mag with no limiter, and getting a pump unloaded at WOT at max Rs.

My gut says he will have a PV collision on the engine stand no matter where he puts the cam



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Discussion Starter #15
This is a gen 4 BBC block bored .100 with 4.00 stroke. The heads are Dart Pro-1 345`s. Intake valve is 2.300 . This cam has been running in the engine but i`ve never ran it except on the trailer. I bought it about two years ago and its been in the corner of the shop being neglected. The only competition it`ll ever see on the lake is those darn bass boats with BIG engines. Thats the reason i considered retarding the cam thinking i`d gain on the big end where i`d need it most. The previous owner said it turned 7200 with a BC impeller and i doubt that a lot. I can see that the block has been decked and now i`ve taken .020 off the heads so its got to be getting close on the pv clearances. I was going to check the them last night but it was about 30 degrees in the shop. Tonight it`ll be heated and i`ll definately find the answer. Sitting here and not knowing is a bummer.
 

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This is a gen 4 BBC block bored .100 with 4.00 stroke. The heads are Dart Pro-1 345`s. Intake valve is 2.300 . This cam has been running in the engine but i`ve never ran it except on the trailer. I bought it about two years ago and its been in the corner of the shop being neglected. The only competition it`ll ever see on the lake is those darn bass boats with BIG engines. Thats the reason i considered retarding the cam thinking i`d gain on the big end where i`d need it most. The previous owner said it turned 7200 with a BC impeller and i doubt that a lot. I can see that the block has been decked and now i`ve taken .020 off the heads so its got to be getting close on the pv clearances. I was going to check the them last night but it was about 30 degrees in the shop. Tonight it`ll be heated and i`ll definately find the answer. Sitting here and not knowing is a bummer.
Richard, that's WAY too much cam for those heads on that engine. They belong on a 565.
 

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Discussion Starter #18
With the timing set at O and a used Fel-Pro head gasket i`m getting in excess of .190 pv clearance on both the intake and exhaust. Thought i`d start at 0 for fear of warping a valve. Checked it three times at 0 lash with modeling clay. The engine was cold as the temp in the shop was 38 when i started. Got it up to nearly a comfortable 60 about the time i finished. Was expecting a lot less clearance since i had .020 took off the heads and no clue how much when the block got decked. These pistons do have a deep valve release area. Any ideas on how much the clearance will tighten up when i advance it 2 degrees? This is a learning experience for me. Thanks again for all the replies.
 

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Richard that's pretty close to what I'm running in the Cheyenne. I'd have to look at my cam card for the specs but its around .750 lift and I'm spinning a B 62/6300. .100 over, 6.535 Rod, 4.00 stroke. SRP 12:1 pistons, Canfield 310 heads. Dynoed 786 @ 6800 uncorrected.
 
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