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Cam timing and piston to valve #196396 01/17/09 07:50 PM 01/17/09 07:50 PM
Joined: Jan 2007 Posts: 124 louisiana S sixty9bee OP member
sixty9bee OP member S Joined: Jan 2007 Posts: 124 louisiana	How much effect does cam timing effect piston to valve clearence? subject engine is: 0 deck ross flattop 4.15 stroke 400 277 at 0.050 roller cam 700 lift 110 centerline installed at 110 edelbrock heads

Re: Cam timing and piston to valve [Re: sixty9bee] #196397 01/17/09 07:54 PM 01/17/09 07:54 PM
Joined: Jan 2007 Posts: 124 louisiana S sixty9bee OP member
sixty9bee OP member S Joined: Jan 2007 Posts: 124 louisiana	exhaust valve with no head gasket and 0 lash has contact with piston. What suggestions to get the minimum clearance? quench is already set for .039 gasket?

Re: Cam timing and piston to valve [Re: sixty9bee] #196398 01/17/09 08:05 PM 01/17/09 08:05 PM
Joined: Apr 2005 Posts: 1,505 TN S SCATPACK 1 pro stock
SCATPACK 1 pro stock S Joined: Apr 2005 Posts: 1,505 TN	You could advance the cam some to get clearance. But if you are hitting, I would flycut valve relief notches into the pistons. I do not feel safe with less than .100 thou on the exhaust to piston. I know it is more time consuming but do it any way and never have to worry about it. Old Geezer Racing

Re: Cam timing and piston to valve [Re: sixty9bee] #196399 01/17/09 08:05 PM 01/17/09 08:05 PM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Whats the intake at. Advance it 4* and check it again. I prefer to check it with the head gasket but thats me. Use a pushrod length checker with 0 lash then you can figure your lash in

Re: Cam timing and piston to valve [Re: sixty9bee] #196400 01/17/09 08:10 PM 01/17/09 08:10 PM
Joined: Jan 2003 Posts: 16,923 NC 440Jim I Live Here
440Jim I Live Here Joined: Jan 2003 Posts: 16,923 NC	Double check when you change the cam installed position. But as I recall, advancing the cam (going from an intake lobe installed position of 110 ATC to 106 ATC) will reduce intake piston to valve clearance, but increase the exhaust P2V clearance. If you are running 1.5 ratio rockers, it should be around 0.023" change. But the lobe profile can be different than what I am used to. Let us know what numbers you measure. I check this when I "map" a cam. And I see around 0.015" lobe lift change with 4 degree advance, measured atg +/- 8 degrees of TDC (that is where min piston to valve usually occurs).

Re: Cam timing and piston to valve [Re: 440Jim] #196401 01/17/09 08:21 PM 01/17/09 08:21 PM
Joined: Apr 2007 Posts: 1,165 Central Ohio, USA Bigbeep super stock
Bigbeep super stock Joined: Apr 2007 Posts: 1,165 Central Ohio, USA	Good stuff here. I am in the process of chosing a new cam and will be doing this soon, I hope. Beep 4954823-09-111(2).JPG (66 downloads)

Re: Cam timing and piston to valve [Re: Bigbeep] #196402 01/17/09 09:02 PM 01/17/09 09:02 PM
Joined: Nov 2004 Posts: 2,119 sc T tjmarcus1 top fuel
tjmarcus1 top fuel T Joined: Nov 2004 Posts: 2,119 sc	if he has contact with 0 lash and no headgasket, he has problems! the question is how much interference is there? also are you sure the cam is in at 110? if you factor .040 for gasket,.020 lash that's still only .060 minus the exact amount of interference. advancing to 106 might help, but not fix the prob.

Re: Cam timing and piston to valve [Re: tjmarcus1] #196403 01/17/09 10:24 PM 01/17/09 10:24 PM
Joined: Jun 2008 Posts: 3,916 usa L lewtot184 master
lewtot184 master L Joined: Jun 2008 Posts: 3,916 usa	going from a 110 installed centerline to 106 will probably only net .015" additional clearance. recheck installed centerline and true rocker ratio. if the centerline is correctly installed and the rocker ratio isn't way off then the pistons will need work.

Re: Cam timing and piston to valve [Re: sixty9bee] #196404 01/17/09 11:06 PM 01/17/09 11:06 PM
A Anonymous Unregistered
Anonymous Unregistered A	before you go any further, check your intake valve clearance. if you have more clearance there you might be able to advance the cam and get enough for both. if not, you'll be flycustting pistons. most shelf ross pistons will not handle .700 lift safely.

Re: Cam timing and piston to valve #196405 01/17/09 11:28 PM 01/17/09 11:28 PM
Joined: Jan 2007 Posts: 124 louisiana S sixty9bee OP member
sixty9bee OP member S Joined: Jan 2007 Posts: 124 louisiana	the rocker ratio is 1.5 the lash was at 0 and the interference was minimal, as a matter of fact was not noticable until a dial indicator was used to check exact clearance. the intake was checked and has more than enough room through entire range. we could have 60-80 thou removed from the intake clearance and still be around 90 through the cycle.

Re: Cam timing and piston to valve [Re: sixty9bee] #196406 01/17/09 11:47 PM 01/17/09 11:47 PM
Joined: Nov 2004 Posts: 2,119 sc T tjmarcus1 top fuel
tjmarcus1 top fuel T Joined: Nov 2004 Posts: 2,119 sc	Quote: the rocker ratio is 1.5 the lash was at 0 and the interference was minimal, as a matter of fact was not noticable until a dial indicator was used to check exact clearance. the intake was checked and has more than enough room through entire range. we could have 60-80 thou removed from the intake clearance and still be around 90 through the cycle. with that much int. clearance, are you sure the cam is in right?

Re: Cam timing and piston to valve [Re: tjmarcus1] #196407 01/18/09 12:00 AM 01/18/09 12:00 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: Quote: the rocker ratio is 1.5 the lash was at 0 and the interference was minimal, as a matter of fact was not noticable until a dial indicator was used to check exact clearance. the intake was checked and has more than enough room through entire range. we could have 60-80 thou removed from the intake clearance and still be around 90 through the cycle. with that much int. clearance, are you sure the cam is in right? The cam does sound like its installed retarted more than straight up

Re: Cam timing and piston to valve [Re: sixty9bee] #196408 01/18/09 12:03 AM 01/18/09 12:03 AM
Joined: Jan 2003 Posts: 6,591 Canton, Ohio S Sport440 master
Sport440 master S Joined: Jan 2003 Posts: 6,591 Canton, Ohio	Quote: How much effect does cam timing effect piston to valve clearence? On the intake side a 1* at the crank is equal to around .003 to .004 lift at the lobe times rocker ratio. Now if the exhaust lobe profile is similer you should see the same. It may be less since its Landing the valve. But, requardless, your probably looking at around a extra .020 exhaust P/V clearence, with a 4* advance. mike Last edited by Sport440; 01/18/09 12:06 AM.

Re: Cam timing and piston to valve [Re: Sport440] #196409 01/18/09 12:14 AM 01/18/09 12:14 AM
Joined: Jan 2007 Posts: 124 louisiana S sixty9bee OP member
sixty9bee OP member S Joined: Jan 2007 Posts: 124 louisiana	I know, it sounds like its in retarded. that was my first thought. checked and started over checked again. the valve relief is deeper on intake side. the only question on install is the cam is ground on 110 but my understanding is comp puts 4 degrees advance into the grind. if that is correct, it should probably not be installed at 110 right? by the way thanks for all the replies

Re: Cam timing and piston to valve [Re: sixty9bee] #196410 01/18/09 12:28 AM 01/18/09 12:28 AM
Joined: Jun 2003 Posts: 52,972 Romeo MI MR_P_BODY Master
MR_P_BODY Master Joined: Jun 2003 Posts: 52,972 Romeo MI	Quote: I know, it sounds like its in retarded. that was my first thought. checked and started over checked again. the valve relief is deeper on intake side. the only question on install is the cam is ground on 110 but my understanding is comp puts 4 degrees advance into the grind. if that is correct, it should probably not be installed at 110 right? by the way thanks for all the replies Yes they grind in advance but you still start at 110 for 0 then advance it from there if you want advance

Re: Cam timing and piston to valve [Re: MR_P_BODY] #196411 01/18/09 01:43 AM 01/18/09 01:43 AM
Joined: Jan 2003 Posts: 6,591 Canton, Ohio S Sport440 master
Sport440 master S Joined: Jan 2003 Posts: 6,591 Canton, Ohio	Quote: Quote: I know, it sounds like its in retarded. that was my first thought. checked and started over checked again. the valve relief is deeper on intake side. the only question on install is the cam is ground on 110 but my understanding is comp puts 4 degrees advance into the grind. if that is correct, it should probably not be installed at 110 right? by the way thanks for all the replies Yes they grind in advance but you still start at 110 for 0 then advance it from there if you want advance Where your cam is installed now at a 110* ICL with a 110* LS you are neither advanced or retarded. Your at 0* Even if the cam had 4* advance ground into it. mike

Re: Cam timing and piston to valve [Re: sixty9bee] #196412 01/18/09 12:26 PM 01/18/09 12:26 PM
Joined: Jan 2003 Posts: 16,923 NC 440Jim I Live Here
440Jim I Live Here Joined: Jan 2003 Posts: 16,923 NC	The best solution is the machine the exhaust valve reliefs in the pistons. But with a 110 LSA cam, I would not be afraid to install it with the intake lobe centerline at 104 ATC if needed, and you are willing to accept the trade offs.

Re: Cam timing and piston to valve [Re: sixty9bee] #196413 01/18/09 12:54 PM 01/18/09 12:54 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	If comp cams says 106 on a 110 lobe center cam they install the dowel pin to try and have straight up be at 106 everything being equal. but the crank keyway , gear set and drilling the dowel in the pin is not an exact science With the exhaust being that

Re: Cam timing and piston to valve [Re: Dodgem] #196414 01/18/09 01:01 PM 01/18/09 01:01 PM
Joined: Mar 2008 Posts: 5,746 Ontario, Canada Dodgem master
Dodgem master Joined: Mar 2008 Posts: 5,746 Ontario, Canada	With the exhaust being that close and the intake that loose I'd say something is way out of whack and that cam is severly retarded? The intake valve is usually the issue. Check and re check your marks rolling over but at this point I would suggest a true cam degree job Just my thoughts have degreed lots and lots of cams Lost some in my copy and past?? LOL???

Re: Cam timing and piston to valve [Re: Dodgem] #196415 01/18/09 01:08 PM 01/18/09 01:08 PM
Joined: Jan 2007 Posts: 124 louisiana S sixty9bee OP member
sixty9bee OP member S Joined: Jan 2007 Posts: 124 louisiana	probably should have also stated its split duration 277 intake 285 exhaust. degree'ed several but not an expert by any means. does the procedure change any for split duration? the only explanation i can come up with is that the valve pockets are deeper on the intake side (according to the paperwork on the pistons) and the longer exhaust duration is the culprit. is this logical or am i grasping straws? the pistons have no additional fly cutting only the ross factory reliefs

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