Do I need longer pushrods?
Le Mans Master
Joined: Mar 2002
Posts: 5,889
Likes: 2
From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Re: Do I need longer pushrods? (cprgmr)
OK, at this point you're going to need a pushrod .100 longer, maybe .200 give or take because of preload compensation. That might get you the clearance on the retainer too :D
Call Comp cams Monday and tell them you've got a good pattern without preload and they can probably tell you 'cause they do this all the time. Sorry, I just can't be certain myself. When you talk to them, mention the clearance problem and they can tell you what diameter spring for that rocker too. As Jake mentioned earlier, you want a minimum .030......I'd like more. As for grinding the rocker (or trimming if you prefer a softer word), that's a call you gotta make...........you'll probably be OK doing that........probably........ Me? No way on a motor that's already cost a buncha money, but that's just me........
[Modified by Caboboy, 10:32 AM 4/4/2004]
Call Comp cams Monday and tell them you've got a good pattern without preload and they can probably tell you 'cause they do this all the time. Sorry, I just can't be certain myself. When you talk to them, mention the clearance problem and they can tell you what diameter spring for that rocker too. As Jake mentioned earlier, you want a minimum .030......I'd like more. As for grinding the rocker (or trimming if you prefer a softer word), that's a call you gotta make...........you'll probably be OK doing that........probably........ Me? No way on a motor that's already cost a buncha money, but that's just me........
[Modified by Caboboy, 10:32 AM 4/4/2004]
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,710
Likes: 1
From: Green Bay WI
Re: Do I need longer pushrods? (Caboboy)
OK, at this point you're going to need a pushrod .100 longer, maybe .200 give or take because of preload compensation. That might get you the clearance on the retainer too :D
Call Comp cams Monday and tell them you've got a good pattern without preload and they can probably tell you 'cause they do this all the time. Sorry, I just can't be certain myself. When you talk to them, mention the clearance problem and they can tell you what diameter spring for that rocker too. As Jake mentioned earlier, you want a minimum .030......I'd like more. As for grinding the rocker (or trimming if you prefer a softer word), that's a call you gotta make...........you'll probably be OK doing that........probably........ Me? No way on a motor that's already cost a buncha money, but that's just me........
[Modified by Caboboy, 10:32 AM 4/4/2004]
Call Comp cams Monday and tell them you've got a good pattern without preload and they can probably tell you 'cause they do this all the time. Sorry, I just can't be certain myself. When you talk to them, mention the clearance problem and they can tell you what diameter spring for that rocker too. As Jake mentioned earlier, you want a minimum .030......I'd like more. As for grinding the rocker (or trimming if you prefer a softer word), that's a call you gotta make...........you'll probably be OK doing that........probably........ Me? No way on a motor that's already cost a buncha money, but that's just me........
[Modified by Caboboy, 10:32 AM 4/4/2004]
Burning Brakes
Joined: Jan 2004
Posts: 933
Likes: 0
From: Inland Empire CA
Re: Do I need longer pushrods? (cprgmr)
That's a common problem with those dished retainers. As the others have said geometry is the most important thing. If you could find another titanium retainer that would work with those springs, it would be cool if you could get a flat one (or less of a dish). That would eliminate clearance in that area... but it would also increase spring pressure. Possibly too much and might cause coil bind (depending on cam) among other possibilities.
Just be patient... the right answers will come. Keep asking questions and you'll eventually dig the information out of them. Good luck
Just be patient... the right answers will come. Keep asking questions and you'll eventually dig the information out of them. Good luck
Melting Slicks
Joined: Jun 2000
Posts: 3,215
Likes: 6
From: Tampa Florida
Re: Do I need longer pushrods? (cprgmr)
cprgmr: I would try it first before you buy new pushrods. I'm betting you did like I did and the lifters are bled down a bit, making for less clearance.
I have the same heads/rockers and thought the same thing. I did have to play with the guide plates quite a bit to center the rockers over the stems as good as possible-they won't be perfect, but try for the best.
I ran stock length pushrods and no problems.
One more note: the rockers are 'hollowed' out underneath so from a side view they may look like contact to the retainers, but there is still clearance...have to use a feeler guage-even then I could swear it was hitting...nope.
Good luck!
I have the same heads/rockers and thought the same thing. I did have to play with the guide plates quite a bit to center the rockers over the stems as good as possible-they won't be perfect, but try for the best.
I ran stock length pushrods and no problems.
One more note: the rockers are 'hollowed' out underneath so from a side view they may look like contact to the retainers, but there is still clearance...have to use a feeler guage-even then I could swear it was hitting...nope.
Good luck!
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,710
Likes: 1
From: Green Bay WI
Re: Do I need longer pushrods? (No Go)
the lifters are bled down a bit, making for less clearance.
One more note: the rockers are 'hollowed' out underneath so from a side view they may look like contact to the retainers, but there is still clearance...have to use a feeler guage-even then I could swear it was hitting...nope.
Thanks for the info! :cheers:
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,710
Likes: 1
From: Green Bay WI
Re: Do I need longer pushrods? (WickedC4)
That's a common problem with those dished retainers. As the others have said geometry is the most important thing. If you could find another titanium retainer that would work with those springs, it would be cool if you could get a flat one (or less of a dish). That would eliminate clearance in that area... but it would also increase spring pressure. Possibly too much and might cause coil bind (depending on cam) among other possibilities.
Just be patient... the right answers will come. Keep asking questions and you'll eventually dig the information out of them. Good luck
Just be patient... the right answers will come. Keep asking questions and you'll eventually dig the information out of them. Good luck
Burning Brakes
Joined: Nov 2001
Posts: 1,241
Likes: 9
From: Houston TX
Re: Do I need longer pushrods? (cprgmr)
the geometry is very bad from a sweep standpoint, judging from that picture. you should have .050" or less sweep. besides wear on the guides and parts, you're literally losing lift at some points. you will need pushrods on the order of .150" to .300" longer to fix that.
beyond that, you have the wrong guideplates. the LTx heads have different geometry than any other sbc head. they're close enough that most people get away with sbc guideplates, but your tips being off center shows you how far off they are. gm makes a special guideplate for the "lean-burn" and LTx heads. use those and the tips will be centered side to side. part number is 14011051 in the GMPP catalog. (ignore the blurb, this part number is indeed the special spacing required for LTx heads.)
-michael
beyond that, you have the wrong guideplates. the LTx heads have different geometry than any other sbc head. they're close enough that most people get away with sbc guideplates, but your tips being off center shows you how far off they are. gm makes a special guideplate for the "lean-burn" and LTx heads. use those and the tips will be centered side to side. part number is 14011051 in the GMPP catalog. (ignore the blurb, this part number is indeed the special spacing required for LTx heads.)
-michael
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,710
Likes: 1
From: Green Bay WI
Re: Do I need longer pushrods? (MSR)
the geometry is very bad from a sweep standpoint, judging from that picture. you should have .050" or less sweep. besides wear on the guides and parts, you're literally losing lift at some points. you will need pushrods on the order of .150" to .300" longer to fix that.
beyond that, you have the wrong guideplates. the LTx heads have different geometry than any other sbc head. they're close enough that most people get away with sbc guideplates, but your tips being off center shows you how far off they are. gm makes a special guideplate for the "lean-burn" and LTx heads. use those and the tips will be centered side to side. part number is 14011051 in the GMPP catalog. (ignore the blurb, this part number is indeed the special spacing required for LTx heads.)
-michael
beyond that, you have the wrong guideplates. the LTx heads have different geometry than any other sbc head. they're close enough that most people get away with sbc guideplates, but your tips being off center shows you how far off they are. gm makes a special guideplate for the "lean-burn" and LTx heads. use those and the tips will be centered side to side. part number is 14011051 in the GMPP catalog. (ignore the blurb, this part number is indeed the special spacing required for LTx heads.)
-michael
Le Mans Master
Joined: Oct 1999
Posts: 9,713
Likes: 3
From: Sachse Texas
Cruise-In I Veteran
Cruise-In II Veteran
Re: Do I need longer pushrods? (cprgmr)
What ratio rockers are you using? I have a set of Pro Magnum 1.52 ratio that have been clearanced for 1.550" springs. I had no issues with the rockers. They are very strong and have plenty of material for strength.
What springs are those (diameter, installed height)? Every setup may be slightly different so just becuase the same parts are installed in another car with the same heads does not mean they will use the same length pushrod.
Looks like you have plenty of good advise being given in the thread already...
What springs are those (diameter, installed height)? Every setup may be slightly different so just becuase the same parts are installed in another car with the same heads does not mean they will use the same length pushrod.
Looks like you have plenty of good advise being given in the thread already...
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,710
Likes: 1
From: Green Bay WI
Re: Do I need longer pushrods? (Vette92)
What ratio rockers are you using? I have a set of Pro Magnum 1.52 ratio that have been clearanced for 1.550" springs. I had no issues with the rockers. They are very strong and have plenty of material for strength.
What springs are those (diameter, installed height)? Every setup may be slightly different so just becuase the same parts are installed in another car with the same heads does not mean they will use the same length pushrod.
Looks like you have plenty of good advise being given in the thread already...
What springs are those (diameter, installed height)? Every setup may be slightly different so just becuase the same parts are installed in another car with the same heads does not mean they will use the same length pushrod.
Looks like you have plenty of good advise being given in the thread already...
As far as the springs go, I tried to get in touch with Pete at CNC Heads to get the exact specs on them, but he's on vacation for a few weeks (figures - just my luck).
They're CC double valve springs, but I don't know the specifics...
