1.65rr or 1.7rr's......Can it be done?
10-19-2002, 07:12 AM
#1
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1.65rr or 1.7rr's......Can it be done?
Just would like to know what modifications i would have to do to run at least 1.65 stud mounted rr's. I know i will need new valve covers. are their any composite valve covers that will fit ( lt4 ) ??
Also, just a reassurance question: If i was to run the hotcam with 1.65 or 1.7 rr's mounted on a good set of ported heads, would i run into any problems??
thanks guys
thomas
Also, just a reassurance question: If i was to run the hotcam with 1.65 or 1.7 rr's mounted on a good set of ported heads, would i run into any problems??
thanks guys
thomas
10-19-2002, 08:47 AM
#2
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Higher rocker ratios put more side load on the valve stem. The result is an increased wear rate on the valve guides. The entire valvetrain can be designed to use them, but I am not enough of a mechanical engineer to know what aspects of the geometry are changed to accomplish this. I do know that on a standard small block head it does become an issue if you are planning on building a motor to last a very long time.
Higher rocker ratios will also increase pressure on the cam lobes and lifters, just as if stronger springs were installed. Cam lobe wear isn't an issue with roller lifters. But if you already have very stout valve springs it's possible that the increased presuure will collapse the lifters. This is very unlikely, IMHO.
The above aside, other than insuring that the springs can accomodate the higher lift, and that there is adequate valve cover clearance and piston to valve clearance just go for it.
Rich Krause
Higher rocker ratios will also increase pressure on the cam lobes and lifters, just as if stronger springs were installed. Cam lobe wear isn't an issue with roller lifters. But if you already have very stout valve springs it's possible that the increased presuure will collapse the lifters. This is very unlikely, IMHO.
The above aside, other than insuring that the springs can accomodate the higher lift, and that there is adequate valve cover clearance and piston to valve clearance just go for it.
Rich Krause
10-19-2002, 09:58 AM
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so you say that it might shorten the life of my motor and then tell me what the hell, do it ?? WTF? if the valve wear isn't that big of a deal then i might go ahead and do it. i just want to make sure.
thomas
thomas
10-19-2002, 02:52 PM
#4
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You can run 1.8:1 on the car if you want.
First thing is you need the springs to do it. Lift is what kills springs and that is something you are going to have to check every once in a while.
Yeah loading on the valvetrain is the main problem, the big thing is the springs and the lift. Most times you need to machine the spring pockets in the heads to get the right springs in there. So that's an added cost.
Also Piston to Valve clearance is another problem. This means you need to check that. If you run into problems you gotta take the pistons out and fly cut valve reliefs in them. If you are not building up a engine to drop in this is not going to be a fun undertaking.
One more thing. Some cam lobes are not designed for high rocker arm ratios. You can have some bad loading conditions with that and it will seriously reduce the valvetrain life. It happens.
I can check into this further, but you really have to do it the right way like I said. This is not something you can half ***.
Good luck,
Bret
First thing is you need the springs to do it. Lift is what kills springs and that is something you are going to have to check every once in a while.
Yeah loading on the valvetrain is the main problem, the big thing is the springs and the lift. Most times you need to machine the spring pockets in the heads to get the right springs in there. So that's an added cost.
Also Piston to Valve clearance is another problem. This means you need to check that. If you run into problems you gotta take the pistons out and fly cut valve reliefs in them. If you are not building up a engine to drop in this is not going to be a fun undertaking.
One more thing. Some cam lobes are not designed for high rocker arm ratios. You can have some bad loading conditions with that and it will seriously reduce the valvetrain life. It happens.
I can check into this further, but you really have to do it the right way like I said. This is not something you can half ***.
Good luck,
Bret
10-19-2002, 02:58 PM
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Eh.. it all depends on what youre trying to do. Cam, etc. ...
If you do hafta flycut pistons, that's cake... dont need to disassemble anything. Still.. hp/$.. guess it just depends on the rest of your setup
If you do hafta flycut pistons, that's cake... dont need to disassemble anything. Still.. hp/$.. guess it just depends on the rest of your setup
10-19-2002, 07:23 PM
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Originally posted by twells
so you say that it might shorten the life of my motor and then tell me what the hell, do it ?? WTF? if the valve wear isn't that big of a deal then i might go ahead and do it. i just want to make sure.thomas
so you say that it might shorten the life of my motor and then tell me what the hell, do it ?? WTF? if the valve wear isn't that big of a deal then i might go ahead and do it. i just want to make sure.thomas
Rocker ratio can be a big deal, but as Bret stated, the bottom line is the lift that the rocker ratio is generating. Frankly, the valve end of the rocker arm doesn't care where (or from whom) the extra 'push' came from. It is a case of one end doesn't know or care how the other end generated the extra lift. It just knows that now, it, the valve stem end of the RA, is now moving the valve more off it's seat. Along with the reasons given by Bret, the kicker is, with the poor rocker arm geometry that is characteristic of the sbc, an engine that originally possessed a lift all of .400", it (RA) now finds itself moving from one side of the valve stem to the other during it's travel from zero to full lift. That is cuz the rocker tip is scrubbing across the stem tip as it is pushing down on the stem. This puts side thrust on the stem, generating unnecessary guide wear. One has theeir hands full, what with .600-650" lift, to keep the rocker tip on the stem. This the reason relocated rocker studs and shaft mounted rockers came into being, along with roller rocker arms. It cuts down on the friction by improving the RA geometry.
Bottom line from my POV is this. If the engine's use is 1320 ft. at a time, go for it, the sky is the lift. If it is a daily driver, personally, I'd keep the lift under .575" lift. To me, the extra lift isn't worth the wear it generates. Make your choice based on your intended useage. And, as is usually the case, with anything (or anyone) that appears controversial, YMMV.
10-19-2002, 07:40 PM
#7
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This is the way I see it.... you bolt stuff onto your motor to make it faster... you decrease it's longevity. You usually can't have the cake and eat it too.
Just look around and you'll see guys with 2-3 year old hi-po engines getting ready for a rebuild. Been there and am still doing that.
My opinion, is t run as much rocker ratio as you can. 1.7:1 is nothing extreme in my book, just make sure you run a full roller rocker (duh) and make sure the geometry/clearances are correct.
-Mindgame
Just look around and you'll see guys with 2-3 year old hi-po engines getting ready for a rebuild. Been there and am still doing that.
My opinion, is t run as much rocker ratio as you can. 1.7:1 is nothing extreme in my book, just make sure you run a full roller rocker (duh) and make sure the geometry/clearances are correct.
-Mindgame
10-19-2002, 10:08 PM
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Forgive me if it seems I am putting you on the spot, but how would you Mindgame, make sure the geometry is correct, when it is known that it (oem) is incorrect, as is hi-lited/emphasized by the lift you are suggesting? Afterall, that is the 'roadblock' many balk, B4 proceeding. The 'fix' is expensive, for the resulting gains, if for a daily driver.
I might even be able to get 200hp at the flywheel) from it 
10-20-2002, 12:05 AM
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<~~Aint skeered of the 'spot'.
In my opinion, every 'high-performance' engine needs valvetrain geometry optimization. I don't care what you do, it needs to be checked and optimized. That's what they make pushrod length checkers for. Every wrench-head should have one and they should learn how to use it.
Anyways... to the situation at hand...... I don't know what the author of this thread really has in mind. Me, I'm a hardcore drag racer, so I kinda think about things from that mentality. I guess what we really need to know are his intentions???
In my opinion..... a 1.7:1 rocker ratio will work just as well as a 1.6:1. I don't necessarily agree with the wear issues either... especially when you look at the geometry of a (1.7:1) long-arm/backset type rocker arm like the ones Crower makes. I'd venture to say that they're easier on valve guides than your standard 1.5:1 non-roller type rockers are too. Look at the ratios being run on the new engines.
Not a bolt on and go deal and it definitely shouldn't be looked at in that way, but when you're looking for every last little tinkle of power... hey who cares what it takes. I don't.
-Mindgame
In my opinion, every 'high-performance' engine needs valvetrain geometry optimization. I don't care what you do, it needs to be checked and optimized. That's what they make pushrod length checkers for. Every wrench-head should have one and they should learn how to use it.
Anyways... to the situation at hand...... I don't know what the author of this thread really has in mind. Me, I'm a hardcore drag racer, so I kinda think about things from that mentality. I guess what we really need to know are his intentions???
In my opinion..... a 1.7:1 rocker ratio will work just as well as a 1.6:1. I don't necessarily agree with the wear issues either... especially when you look at the geometry of a (1.7:1) long-arm/backset type rocker arm like the ones Crower makes. I'd venture to say that they're easier on valve guides than your standard 1.5:1 non-roller type rockers are too. Look at the ratios being run on the new engines.
Not a bolt on and go deal and it definitely shouldn't be looked at in that way, but when you're looking for every last little tinkle of power... hey who cares what it takes. I don't.
-Mindgame
Originally posted by arnie
Forgive me if it seems I am putting you on the spot, but how would you Mindgame, make sure the geometry is correct, when it is known that it (oem) is incorrect, as is hi-lited/emphasized by the lift you are suggesting? Afterall, that is the 'roadblock' many balk, B4 proceeding. The 'fix' is expensive, for the resulting gains, if for a daily driver.
Forgive me if it seems I am putting you on the spot, but how would you Mindgame, make sure the geometry is correct, when it is known that it (oem) is incorrect, as is hi-lited/emphasized by the lift you are suggesting? Afterall, that is the 'roadblock' many balk, B4 proceeding. The 'fix' is expensive, for the resulting gains, if for a daily driver.
10-20-2002, 01:12 AM
#11
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If you integrate the various comments you get a pretty full picture. The following is an attempt to sum it up.
1. high ratio RR (>1.6:1) can be installed on a SBC and has been done sucessfully (many times).
2. the springs need to be able to handle the lift without binding. This must be checked.
3. all other things being equal, the higher the rocker ratio the greater the stress/wear on the valvetrain. I would say that the main area of concern are the valve guides due to increased side loading. But as was pointed out spring wear is an issue as lifts get higher. RPM will also play a big role in shortening spring life. There will also be more wear on the cam lobes and on the valve seats. All of these are difficult to quantify. That's why I urged some caution based on your intentions for the motor. If it's a high-po setup not intended for high mileage I think the wear won't be much of an issue. These things tend to get rebuilt every couple of years even if nothing breaks. People tend to want to upgrade or try something new. I have had street strip cars for years and have had rebuilt on the average of every two years. The ratio of elective/forced rebuilds is ~2/1.
4. a shorter pushrod may be needed (you want to center the rocker tip on the valve stem) and this should be checked.
5. piston to valve clearance will decrease and should be checked.
6. Rocker to valve cover interference is possible.
What has not been addressed is the issue of: will there be any performance gain. There are a lot of variables. In general the answer is that it will gain a few hp (typically 5-15hp). You might gain more or gain nothing. I suppose you could even lose a few hp, though it's hard to construct a scenario where this would actually occur. I would say it's not worth it from a cost/benefit viewpoint unless you need rockers anyway.
What do you have in mind for this motor?
Rich Krause
1. high ratio RR (>1.6:1) can be installed on a SBC and has been done sucessfully (many times).
2. the springs need to be able to handle the lift without binding. This must be checked.
3. all other things being equal, the higher the rocker ratio the greater the stress/wear on the valvetrain. I would say that the main area of concern are the valve guides due to increased side loading. But as was pointed out spring wear is an issue as lifts get higher. RPM will also play a big role in shortening spring life. There will also be more wear on the cam lobes and on the valve seats. All of these are difficult to quantify. That's why I urged some caution based on your intentions for the motor. If it's a high-po setup not intended for high mileage I think the wear won't be much of an issue. These things tend to get rebuilt every couple of years even if nothing breaks. People tend to want to upgrade or try something new. I have had street strip cars for years and have had rebuilt on the average of every two years. The ratio of elective/forced rebuilds is ~2/1.
4. a shorter pushrod may be needed (you want to center the rocker tip on the valve stem) and this should be checked.
5. piston to valve clearance will decrease and should be checked.
6. Rocker to valve cover interference is possible.
What has not been addressed is the issue of: will there be any performance gain. There are a lot of variables. In general the answer is that it will gain a few hp (typically 5-15hp). You might gain more or gain nothing. I suppose you could even lose a few hp, though it's hard to construct a scenario where this would actually occur. I would say it's not worth it from a cost/benefit viewpoint unless you need rockers anyway.
What do you have in mind for this motor?
Rich Krause
10-20-2002, 06:14 AM
#12
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Originally posted by rskrause
2. the springs need to be able to handle the lift without binding. This must be checked.
3. all other things being equal, the higher the rocker ratio the greater the stress/wear on the valvetrain. I would say that the main area of concern are the valve guides due to increased side loading. But as was pointed out spring wear is an issue as lifts get higher. RPM will also play a big role in shortening spring life. There will also be more wear on the cam lobes and on the valve seats. All of these are difficult to quantify. That's why I urged some caution based on your intentions for the motor. If it's a high-po setup not intended for high mileage I think the wear won't be much of an issue. These things tend to get rebuilt every couple of years even if nothing breaks. People tend to want to upgrade or try something new. I have had street strip cars for years and have had rebuilt on the average of every two years. The ratio of elective/forced rebuilds is ~2/1.
4. a shorter pushrod may be needed (you want to center the rocker tip on the valve stem) and this should be checked.
5. piston to valve clearance will decrease and should be checked.
6. Rocker to valve cover interference is possible.
2. the springs need to be able to handle the lift without binding. This must be checked.
3. all other things being equal, the higher the rocker ratio the greater the stress/wear on the valvetrain. I would say that the main area of concern are the valve guides due to increased side loading. But as was pointed out spring wear is an issue as lifts get higher. RPM will also play a big role in shortening spring life. There will also be more wear on the cam lobes and on the valve seats. All of these are difficult to quantify. That's why I urged some caution based on your intentions for the motor. If it's a high-po setup not intended for high mileage I think the wear won't be much of an issue. These things tend to get rebuilt every couple of years even if nothing breaks. People tend to want to upgrade or try something new. I have had street strip cars for years and have had rebuilt on the average of every two years. The ratio of elective/forced rebuilds is ~2/1.
4. a shorter pushrod may be needed (you want to center the rocker tip on the valve stem) and this should be checked.
5. piston to valve clearance will decrease and should be checked.
6. Rocker to valve cover interference is possible.
I need reliability. When I do go with a cam, I will go with one designed to work with these rockers.
10-20-2002, 11:23 AM
#13
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my "intentions" are to try to maximize the hotcam set-up as in one of my previous posts about camshafts, i was told that cars don't need a big duration cam to make good power below the curve where i need it. The hotcam is an inexpensive kit and i wanted to maximize the lift inorder to gain more power out of this setup. I was just wanting to know the max rr size that i could run on my lt1. I wanted to know what valve covers would work and if i need different length pushrods, etc......
I have had several of points brought up that i had originally overlooked.
If i were to do this the new lift on my hotcam would be:
1.65-----> .541
1.7------->.557
why would i have to have my head machined for special springs?
with those "new" lift numbers on the hotcam, i could still run the crane# 10308-1 spring that is rated to .600" lift, correct?
wouldn't i need longer pushrods if i was increasing the lift of the cam?
who makes 1.65's and 1.7's? all that i have ever seen were the harland sharp 1.65's
what do i do about the alternator? I am pretty sure that i will need new valve covers. I would like to get some composite ones like the lt4 ones. I will have to move the alternator somewhere else wont i ? could i put it on the bottom where the air box use to be? If so, does anyone have any pics of this?
sorry about i being so long, i am just trying to get all of my questions out!! I appreciate all of you guys that are always there to answer my questions ( phil, brent, mindgame, rich....)
thanks guys
thomas...................i am not worthy
I have had several of points brought up that i had originally overlooked.
If i were to do this the new lift on my hotcam would be:
1.65-----> .541
1.7------->.557
why would i have to have my head machined for special springs?
with those "new" lift numbers on the hotcam, i could still run the crane# 10308-1 spring that is rated to .600" lift, correct?
wouldn't i need longer pushrods if i was increasing the lift of the cam?
who makes 1.65's and 1.7's? all that i have ever seen were the harland sharp 1.65's
what do i do about the alternator? I am pretty sure that i will need new valve covers. I would like to get some composite ones like the lt4 ones. I will have to move the alternator somewhere else wont i ? could i put it on the bottom where the air box use to be? If so, does anyone have any pics of this?
sorry about i being so long, i am just trying to get all of my questions out!! I appreciate all of you guys that are always there to answer my questions ( phil, brent, mindgame, rich....)
thanks guys
thomas...................i am not worthy
10-20-2002, 04:05 PM
#14
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Thomas, IMO if i was trying to do what you were doing i would go about it a difrent route.
IMO try to not complicate things if at all possible, this is a rule that i try to go buy and it helps to avoid a lot of headaches. If you want to keep small duration but gain a lot of lift, why not order a custom ground cam with the exact #s you want. It should only be like $250. You could most likely use those same springs, pushrods, rockers, and wouldnt need to mess with the valve covers.
Other route is keep the hotcam, change rockers, pushrods, and valvecovers. You probably looking at minimum of $500 if you find some 'deals' on things. Also with this senario you raise the chances of running into problems.
Maybe i missed something, and you debunked my idea already... but i dont see why you wouldnt just get a new custom ground cam??
IMO try to not complicate things if at all possible, this is a rule that i try to go buy and it helps to avoid a lot of headaches. If you want to keep small duration but gain a lot of lift, why not order a custom ground cam with the exact #s you want. It should only be like $250. You could most likely use those same springs, pushrods, rockers, and wouldnt need to mess with the valve covers.
Other route is keep the hotcam, change rockers, pushrods, and valvecovers. You probably looking at minimum of $500 if you find some 'deals' on things. Also with this senario you raise the chances of running into problems.
Maybe i missed something, and you debunked my idea already... but i dont see why you wouldnt just get a new custom ground cam??
Last edited by kmook; 10-20-2002 at 04:07 PM.
10-20-2002, 07:27 PM
#15
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Ken,
thanks for letting me know of that option. I don't know why i didn't think of that before. If i was to go with a custom grind, i would want to make sure that i did it right the first time. I will most likely use your idea to further my quest for power.
Thanks all
thomas
thanks for letting me know of that option. I don't know why i didn't think of that before. If i was to go with a custom grind, i would want to make sure that i did it right the first time. I will most likely use your idea to further my quest for power.
Thanks all
thomas