1.52:1 vs 1.6:1 .....how much gain?
03-25-2003, 10:15 AM
#1
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
1.52:1 vs 1.6:1 .....how much gain?
They are going on a 305. My concern with the 1.6's is that I may have to make more clearance for the push rods.
The 1.6's would give me a total lift of nearly .500 with the cam I have.
The price is the same for either set.
Is there really that much gain between a 1.52 and a 1.6, enough gain that it would be worth more work on the heads?
I want to be about 300 horsepower out of my 305. I have Comp Cams XE-262, will have roller tip rockers of one type or another, World S/R Torquer 305 heads ported, Holley Dominator intake, 1 3/4" SLP headers, 3" catback, Jacob's prostreet ignition, high flow 3" cat, and an edelcrap carb. I expect I'll have to do some serious carb tuning.
If I'm not there, would 1.6 rockers really get me there?
The 1.6's would give me a total lift of nearly .500 with the cam I have.
The price is the same for either set.
Is there really that much gain between a 1.52 and a 1.6, enough gain that it would be worth more work on the heads?
I want to be about 300 horsepower out of my 305. I have Comp Cams XE-262, will have roller tip rockers of one type or another, World S/R Torquer 305 heads ported, Holley Dominator intake, 1 3/4" SLP headers, 3" catback, Jacob's prostreet ignition, high flow 3" cat, and an edelcrap carb. I expect I'll have to do some serious carb tuning.
If I'm not there, would 1.6 rockers really get me there?
03-25-2003, 10:28 AM
#2
Supreme Member
Join Date: Jul 1999
Location: Loveland, OH, US
Posts: 18,457
Likes: 0
Received 15 Likes
on
15 Posts
Car: 4
Engine: 6
Transmission: 5
The more the rest of the induction flows, the more difference they make.
Use the "series of pieces of garden hose" mental picture... if the valve gross lift is the limiting factor to the overall system flow, then increasing it will produce results. If something else is the limit, then you could increase the lift to 1", and it would still only flow the same overall.
In your setup, I fell that the rocker ratio increase would make a significant difference (well worth the install effort), since you have heads with good flow. With a set of unported stock heads, there would be very little difference from the increased lift, because the ports are the flow limit, not the valve lift.
Use the "series of pieces of garden hose" mental picture... if the valve gross lift is the limiting factor to the overall system flow, then increasing it will produce results. If something else is the limit, then you could increase the lift to 1", and it would still only flow the same overall.
In your setup, I fell that the rocker ratio increase would make a significant difference (well worth the install effort), since you have heads with good flow. With a set of unported stock heads, there would be very little difference from the increased lift, because the ports are the flow limit, not the valve lift.
03-25-2003, 10:30 AM
#3
Supreme Member
Join Date: Jul 2001
Location: New Palestine, IN (Just East of Indy)
Posts: 1,766
Likes: 0
Received 2 Likes
on
2 Posts
Car: '85 Z28
Engine: 305
Transmission: WC T5, 3.23 posi
If you're going for 300 ponies you might want to do some porting to those S/R heads. The 1.6's will also give you a few degrees more duration than 1.5's. Most likely you'll have to modify the pushrod holes with the 1.6's. If it were me I'd probably go with the 1.5's.
03-25-2003, 10:45 AM
#4
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Originally posted by kfoley
If you're going for 300 ponies you might want to do some porting to those S/R heads. The 1.6's will also give you a few degrees more duration than 1.5's. Most likely you'll have to modify the pushrod holes with the 1.6's. If it were me I'd probably go with the 1.5's.
If you're going for 300 ponies you might want to do some porting to those S/R heads. The 1.6's will also give you a few degrees more duration than 1.5's. Most likely you'll have to modify the pushrod holes with the 1.6's. If it were me I'd probably go with the 1.5's.
RB, you've got a good illustration there. Everything else in my set up is going to breathe well.
Is there a way I can tell about the push rod clearance before I bolt everything up?
How difficult would it be to get the extra clearance I'd need?
03-25-2003, 11:04 AM
#5
Supreme Member
Join Date: Jul 1999
Location: Loveland, OH, US
Posts: 18,457
Likes: 0
Received 15 Likes
on
15 Posts
Car: 4
Engine: 6
Transmission: 5
No way to tell about push rod clearance for sure without a trial fit. Same goes for push rod length.... we can guess all day long, but the only way to get it right for certain is to assemble the motor and dummy up a cylinder, and check it with a push rod length checker (adjustable push rod). You can make that yourself fairly easily by cutting one, putting a ¼"-20 threaded rod in one half, and threading the inside of the other to that thread; that gives you .050" per turn of adjustment.
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
03-25-2003, 11:18 AM
#6
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Originally posted by RB83L69
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
I'll take a closer look and see when I get home.
Ever wonder why turn key motors are so appealing to dufuses like me?
03-25-2003, 11:29 AM
#7
Supreme Member
Join Date: Jul 1999
Location: Loveland, OH, US
Posts: 18,457
Likes: 0
Received 15 Likes
on
15 Posts
Car: 4
Engine: 6
Transmission: 5
I would not buy a turn-key motor.... I'd be too afraid that they were in such a hurry to finish building it in order to keep from either losing their a$$ on it or running up the price so high that nobody would buy it, that they'd skip checking things like this. Happens more often than you might think. Don't fool yourself into believing that all motors are built as carefully as they should be just because they're sold as "complete" "ready to run" packages.
Besides, I'm a builder not an appliance operator, and I'm proud of my ability to do a superior job to the competition. As you will be too, when you stomp somebody with what seems to be an identical motor (or even a superior one), but yours works better because you got all the details right and theirs was a mass-produced slap-together.
Besides, I'm a builder not an appliance operator, and I'm proud of my ability to do a superior job to the competition. As you will be too, when you stomp somebody with what seems to be an identical motor (or even a superior one), but yours works better because you got all the details right and theirs was a mass-produced slap-together.
Trending Topics
03-25-2003, 11:40 AM
#8
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
I hear that. I would much rather take my time, plan it all out and get it right the first time, the old measure twice cut once philosophy. I sometimes get hurried and don't ask enough questions, but that's the objective anyhow.
I wouldn't buy a turn key either, but they are appealing when someone with limited experience starts getting into some of the problems I have run into. The appeal is that you THINK there won't be any problems.
I've swapped a lot of engines and transmission, but they were deisels. I've only built one engine before and that was a volkswagen type 1 engine. So I'm fairly lost when it comes to some of the specific applications like I've been posting the past two or three days. Your help is appreciated, believe me!
I wouldn't buy a turn key either, but they are appealing when someone with limited experience starts getting into some of the problems I have run into. The appeal is that you THINK there won't be any problems.
I've swapped a lot of engines and transmission, but they were deisels. I've only built one engine before and that was a volkswagen type 1 engine. So I'm fairly lost when it comes to some of the specific applications like I've been posting the past two or three days. Your help is appreciated, believe me!
03-25-2003, 01:28 PM
#9
Supreme Member
Join Date: Jul 2001
Location: New Palestine, IN (Just East of Indy)
Posts: 1,766
Likes: 0
Received 2 Likes
on
2 Posts
Car: '85 Z28
Engine: 305
Transmission: WC T5, 3.23 posi
I didn't see that they were ported... 
School was on the mind, VB programming to be specific, that stuff will screw you up (if you couldn't tell I hate VB)...
School was on the mind, VB programming to be specific, that stuff will screw you up (if you couldn't tell I hate VB)...
03-25-2003, 01:45 PM
#10
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Originally posted by RB83L69
No way to tell about push rod clearance for sure without a trial fit. Same goes for push rod length.... we can guess all day long, but the only way to get it right for certain is to assemble the motor and dummy up a cylinder, and check it with a push rod length checker (adjustable push rod). You can make that yourself fairly easily by cutting one, putting a ¼"-20 threaded rod in one half, and threading the inside of the other to that thread; that gives you .050" per turn of adjustment.
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
No way to tell about push rod clearance for sure without a trial fit. Same goes for push rod length.... we can guess all day long, but the only way to get it right for certain is to assemble the motor and dummy up a cylinder, and check it with a push rod length checker (adjustable push rod). You can make that yourself fairly easily by cutting one, putting a ¼"-20 threaded rod in one half, and threading the inside of the other to that thread; that gives you .050" per turn of adjustment.
Do the heads have the narrow push rod guide slots? If so, you can't use guide plates, and instead, you'd need to get the slots lengthened toward the stud. If the heads have huge holes that don't fit tight to the push rod, then you need to use guide plates or self-aligning rockers, and you probably don't have to do anything to use the higher-ratio rockers.
If the slots are exactly the same, I shouldn't need to buy new rocker arms should I?
Attached is a picture of the new head's pushrod hole.
03-25-2003, 02:13 PM
#12
Supreme Member
Join Date: Jul 1999
Location: Loveland, OH, US
Posts: 18,457
Likes: 0
Received 15 Likes
on
15 Posts
Car: 4
Engine: 6
Transmission: 5
The way rocker ratio works, is that it is the ratio of the distance from the stud to the valve stem, divided by the distance from the stud to the push rod. Since you can't change the distance from the stud to the valve by replacing the rocker, the way it works, is that the higher ratio rockers move the push rod seat in the rocker inwards toward the stud, thereby increasing the ratio of the 2 distances.
The push rod seat in the end of the rocker does not move in a straight line. Instead, it moves in an arc, whose radius is the distance from the stud to the push rod seat. Obviously if that was a very large distance, the tip of the push rod would almost move in a straight line; but the shorter the distance, the more the push rod moves toward and away from the stud during its travel. So with the higher ratio rockers, not only is the push rod closer on average to the stud than stock, but it also moves more toward the stud during its travel.
Those slots are clearly quite short in that direction. In fact they look dangerously short even for 1.5 ratio rockers.
http://www.competitioncams.com/catalog/346.html bottom of the page, for a solution.
The push rod seat in the end of the rocker does not move in a straight line. Instead, it moves in an arc, whose radius is the distance from the stud to the push rod seat. Obviously if that was a very large distance, the tip of the push rod would almost move in a straight line; but the shorter the distance, the more the push rod moves toward and away from the stud during its travel. So with the higher ratio rockers, not only is the push rod closer on average to the stud than stock, but it also moves more toward the stud during its travel.
Those slots are clearly quite short in that direction. In fact they look dangerously short even for 1.5 ratio rockers.
http://www.competitioncams.com/catalog/346.html bottom of the page, for a solution.
03-25-2003, 02:32 PM
#13
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
What I'm wondering now is if I in fact even need self-aligning rockers with these heads. The slots are absolutely identical to my old heads with the non-self-aligning heads.
The only reason I was considering purchasing a set of 1.6:1 ratio rocker arms right now was because I thought I needed a set of self-aligning rocker arms. If I was going to have to buy a set, why not spring for something that I won't really need to replace.
But if I in fact do NOT need a set of self-aligning rocker arms, then I'm not going to be purchasing a set of 1.6:1 ratio rockers, at least not right now. I have a set of crane steel roller tip 1.52:1 right now, and I'm happy with those.
World Castings
I have to apologize. As I am writing this post, I checked the website again and it says right there, in plain english,
I apologize for not having seen that before, I need to get my eyes checked. I read that thing a million times last night, but it was late and I couldn't sleep when I read it.
So that means that the manifold bolt pattern is different (on the 87 up casting opposed to the pre 87), but the rocker arm configuration remains the same with the S/R Torquer heads, right?
The only reason I was considering purchasing a set of 1.6:1 ratio rocker arms right now was because I thought I needed a set of self-aligning rocker arms. If I was going to have to buy a set, why not spring for something that I won't really need to replace.
But if I in fact do NOT need a set of self-aligning rocker arms, then I'm not going to be purchasing a set of 1.6:1 ratio rockers, at least not right now. I have a set of crane steel roller tip 1.52:1 right now, and I'm happy with those.
World Castings
I have to apologize. As I am writing this post, I checked the website again and it says right there, in plain english,
[qb]
S/R Torquer heads utilize a standard offset rocker designed for the Small Block Chevy.
[/qb]
S/R Torquer heads utilize a standard offset rocker designed for the Small Block Chevy.
[/qb]
So that means that the manifold bolt pattern is different (on the 87 up casting opposed to the pre 87), but the rocker arm configuration remains the same with the S/R Torquer heads, right?
03-25-2003, 02:42 PM
#14
Supreme Member
Join Date: Jul 1999
Location: Loveland, OH, US
Posts: 18,457
Likes: 0
Received 15 Likes
on
15 Posts
Car: 4
Engine: 6
Transmission: 5
Yes, you can use the rockers you have. You absolutely must not use SA rockers on those heads. The rockers in the pic should work fine, as long as they clear the ends of the push rod slots.
"Offset" refers to one of the ways of getting around the problem of the intake port in a SBC motor. If you look at the head, you can see that the "outer" wall of each intake port (opposite the "common" wall that is shared by 2 intake ports) is almost up against the push rod; in fact many real racing heads acutally have a dimple down that side of the port on the inside, and the outside of the port machined to clear the push rod.... imagine the slots in your heads extending all the way down along the side of the intake port to the deck. Some heads are designed to move the push rod over to allow a larger (wider) port; there are offset roller lifters, with the push rod hole moved over to the side, and offset rocker arms to accommodate the moved-over push rod. That's what they're referring to.
"Offset" refers to one of the ways of getting around the problem of the intake port in a SBC motor. If you look at the head, you can see that the "outer" wall of each intake port (opposite the "common" wall that is shared by 2 intake ports) is almost up against the push rod; in fact many real racing heads acutally have a dimple down that side of the port on the inside, and the outside of the port machined to clear the push rod.... imagine the slots in your heads extending all the way down along the side of the intake port to the deck. Some heads are designed to move the push rod over to allow a larger (wider) port; there are offset roller lifters, with the push rod hole moved over to the side, and offset rocker arms to accommodate the moved-over push rod. That's what they're referring to.
Last edited by RB83L69; 03-25-2003 at 03:18 PM.
03-25-2003, 02:47 PM
#15
Supreme Member
Thread Starter
Join Date: Jan 2001
Location: Rio Rico, AZ 85648
Posts: 1,116
Likes: 0
Received 0 Likes
on
0 Posts
Car: 1989 IROC-1
Engine: L98
Transmission: 700r4
Sorry I took you around the barn instead of through it! I did learn a lot though. Wish you where here to help me on some of this stuff, the only mechanical input I get in person is from my 9 year old daughter. She may be smarter than her pop, but not much help in this arena!
I'm happy that I don't have to fork over $200 now for a new set of rockers.
:hail: RB
I'm happy that I don't have to fork over $200 now for a new set of rockers.
:hail: RB
Thread
Thread Starter
Forum
Replies
Last Post
