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Engine Builders: How come no one runs a 1.7 rocker?
#536722
11/25/09 08:54 PM
11/25/09 08:54 PM
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Joined: Jan 2003
Posts: 2,697
Renton Wa
topfueldart
OP
master
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OP
master
Joined: Jan 2003
Posts: 2,697
Renton Wa
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Considering purchasing a set of T&D's or similar for my CNC 360-2 heads, I have a street strip turbocharged combo, and dont wanna run anymore than 250 @ .050, but my heads flow well into the mid 600's. Comp shows lobes in the mid 240's with like .385-.389 lift, which puts me at .654 minus lash with 1.7's, which I think would be better than the .616 1.6's would result in.
Im basically wondering why very few people go to a 1.7 unless its a pretty wild combo in Mopar land. Are there any downfalls? Harder to make the valve wear right? More sideloading on the guides? Alot of the new LSX based stuff runs ALOT of Rocker Arm ratio, as well as SB Ford stuff. I realize its completely different, but im just wondering why I couldnt take advantage of the same.
Is it just that none of the "basic" aftermarket options are sold that way for Mopar guys? I realize going to T&D's or similar is alot different than ordering pre-boxed Cranes.
11.48 @ 120 with a 1.80 60' 318, stock 1.88 heads, stock 904, Pump Gas, 13 lbs of boost.
9.94 @ 134, 318 on pump gas, 14 lbs w/ Eddies, transbrake 727, 3600 lbs, 3.54 gear and 28's.
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: topfueldart]
#536723
11/25/09 09:14 PM
11/25/09 09:14 PM
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Joined: Feb 2007
Posts: 6,295
U.S.
moparniac
master
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master
Joined: Feb 2007
Posts: 6,295
U.S.
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I ran 1.7 harlands in my challenger ... .388 lobe 248/254 roller
Mopar Performance
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: tilt]
#536725
11/25/09 09:33 PM
11/25/09 09:33 PM
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Joined: Mar 2009
Posts: 1,169
Virginia Beach, VA
Old School
super stock
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super stock
Joined: Mar 2009
Posts: 1,169
Virginia Beach, VA
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i use them in my 580".i switched from 1.55,s and it really woke the motor up.i'm trying a set of 1.7 t&d,s on one of my 500" motors.i hope it wakes it up too.the downside is more wear on the lifter/roller,the rocker arms,and needing to use stronger springs.
68 cuda formula S 588" bb 5sp
70 CUDA CONVERT 500" 5SP (SUBLIME)
70 CUDA CONVERT 500" 5SP (PLUMCRAZY):TOO MUCH HORSEPOWER, IS ALMOST ENOUGH!
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: topfueldart]
#536726
11/25/09 09:33 PM
11/25/09 09:33 PM
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Joined: Nov 2004
Posts: 3,544
Syracuse,NY
CompWedgeEngines
master
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master
Joined: Nov 2004
Posts: 3,544
Syracuse,NY
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A faster rocker ratio ( larger numerically) opens the valve sooner in relationship to the piston position basically keeping in mind it is doing this faster once the valve lift curve starts to "open" so to speak. It doesnt change the opening and closing point of the cam lobe of course. It kind of is like increasing duration of the cam, or at least has somewhat of the same effect as such. Again, this is changing the valve lift curve. Doing this obviously creates a much quicker opening and closing of the valve, and especially on the exhaust side, this can get very radical.It ramps the opening of the valve up faster, and hence also the closing of the valve.
You stand the chance of bouncing the valve off the seat, amongst other things that are also associated with faster valve movement. It becomes way more critical to select the proper valvetrain compenents, and especially springs. The valve springs and harmonics, clearances and such are much more sensitive at that point, and it takes more knowledge and effort to choose these parts properly and know what you really need. A valve spring that is not up to the task for a 1.7 or higher ration will do lots of damage. You cant ever assume a spring thats doing a good job on a 1.5 or 1.6 ratio to be capable of handling a 1.7. A lot of this theory and design is built into the characteristics of the cylinder heads and especially camshafts. All in all, the higher ratios are better left for the high end all out race motors and has someone involved that is experienced in them.They do have the ability to create much more stress and wear on the WHOLE valvetrain.The high end racers, Top Sportsman type guys and faster are doing frequent valve spring checking and often know beforehand if there is a problem.
Hope this helps, a bit generic, but maybe useful to some degree.
RIP Monte Smith
Your work is a reflection of yourself, autograph it with quality.
WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: AndyF]
#536728
11/25/09 11:10 PM
11/25/09 11:10 PM
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Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
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I am going to run a 1.7 on my magnum motor with a 231@.050 cam my lift will be about .580 I will be running chevy LS style behive springs and titanium retainers to keep it light and under control. I hate big cams and I love HP so this seemed like the best route for me. If there were say 2.0 rockers for an LA you would not even need to swap out your factory 340 cam but still make mondo power.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: AndyF]
#536729
11/25/09 11:15 PM
11/25/09 11:15 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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I always run 1.7 oin my stroker motors 
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: topfueldart]
#536733
11/26/09 01:50 AM
11/26/09 01:50 AM
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Joined: Jan 2007
Posts: 1,668
Mi,U.S.A.
mike s
top fuel
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top fuel
Joined: Jan 2007
Posts: 1,668
Mi,U.S.A.
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Quote:
Considering purchasing a set of T&D's or similar for my CNC 360-2 heads, I have a street strip turbocharged combo, and dont wanna run anymore than 250 @ .050, but my heads flow well into the mid 600's. Comp shows lobes in the mid 240's with like .385-.389 lift, which puts me at .654 minus lash with 1.7's, which I think would be better than the .616 1.6's would result in.
Im basically wondering why very few people go to a 1.7 unless its a pretty wild combo in Mopar land. Are there any downfalls? Harder to make the valve wear right? More sideloading on the guides? Alot of the new LSX based stuff runs ALOT of Rocker Arm ratio, as well as SB Ford stuff. I realize its completely different, but im just wondering why I couldnt take advantage of the same.
Is it just that none of the "basic" aftermarket options are sold that way for Mopar guys? I realize going to T&D's or similar is alot different than ordering pre-boxed Cranes.
I think I understand you are using a stock block.I will disagree with most here but I do not recommend 1.7 rockers on your set up.Valve train dynamics and stability are terrible at stock lifts.The higher the lift the worse it gets and adding the 1.7 rockers only adds to that.High lift early LA engines (aka Pro-stock) were parts killers.They was very little progress until people started moving the cam and lifter bores. One reason the late Bowtie stuff gets away with it is the fact of the cam being very high in the block and uses very short push rods.
Leave the gun.......take the Cannoli's....Mike
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: mike s]
#536734
11/26/09 02:19 AM
11/26/09 02:19 AM
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Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
HotRodDave
I Live Here
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I Live Here
Joined: Jan 2005
Posts: 12,419
Kalispell Mt.
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Another thought is the higher ratios on a small block improves the PR angle slightly because it moves the top end of the PR towards the shaft, closer to where it should be but still not great.
With a higher ratio and smaller cam you should get better valvetrain action because the lifter and PR need to move less to get the same valve action.
All that being said I would recomend the highest ratio you can afford and run a smaller cam to keep the same net valve action.
You could make it work good on a SB because they have shorter pushrods and lighter valves than a BB and if you run an 8mm valve it is even lighter and you can run chevy LS style beehive springs with very light retainers.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: topfueldart]
#536735
11/26/09 02:25 AM
11/26/09 02:25 AM
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Joined: Apr 2007
Posts: 871
WA 98043
thecarfarmer
super stock
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super stock
Joined: Apr 2007
Posts: 871
WA 98043
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I guess I really AM no one!  1.7:1 Harland Sharps here. Yeah, they make 'em; when I bought a replacement for a damaged one, I found out what ratio I really have. -Bill
Seduce the attractive, and charm the rest.
******
489 C.I.D., roller cam, aftermarket heads, tunnel ram, stock '54 Dodge rear axle assembly: which of these doesn't belong?
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Re: Engine Builders: How come no one runs a 1.7 rocker?
[Re: mike s]
#536736
11/26/09 02:41 AM
11/26/09 02:41 AM
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Joined: Jan 2003
Posts: 5,484
SoCal
Brian Hafliger
master
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master
Joined: Jan 2003
Posts: 5,484
SoCal
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Quote:
Quote:
Considering purchasing a set of T&D's or similar for my CNC 360-2 heads, I have a street strip turbocharged combo, and dont wanna run anymore than 250 @ .050, but my heads flow well into the mid 600's. Comp shows lobes in the mid 240's with like .385-.389 lift, which puts me at .654 minus lash with 1.7's, which I think would be better than the .616 1.6's would result in.
Im basically wondering why very few people go to a 1.7 unless its a pretty wild combo in Mopar land. Are there any downfalls? Harder to make the valve wear right? More sideloading on the guides? Alot of the new LSX based stuff runs ALOT of Rocker Arm ratio, as well as SB Ford stuff. I realize its completely different, but im just wondering why I couldnt take advantage of the same.
Is it just that none of the "basic" aftermarket options are sold that way for Mopar guys? I realize going to T&D's or similar is alot different than ordering pre-boxed Cranes.
I think I understand you are using a stock block.I will disagree with most here but I do not recommend 1.7 rockers on your set up.Valve train dynamics and stability are terrible at stock lifts.The higher the lift the worse it gets and adding the 1.7 rockers only adds to that.High lift early LA engines (aka Pro-stock) were parts killers.They was very little progress until people started moving the cam and lifter bores. One reason the late Bowtie stuff gets away with it is the fact of the cam being very high in the block and uses very short push rods.
We continually run .700-.750 lift on our fast bracket small blocks with 59° lifter bores and Indy -1 or -2 heads, TD 1.7 rockers.
The geometry is great and these engines rpm in the 7000-7600 range.
The key is to use the baddest strongest pushrod you can get in the thing. But it works everytime!!
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