Author Topic: Benefit of 1.7 rocker arms  (Read 605 times)

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Offline 08flstf

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Benefit of 1.7 rocker arms
« on: February 12, 2018, 11:17:43 AM »
Considering bumping up my 124. It's a Drago's crate motor at 10.8/1 comp, 640's, S&S 58 mm tb, untouched super stock heads, and a Dragula 1 pipe with the 2.55 baffle. Am considering bumping comp up to 11.5/1 and having heads ported. Looking at hpi 62-64 mm tb or possibly the 68 mm unless that's just too big. Also have the 3.05 baffle if needed. What I'm wondering is if I could keep the 640's and use 1.7 rocker arms whether on intake and exhaust or only intake and get good gains, or if I'd be better off just getting different cams altogether. Power in the 3000 rpm and up range is good for me, don't want a tractor.

Offline kd

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Re: Benefit of 1.7 rocker arms
« Reply #1 on: February 12, 2018, 11:22:42 AM »
I think NoCents tried the 640's both ways. It may be in his "Cat out of the Bag" thread or he may chime in with his results.
KD

Offline 08flstf

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Re: Benefit of 1.7 rocker arms
« Reply #2 on: February 12, 2018, 11:40:29 AM »
Thanks
Wow! That's 196 pages. LOL
« Last Edit: February 12, 2018, 11:47:35 AM by 08flstf »

Offline No Cents

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Re: Benefit of 1.7 rocker arms
« Reply #3 on: February 12, 2018, 12:19:35 PM »
  if you bump the compression up into the 11.5 (or higher) with the 640's you will see a small gain running the 1.725 arms. It might gain you a couple of horsepower on the top end. I ran them on the intake sides only.
  You'll definitely need the heads set up for the extra lift you'll have. Make sure you tell the head porter that you want your heads set up for the higher lift that you will be gaining when running the stilts. The 640's on stilts goes to .679" lift on the intakes, and the TDC lift on the intakes goes to .242".
08 FLHX grocery getter, 124ci, wfolarry 110" heads, Burns pipe, 158/152 sae

Offline 08flstf

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Re: Benefit of 1.7 rocker arms
« Reply #4 on: February 12, 2018, 01:49:30 PM »
Thanks No Cents. Was just wondering if it would make that much difference versus going with something like the S&S 675's or even the Wood tw68's. I ran the tw68's in a 117 I had before and really liked them.

Online sfmichael

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Re: Benefit of 1.7 rocker arms
« Reply #5 on: February 12, 2018, 02:59:43 PM »
If your heart's set on more lift I'd swap the cams - gains from adding 1.7's are typically very low

Porting the heads and bumping compression should yield decent / noticeable results  :up:
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Offline No Cents

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Re: Benefit of 1.7 rocker arms
« Reply #6 on: February 12, 2018, 03:21:11 PM »
    Either the 675's or the TW68 cams should be able to pull a little more horsepower on the top end, vs the 640's...that is if your wanting to rev it up past 6400 rpm's.
08 FLHX grocery getter, 124ci, wfolarry 110" heads, Burns pipe, 158/152 sae

Offline Jonny Cash

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Re: Benefit of 1.7 rocker arms
« Reply #7 on: February 12, 2018, 04:20:41 PM »
I'd try the rocker arms, that 675 S&S wouldn't shine at just 11.5.  It really likes about 13:1 or more.
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Offline 08flstf

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Re: Benefit of 1.7 rocker arms
« Reply #8 on: February 12, 2018, 07:15:56 PM »
I'd try the rocker arms, that 675 S&S wouldn't shine at just 11.5.  It really likes about 13:1 or more.

I want a little more of a hotrod motor but I don't want to go 13/1. This will still have to run on pump gas.

Offline N-gin

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Re: Benefit of 1.7 rocker arms
« Reply #9 on: February 12, 2018, 07:37:24 PM »
Have you done a compression check with a gauge?
You may want to start there before you make any solid decisions. Just because you have 13:1 static, doesn't mean you need to run race fuel.

If your engine cranks over at 185 psi, you may have a lot more in that engine. You say that the engine is 10.8 or, want to bump to 10.8..thats only around 185 psi in the hole.. not good if you are looking for performance. Usually performance starts around 200psi.
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Offline 08flstf

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Re: Benefit of 1.7 rocker arms
« Reply #10 on: February 13, 2018, 05:08:41 PM »
Have you done a compression check with a gauge?
You may want to start there before you make any solid decisions. Just because you have 13:1 static, doesn't mean you need to run race fuel.

If your engine cranks over at 185 psi, you may have a lot more in that engine. You say that the engine is 10.8 or, want to bump to 10.8..thats only around 185 psi in the hole.. not good if you are looking for performance. Usually performance starts around 200psi.

It's 10.8 now, was thinking of going up to 11.5. I've done 12/1 before on a 117 with tw68's. It did ok on pump gas, I just though 11.5 might be a little easier to live with. Was hoping 11.5 would be enough to gain some performance.

Offline build it

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Re: Benefit of 1.7 rocker arms
« Reply #11 on: February 13, 2018, 10:48:02 PM »
It is

Offline dsvracer

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Re: Benefit of 1.7 rocker arms
« Reply #12 on: February 14, 2018, 06:00:26 AM »
it is the heads that make the power and it is the cam that determines where the power will be in the rpm range. 
You want more power ??  then do the heads.
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Offline 08flstf

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Re: Benefit of 1.7 rocker arms
« Reply #13 on: February 14, 2018, 08:32:23 AM »
Considering bumping up my 124. It's a Drago's crate motor at 10.8/1 comp, 640's, S&S 58 mm tb, untouched super stock heads, and a Dragula 1 pipe with the 2.55 baffle. Am considering bumping comp up to 11.5/1 and having heads ported. Looking at hpi 62-64 mm tb or possibly the 68 mm unless that's just too big. Also have the 3.05 baffle if needed. What I'm wondering is if I could keep the 640's and use 1.7 rocker arms whether on intake and exhaust or only intake and get good gains, or if I'd be better off just getting different cams altogether. Power in the 3000 rpm and up range is good for me, don't want a tractor.

Yes, fully intend to have heads done. Was just curious of the benefit of using the 1.7 rockers vs different cams. This may end up being my last hotrod HD motor, just want to squeeze a little more out of it and have some fun.

Offline turboprop

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Re: Benefit of 1.7 rocker arms
« Reply #14 on: February 14, 2018, 12:35:05 PM »
Considering bumping up my 124. It's a Drago's crate motor at 10.8/1 comp, 640's, S&S 58 mm tb, untouched super stock heads, and a Dragula 1 pipe with the 2.55 baffle. Am considering bumping comp up to 11.5/1 and having heads ported. Looking at hpi 62-64 mm tb or possibly the 68 mm unless that's just too big. Also have the 3.05 baffle if needed. What I'm wondering is if I could keep the 640's and use 1.7 rocker arms whether on intake and exhaust or only intake and get good gains, or if I'd be better off just getting different cams altogether. Power in the 3000 rpm and up range is good for me, don't want a tractor.

Years ago, some friends and I did some A-B-C comparisons of various brands and ratios of rocker arms. What we saw after swapping out stock ratio rockers for ones with a higher ratio was the entire torque curve was shifted to the left of the page. We saw this same phenomenon on engines of varying sizes and build levels.

On an LSR engine, we saw a difference in power in the middle of rpm range when swapping out rockers of the same ratio but of different brands. A very famous engine developer attributed the difference in the power level to harmonic twist. In this incidence, the valves (huge titanium) were being opened more than .710" and the crank was being spun above 7k rpm. As i recall, the area where the harmonic twist became noticeable was around 4k-5k rpm.
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Offline 1workinman

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Re: Benefit of 1.7 rocker arms
« Reply #15 on: February 15, 2018, 03:57:44 PM »
Considering bumping up my 124. It's a Drago's crate motor at 10.8/1 comp, 640's, S&S 58 mm tb, untouched super stock heads, and a Dragula 1 pipe with the 2.55 baffle. Am considering bumping comp up to 11.5/1 and having heads ported. Looking at hpi 62-64 mm tb or possibly the 68 mm unless that's just too big. Also have the 3.05 baffle if needed. What I'm wondering is if I could keep the 640's and use 1.7 rocker arms whether on intake and exhaust or only intake and get good gains, or if I'd be better off just getting different cams altogether. Power in the 3000 rpm and up range is good for me, don't want a tractor.
  I far from a expert except for spending a few dollars on Harleys , your running EZ starts I guess , if you were not I suggest the 630i like Ray has and a good set of heads . Regards heads is where I would spend my money on . I personally want the compression around 200 ish with what ever cam you go with . There was a example on here a while back a SS crate motor with compression increase an head work and I think hit 150 or close to that . The 2.5 will I expect bring on the torque sooner also . I know your asking about the bigger intake rockers but I suggest taking to your porter