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Would you install 1.6 or 1.7 rockers? |
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PHAT69AMX 
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Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5926 |
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 Posted: Sep/28/2018 at 12:21am |
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Yes, no Pushrod Guide Plates should be needed with early stock Screw-In Stud AMC Heads.
And kinda agree, may want to "re-visit" what Static CR and Dynamic Effective Comp Ratio you'll have. A "too low" Dynamic Effective Comp Ratio will seriously "kill" the low end torque & power imho...
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Boris Badanov
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Joined: Dec/14/2013 Location: NH USA Status: Offline Points: 4210 |
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Posted: Sep/28/2018 at 4:46am |
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1.6 ratio. As was already pointed out With that combination you already have marginal compression for that cam. |
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Gremlin Dreams
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rang-a-stang
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Joined: Sep/25/2018 Location: Camarillo, CA Status: Offline Points: 272 |
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Posted: Sep/28/2018 at 11:16am |
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Uh oh... Did I do my math wrong? Here's how I did my math: Bore: 4.195 Stroke: 3.68 Comb Chamber: 58cc Gasket thickness: .048 Piston dome: -27cc Deck Clearance: .002 |
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rang-a-stang
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Joined: Sep/25/2018 Location: Camarillo, CA Status: Offline Points: 272 |
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Posted: Sep/28/2018 at 11:23am |
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amxdreamer, you're right. I doubt it will ever see north of 6k RPM. Right now I have a TH400 but the next big project (probably next year) will be gears and a 4L60E. My TH400 shifts (at WOT) at about 5k. I will occasionally manually shift it at up to 6k but I don't plan on doing that often at all.
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PHAT69AMX
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Posted: Sep/28/2018 at 12:46pm |
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Reconditioned Connecting Rods are usually .003" shorter than stock
1.500 is the nominal Wiseco Piston Compression Height 0.013" would then be the nominal Piston to Deck Clearance. But nominal Values are just that, nominal, you gotta measure all your real parts. 58cc Head is nominal, they may be larger, same with 9.208" block deck. 4.265" dia x 0.045" is the head gasket dims I use. All these nominal dims give 9.47:1 Static CR in my spread sheet. Guess it depends how safe one wants to be... as always... the critical value is what is "tolerable" Dynamic Effective Compression Ratio for Pump Gas which depends on Static CR, Camshaft, and Intake Valve Closing Angle...
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rang-a-stang
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Joined: Sep/25/2018 Location: Camarillo, CA Status: Offline Points: 272 |
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Posted: Sep/28/2018 at 1:51pm |
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OK, copy that. My original aim was 9.5 so it would run OK on 87 octane when just cruising around. 89 would be OK, too. I didn't want to require 91 but I also didn't want to leave power on the table.
(feel free to call me an idiot if I am in left field on any of this)
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PHAT69AMX
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Posted: Sep/28/2018 at 8:37pm |
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Guess "point being" is... -IF- Dynamic Effective Compression Ratio is "Low"...
It won't run worth squat... Y'all agree ?... ( edit ) That's probably an exaggeration... in relative terms... Realistically, 9.5-ish to 1 Static CR with Iron Heads is a good number.
Edited by PHAT69AMX - Sep/29/2018 at 3:47pm |
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JERSEYJOE
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Joined: Oct/23/2008 Location: TUG HILL NY Status: Offline Points: 1718 |
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Posted: Sep/28/2018 at 10:01pm |
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HARLAND SHARP IN 1.6 END OF STORY
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1985 J-20 PLOW TRUCK
1977 CJ 7 360 T-18 D 300 1970 AMX ex-SCCA car SPEED COSTS MONEY HOW FAST DO YOU WANT TO GO? |
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Hurst390
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Joined: Apr/20/2008 Location: secret Status: Offline Points: 5822 |
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Posted: Sep/29/2018 at 7:55am |
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1.7 rockers will change the position of the pushrod in the guide plate or head hole..You would have to make sure you have pushrod clearance.
1.7 rockers made a 1mph difference best I can tell on a mid 9 sec. 140+ mph car. I've also ran 10'90's with a bone stock 8.5-1 401 shortblock with a big solid cam. 1.7 is up to you. I don't see you losing any performance but don't see much to gain either. just my opinion... |
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SC/Hurst Rambler
11.62 120 100% Street Legal |
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rang-a-stang
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Joined: Sep/25/2018 Location: Camarillo, CA Status: Offline Points: 272 |
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Posted: Sep/29/2018 at 2:18pm |
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Well, for the most part I am hearing a whole lot of "get 1.6's" and 1.7's aren't going to do much for me. I appreciate you all chiming in. I will order HS 1.6s.
PHAT69AMX, I think you may be right but at this point, it is what it is. Comp Cams says this cam was designed for ''daily drivenStreet Machines. Slightly rough idle, broad powerband. ...8:1 to 9:1 compression ratio" (I'm assuming static CR). Oh, and thank you for confirming I won't need guide plates. I forgot to mention that earlier, too. I hope to have it running in early to mid Dec. I will let you all know how it goes!
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