Slant Six Forum :: lash games

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Author:	HyperValiant [ Mon May 30, 2011 7:27 pm ]
Post subject:	lash games
A couple of weeks ago I installed my Aussiespeed short intake and Offy valve cover and figured I would set the valve lash while I was in there.The cam is a Comp 264 installed in a .030 over 170 with 9.3 C.R., and I never liked the exaust lash setting of .012 so I set it on .015 and noticed that the idle was smoother and vacumm went up about an inch ,so I double checked the intakes and set those the specified specs of .010 and buttoned every thing up.I noticed that it pulled a lttle better but only took it on a short run.Saturday we decided to take the car on a small trip (80 miles round trip) and after we got where we were going I noticed the unmistakable sound of a tight valve,so while my wife was in Petsmart I decided to do a quick valve check and sure enough one of the intake valves werte slightly tight so I set it specs then rememberd how I set the exaust valves and reset all of the intakes to.012 and was rewarded with an even smoother idle and the mileage was just a tick better on the ride home and it still pulls to 6000 rpm although it started to go kinda flat after 5600. Now I realize that I basically made a smaller cam but it didnt really hurt performance and I didnt think that such a small amount would make that much of a difference but it did.Now will the extra lash hurt any thing or just be noiser.Also ,I am running the stock unknown springs on this cam and was gonna change them when the cam got broke in but havnt done it yet.I do have the springs that Comp recomends for the cam but they really dont appear much different from any other stock slant spring,would it be worth the effort to change them?Also has anybody else experimented with the lash settings on their aftermarket cam? Thanks in advance HyperValiant

Author:	ceej [ Mon May 30, 2011 9:39 pm ]
Post subject:
Yep. There is a secondary method for setting valves that won't hurt you too much for lift, especially since you've got a 170 that you can wind up. Loose lash at high rpm doesn't necessarily mean less lift with basically stock springs. Set the lash hot, Loosen until you hear it go loose. It will make a loud "Tack" as opposed to a "tick." Measure clearance At that point, then tighten by .002" tighter than that setting. Repeat across the valves. Note where everything is. This allows you to take advantage of the lash ramps. Average tight, and that's your new numbers Intake/Exhaust. This is a more subjective method, but will give you good results for idle quality, and once you are done, will result in a gross valve lift decrease that is negligible. 2Â¢ CJ

Author:	Dart270 [ Mon May 30, 2011 9:43 pm ]
Post subject:
Springs are probably fine if new or new-ish. Those are very tight lash settings, and I wouldn't hesitate to open them up another 0.002-0.005" if it improves idle vac and mileage. I run my '64 Dart at 0.025"/0.030" and 50k miles with no issues except for wearing rocker tips on the road course (sustained heat). I usually play with lash settings (looser/tighter) in 0.002" increments until I get tightest settings where the idle quality doesn't change when it gets good and hot vs. just barely hot. Lou

Author:	HyperValiant [ Tue May 31, 2011 6:30 pm ]
Post subject:
Thanks for the replys.I guess I should take it out one day and play with lash settings.It only takes about 10 minutes to lash the valves.The .010 and .012 settings were what was listed on my cam card buts nice to know I can experiment without hurting anything as long as I dont go too tight. Thanks HyperValiant

Author:	Dart270 [ Wed Jun 01, 2011 9:06 pm ]
Post subject:
Those are already too tight... Lou

Author:	HyperValiant [ Fri Jun 03, 2011 6:39 pm ]
Post subject:
Lou,could you please explain why .010 and .012 is too tight?I can see why the exaust would be too tight at .012.Is it because of the chevy lobe pattern that Comp uses or somthing about the profile?I am just trying to get a better understanding of how a cam affects performance. Thank you HyperValiant

Author:	Doc [ Mon Jun 06, 2011 9:05 am ]
Post subject:
Funny... I have had to "discover" the correct lash setting for every Comp cam I have had to adjust... for some reason, they do not know (or correctly document) the best lash settings for each profile they sell. On the Comp 264, try .016 & .018 to see if those settings give you good idle quality, a nice vacuum signel and acceptable noise control. Even a looser lash will give higher vacuum & smoother low speed operation... if the "ticking" is acceptable. My bet is that this is a single pattern cam... based on a GM .842 lifter diameter. I have always wondered if those profiles are really mechanical profiles and if that profile was designed as an intake or an exhausr lobe...?? (Chrysler uses different lobes for the intake vs the exhaust) A detailed lash ramp test & review would be required to figure all that out. Lash is set, based on the shape (slope) of the cam lobe's lash ramp. The extra .002 shown above, on the exhaust lash is to compensate for additional expansion we get from a "red-hot" exhaust valve, in high load operation. DD

Author:	HyperValiant [ Mon Jun 06, 2011 8:04 pm ]
Post subject:
Thanks for your input Doug.I think that one of my problems is trying to run this cam in a 170.I did try .015int and .020ext. and my engine hit a wall at about 5800 and passing pwer on the freeway wasnt as good so I set it back to .012 and.015 but maybe Ill try the .016 and .018 and see what that does. Thanks HyperValiant

Author:	mopardean [ Tue Jun 07, 2011 6:36 am ]
Post subject:
I really dont like this cam. I put it in a fresh 225 and have had nothing but problems. I cant seem to get it lashed in for a smooth idle or for decent driveability unless i get it to 2500 rpm. At that rpm level the truck is travelling 70 or so mph which it rarely sees i am about ready to replace it with the original. I really do not know how to tell if the original is ok or not but i am just fed up fighting this cam over the past 1.5 years Good luck

Author:	Dart270 [ Tue Jun 07, 2011 6:57 am ]
Post subject:
The difference between 0.015 and 0.010" should not be noticeable on high revving. 0.010" could be OK on intake, but every performance cam I've used is best with more than stock lash. Lou

Author:	sandy in BC [ Tue Jun 07, 2011 6:59 am ]
Post subject:
Until it ate up my OPDG my Comp 264 was the cam in my similar build. It was a disappointment. I replaced it with the Erson 280/270 and was delighted with much better performance and idle. The Erson is a piece of cake to lash......and it doesnt eat the OPDG.

Author:	66Dart [ Tue Jun 07, 2011 8:16 am ]
Post subject:
Interesting observations and good input from Doc, Lou and Sandy. In contrast, I have had good and reliable results from the Comp 264 used in my rebuild that DusterIdiot and I performed in 2004. Rebuild consisted of: - 1966 225 block, bored .040 over - Head with O/S valves, (pocket ported by Josh Skinner) - Push rods by Smith Brothers - Compression Ratio 9.22:1 - Comp Cams 264S - Dutra Duals - Cox Brother's Roller timing set - MP slant six distributor - A-833OD I have the valves lashed at .010 & .012 per the card. Have had no problems with idle and overall power / performance. I may try the recommendations by Doc and open them up to see what changes occur ! Matt

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