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What determines lash on solid cams ???

Posted By: The Shocker

What determines lash on solid cams ??? - 12/15/12 02:27 AM

I realise i have alot of questions lately ,but here is another.What dictates how much valve lash one solid cam will have over another ?The Iskenderian solid flat tappit cam i just installed in my stroker SB recomends lash at .028 /.028 hot.I noticed on Isky's site that the cam right above and below this grind call for much less lash.Its like .014 -.016 .What is this based on ? The same Isky lifters are used on all 3 .The only other SBM solid flat tappit they have with this much lash is their nastiest max effort race cam ,but it is like 296 duration at 50.Mine is only 254 at 50. Do i have to run this much lash ? I hate to give up lift and duration with a foot of lash .I have done sum research on this subject ,but cant really find out why ...
Posted By: fourgearsavoy

Re: What determines lash on solid cams ??? - 12/15/12 03:14 AM

I think it's personal preference myself I like .006 intake and .010 exhaust cold and add .010 when hot with aluminum heads and iron block been doing it that way for over 30 years
Gus

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Posted By: AndyF

Re: What determines lash on solid cams ??? - 12/15/12 03:50 AM

Lash requirement comes from the ramp design selected by the cam designer. You have to follow the recommendation of the cam mfg or else you run the risk of ruining the camshaft.

If you want a more technical explanation then go to SpeedTalk and do a search. Those guys argue about cam lash on a regular basis. But in the end it boils down to the ramp design which the cam designer selected. It cannot be changed once the cam is designed. The ramp determines the lash required.
Posted By: The Shocker

Re: What determines lash on solid cams ??? - 12/15/12 04:22 AM

Quote:

Lash requirement comes from the ramp design selected by the cam designer. You have to follow the recommendation of the cam mfg or else you run the risk of ruining the camshaft.

If you want a more technical explanation then go to SpeedTalk and do a search. Those guys argue about cam lash on a regular basis. But in the end it boils down to the ramp design which the cam designer selected. It cannot be changed once the cam is designed. The ramp determines the lash required.



So its the ramp of the lobe that determines the lash.That makes sense ,and explains why just because two cams have a simular duration and lift they would have different lash.I guess the more aggresive the ramp ,the more lash required ...
Posted By: jamesc

Re: What determines lash on solid cams ??? - 12/15/12 04:26 AM

the clearance ramps
Posted By: polyspheric

Re: What determines lash on solid cams ??? - 12/15/12 06:18 AM

What dictates how much valve lash one solid cam will have

The designer's preference.
Posted By: lowflyingdart

Re: What determines lash on solid cams ??? - 12/15/12 03:33 PM

We view cam lash specs as a recomendation. We dyno and track test varying the lash on proven combinations. For example, we ran a 499 low deck with a solid flat tappet Cam Motion cam. The spec for lash is .023 hot. We found that the car went quicker at .014 hot lash adjustments. On the flip side, I had a 511 RB FAST type engine that the lash spec was .006 hot and it liked .030 hot. Lash specs are a starting point.
Posted By: The Shocker

Re: What determines lash on solid cams ??? - 12/15/12 03:51 PM

Quote:

We view cam lash specs as a recomendation. We dyno and track test varying the lash on proven combinations. For example, we ran a 499 low deck with a solid flat tappet Cam Motion cam. The spec for lash is .023 hot. We found that the car went quicker at .014 hot lash adjustments. On the flip side, I had a 511 RB FAST type engine that the lash spec was .006 hot and it liked .030 hot. Lash specs are a starting point.



I was reading an article recently about how lash can affect the lowend vrs highend power .You say the car "went quicker" with a tighter lash on the first example.Was it a real obvious gain.Not doubting you in anyway .I just find this crap interesting (while others may find it boring).Just trying to learn by pumping others for info ...
Posted By: Crizila

Re: What determines lash on solid cams ??? - 12/15/12 04:06 PM

Generally speaking, the looser the lash the more low rpm improvement ( less overlap )and the tighter the lash the more high rpm improvement ( more overlap ). Ofcourse lift and area under the curve is also effected. It is a fine tuning adjustment that is not too difficult to do at the track.
Posted By: Anonymous

Re: What determines lash on solid cams ??? - 12/15/12 04:14 PM

Honest, I have never seen a cam damaged because the lash was not run as card said. Most tight lash cams do it to gain some small advantage on the numbers I believe. You have to see what it likes, there is a line you can cross, with lash too tight --cross it, the valves never fully seal shut. The engine will sound fine, go down track great but will be tenths slower--open the lash back up and surprise--she can pick those tenths right back up! I have seen it again and again, year after year. Set ( or at least check it ) with the engine Hot or you will never know where you are.
I have sold several 800HP range units with Cam Motions in there--they had Crazy lobes and the bottom of the base was never the low spot. Owners would call, hey she slowed down 3 tenths in the 1/8th! Open the lash ( or set it correctly ) and Yahoo!! Back flying again. The Cam Motion stuff is the worst but other brands use inverse radius and all sorts of Computer Aided nonsense to get great looking numbers on paper --those guys usually do not run or race what they make--they SELL cams , that's it! These days it takes crazy numbers on paper to convince buyers to use their cam vs. another--that is the game as it is played today. It used to just be a fat guy with a cigar that looked like your grandfather ( Isky) BTW I met him and he was a prince of a man and 100 times smarter than most.
My opinion has always been that in a good race engine you could take every cam on a single page, dyno back to back and the HP spread would not be that much. Fill the cylinder at the RPM she will run at, close the intake at the right time and the lobes could be made of stone IMO--They make a science out of it to fool the buyers ( and maybe themselves) Oh...does it work so well for them!! CALL BULLET CAMS and run what they tell you , How they tell you and forget the rest
Posted By: Crizila

Re: What determines lash on solid cams ??? - 12/15/12 05:19 PM

Quote:

Honest, I have never seen a cam damaged because the lash was not run as card said. Most tight lash cams do it to gain some small advantage on the numbers I believe. You have to see what it likes, there is a line you can cross, with lash too tight --cross it, the valves never fully seal shut. The engine will sound fine, go down track great but will be tenths slower--open the lash back up and surprise--she can pick those tenths right back up! I have seen it again and again, year after year. Set ( or at least check it ) with the engine Hot or you will never know where you are.
I have sold several 800HP range units with Cam Motions in there--they had Crazy lobes and the bottom of the base was never the low spot. Owners would call, hey she slowed down 3 tenths in the 1/8th! Open the lash ( or set it correctly ) and Yahoo!! Back flying again. The Cam Motion stuff is the worst but other brands use inverse radius and all sorts of Computer Aided nonsense to get great looking numbers on paper --those guys usually do not run or race what they make--they SELL cams , that's it! These days it takes crazy numbers on paper to convince buyers to use their cam vs. another--that is the game as it is played today. It used to just be a fat guy with a cigar that looked like your grandfather ( Isky) BTW I met him and he was a prince of a man and 100 times smarter than most.
My opinion has always been that in a good race engine you could take every cam on a single page, dyno back to back and the HP spread would not be that much. Fill the cylinder at the RPM she will run at, close the intake at the right time and the lobes could be made of stone IMO--They make a science out of it to fool the buyers ( and maybe themselves) Oh...does it work so well for them!! CALL BULLET CAMS and run what they tell you , How they tell you and forget the rest

Posted By: Cab_Burge

Re: What determines lash on solid cams ??? - 12/15/12 07:32 PM

Isky must have decided to run some modern lobes on those tighter lash cams All there older cams where like the Mopar solid lifter cams, .028 to .032 lash hot I have a 426 hemi in the shop now that I'm putting back together for a freinds son, it had sar for years and needed a thorough cleaning. It has a Isky 505T solid lifter cam in it, it calls for .028 lash, that cam is the slowest opening cam I have seen in a long time I'll bet it moves 40 degrees( I haven't measure it, yet )from when the lifter starts to rise and gets to .050 lift I have ran a lot of the older Isky loose lash cams, we have ran the lash as tight as .016 with no noticeable harmful effects, it help on the ET and MPH at the track
Posted By: lowflyingdart

Re: What determines lash on solid cams ??? - 12/16/12 08:34 PM

Quote:

Quote:

We view cam lash specs as a recomendation. We dyno and track test varying the lash on proven combinations. For example, we ran a 499 low deck with a solid flat tappet Cam Motion cam. The spec for lash is .023 hot. We found that the car went quicker at .014 hot lash adjustments. On the flip side, I had a 511 RB FAST type engine that the lash spec was .006 hot and it liked .030 hot. Lash specs are a starting point.



I was reading an article recently about how lash can affect the lowend vrs highend power .You say the car "went quicker" with a tighter lash on the first example.Was it a real obvious gain.Not doubting you in anyway .I just find this crap interesting (while others may find it boring).Just trying to learn by pumping others for info ...



The car in question ended up going 0.15 sec quicker on the same day at the track, we tightened the lash in .002" incraments until we saw no gains and the went back and ended up at .014 on a cam speced for .023.
Posted By: sam64

Re: What determines lash on solid cams ??? - 12/16/12 09:50 PM

you did get different pushrods for the solid lifters right?
Posted By: The Shocker

Re: What determines lash on solid cams ??? - 12/16/12 10:17 PM

Quote:

you did get different pushrods for the solid lifters right?


Not yet Sam.I will be getting the heads back from the machine shop early this week.I wont know the length till i get them bolted on.I went ahead and ported/blended the heads while they were off .6 of the intake valves were boogered up around the lock groove ,so i bought a new set of Ferrera stainless intake valves .I also bought all new comp springs ,retainers ,and locks while i was at it and the machinest is also setting up the spring installed height along withthe 3 angle valve job.This little cam upgrade turned into 3 times what i had planned on $$ wise ,but i want it to stay together ,so im doing it right on the valvetrain .I know its a long shot but do you happen to remember what head gaskets you used on it ?They are pretty thin and i would like to use the same type again.Cant find any markings on them ...

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Posted By: sam64

Re: What determines lash on solid cams ??? - 12/16/12 11:21 PM

Quote:

Quote:

you did get different pushrods for the solid lifters right?


Not yet Sam.I will be getting the heads back from the machine shop early this week.I wont know the length till i get them bolted on.I went ahead and ported/blended the heads while they were off .6 of the intake valves were boogered up around the lock groove ,so i bought a new set of Ferrera stainless intake valves .I also bought all new comp springs ,retainers ,and locks while i was at it and the machinest is also setting up the spring installed height along withthe 3 angle valve job.This little cam upgrade turned into 3 times what i had planned on $$ wise ,but i want it to stay together ,so im doing it right on the valvetrain .I know its a long shot but do you happen to remember what head gaskets you used on it ?They are pretty thin and i would like to use the same type again.Cant find any markings on them ...

i sure don't,i was trying to remember where i got the pushrods.i usally use a place called the pushrod factory,nice to deal with.now if those 8 inch slicks will hold the extra power you should have a big smile going on.
Posted By: The Shocker

Re: What determines lash on solid cams ??? - 12/16/12 11:48 PM

Those little "Mini Spare" slicks have crossed my mind here lately ,but i think its gunna be okay or alot of fun.I didnt really plan on doing port work on the heads at this point ,but i couldnt see not doing it since i had to take them off anyway for the new valves.Im sure i will be glad i did when i get sum new timeslips .I also removed the casting lines / marks from inside the intake and gasket matched the ports along with the header flanges ...
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