Struggling to get my fresh 70 LT1 running better. I have an original spec 350 and have the Crane solid lift blueprint cam in it. Cam card says .020/.025 IE hot lash.
I use the EOIC method. Went for a long warm up drive to get everything up to temp, my valves were pretty loose and chattering really loud. Did a very meticulous lashing on all 16. Went back through and re checked all 16 to be sure I was on the number.
Back together and running something must still be off - I have absolutely zero rocker chatter. Sounds like a normal hydraulic cam. And my idle vacuum is much lower, by 10", and idle speed is several hundred rpm lower too. Terrible spark knock on acceleration too. Should I go back through and add a few thou to the lash? I'm thinking I've got valves off their seats?

 

I suspect you have high zinc oil or an additive ? And I would have set them cold lash , then drove it and rechecked them. At this point all you can do is set them again being careful to ensure each lifter is on the base of the cam as you set the lash

 

Yes to the high zinc and all lobes are fine.
Whats really got me puzzled is the silence. Never heard a quiet solid cam (yes I am the engine builder so I know what's in there). I guess I'll hot lash it again tonight and add maybe .002 to all and see what changes result. I have heard that little bit isn't enough to hurt anything.
I initially did the cold lash at .004 less (the general consus) and the motor didnt like that one bit. Very difficult to start and ran BADLY

 

Do you have a copy of the cam card you can post?
I do them stone cold (around 70is deg) that way the engine isnt cooling off as Im lashing.
Or do 1 intake, 1 exh when its nice and hot then let it cool see where your cold lash is. Go from there
Iron heads right?

If the lash is too tight it will hang the valves open...and either not start or run terrible

This one?

 

 

Just for giggles I set a hot lash then let it completely cool overnight, the gap didn't change. Yes iron heads

 

Go too the C2 forum, search Duke Williams valve adjustment. He addresses LT1 valve adjustment procedure.

 

Here is the article by Duke on how to adjust the solid lifter SBC cams, and why.
Even at TDC they are not completely on their base circle, or lowest point.
I heard the Blueprint series meant they were built using the original GM blueprints, so the same rules may apply.

 

I use Duke's method of adjusting, with his suggested lash, still using the stock LT-1 cam. My valves are very quiet, barely know that they are solids.
My vacuum is about 12", idle is very stable, (800), runs great. I use high zinc oil and best gas I can get here is 91. With vacuum advance & mech advance tuning, I have no spark knock in any driving situation.

 

Should be relatively quiet. If you have lash...valves aren't hanging open. Iron heads/block don't move too much...but with lash settings that loose....004" isn't a giant deal.....but it WILL change things. Tighter will have less vacuum and low speed cylinder pressure. If they were real loose...they will typically idle real well...just noisy and with more vacuum.

Are you SURE you're only adjusting TO lash? Should be easy to insert and remove feeler gauge after set.

JIM

 

Guess if you reallly wanted to double ck or be positive where the lifter was positioned pull the intake out so you can see whats going on.

 

I, too, follow Duke's method. Vacuum maybe 14" (I could go look at my notes, LOL, but I'm tired and lazy). Run 93. Very occasional knock with heavy load at low rpm.

 

427Hotrod what do you mean by TO?

Are you SURE you're only adjusting TO lash?

 

this is the updated method of adjustment by By John Hinckley and Duke Williams, go to bottom for LT1, adjusted cold, no valve clatter

 

Meaning it is actually .020" or whatever. It's easy to get over aggressive and tighten too much and still pull feeler gauge out. That's why I mentioned to be sure you can easily re-insert the gauge after you pull it out. Not sure what rockers he has....rollers with adjuster nuts having locks are a lot more positive feeling than stock rockers which sort of flop around on the pivot ball/stud.

This is a pretty mild cam...even has a 116* LSA.....so shouldn't be too tricky to get it set right.


JIM

 

Good point - using stock rockers and yes if you tilt them a tad each way the lash closes up so I wiggle each until I get the loosest reading - I kinda assume the engine does the same thing once running, it seeks the loosest point also?

 

you have to use the method in the PDF's above, it is NOT the method you used.

 

You do understand that driving with "pretty loose and chattering" can destroy stuff? If a motor isn't right shut it OFF! Cold lash and hot lash are only minor variances. You have to measure your motor cold and then check it when it's hot and record the differences. I won't go into a discussion of why 50 year old cam designs are VERY POOR choices along with weak springs and stamped rockers.

Part of Dukes PDF is referring to the 30-30 cam and I would question if the Crane cam has the same lobe design requiring altered solid lifter adjustment away from typical adjustment?

I worked at a historic road racing shop and learned a lot. One fact is the ambiguity on one persons .020 valve lash and another persons .020 valve lash. The tool to buy for setting valve lash is the magnetic or vice grip with dial indicator. I have some expensive dial indicators, but cheaper do work. How you use this tool is put the indicator on the rocker valve tip and set the dial to Zero, then you lift the rocker up and read the dial. You can run the rocker nut up or down to correctly set the lash every time.



This is just an example and you can find them for under $50. You want a stiff articulating arm and better dials always read the same consistently.

https://www.flexbar.com/products/fle...-indicator-kit

 

Ok and thanks to all.
If I understand lash theory correct, every method under the sun is searching to get the lifter on the base circle to get the most accurate lash setting. Any other lifter position is on a ramp and your lash will be too much (once you come back around to the base circle)

 

yes, but it also points out stock rockers are not 1.5 but typically 1.37.