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  #46 (permalink)  
Old 12-26-2012, 02:30 AM
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A OHC motor is not the same thing.

On a typical american pushrod V8 engine you can set the lash cold about .004" tighter than the "hot lash" spec and it will be to spec when the motor is at operating temperature. Pretty simple, pain free and a lot easier than setting it "hot".

You can generally vary the lash by .012" tighter to about .004" looser than the spec.
These are not the absolutes but a good guide line. You have to watch setting the lash too loose.
There is a practical limit.

The hot -cold lash change on a OHC engine is not the same.

Last edited by F-BIRD'88; 12-26-2012 at 02:36 AM.
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  #47 (permalink)  
Old 12-26-2012, 06:49 AM
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Quote:
Originally Posted by Deathmunchy View Post
Normally I just set it to factory specs. This is just something we were discussing to see about how tight we could get it. He raised some concerns to look into. Not sure if pushrod engines are going to be different in this regard to OHC engines but I'd imagine it will be damn near the same exact annoying thing.
I have seen w/my own eyes a cast iron head/block engine having a tighter lash after the engine was hot than when cold.

How much you can safely deviate from the recommended lash settings depends on a few things, not the least of which is, if you are using a solid cam that recommends </= 0.015" hot lash, you should not add more than 0.002" (two thousandths looser), or subtract more than 0.004" (four thousandths tighter). This is because of the lobe ramp shape- if you add even a little too much, the lifter hits the lobe away from the clearance ramps and will 'dig in', causing excessive wear in short time. This comes from a cam manufacturer (don't remember which one), not something I yanked outta my butt. Cams having bigger lash recommendations can go up to double the lash settings above in most cases.

Too tight is the lesser evil than too loose, as far as if you're going to make a mistake. Too tight will be apparent by a loss of power caused by the valves not seating and can overheat the valve because of a too-short seat time that doesn't allow the valve to transfer heat into the head seat, but too loose will beat hell out of the cam and lifter as well as the rest of the valve train, because the take up ramp has been removed from the lobe.

FWIW, I use the hot lash setting for initial start-up. After the engine is hot, the valves get lashed correctly. Then after a complete cool-down, the lash is remeasured for future use when checking/setting the lash cold. That's the only way I know of to get it right as opposed to pretty close. Expect the lash to tighten on a new cam and lifters (not a bunch, but noticeable) until the valve train is bedded in together. Once this is done, you'll not be needing to adjust the lash very often, although you still need to occasionally check it with a go/no-go (at least that's what I do).

The main difference I have seen between an OHC and an OHV engine as far as lash goes, is the bucket and shim OHC engines tend to change less between hot and cold. OHC engines w/followers will change a bit more, but still less than a pushrod engine, at least in MY experience. When setting the lash on an OHC, it may still sling oil around pretty good if the engine is running when the valves are adjusted, though.

One real good piece of advice I was given that I'd like to pass on, is to take the thing you hate doing the most and make it the thing you do the best.

On a SBC and most other V8s, you can cut the center out of an old valve cover to use when setting lash hot, engine running. It will keep most of the oil from splashing out. You would use 45 degree bent feelers (or bend them yourself), and if you use polylocs, using a tool like shown below can make things easier.



A tool like that can even help when setting the lash cold because it's easier to get the same 'feel' from valve to valve.

A go/no-go feeler set is not expensive and will make checking the lash uber easy.

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  #48 (permalink)  
Old 12-27-2012, 12:22 AM
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Yea I've never set lash on a pushrod engine. Only the OHC 4 cylinders from Honda and I think one from Nissan.

This car is going to be tinkered with...a lot. I can't wait to have everything together. I also appreciate the advice on the build. I've pretty much got it all figured out atm.
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  #49 (permalink)  
Old 12-27-2012, 09:36 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
I gave you a complete Car engine build recipe. All you need to do is follow it, without substitutions.
Find a qualified auto machine shop that can do the block machining for you.
.. Every knowledgable person he talks to is going to give him a slightly to completely different recipe... and... frankly... your recipe just plain has some weak things in it... and up to the point when you wrote this, he hadn't given enough detailed info on exactly how he is going to use this car... or his budget set aside for it...
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  #50 (permalink)  
Old 12-27-2012, 10:46 PM
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The OP ster's goals are clearly stated here in his first post.

I have a 1980 z28 with the 190hp 350 LM-1. 3.42 slip diff. It is bone stock.

Uses will be late night taco bell runs, The rare relaxing cruise and as much track time as I can afford.


This combo will do that very very well.
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  #51 (permalink)  
Old 12-27-2012, 11:34 PM
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.. OK, LOL!, you guys can stop arguing about whether cold lash is tighter or looser, you're both correct, see Tech Inspectors link.

.. You also need to ask the OP exactly what he is trying to accomplish, you can't just start listing parts/builds... his first list of parts indicate a 500-550HP 11 sec. engine. Later he mentions 13 sec. goal as in 350HP...

.. SOOoo, DeathMunchy, you want an all out racing big cubic dollar$$$$ engine? A bracket racing engine? Got an E.T. class in mind. A buddy's car you want to keep up with/beat? BTW, a 4.56 rear end isn't going to yield a "relaxing cruise"... LOL!

.. Can keep stock rods with 13 sec. engine... need pink rods or better with 11 sec. engine... everything the guys told you about building an engine apply to 5.7" rods or 6" rods... just use pistons with shorter compression height with 6" rods. The shorter rods prolly make slightly more power below 6250 RPMs, the longer more above 6250. If you want a 6500 RPM redline engine that will only spend about 1/4 sec. total time above 6250 in the 1/4, then prolly stay 5.7. 7500 RPM engine and lots of time above 6250, then 6" or longer prolly better...

.. Keep your stock crank for 13 sec., it's better quality than an Eagle China cast crank... use a forged crank for 11 sec.... a used or reground GM forging would be fine...

.. If you have a Q-Jet 4-bbl. carb. already can prolly use that OK for an auto trans car. For a manual trans car, the quicker reaction time of a double pumper mechanical secondaries carb. is desirable...

.. Your LM1 350" is a 225 grossHP engine with 4bbl. and open headers. Was rated 145 - 195 net HP depending on 2 bbl. or 4bbl. carb., accessory package, and how crappy the stock exhaust system was. It could make about 375-385 HP just by adding domed pistons and a modern budget mild performance cam like a Summit #1105 224/234... or a Comp XE268 for more $$$... or good head porting/valves and an even smaller cam...

.. Don't know whether your rear end is a 7.5" or 8.5"... the 7.5 prolly OK for a 13 sec. car... I'd go bigger for much 11's running...

Last edited by BuzzLOL; 12-27-2012 at 11:47 PM.
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  #52 (permalink)  
Old 12-28-2012, 01:06 AM
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Arguing?

~'71-up second gen F-cars = 8.5 corporate rear end.
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  #53 (permalink)  
Old 12-28-2012, 01:20 AM
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people sure like spending other peoples money..
I'd stick with 5.7 rods.. they are a dime a dozen get a set of g.m. rods, spend some time polishing the rod beams and remove the parting line, and add ARP bolts.. (more than strong enough)
pistons,I tend to go forged, some like hyper, I know that I'll at some point spray so.. I go forged
crank, a g.m. forged crank will be fine..
you said your block is 4 bolt.. tobad, a 2 bolt would be better, and add splayed caps.
spend the money in heads and cam.. go roller..
there are alot of 11sec cast crank, g.m. rods engines running around.. on the track..
if planing on a transbrake, then skip right past the cast anything..
and add ARP studs to the mains, ..
if you ever think you'll spray it.. open up the ring gaps some..
I always check the lash hot.. no idea how anyone can have a (standardized) cold seting when alum grows different than iron, and different valves and different alum heads are made from different grade alum.. I'd not chance it.. but do like the set it hot, let cool overnight then check cold to get YOUR cold lash setting.. but for the first setting hot.. is anyone gonna replace your parts if the cold GUESS is wrong.. ? NOPE.. check it hot..
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  #54 (permalink)  
Old 12-28-2012, 01:54 AM
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So exactly how do you set them hot, the first time.?

If you try it : set the lash cold, about -.004" of the "hot lash" setting. (for a typical N american pushrod V8)
And then if you do want to check it with the engine fully warmed up and you are fast enough to get the valve cover off.
You will find it works really good.

Most people set the lash too loose by default and most will never get the hot lash set all the same while all the same temp
(or even close).
One reason is it takes too long to do it.

Most that try to set the lash hot, tend to want to avoid doing it (cause its HOT and takes longer and the result is no better when done hot) and will complain or nag on the evils of mechanical lifter cams.

While those who set the lash cold, done correctly find it a easy quick routine procedure and don't mind doing it.
You will also find the lash tends to stay adjusted, longer cause its done right to start with.
You get a better more consistent result.

90% of it is how you go about it.

Just so you know. To get the motor fully warmed up and expanded you ahve to actually take the car for a drive and drive it.
To get it "hot". Cast iron is slow to warm up and expand. Aluminum warms up quickly.
But the expansion rates are well known and the cast iron block is predominate and takes the longest to heat up fully.

Last edited by F-BIRD'88; 12-28-2012 at 02:22 AM.
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  #55 (permalink)  
Old 12-28-2012, 02:12 AM
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Quote:
Originally Posted by F-BIRD'88 View Post
So exactly how do you set them hot, the first time.?

oh, I don't know, I tend to use the cams cold setings then start it.. and then reset/adjust hot..
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  #56 (permalink)  
Old 12-28-2012, 03:44 AM
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I never do that..... any more....

I set the initial valve lash .004" tighter than the hot lash spec and put the valve covers on. and run it .
Then when the motor is all broke in completely. (about a week of driving) i reset the valve lash again, cold again .004" tighter then the hot lash spec and put the valve covers back on and drive it.

Done..
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Old 12-29-2012, 08:58 AM
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@buzzlol
I did not think I would be making 500hp with my initial setup. I was thinking more like 400-maybe 450. So...crap.

We have a few events that come this way. I have yet to go to any. Thursdays are test and tune. Fun to watch. This is probably where I'll be going a bit.
Yes...a few friends. Specifically my Import driving buddies and my Pontiac loving friend(76 Pontiac, He's trying to get ahold of a 454).
Times on the Imports are higher elevens to low 13's. Pontiac was just purchased a week ago.

My definition of relaxing cruise is anything where I can drive for more than an hour straight.

Ahhh I did not know there would be a power difference. It just seemed like less stress on the engine and less weight for the rotating assembly.
yea got the 4bbl Rochester that came with the engine.
Want a manual eventually.

@gearhead, While money is an issue. I really like the idea of doing this once and doing it right. If something is overkill though I'd like to know. I've about 2500-3000 to spend on parts alone for the engine. The less I spend there the more it goes into other areas.

Also interesting news. Taking apart an 83z28 camaro to check/change the head gasket I've found how very annoying the smog crap can be. Its just in the way. Unfortunately we found rust on some of the pushrods/rockers so I may be rebuilding my friends 305 or dropping in a 350.
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Old 12-29-2012, 09:28 AM
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@ f-bird I'm definitely looking into what you said. May try a combo of the two just to make sure everything seems to be in specs.
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