switching from hydraulic to solid cam questions

[Wolfplace]

I have never found the lash gets tighter when the engine warms up, from cold. It gets looser.
The block grows more than the valvetrain does. The cold lash is always less than the hot lash on a V8.

But the exhaust valves get hot when you run hard for extended time @ WOT so the exhaust valves grow a bit and
reduces the exhaust valve lash a bit when @ WOT. Thus the typical .002" to .004" split on intake to exhaust valve lash.
Try it for your self and you'll see.

Actually I have,,, for about the last 50 or so years,,,,
Iron heads, Iron block the lash will stay very close to the same or get TIGHTER with heat, average about 2 thou so I just set them at hot spec to start.
Aluminum on a SB you are correct it will loosen about 4-5 thou & on a BB about 6-8thou

[Lasher...]

On my last 327 ( iron Block and Iron Heads ) my cam had a suggested hot lash of .022. I always set them cold and then check to see where it goes when hot. In order for me to achieve the proper .022 hot setting I had to set them @ .024 COLD..... On my last BBC an All Iron 427 the suggested hot lash was .020 and in order to achieve that I had to set them @ .023 Cold.......... Note I always set them one at time making sure the lifter is on the base circle and I do not use the multi position method of # 1 TDC fireing set intake #2 & #7 and Ex #4 & 8 then rotate 180 deg and set blah blah blah...... that may work on small lobes but on longer durations or long clearance ramps & wide LSA's you can often times end up setting the lash on the clearance ramp instead of the base circle...... in order to set the lash correctly the lifter must be on the base circle.

[1997bird]

With my CT builds that mandate cast iron heads/cast blocks, my intake lash rarely changes from hot lash to cold lash settings. But my exhaust lash settings are usually .001"-.002" tighter hot lashed from cold settings.

[F-BIRD'88]

I always ensure when setting the lash for each valve that the lifter is on the heel of the cam lobe.
I agree and never use the multi cylinder setting method. never have.
One thing on the hot lash is that if the engine is idlding with not enough idle spark advance the exhaust valves get hotter than they need to at idle (because of the retarded timing and elevated exhaust temp) this will cause to the hot exhaust lash to tighten. up. If its eating exhaust header gaskets its a sure sign that the engine needs more timing at idle.

Very typical to find on cammed up racey motors. that may account for our differences.

I have found my basic-general rule -.004" hot to cold lash rule works pretty good for cast iron heads..

Just recently helped a guy with a tall deck BBC with aluminum heads and a solid street roller.
Hot lash is .020". He always got a noisey valve train set like this so he tried .015" cold and it was better , but still not quite right.
I advised him to try .010" in and .012" ex set cold 70°F and then get it fully warmed up ( take it out and drive it) and then checked the hot lash. He said it is now finally just right.. Thats how much the hot lash grows on a tall deck BBC with aluminum heads. Surprising...

Good to check the hot lash cold lash difference for yourself on your motor.

I find in general most people set valve lash too loose. As a rule.
and yup many people try the multi cylinder set method on high perf cams and then wonder why they got a noisy valve train that won't stay set. And then bad mouth solid lifter cams.

OP check your cold lash... hot lash difference and post your result.

[badassracing]

Will definitely check on the lash. What could I expect the power difference to be with a solid cam?

[F-BIRD'88]

Will definitely check on the lash. What could I expect the power difference to be with a solid cam?

Lits of variables. Put it on a dyno and test it and post your result here.
You can expect more top end power and the ability to rev the engine a lot high.
Assuming you use the right springs. That measn you can gear the car a lot more aggressively
for hard acceleration and it will keep on pulling at the top end.

[MadBill]

In a given engine design, a number of factors can affect the cold to hot lash change. One easily overlooked variable would be oil Vs. water temperature. E.g., a boat might run 130° water temp and 280° oil, whereas a car running on long oval tracks might be 240° water and 240° oil. The former would see significant pushrod growth but little block height change compared to the latter.

[badassracing]

Will definitely check on the lash. What could I expect the power difference to be with a solid cam?

Lits of variables. Put it on a dyno and test it and post your result here.
You can expect more top end power and the ability to rev the engine a lot high.
Assuming you use the right springs. That measn you can gear the car a lot more aggressively
for hard acceleration and it will keep on pulling at the top end.

I ordered a cam yesterday. I went with a comp 252/258 106LSA . Probably the only dyno will be the butt dyno though. I hope it just has more power the whole way through the power range. I'm not really planning on turning it much farther than 6800...hard to get all that air through a 2bbl with a 406.

[F-BIRD'88]

Why don't you let the engine's performance determine that. You could have gone bigger duration.

Why would you go tothe trouble to switch to a solid lifter cam and then not gear the car to take advantage of
the increased rpm limit. ? Let the car tell you what gears it likes best.

I would cold lash it at .012" and .014"...take it out for a few hot laps. Bring it in and quickly check a few of the exhaust valve while it is still good and hot.
It is nice to reduce the installed open spring pressure during the initial cam run in. Then install the inner springs and shim as required. Less spring pressure is better when breaking in new agressive flat tappet camshafts. Lets the new cam and lifters get friendly with each other. A little moly and zinc added to the oil helps too.

http://www.molyslip.com Moly Slip "E" oil Supplement.. It has a good dose of both in it.

When you check your engine's hot lash, after a hot lap or 2-3, post it here.

[F-BIRD'88]

hard to get all that air through a 2bbl with a 406.

Even harder if the camshaft is choking it too.

[F-BIRD'88]

So when you were ordering the cam from Comp Cams did you ask about the allowable valve lash adjustment variation range
of that camshaft?

And the "Butt Dyno" can be very deceiving. Better to run it around the track , say 10 laps against another car that runs close,
Then make a tuning change (like say increase or decrease the valve lash a little bit)( or changing gears) and run it again for 10 laps.

[F-BIRD'88]

You can also play with the cam installed phasing a bit. Cam advance/// retard. This has a effect on the engine's overall torque curve too.
If you want more "torque" or more hit off the corners, try advancing the cam 4 to 6deg (100° intake C/L)
The cam card indicates a "straight up" installed phasing. (106° intake C/L)
Degree it to find out .

Your tires and track condition will probably be the biggest factor.

[badassracing]

I will experiment with the gears eventually. It looks like this project might not happen as soon as I wanted it to though. I planned on running it this weekend but comp didn't get it shipped out fast enough.