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Old 05-11-2012, 01:52 AM
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Cam break in...What do you guys do?

Hi*

I have a 355 sbc with 294S comp cam (solid f/tappet) The specs call for .022" lash hot.*
The engine is all new, fresh valve train, heads , block , pistons etc*

I need to break the cam in, *( I am using the ZDDP additive )*

My question is what do you guys do as far as valve lash 'cold' clearances are concerned. Should I *set the lash at say .020" cold to allow for block expansion and wear during break in or set at .022" cold and then shut the engine down once hot and readjust the lash? And then continue with the 30 min break in?*

I am using the lifters with the little holes in them.*

If you need any more info, please ask.*

Thanks heeps!

Duke

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Old 05-11-2012, 05:16 AM
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If it's got cast iron heads just set them to spec and do your break in. Don't shut it down to reset them until the 20 minutes or so is up. The extra couple of thou of clearance won't mean anything to the break in. If it's aluminum heads go .006 tighter on the clearance.
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Old 05-11-2012, 06:04 AM
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Set the lash cold .004" tighter than spec.

Use light(er) spring pressure for the initial run in.
Either remove all shims, remove the inner spring coil
or use stock springs at max installed height. +1.75"

then install the hi perf springs to spec.
and again set the lash cold .004" tighter than the card says.
www.molyslip.com

The 294S cam likes to run with locked out spark advance
Lock out the mechanical advance and set the locked timing at 34-36deg BTDC.

Limit the engine rpm to around 4500 rpm if /when using light valve springs.

Last edited by F-BIRD'88; 05-11-2012 at 06:13 AM.
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Old 05-11-2012, 11:58 AM
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Thanks guys, yeah cast sportsman two heads. F-BIRD'88 I have the dissy set to 10deg max centrifugal adv, all in by 3000rpm, (from a previous build) Do you think 24deg static timing will be enough? I have 750 Holley with all throttle transfer slots set open to .020" and 4.5 power valve.

Duke
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Old 05-11-2012, 12:51 PM
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Quote:
Originally Posted by F-BIRD'88
I see you tout this stuff all the time. They have many products, which one do you suggest? Looks like they have a break in formula and an engine oil supplement. Do you use both or just the break in?
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Old 05-11-2012, 05:05 PM
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You can use a set of 1.3 rockers for break in, then you dont have to pull the springs. What size studs are you using? **************

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Old 05-11-2012, 05:10 PM
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Quote:
Originally Posted by thinwhiteduke
Thanks guys, yeah cast sportsman two heads. F-BIRD'88 I have the dissy set to 10deg max centrifugal adv, all in by 3000rpm, (from a previous build) Do you think 24deg static timing will be enough? I have 750 Holley with all throttle transfer slots set open to .020" and 4.5 power valve.

Duke
The 24 initial 10deg advance curve will be the minimum you will need.

It will run real sweet with locked out timing. I recomend you simply lock out the mechanical advance for this 294s cam....Try it
(auto transmission.)

reguardless. If you have vacuum advance use it too.

Vacuum advance needs to be limited to 10-12deg at high manifold vacuum
part throttle cruise. Like on the hiway.

Last edited by F-BIRD'88; 05-11-2012 at 05:25 PM.
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Old 05-11-2012, 05:19 PM
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Quote:
Originally Posted by Silver Surfer
I see you tout this stuff all the time. They have many products, which one do you suggest? Looks like they have a break in formula and an engine oil supplement. Do you use both or just the break in?
I use the E oil suplement. I do not drain it out right away.
I leave it on the motor for a few 1000 miles so it can do its work
protecting against metal to metal scuffing. and aiding complete engine break in.....It takes longer that 1/2 hour to break in a street motor.
I just change the oil filter after the initial run in.
Install the hi perf springs or the inner coil or shims and reset the valve lash.

Once the motor is run for few 1000 miles change the oil and use a good racing oil with a ZDDP suplement or run a 1/2 can of the Moly slip E in the oil.

it has zinc and moly in it.

Why would you dump it all out after just 1/2 hour?

All you are doing is making the oil companies rich.

You can use their Moly disulfide paste on the came lobes.
Its essentually the same thing as Isky Rev lube paste.

Last edited by F-BIRD'88; 05-11-2012 at 05:32 PM.
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Old 05-11-2012, 05:22 PM
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low ratio 1.3 break in rockers are a expensive way to do it and won't reduce the installed seat pressure. Its easy to change springs or reinstall the inner coil ( dual spring) using compressed air to hold the valves up.
and a simple leverage type spring compressor hand tool.
You are just spending more money not saving work.
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Old 05-12-2012, 02:56 PM
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Quote:
Originally Posted by Richiehd
You can use a set of 1.3 rockers for break in, then you dont have to pull the springs. What size studs are you using? **************
Studs are 7/16". Those break in rockers are too damn expensive for me, might be ok if a few mates chipped in and we shared em round the (family).

I just took the inner springs out using the rope trick, actually I used thin plastic tubing , feed it in at TDC swaped out the springs using an $8 hand leaver type compresser and then pulled it out, 'twas simple. Easy on the engine stand, might be a different story in the car! , my back is getting a bit dodgy..

Duke
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Old 05-12-2012, 03:13 PM
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Quote:
Originally Posted by F-BIRD'88
The 24 initial 10deg advance curve will be the minimum you will need.

It will run real sweet with locked out timing. I recomend you simply lock out the mechanical advance for this 294s cam....Try it
(auto transmission.)

reguardless. If you have vacuum advance use it too.

Vacuum advance needs to be limited to 10-12deg at high manifold vacuum
part throttle cruise. Like on the hiway.
Yeah it's auto trans, I like the sound of it running 'real sweet' lol , that's the plan!! Ill try it with the locked out timing..
If I want to incorporate an isolation switch to kill the spark for easy hot start cranking, do I simply put an interruption switch in on the low voltage side of the coil? Is that where you put it? The dissy is single points.

Thanks for the tip on just changing the filter after cam break in, that sounds good to me - I can't afford to throw any money away ATM

Duke
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Old 05-12-2012, 03:26 PM
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Quote:
Originally Posted by thinwhiteduke
Yeah it's auto trans, I like the sound of it running 'real sweet' lol , that's the plan!! Ill try it with the locked out timing..
If I want to incorporate an isolation switch to kill the spark for easy hot start cranking, do I simply put an interruption switch in on the low voltage side of the coil? Is that where you put it? The dissy is single points.

Thanks for the tip on just changing the filter after cam break in, that sounds good to me - I can't afford to throw any money away ATM

Duke
Ya that is where the switch would go but surely you are not still using ignition points. You can up grade to good effect using pretty much any CD box. Can be triggered by points. Surely you can dig up A GM HEI distributor to use instead of points.

Make sure the GM starter motor rear support bracket/brace is installed on your starter.
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Old 05-13-2012, 03:20 AM
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Quote:
Originally Posted by F-BIRD'88
Ya that is where the switch would go but surely you are not still using ignition points. You can up grade to good effect using pretty much any CD box. Can be triggered by points. Surely you can dig up A GM HEI distributor to use instead of points.

Make sure the GM starter motor rear support bracket/brace is installed on your starter.
Yeah, got the starter bracket. My budget is right down to the bone ATM with this, but an upgraded ignition system is first on the list in the future. Ill try to pick up GM HEI meantime if I can get one for fifty bucks or so, if it's gonna be THAT much better.

Thanks so much for our help.

Duke
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