Sbc cam break in.....

[BadAC]

Hi guys not quite there yet, but, I'm looking at a pair of heads for my build. In the small print tech sheet it says if installing a new cam as well as the heads to remove the inner valve springs while breaking in the cam.

Really! Bolt heads on set it it all up, breakin cam, then pull all the top end, reinstall inner springs, put it all back together again!!!!!!

Surely not, i never heard or done this before. Though this is my first chevy lump.

Is this for all new heads?

Is it a chevy thing,?

Is it not a case of loadsa lube zinc rich etc and gently run it?

Gary

[mygasser]

you don't have to rtemove the heads to swap valve springs gary. get the insitu valve spring tool cheap off ebay and do one cylinder at a time. there are 2 main ways to keep the valves from dropping into the bore during the job. make an airline adapter from an old spark plug and pressurise the cylinder you're working on. my preferred method is turn the cylinder to bdc, push as much cotton rope (washing line pulley rope) into the bore as you can then turn the crank' 'til the rope jams up into the combustion chamber holding the valves. my reasons for this method is you don't need to run your compressor and if you knock the valve it can't move. also give the spring retainers a tap on one edge so the collects unstick from the valve and retainer.
it's an easy job to do so don't fret.
neil.
tool on ebay ..... https://www.ebay.co.uk/itm/186653729...Bk9SR-qvy-SXZQ

[Happydaze]

Not sure if it's a Chevy thing or not but it's nothing to do with the heads as such, it's about giving the new cam the best chance of a successful break in. Pretty sure break in valve springs exist too, but let's not go there! Neil has outlined the procedure / rope trick.

For extra fun after break in you could also pull the inlet to access the lifters to inspect the break in wear, swirly, pattern. Or do as most do, and don't do that as its probably OK, and what to do if its not right at that point? Big drink time! Fun with cars!

Chris

Ps the 'run in' is a 20 minute high but variable idle, on an engine that's just been fired, needing to be timed, possibly tuned to be able to keep running, all whilst not overheating, leaking, catching fire, or waking the neighbours. What fun we have!

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[mygasser]

yep, as chris says 20 minutes at 2000rpm or above. the reason is the cam lobes are only lubed by 'splashing' oil from the spinning crankshaft. below that revs there's not enough oil flying off of the crank to properly lube the cam while the lobes work harden to the lifters. so if you have a leak, overheating, low oil pressure etc during the 20 minutes then stop the engine 'til the issue is resolved. also make sure the engine is pre lubed before startup with high zinc oil plus a cam break in additive, the timing is close enough to run for cam break in and there is fuel at the carb ready to run. any time spent winding over before running can damage the cam as it won't be getting the needed lube. this all sounds dramatic but in the last 20 years cam and lifter quality has really taken a dump.
i have a sbc oil priming tool you can borrow if you want mate.
high zinc oil i use .... https://www.ebay.co.uk/itm/373537080...Bk9SR87utemXZQ
break in additive .... https://www.ebay.co.uk/sch/i.html?_n...acat=0&_sop=15
neil.

[Captain Scarlet]

I tried rope/string for holding the valve up on my Chevy engine but I found a short piece of 8mm HT lead worked best, just let it a slight curve of it to go left or right depending on which valve you're working on,and just 2 to 3 inches in.

[BadAC]

Blimey I thought maybe it was just these heads I'm looking at, as not seen it mentioned anywhere else.

I know break should be 20 mins etc, seen a couple of vid's showing the how to etc, but no mention of the valve malarkey. Might look into some other heads.

But cheers guys seems fun

Never had prob with rovers or minis or pinto or triumphs. It must a yank thing.

Im not using a huge lift cam, mild lift comp cam.

Oh well, another drink is needed

G

[Happydaze]

Like I said earlier, it's not an issue with the heads, it's the cam, and kinda standard practice. The manufacturer of the head you're looking at probably included the break in procedure to cover their ass / reduce complaints? If others omit it so be it, its still applies.

Chris

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[mygasser]

agreed, the yanks pretty much started the 'where there's a blame, there's a claim' culture so they just cover their ar5ses as standard procedure. you don't have to remove the inner springs, it's just covering your ar5e, lol. it's only a faff when refitting the inner springs, removing them is easy as the heads will be on the bench. for the extra 1-2 hours spent your much less likely to have issues with flat cam lobes. that's cheap insurance as far as i'm concerned.
neil.

[BadAC]

Cheers Guys

After more reading I found the reason theses specific heads needing springs removed, the ones i was viewing were for solid flat tappet cam, their other model with different suffix is for hydrualic flats and does not need inner springs removing

Cheers for info and i will be taking max effort to do breakin properly.

Cheers

Gary

[Blackpopracing]

Late to the party as I've been away, but although more expensive - I'd look at the roller cam kits for SBC's it removes all the problems of flat tappet cams.

[BadAC]

Cheers blackpop but already got cam etc for flat tappets.

G