738 replies to this topic

[claysummers]

This morning I reinstalled the old rear main shells and the plastigauge indicates excessive clearance. The journal and bearing surfaces don’t appear worn. I wonder if the cap is being prevented from torquing down completely. There was some burring on one side of the cap face which I cleaned up. I honestly have no idea how this occurred and certainly don’t recall dropping or damaging the cap, but there it is. I’m going to go back and revisit my notes on the previous build and see if there was any issue with clearance on the rear main.


FB ute fixer upper, EK van on rotisserie


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[claysummers]

Post #115 I stated the mains all checked out around 0.0025. Time for a re-think.


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[Bruiser]

Howdy Clay
That rear main crank journal might be a bit out of round
Maybe worth plastigaugeing it in a couple of other spots to find out.
If you found a low spot it might be tighter everywhere else and
you may get away with it. Worth at least looking into further then, anyway
1.5 thou seems pretty tight? But those ones looked good
Did you have good oil pressure before it all came apart?

[claysummers]

Thanks Bruce good oil pressure and yes pretty tight but I'm happy with it now, after linishing the thrust surfaces, tidying up the cap face a bit more and oiling the bolts, I re-measured and got near enough 0.003" so rotating assembly is done and spins nicely.

I an thinking of fitting thus chrome sump, but a mate thinks it will be prone to leak. It was on an old speedway car if I recall. Came from a guy on here a couple of years ago. I suppose he thinks it may be brittle from the chroming, and crack.

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[Bruiser]

Why would it leak more than any other one?
If you check around the mounting flange and panelbeat
it back to flat before it goes on I would think it’d be ok
And lovely and shiny
Could check you look ok next time you are under the car grumbling and swearing

Looking for oil leaks

[claysummers]

I got brand new seals and studs for the rocker cover so there won’t be any more oil leaks now……….


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[claysummers]

It is official. I am a moron......

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[yel327]

Clay, I want to hear why you think you are a moron, not figure it out myself!

[claysummers]

Says on the spec sheet that the thrust surfaces are stock + 0.004” Byron, that’s why.


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[claysummers]

Magic stuff for the new cam

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[claysummers]

Measured the deck height with the new flat top pistons at 0.035” or 0.9mm, near as I could with the stub of a digital micrometer.

Assuming 1.1mm head gasket and factory chamber volumes quoted by Byron, gives me 8.6:1 large chamber, and 9.6:1 small chamber head.


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[yel327]

Can you get a thinner gasket? Others here will know a lot more than me about these, but when I was reading up about what to deck the 350 block for my HK I remember reading the following (and remember this is on a SBC but I guess it translates):

 

Target quench area is 0.038-0.041" (piston clearance to head surface). Most factory pistons sat 0.020-0.025" down the hole so the original steel shim head gaskets (part number 10105117) were around 0.015-0.020" to maintain that approx 0.040" quench distance. Aftermarket generic gaskets are typically about 0.040" as they assume you are cleaning up both the head and deck surfaces about 0.010", or you are near zero decking the pistons and have new heads. The revised version of 10105117 to make it more suitable for used engines is now 0.028" thick. 

 

So, if the above applies to a red 6, with your pistons down the hole 0.035" you want a thinner gasket but finding one is going to be the challenge! Ideally you should have decked the block so the pistons sat maybe 0.005-0.010" down the bore and used a 0.030" thick head gasket? But it looks like the thinnest around is a 0.040" Cometic. For SBC's they are available from about 0.025 up to over 0.100".

[claysummers]

Only rough figures at this stage Byron. I haven't got a dislike gauge and can't find my feeler gauges. The high comp head would be around 0.05" quench height but the low comp head I am reinstalling for run in will be quite a bit more.

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[Bruiser]

I couldn’t find anything except the pricey cosmetic brand in .040” thickness earlier this year.
Everything else I found was a variant of the ag390 part number, and no decent info on
any of the differences between them all. Gsag390d, ag390r etc.
permaseal, durapro same part numbers
They all also have bh110 as a part number, and the same “gs” pre and “d” after version.
Don’t know what they’re playing at
Seem to remember finding only one place stating they were .047”which is 1.194mm
Almost as if it was some kind of secret

[claysummers]

Measured an old one at 0.028”. I’ve got one here I was going to use which turns out to be a blue motor one which has BH110 on it. I could modify but might save it.


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[I'm a Red Motor fiend]

Clay, What do you mean by the hi comp head will have 5 thou quench height and the lo comp even more?
Slugs 35 thou down the bore is a long way.
With a 40 thou gasket your quench are will be 75 thou and right in the so called danger area (more prone to detonate) or so i have read. Probably not an issue because your not running big comp, just wont be as efficient i guess.
Bruce is right, 40thou cometic is the thinnest we can get.
I believe the thinnest stock gaskets install to 47thou. Get a graphite one if you dont want to pay for a cometic.

[Bruiser]

The quench measurement is from the top of the piston to the deck of the head
Would be the same for either head
Small chamber one would have a bigger quench area to quench with

What was the ideal comp ratio Marshalls gave you for the cam, Clay?
Just mathed it out, 35 thou at a 186 bore of 3.625 is 5.9cc
If it’s any use to you, I vaguely remember my motor’s maths telling me
that 4cc was worth around half a point of compression ( from 10:1 up)
Maybe could help choosing which head to use , if you deck the block.
You’ve got me wondering since you measured a used gasket at .028
wether they squeeze down to that or not??
Would give you .063”
Maybe too much for folks chasing bulk power, but might be ok for your sensible motor
Have seen discussions saying .040 is game, and .030 is risky.
We’re the old pistons closer to the top?
I wonder what factory engines pistons measured up to

Actually, looking at Adam’s point about .075 being no good,
.063 isn’t too far off that, really

[claysummers]

0.05” fifty thou Adam. The measurements are a bit rough so left off the trailing zero. Remeasured and got 0.028”. I meant to get some feeler gauges today when I was out your way at Mt Barker.


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[claysummers]

Jonny didn’t give me a figure Bruce. I take your point on the low comp quench area. I didn’t measure the deck height of the old pistons. I really need to get a more accurate reading. I will look at sourcing thinnest gaskets when I do the high comp head.

[yel327]

The advice the machiners gave me was to try and sit the pistons 10 thou down the bore and use 28 thou gaskets to get that magical 40 thou-ish quench height. The 10 rather than zero or 5 thou was to allow for a future deck clean up if needed, at which time I'd jump to 35 or 40 thou gaskets. But I have that luxury with SBC head gaskets. This is actually where I'm up to with this 377ci engine at the moment, I just have to get the time so dummy fit the crank and a piston in each corner to check the deck height and piston clearance in each corner so they deck the block to make it 10 thou across the decks.

[Bruiser]

Found this rule of thumb type table on another forum


Advertised duration cam families vs static compression ratio's here.

248/250/252 = 8 to 1;

258/260/262 = 9 to 1; (The 266 can go either way).

268/270/272 = 10 to 1; (Same with the 274 can go either way).

278/280/282 = 10.5 to 1; (Same with the 284).

288/290/292 = 11 to 1; (Same with the 294/296).

and

300 = 12 to 1.

Seemed to work pretty good, but these are for the older cams.

There are a whole bunch of things that affect this such as; aluminum head vs iron, camber shape and type; quench distance and headgasket thickness; of course fuel octane; timing; etc., etc...

Degrees at the seat, obviously
Just a bit more food for thought

[claysummers]

I'm not chasing 100ths of a second on the track, so the head is back on for now, with a modified swapmeet blue motor gasket.

I didn't fill the lifters with oil prior to installing, just drizzled some in the tops, and when I adjusted the rockers, I set them so the lifter started compressing very slightly.

I packed Vaseline around the pump gears, but I think I will fill the pump with oil before I install the pick-up. So I've packed the tube with more Vaseline to prevent gravitating back into the sump. I will fill the filter as well.
Considering this I plan to install plugs and fire straight up to 2000rpm, rather than try and prime with the starter motor. Cam and lifters are well covered in molybdenum and will get oil quickly.

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[yel327]

Only thing to be careful of Clay. I've used Vaseline in the past and it formed a plug that blocked oil flow and stopped it building pressure. So since then I've always used thin grease. This was on a red V8 that I had the issues.

[claysummers]

Where did it block? This will go through the pump in to the filter.

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[yel327]

Where the filter screwed to the pump. Formed a plug.