Checking the bottom end bearings, crank etc.

[Toecutter]

Hi guys, you will probably think I'm really lazy but I just wanted to ask about inspecting the bottom end without pulling out the pistons or crank. My current funds for my L28 are limited as the bulk of my money is going into 120K of extending/renovating we're in the process of doing so I'm trying to get the most gains out of the cash spent on the motor with the hope of putting most money into a new cam, a valve job with and hopefully some tripples at some point.

 

When I bought this motor Warren (Zworx) told me it was running well in previous car with no smoke not much info but a good starting point.

The is motor is currently on a stand in the garage. I was planning to check the following:

-see if the cylinder bores are smooth,

-check the crank movement in a horizontal plane within spec

-and check the bottom half of the bearings ok?

 

Is there anything further I can check to ascertain if the bottom end is good to go for a year or two until funding allows for new components down there or am I being foolish not to change things like bearings and rings whilst it's on a stand?

 

OK More questions, bear with me it's a learning curve atm.

Also, (ZD44TT asked similar question), If I take the head to get a mild cam installed, and the valve seats done do the valves them selves need to be upgraded and how big can the performance benefit be from changing valves, (I suppose some would say depends on condidtion of the currrent ones and the head engineering place would advice!??)? What is a reasonable CR that I can expect no pinging at using normal octane feul on an L28? Can this CR be acheived by just using a thinner head gasket or does the head need to be shaved?

 

Thanks,

Sulio

 

*EDIT: Currently stock as far as I know N42/N42 combination.

[sco_aus]

Look for cracks, lots of metal filings/chunks (obvious kinda) and pitting (cylinder). Im guessing you already know a completely smooth cylinder (glazed) is bad.

My 3c worth.

[Toecutter]

no sco_aus I did'nt so what should the surface on the bores be like?

[sco_aus]

It should have fine scratch marks that are in a criss, cross, up and down fashion like the letter X all around the bore. Does your engine use much oil?

[Toecutter]

the engine in question was never in my car. It's an L28 I bought last year with the intention of learning on it and then putting it in my car. Thanks for the info, I will post pics when I get the head off.

[Zeddophile]

My suggestion would be, as its on a stand out of the car, and your car has a running motor (plus you have a company car?) you might as well rebuild it while its out - why put it in if you're intending to pull it back out again? Build it up and do it properly rather than spending money doing the same things over again later.

 

That was the approach I took with my rangie motor, and I know as it sits now, there is nothing I can change inside the motor to make any real power difference - any big gains will be in the form of a hairdryer hanging off it. I also know that the internals are in good condition, because I've cleaned and inspected (and sometimes ground :twisted:) everything in it. And I'm pretty happy with the way it goes, knowing that.

 

But if you really want to just put it in, you can check both bearing shells in the big end bearings without removing the crank. Look for scrapes in the bores (top to bottom). Check the ovality and taper of the bores.... theres millions of things to look at, it depends how involved you want to get.

 

As for your cam question, there are a few parts to it which aren't necessarily related. How mild is a 'mild' cam? Most decent camshaft manufacturers (example crow) will recommend various upgrades for their bigger cams. For the L series, I think stronger valve springs are fairly common.

 

Re your valve upgrade - I'm not sure what you mean by upgrading the valves? You can generally get valves reground to tidy them up if they are worn (Unless they are rooted), which should automatically be done by your head place if they are at all decent, since you want the seats done. They should regrind the valves and reset their height, if they are redoing the seats. The performance benefit of all this is none over factory. Its only a benefit when your valves aren't seating properly in the first place.

 

If you wanted to fit BIGGER valves, then yes, there would be a performance CHANGE here. I'm not necessarily going to say benefit, because ultimately it depends on the rest of your motor. Off the top of my head, bigger valves hurt low down power, but make more up top.... or maybe its the other way round, I can't remember - this is where you really need to do your research and find out what YOU want to do. However, I will say that you probably wouldn't put bigger valves in with a mild cam. Would be rather pointless, considering the cost of getting the heads ported to match the bigger valves etc etc etc.

 

Not sure on biggest compression ratio for an L series - and do you mean on 98 octane fuel, or on 91 octane? If on 98 I would imagine you should be able to run up towards 9.5:1, but thats just a guess, and again you should do some research. I'm running somewhere between 9.3-9.5:1 in my rangie on 98 octane fuel quite happily, haven't even tried 91 octane in it since putting the new motor in.

 

Generally the thickness of a head gasket doesn't make a lot of difference to the compression ratio - ie. the difference between tin and composite gaskets on a rover V8 made about 0.1-0.15 points of compression difference, from memory. My preference for raising compression would be higher compression pistons, over a head shave, as you tend to run into other issues when you shave heads. However, if you start playing with the L-engine calculator, it should give you some ideas.

[Toecutter]

Thanks guys. Ben, your right about there being no real urgency to getting the motor in the car but I've just got a bit of an itch wanting to get into this spare motor. It certainly would be false economy putting it in only to pull it out a year later.

 

Check the ovality and taper of the bores

 

So the cylinders are not a perfect circle? Is it preferable to have minimal to no taper in the bores?

 

In regards to the mild cam I was looking at the same one as I believe ZD44TT is lloking at, The Stewart Wilkins 74 deg duration cam shown as mild.

 

In regards to the valves my undersatnding is the seats can be machined at of "angles" to provide better sealing. Keep size the same.

 

Your advise has been great. I know a bloke that works at MAHLE I'll see what he can get for me in terms of suitable performance pistons for the L series motor.

[thehelix112]

Sulio,

 

To be honest, IMHO there is no point doing something half-assed. Either completely strip it and build it up from scratch and know what you've got, or throw some bearings at it and be done.

 

Oh and as far as checking the bores for roundness/taper, you probably want a machine shop to do this, unless you're willing to invest in the guages required. Note, buy a cheap piece of crap gauge, and guess what sort of engine build you will end up with?

 

Dave

[nat0_240_chevZ]

yep, tep and yep.

i would have chimed in earlier but coulnt be bothered writing a novel.

 

Just leave the motor u have in, provided its a good runner.

 

otherwise there is no real cheap rebuild unless you know what you are doing and what you need to be checking, by the souns of it you dont, so i would recommend getting it done be someone who does, no pun intended.

 

Learning about what needs to be done is most certtainly useful and a practic here or there would be worth its weight in gold but you dont necessarily have 3 motors now do you?

 

Good/decent measuring equipment is almost a must, more importantly is How To Measure correctly moreso than the guages. Im able to do wonders with cheap digi verniers. Objective measurement is a must and must be carried out in the same objective manner.

 

Ovality/ roundness and taper are all things to be aware of and know what sort of limit can be tolerated, you should really read the engine rebuild section over and over and take a keen eye to diagrams and pics of the rebuilder/engineer and what he / She (Ha i doubt it) is doing, aswell as how they are doing it.

 

a cylinder ideally should be perfectly round and not taper. during use/wear it wears out of shape, and losses its surface finish etc hence an old engine will not seal like a newly built one. (Think of an oldie trying to keep their but hole plugged and not fart lol :lol: :lol: ).

 

I would say again get your nose inta a rebuild manual, a chev v8 one is best as they tend to go over building theory also, and trick of the trade as these motors have been heavily built and modded since the 50's there is a couple on ebay now,would recommend the building and blueprinting one with the light blue cover and red motor on the cover, a great read.

 

nato, sorry bout the long boring post.

[Toecutter]

Thanks guys. Don't appologies about feeding me with good advice thats what I'm after. Your all right, my current L26 is actually fine, it's just that I get a little obsessed and loose patience sometimes. I'm gonna bring the motor in to work and pull the head off at some point, send it away after more research and I know exactly what I am to achieve with my hard earned dollars.

As far as the bottom end goes I'll be asking a collegue at work a lot of questions and getting guidance there. He's been involved in building a lot of hot rods in his days and managed a engine building shop in the 80's, so the good quality tools should'nt be too much a problem as he's very helpful.

I'll take my time and do it properly. In the meantime I'll continue my research and keep picking the brains of you blokes!

 

Thanks again,

Sulio