How are these compression results??

sticky nicky · Postby **sticky nicky** » Fri Sep 07, 2012 8:08 pm

Hi,

Just had my replacement engine (1.6, long nose crankshaft) tested for compression before it goes in. Results were 225, 225, 225, 175. how does that sound?

Next step is to get the head pressure tested and possibly new valve stem seals, then the mechanic is going to check out the bottom end for me.

It will all go back together with a cometic head gasket and ARP head studs.

Anyone know how much forged pistons would cost? The engine will have a turbo.

Interested to hear you opinions and advice.

Cheers

Mr Morlock · Postby **Mr Morlock** » Fri Sep 07, 2012 8:28 pm

my guess is you have a problem- its the variation that is critical - something over 10% waves a red flag . A mechanic should be able to assess the situation and give you a report. If there is a problem with one cylinder then it has to be addressed. It then raises questions about the condition of that engine. You do not turbo a suspect engine. However expert I am not.

bigdog · Postby **bigdog** » Fri Sep 07, 2012 8:31 pm

Nicky, you have some very knowledgeable turbo guys in Perth. PM forum sponsor Les (mx52nv) and have a good talk to him about your project. I bought my rods and forged pistons through Les, he's a good guy and can give you some good advice. Compression result is not really relevant if you are rebuilding the engine anyway. Everything needs to be measured and checked, and at the very least you will replace the rings, bearings and re-seat the valves, plus replace the valve seals and gaskets.

Postby **NitroDann** » Fri Sep 07, 2012 8:32 pm

Yep theres some issue.

What turbo gear is on it?

This will help us to help you decide what internals to change and what to keep.

Dann

sticky nicky · Postby **sticky nicky** » Fri Sep 07, 2012 9:47 pm

I have an AVO turbo stage1, running at 7psi making 170rwhp. I wont be increasing the boost as Im happy with that at the moment.

My mechanic said it may be due to slight rust and if so, will go after running for a short time. The engine hasnt run for a couple of years, just been stored.

Postby **NitroDann** » Fri Sep 07, 2012 10:10 pm

Ah ok

Yeah just drive it, Dont stress.

Worry if it gets noisy or uses oil.

Everything else Id leave it, definately dont waste money on internals at 170hp.

Dann

sticky nicky · Postby **sticky nicky** » Fri Sep 07, 2012 10:57 pm

OK, thanks for that Dann, thats put my mind to rest, Im not talking massive power here, im more interested in improving my driving at the moment, I think I can gain a few seconds in that department.

bigdog · Postby **bigdog** » Sat Sep 08, 2012 1:08 pm

I am a little confused - if the engine is out of the car now (which is what your post indicates) and you are going to replace the head gasket and valve stem seals then it would be silly not to inspect the bottom end and check for crank and bore wear, replace the rings and bearings before re-assembly and putting it in the car.

If the engine is already in the car then Dann is right - just drive it until you see an oil consumption issue then fix it. Either way you don't need to spend money on pistons or rods unless you want to run more boost.

sticky nicky · Postby **sticky nicky** » Sat Sep 08, 2012 2:55 pm

Hi Bigdog,

Yes the engine is out of the car at the moment, so my plan is to get the head tested and redo valve stem seals, my mechanic is also going to inspect the bottom end to see if all is good, replace timing belt and water pump, and then put it all back together and into the car. I dont plan on increasing the boost, its fun enough with 170 rwhp and I dont wont to be putting the engine under too much stress which usually = dollars!

Thanks guys

Mr Morlock · Postby **Mr Morlock** » Sat Sep 08, 2012 3:57 pm

I seem to have missed something here - I cannot see any reason to be relieved. With a > 20% variation on compression it signals an engine problem at least from what I have been told. Comp checks have always been a good guide to engine condition. Even with stock KW's the engine has a question mark. It will not fix itself. Running high KW - 170 HP at the r/wheels is well above a stock engine adding stress to an engine which may well be worn and further reduces its operational life.

The old rule of thumb was a loss of 50% to the rear wheels- call it 30% say 70KW converted to bhp = 94 . If you are getting 170 its significant more than stock. Are the numbers out of court? These things then become an issue of what to spend and what are the best options.

sticky nicky · Postby **sticky nicky** » Sat Sep 08, 2012 8:53 pm

Interesting, any other opinions on the loss of compression in one cylinder? I really dont want further major problems with the engine after spending a couple of grand on it.

Postby **NitroDann** » Sat Sep 08, 2012 10:15 pm

I agree something isnt right, however a complete replacement engine is only a few hundred dollars.

this is a 1.6 right?

Dann

sticky nicky · Postby **sticky nicky** » Sun Sep 09, 2012 2:12 am

Yes, its a 1.6........its also the replacement engine I just purchased to replace my other one that is stuffed.

Postby **NitroDann** » Sun Sep 09, 2012 2:19 am

Ok,

the mechanic will find if anything is wrong and the currently planned work will fix anything in the head, so yeah, dont stress and you dont need rods or anything.

Dann