Vauxhall Owners Forum banner

1 - 20 of 23 Posts

·
Registered
Joined
·
3,963 Posts
Discussion Starter #1
Aparantly the 16XE rods are not that strong in standard form. But if they are stress relived they are fine. Anyone know who can do this and how much it would cost?
 

·
Registered
Joined
·
6,684 Posts
sbd, at a guess, but try south cernery engineering
 

·
Registered
Joined
·
7,121 Posts
Yes I know someone.

They were at Autosport this year. Got their card. I'll try and remember to find it tonight and post details.

They do some really good stuff - their only purpose in life is to de-stress metal.

We were looking at some gearbox cogs and they looked polished - turns out it was something like 'micro deressing' or something. Bascially it had been checked for cracks/imperfections then blasted with such a fine medium that it looked polished althought was actually covered in very very very fine dimples.
 

·
Registered
Joined
·
6,684 Posts
cool, I'll be interested as well, then , as I'm keen to de-stress the v6 rods!
 

·
Registered
Joined
·
4,183 Posts
well de burring the rod and shot peening it relieves any potential stress points through inferfection of the edges of the cast on the rod which make its more durable for increased loads

 

·
Registered
Joined
·
3,963 Posts
Discussion Starter #7
tomstickland said:
How not strong is "not that strong"?
I'm not too sure really. It's just information passed on from Velos and SBD. Ultimately we're looking for a 100% increase in power and torque so something's going to have to be done.

Yeah, any contact info would be great Giles. :cool:
 

·
Registered
Joined
·
1,561 Posts
Do it yourself!

Get yourself a flap wheel or something and work up the rod, not across it.

Thats what most places do, you want the casting seams (flash) ground flat with the rest then get the rest of the surface to match. Then get it shot peened.

Dressing the block etc is the same.

You want to get rid of stress risers and sharp corners. This is where things split.

Shot peening just bombards the surface with ball bearings basically, the metal swells as well btw. Its a surface hardening treatment. It doesn't actually increase the materials over all strenght (you can't unless you change its make up by adding other things).

The pic that Observer posted shows a nicely done rod (doesn't look shot peened though), you can achieve that without to much hassle and it will be stronger than a normal rod.

Rods take a lot of battering in an engine, they go through cycles of tensile (stretch basically) and compression. The hardest time on a rod is on the exhaust cycle and when the timings over advanced.

Rods see pressures of several tons thats why they let go. High revs basically seal their fate. The loadings increase with speed you see.

It takes some serious power to bend a rod from power alone.

Chris
 

·
Registered
Joined
·
6,684 Posts
ta very much Chris, I've just invested in a pillar drill, so now it's time to invest in a flap wheel.
 

·
Registered
Joined
·
1,561 Posts
Also before you get all excited and work the con rods to perfection, make sure they ain't bent!

If you can't measure the con rod accurately to see if its bent you can do it by examining the cyl bore and the cranks journal.

if the con rods bent you will have taper on the journal and an oval bore but not the normal thrust oval wear but side on.

Chris
 

·
Registered
Joined
·
6,684 Posts
nice one.

I've got 2 3.0L bottom ends, I'm sure I can find 6 straight rods in that lot. would it be worth getting them measured by a reputable engineering company as well?
 

·
Registered
Joined
·
3,963 Posts
Discussion Starter #12
I guess it's worth accurately checking weights after this work too?

Although I don't think Vaux rods have any ballancing thingys.
 

·
Registered
Joined
·
1,561 Posts
I personnal wouldn't get them measured seperatey by an engineering co.

If you get them shot peened then yeah get them checked and measured, sometimes they can bend with the process.

I would be happy with measurements of taper across a bearing journal.

In case anyone doesn't know the taper means measurign the dia of the journal at one side then the dia at the other side of the same journal. The measurements should be equal, if it narrows (so the journal is cone shaped) then the con rod is most likely bent.

Other bottom end tricks can be performed like deaseaming and removing casting flash and sorting out oil flow and so on.

But other good measuerments for the bottom end include making sure the bores are 90 degrees to the crank in both directions and that the bores are not offset. You want it all in line.

Why? For long life, reduced friction thus more power due to less parasitic losses.

Chris
 

·
Registered
Joined
·
9,212 Posts
Should the pistons not also tell a story if the rod is bent. i.e. excessive wear to one side, etc. Might be a good indication that a rod is bent.

Or can a rod be bent enough to be a worry without the piston giving any noticeable give-aways...

( Guess who checked for bent rods by piston wear!? :p )
 

·
Registered
Joined
·
1,561 Posts
Yep you want the rods to be equal in weight as well. Rods don't have any balancing thingies (counterweights) thats the crank.

Brian the bore will also show, lierk I said in a previos message the borer will be oval and the piston worn on one side more than another. The ring lands usually also take a fair battering.

Chris
 

·
Registered
Joined
·
3,963 Posts
Discussion Starter #16
I didn't mean counterweights. I've seen rods before with a surpless lump in them for balancing. You can machine material off that to equalise the weight. Vauxhall rods don't have that AFAIK.
 

·
Registered
Joined
·
3,963 Posts
Discussion Starter #18
Aye, gives you somewhere to remove weight without creating more stress points through drilling.

The old small block bottom ends are said to be balanced quite well from the factory. Anyone know about the newer small and big XE engines?

Trying to figure out if it's worthwhile. Although proberbly not as with a turbo the rev range won't be that high.
 

·
Registered
Joined
·
1,561 Posts
The old 993cc nova OHV engine had quite a bit on them that you could machine.

Crappy 3 bearing crank and OHV, oh how my mum despised that hunk of crap.

Balancing them and stress relieveing them is worth it as it reduces the stresses thus prolongs the life and if properly balanced along with the rest you get a nice smooth engine to.

Chris
 

·
Registered
Joined
·
3,963 Posts
Discussion Starter #20
Thats proberbly where i've seen it from. Proberbly just there because they are craply cast and are miles out weight wise. My first car (Nova) stayed as a 1.0 for about 2 months till the wonderfull cam chain design cut through it's cover plate. Oil used to leak out faster that you could poor it in! Fitted an ex-rally 1.3 from an SR I bought for £40. Ahh them's were the days.. :p lmao

If it's as easy as you describe i'll give it a go myself on the rods. What other areas of the bottom end do you mean? Just look for similar seams and whatnot and clean them up? Of course not on mating faces. Then the whole lot will go off to be balanced.

Is shot peening worth it?
 
1 - 20 of 23 Posts
Top