Arp Rod Bolts In Vauxhall 16v

[Richard Grove]

Hi,

 

I came accross this link to Lotus 7 Chat room where they are discussing the need to machine the Con Rod End Caps before fitting the heavy duty ARP rod bolts.

 

http://www.blatchat.com/t.asp?Id=43945

 

Hmmm have I got a problem. I fitted ARP Rod Bolts to my Vx engine but did not touch the End caps. Have I got a problem? Looking back at the instructions that came with the ARP bolts it does say make sure there is enough Chamfer in the End Cap to clear the radius of the Bolt.

 

In my haste to fit the new bolts I did not read the instructions properly at the time!!!!

 

Do I need to take them out and check?

 

Richard

[Guest rizla]

i think it may be prudent if nothing else it will set your mind at rest or it will be bugging you forever

[Big Jim]

I would suggest that you do check, it's only a matter of chamfering the corner of the hole, so that it clears the slight radius that's on the bolt /shank. Then make sure that you torque them up correctly.

 

Next time at least read the distructions! even if you don't follow them to the letter.

[Richard Grove]

I managed to escape to the Garage for some much needed fresh air and quiet this afternoon. Had a quick look at the sump and it should drop straight down without having to move the engine. I will remove the sump and check the bolts tomorrow.

 

Richard

[Big Jim]

Richard,

If you remove the sump, turn the engine until a pair of big-ends are 'get-at-able' take one bolt out at a time, put a bit of cloth into the bolt hole, then use a chamfer bit and just lightly chamfer the edge of the hole (mind you don't get knotted up with the cloth) hook out the cloth, refit & retorque the bolt. Do the next one, until you've done them all, spin the engine by hand, then just check the torque's again.

 

It would be better to use a manual hand operated drill rather than an electric one, or at least turn the speed right down, this will stop you taking too much out, and spining swarf all over the internals of the engine block.

[Richard Grove]

I dropped the sump this afternoon and removed an End Cap and ARP bolts. I got my Dad to check them (he's worked in engineering for 40 years) and he assured me they were fine as they were and there eas no need to chamfer the end caps as the radius of the bolt was recessed slightly at the head.

 

Getting the sump, baffle and gaskets back on was a bit fiddly but at least I won't be worrying abou it now.

 

Lesson learnt - always read the instructions properly.

 

Richard

[Big Jim]

Hmmm..........! sorry, but unless they have been done previously, I don't believe him!

 

If the bolts that you took out had threads all the way to the head, then they were the original Vauxhall bolts, and the caps will need a small chamfer putting on the hole to clear the slight radius on the ARP bolts.

 

PS, the trick to putting the sump, 2 gaskets and the windage plate on all at once, is to use around 5 or 6 very long 8mm bolts so that you can feed them through everything with it 'hanging' away from the actual engine block, then you just lift it up using these long bolts as guides.

[Richard Grove]

Darn - now you have got me worried again.

 

I guess the best thing to do would be just chamfer the caps and be done with it, but I would still like to understand why.

 

I have attached a drawing of the bolt. The shank of the bolt at B fits nicely into the End cap and is recessed slightly at A (just a few thou according to my Dad). There does not appear to be a slight radius to clear, not that we can see on the bolts we removed.

 

I guess that the theory is that when the bolts are under real stress they are designed to stretch rather than break and if there was a small radius under the bolt head it would be sitting on the un-chamferred edge of the End Cap and the stresses would not be spread equally across the head of the bolt.

 

Oh no I feel the sump coming off again.

[Big Jim]

I have attached a drawing of the bolt

The ARP bolts that I fitted were certainly NOT undercut at the fitting face like the drawing, but did have a small "blend in radius" there, (as the distructions tell you)

 

not that we can see on the bolts we removed.

The bolts that you removed originally, weren't ARP bolts, but standard Vauxhall.

 

they are designed to stretch rather than break and if there was a small radius under the bolt head it would be sitting on the un-chamferred edge of the End Cap and the stresses would not be spread equally across the head of the bolt.

You are partly correct in what you say, the bolt should sit on the full face under the head, if you don't relieve the holes, then there is a danger of the bolt sitting on the slight radius (that we are on about) thus the head isn't *down* properly, giving you incorrect torque readings as well.

 

Oh no I feel the sump coming off again.

I would! And believe me, when it's all done, and youre on the road, it'll have been worth it, just to see that rev counter hit the pin at 7,000+ rpm and know it's safe.

[Guest Simon cooper]

Hi Jim,

Do you only hit 7k. He He......Chicken !!!

I agree with all you say. Just counter sink the caps a little. Play safe.

I have seen 3 good engines throw a "Leg" out of bed and through the crank caseing through the original bolts letting go.

"Jockite" John has done it twice, bless him.

Simon

[Big Jim]

7K plus was what I said, 'cause the rev counter only goes to 7K!!!

 

Nope! I've hit the 'burble stop' (7750rpm) on numberous times in the lower gears, but I can tell you that 5½K in 5th (and it was still picking up!!) was 125 mph, and it was white knuckles on the steering wheel and arse twitching stuff. Christ knows what it will peak out at, I ran out of lane on the M6 (private bit obviously, Constable, Sir!)

The driver of the Golf GTI was upset!

 

[Guest Simon cooper]

HeHe, Sorry, miss read. lol

I chased a bike up to 125, still pulling, but thought of my licence when I saw him change up and pull away. Mind you, he did look over his shoulder and wonder "What the F*$%".

Happy New year Jim.

[Richard Grove]

I'm convinced. I will play it safe and do the counter sinking before she goes back on the road.

 

I fired the engine up for the first time this morning. WOW that felt good, it started at the first attempt and once the tapets settled down sounnded great.

 

Thanks for the advice.

 

Richard

[Guest Bazwaz]

Congratulations. I had a big smile on my face when i first fired up my engine. I couldn,t decide which was the loudest, carbs or exhaust. I may go the same route as big Jim and get a Wunoff silencer (i've got a custom chrome one at the moment). They're only a couple of miles away from where i live so it won't be too much hassle. I'm going to tax it next month so i can give it a good shake down before i venture down to Wales with the Northwest crew for the weekend.

Barry.