F7R 714, Woessner forged rods and ARP bolts problem

[robi1000]

After assembling the engine I realised that ARP bolts on the conrod foul on the oil pump drive shaft (714 has chain driven pump).









That's how deep the hole is in the bolt centre






Because I don't want to cut into oil pump driveshaft for obvious reasons, I'm thinking about lowering the ARP bolt's head for a few mm. I just not sure how this affects bolt strength.

Are there any other uprated bolts with lower head available?

[dkrevs]

Maybe it would be better if you could lower(on lathe ofcourse) bolt head from the thread side.

[snowman]

Are the heads hitting the underneath or just those 2 fins on the side?

What are those fins,are they important,if not maybe consider removing them?

[Coops]

its hitting the shaft cover itself, clearing the fins

that's a bit of a puzzler really. I wouldn't say trimming the bolts down from the top would affect their strength, but I don't really know, theres a lot of forces inside that engine acting on the big ends etc so it'd be hard to condone modifying them

is it the bolts or the rods that are the issue? have you seen if std bolts fit and if arp bolts fit with std rods?

[tutuur]

I don't know how the chain driven pump works exactly so: is there a tensioner on the vhain? If not how much play do you have?

You could try to put some bushings between block and pump which gives some more room...

[robi1000]

Ok, just to write my conclusions to make this thread helpful if someone else will have the same problem in the future...

Maybe it would be better if you could lower(on lathe ofcourse) bolt head from the thread side.

Making bolt shorter on the thread side makes no difference how high bolt head is. It would just affect clamping ability. It's possible to modify big end to make the bolt sit lower, but due to the design of Woessner rods, that's not a good idea, because there's not that much material you could take away without compromising rod strength.

its hitting the shaft cover itself, clearing the fins

that's a bit of a puzzler really. I wouldn't say trimming the bolts down from the top would affect their strength, but I don't really know, theres a lot of forces inside that engine acting on the big ends etc so it'd be hard to condone modifying them

is it the bolts or the rods that are the issue? have you seen if std bolts fit and if arp bolts fit with std rods?

It's not hitting the shaft cover, that is the shaft. So decision between thinning the oil pump drive shaft or shaving the conrod bolt head is like choosing between being shot in the face or in the back of your head. Both options have equally bad outcome.

But when I fitted original Renault bolt (6.90mm head height) it cleared the pump shaft with big gap. It's also just the near bolt, other bolt on the same conrod clears the shaft easily (ARP). Head height on ARP bolt is 10.00mm so it's much higher than original bolt. Forces act on the bolt head with angle of 45 degrees from bolt center line. That's why there can be a hole in the middle of the bolt, as that is essentially a dead material that just adds weight. So in theory by shaving the bolt down you could compromise it. But it's also true that heads are so big to have enough surface area to be able to take bigger tightentng torques compared to the OEM bolt.

I also contacted ARP factory in USA and they said I could shave the head down a bit as long as I will be careful not to heat up the bolt too much during the milling process. Also tightening the bolt should be done with more care, since there will be less surface area for the socket to transfer the torque to the bolt.

I will shave the bolt between 1-2mm, will have to do some precise measurements so I can take away as little as possible.

So remember... Woessner rods, F7R 714 and ARP bolts (not just ARP 2000, all their bolt designs have roughly the same bolt head) are a big no no, unless you are prepared to do some modifications...

Thanks for reading! :D

[robi1000]

Also forgot to mention that OEM rods are 2mm lower than Woessner rods, so ARP bolts would probably clear the pump with OEM conrods.

[dkrevs]

That's how I meant:

If the manifacturer says that it's ok to remove the top of the bolt head a little, well probably then there is no easier option really.

[snowman]

I would suggest that you use a linisher rather than a miller,less chance of catching and bending the bolt

[sideways danny]

I would buy new bolts, but I've told you that