re use arp rod bolts?
 

so im at another cross roads. bought a set of shot peened rods including some 400 mile old arp rod bolts from strokher (eric hood) which LOOK fine but........im soooooo paranoid! especially after speaking to the blokes at arp! should i just bin them and buy new or are the arp guys being overly cautious?


Andy

Andy

If the guy you bought these rods from carefully measured the rod bolt lengths before he torqued them, and wrote the measurements down so you can figure out which bolt goes with which length, then you can just remeasure them (untorqued) and note how much longer each one now is. ARP should give you a spec as to how much residual stretch is acceptable for re-use.

If they are a bit over that, well maybe they would be good bolts for a stock street engine (really good steel in those bolts), but I doubt you'd find many guys willing to re-use in a race motor.

Walt Fricke

cheers walt, i don't have any data for the bolts before they were installed the first time round and the motor is going to be a turbo monster so im thinking i should not bother using th

For a Turbo Monster I would not reuse rod bolts from any manufacturer.

yep, thats my view now. im about to buy a set plus a stretch gauge and be done with it.

Anyone know the cheapest place for arp stuff?

Sounds a bit exciting, Andy!

what is it to be then?..spill the beans!

And I'm sure I have a home for those bolts if you toss them..I have the facility to check them well enough for a road motor at least..

Regards
David

David Im building a 3.3 turbo. ingredients are as follows

ARP (new!) rod bolts, shot peened 930 rods, je 8.5-1 pistons shimmed to 8-1, refurbed and flame ringed 3.2 carrera twin plugged heads with ss valves, 964 cams, 3.2 intake, sds efi (easy) 1 bar, full bay intercooler (if the ducktail gets in the way ill just keep removing more and more of it till it fits!) some sort of headers (not sure yet) some sort of turbo (not sure yet, maybe k27hf2) and not a lot of silencing. im hoping for 500 reliable horses.

ill have a think about the used rod bolts too!

Oh my!

Very very guick...

I'm not familiar with the efi you plan..if I was giving advice I;d advise Megasqurt for this app every time..mainly for the excellent support available..

I have a pair of 954 cans here if you need them...

Good Luck!
David

Andy,
Before you go with shimmng to reduce the compression I would do a search on "deck height". The general consensus is that you don't want to run more than 1mm (.04") of deck height because it will increase the chance of detonation starting in the resulting pocket at the edge of the piston.
Sounds like fun.
-Chris

fair point chris. im going to put the engine together without shimming and measure my deck height/comp. hopefully i can shim enough to reduce the comp without compromising the safety of the engine. plus im trying to build in as many detonation reducing features as I can i.e twin plugging and efi and not too much boost and big intercooler.

Andy,
You can trim a little off the piston to reduce the compression.
-Chris

Do you already have the pistons? you can flat top the JE's to reduce the compession. I would go that route instead of shimming.

Andy,

I think I missed something somewhere. What did you learn that made you nervous about re-using ARP rod bolts? Everything I've read, and everyone I've talked to, says this is not only appropriate, but it's one of the many advantages of ARPs -- you buy one set and that's the last set you'll ever need. Not only that, ARP even recommends that they be torqued to spec a number of times (either 3 or 5 times) before final assembly, ostensibly to burnish the surfaces and stabilize stretch values for a given torque.

The reason I'm interested is that I just went through this and blissfully re-used the ARP bolts on my 930 (ARP bolts, model 204-6005). The bolts had one previous use, with 660 miles on them. I re-used them on my new build, and tightened them using both a stretch gauge and a torque wrench. When they reached the stretch spec, all six were at 41 ft-lb (spec is 35 ft-lb for these bolts). This checks with Chis Bennet's observations (in another thread) that ARP's published torque specs tend to "under stretch" the bolts to some degree.

I don't think you should have any concerns whatsoever in re-using those bolts. Or do I have that backwards: should *I* now be concerned?

I think with a stretch guage and if you have prior values you are ok. if you bought a set used and do not know what the prior values were - it can be kind of a pot luck... not somewhere I personally would take a chance...

Jeremy, I see the point you're making -- there could have been some abuse in the past. That's good caution in general. But one of the nice things about these used bolts is that Andy knows where they came from: Eric Hood. Eric is very meticulous and particular. Furthermore, I would suspect (and I'm sure Eric would be able to confirm my hunch), that Stephen Kaspar of Imagine Auto was the guy (the only guy) who has ever torqued those bolts. And he's an exceptionally capable and trusted engine builder. The history of Andy's bolts is traceable to some very qualified hands. If it were me building Andy's engine, I might give Eric or Stephen a call or email to confirm the history of those bolts and maybe I'd check their current unstretched length (looking for consistency). Then I'd torque them using a stretch gauge along with the a torque wrench. If I found consistent torque levels at the specified stretch, just like I saw in mine, and I'd call it good and never look back. As critical as those fasteners are, I think that a little homework could verify their history, condition, and serviceability. I think it is possible to get carried away with paranoia...

Hi Rob, very good point. I think you are right when you talk about paranoia. im so paranoid about every area in this build now, mainly down to the fact that its eaten so much money already. im of the mentality now that i just have to do everything. having said that, you are correct about the credibility of the bolts so i think that maybe this is an area that i could save a few quid by just having a quick word with Stephen. he is a very helpful guy. ill let you know the outcome.
P.S. hows did your bottom end go? ive just finished installing my bigger squirters (update on the thread to follow) which went ok...........i spose....!

Rob - I agree with you there = I have a set of cylinders from Eric that I plan on using with 100% confidence. Again if you know (or they know) what the the initial values were and if they were assembled with a stretch guage the first time then OK, especially by someone as competent as Stephen Kaspar. This is what I was told by ARP.

Now - that said - would I make a $200 cut on what I would consider is the one of the most important engine components?

Andy,

I hear you on this:

"im so paranoid about every area in this build now, mainly down to the fact that its eaten so much money already. im of the mentality now that i just have to do everything."

I feel like I'm sort of in the same boat. I'm not sure I'd call myself paranoid, but I'm so deep into it now, it's more the "while I'm at it I might as well do ________" mentality. But I'm always looking for a reality check too, and a place to shift hard earned money to a cause that will actually do me some good. I admit that in my build, I've spent where spending probably wasn't necessary.

In fact, just yesterday I bought new rings for my Mahle 3.4 7.5:1 pistons that have 660 miles on them. That's the subject of another thread somewhere. I probably could have re-used them; I may be overly conservative here, but I don't want to risk, after all this work, that my rings wouldn't seat. Then comes the "do I hone the cylinders" question. Again, more threads, including some long ones, as well as a dozen expert opinions, all of them different. The outcome: I'm going to use scotch brite on them, by hand.

But I'd be pretty confident in those rod bolts. The good news is that when you torque them up, you'll have a sense of their consistency, so you'll be in a position to make a final judgement at that time. In fact, you might as well torque them up on the bench right now, as an exploratory/practice run.

My 930 engine is slowly coming together. The bottom end is done. My machinist found one rod journal was slightly undersize (0.0005 in), so he custom fit one of the rods to the crank, using std/std bearings. I'd never seen that done -- very interesting process. Now all the clearances are .0025 in, for all journals, mains and rods. The heads are done and looking beautiful. They are based on 930 heads, but they now have 52.5 mm intake valves (stainless), 42.5 mm exhaust valves (inconel) that are lighter than stock and have 8 mm valve stems instead of 9 mm. The valves alone make a huge difference to airflow. But the porting is incredible. Runner to runner flows are very healthy and consistent, at +/- 1 cfm through the heads and manifolds (either separately or when the manifolds are bolted to the heads). I'm going with GT2 Evo cams. Next step for me is setting deck height, then piston-to-valve clearance. But I'm considering cc'ing the heads and piston domes as well, prior to any of that. So, it's coming, but at my rate, it will still be weeks before I'm done with the mechanical build.

Good luck to you on your build.

Rob

Hey Rob - I'm right there with you too... it's such a large grey area - where do you draw the line. You have to draw it somewhere (or I'll end up living in my car)

The good part is once it's done you can get a sense of pride on how it's done - and the self satisfaction that it was done right.