For background, I am building a 550-600 hp engine for my TT and need to address the weakness of rods/rod bolts in these engines. For practicality and budget purposes, I decided to just change the rod bolts for ARPs and try to do the job myself. Never done this or anything mechanically close to it before. So I hope someone can help me with a few questions or things I should know:

1- Is it advisable to do this, i.e. changing the rod bolts without opening the case rather than a full job.
2-If it's ok, then what are some watchouts...such as having the bolt or lower part of the rod falling into the case when you loosen the nuts etc..
3- Is it advisable to change the bearings, assuming they are in good condition still (low mileage). Would changing bearings mean I would have to polish the crank or is it just a straightforward replacement
4-Torquing the nuts, what is the recommended torque level?
5- Do I need to put some oil on the bearings before assembly

To name a few things that came to mind. I would really appreciate some feedback before I get myself in unknown territory.

I can do this through a mechanic but would like to learn to do it myself.
Thanks.
Jean

 

You can do the rod bolts without opening the case. Not a problem there. But why not just split it and do new chains and bearings. You are so close and the added piece of mind is worth it.

When you loosen the nut holt the cap with a magnet and pull the big end off. Swing the cap around with the magnet and pull it out.

ALWAYS CHANGE bearings when removing them. They are far cheaper than a thrown rod.

For ARPs, tighten to 38, loosen, and tighten 3 times with their grease on the threads. You can also use the stretch method and a gauge. Set them to .0117-.0122

Use a dab of oil and coat them with a prelude like redline.

BTW if you are using 993 rods you will need to press the bolts out.

 

Stephen,

Very lucky to have your attention here..Thanks.

Just to make sure, when you say 38, what measurement scale are you using, I guess in the US you use lbs?
Might sound stupid, but do you mean I tighten to 38 , then loosen and tighten again to 38 each of the three times?

I might end up opening the whole case, just want to make sure I don't get myself in a mess..
Thanks so much for your advise.
Jean

 

Jean;

It's not prudent to pull your rods just to change the rod bolts. You need to have the rods resized. Pay a machine shop to install the rod bolts and resize the big end to factory spec. You should also install a new wrist pin bushing. These things are improtant, and need to be done by a pro. If it was my engine I'd strip it down and pull the entire rotating assy and have it balanced, crank, pulley, flywheel, pressure plate, piston/pins and rods.. And have your crank check for straightness and polished..

 

Hi Jean:

Given what kind of engine you are going to build up, Kevin's advice is very sound and I would strongly suggest you follow his advice.

You know the old saying: "If something is worth doing, its worth doing it correctly".

Personally, I would not use the OEM rods for an engine like what you are going to build. For a little bit more money over the cost of rebuilding stock rods and ARP bolts, you can get a set of Pauter Engineering 4340 rods (with ARP bolts) that are FAR stronger and are already balanced.

 

Valve springs?

 

Aasco-which is the Aase Bros... List is around $375.00 a set..

 

Certainly if it is in the budget. Consider something like EBS springs and titanium retainers to remove some mass. When using these springs I find setting the springs at 36.5 are a little better. This is almost standard in every motor I build.

 

Thank you all for your responses.

Kevin, Steve, opening the case and changing to Pauter etc.. is what I was planning to do, and I am sure it is the right way to go, I was just exploring a different angle to it by just changing the rod bolts and avoid having to rebalance the whole assembly etc.. No one does this here properly and I will need to ship it overseas, the cost is exponential. But it seems like I will have to do it.
Concerning the other mods, the rod bolts were just the beginning. All what has been mentioned above will be done. Including twin plug, rings, guides, springs, larger valves, and ARP head bolts and fasteners etc..
Great advise from all, I am really greatful.
Kevin...Stage 5?

 

Hi Jean:

I'm afraid that you are correct,...the cost IS exponential, however when you expect 550-600 reliable, durable HP from 3.6 litres, there is only one way to do something,....

 

Jean, don't waste your monies on larger valves... The gains can be picked up in other area's. With the exception that if you seats are trashed! If not replace the valves on do a nice port job on the intake tract.

 

Jean,

I can tell you it all comes down to money. Thats for sure. But as stated, do it properly and you will never be disapointed. I can say that I am very happy with the outcome of the 2 engines I have done, but I can admit the costs haunt me.

 

AMEN to that. I tell my guys, sorry only two ways. Cheap and right. You can't have both. I have tried for 20 years. I will take the right over the cheap.

 

And I also agree gentlemen! For some reason this post was interpreted like I am on a tight budget, and I am not. Do I go all out and do modifications that I don't need? Not necessarily.. There is an inherent satisfaction in doing things yourself and learning in the process, or I would have gone to an FVD 550hp "package" and sleep like a baby...of course I agree that some things must be handled by pros, and this might be one of them.
It all depends on the objective. This engine will see 0.8 Bar 95% of the times, and when it does not, it will be for a few seconds, enough to brake it? Maybe..but at 1 Bar and probably 600FWHP max, maybe not..
For insurance I decided to change rod bolts, if it was a DIY. Seems like it is not, and I will do it right. I already sent an email for a quotation on this work but have not received an answer yet, this is another issue we, living overseas, we face, we cannot call and discuss for hours, and many tuners don't like email.
Do you put a swimming pool in your house if you don't swim? Maybe but you might not need it, it sure looks nice though!
This is only intended to clarify that budget is not the only reason for trying to do things differently.
And again, thank you very much for your insight. Many of you have helped me several times and it is very appreciated.
Jean