factory new block, high revs = rod bolts?
factory new block, high revs = rod bolts?
(OP)
Question...
I have purchased a factory new block from overseas to replace the old us spec block in my playcar. The new configuration will be with ITB's, large cams, header, headwork, etc..
My concern is that the engine will see substantially higher RPM than the orig factory intended. I was advised to replace the rod bolts with ARP. I was then told that if I replace the rod bolts that I will need to have the rods resized at a machine shop? Is this true even though the engine is all factory new never ran? I was hoping I could take out one factory bolt..swap in the ARP while leaving the other orig tight.. then swap the other...my thought being as to not disturb anything with the bearing.
Thoughts? I've seen many *many* people over the years have problems with spun bearings on this particuler engine after rebuilds, so that was my reason for purchasing a factory new engine...but I don't want to run into issues taking the stock bolts past their limits either.
Thanks- Josh
I have purchased a factory new block from overseas to replace the old us spec block in my playcar. The new configuration will be with ITB's, large cams, header, headwork, etc..
My concern is that the engine will see substantially higher RPM than the orig factory intended. I was advised to replace the rod bolts with ARP. I was then told that if I replace the rod bolts that I will need to have the rods resized at a machine shop? Is this true even though the engine is all factory new never ran? I was hoping I could take out one factory bolt..swap in the ARP while leaving the other orig tight.. then swap the other...my thought being as to not disturb anything with the bearing.
Thoughts? I've seen many *many* people over the years have problems with spun bearings on this particuler engine after rebuilds, so that was my reason for purchasing a factory new engine...but I don't want to run into issues taking the stock bolts past their limits either.
Thanks- Josh





RE: factory new block, high revs = rod bolts?
Two strategies suggest themselves: Run it with a stock bottom end until something breaks, then replace the broken stuff with something stronger, and repeat. Or, replace rods, bolts, pins, and pistons with stronger parts before you bother to start the engine.
Cheapest way: Find some of those *many* people, and ask them what they did before, and after, their bearings spun.
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: factory new block, high revs = rod bolts?
These are for a Vw watercooled engine, and from my understanding, they just slide right in and out.
I did a search on a VW forum I frequent and here is a post about them with both sides argueing whether anything needs to be done or not, but I figured I would ask for help over here since you guys really know your stuff and are very helpful.
http://forums.vwvortex.com/zerothread?id=1571291
RE: factory new block, high revs = rod bolts?
If you fabricate a special press (kind of like a bg "C" clamp or ball joint press) with appropriate sleeves you might have better luck swapping the rod bolts while the engine is assembled. This will avoid using a hammer.
A better plan is to tear down the engine. This will allow you to inspect the components and do the job properly.
RE: factory new block, high revs = rod bolts?
Actually I have done some testing like that, and I would not change knurled bolts without resizing the rods.
I think Air cooled VDubs used to have very loose bolt>cap fits, and a certain "alignment" was part of the assembly procedure. I think it's significant that Carillo and others use dowels to locate the cap to the rod. A typical spec for a rod's bearing bore is round within 0.0002 inch. Yes, before delta wall type bearings were available it was necessary on some engines to intentionally make the rods oval to get the bearing splint line a little further from the crank. But nobody want an offset cap.It's tough to beat a round hole the correct size.
RE: factory new block, high revs = rod bolts?
Loose bolts would have some other means of alignment such as dowels, sleeves around the bolts, or cracked caps.
If you are concerned enough about the high rpm durability of the engine to replace the rod bolts, you should get all the other blueprinting operations done on the rods as well.
RE: factory new block, high revs = rod bolts?
Words to live by, IMO!
Rod
RE: factory new block, high revs = rod bolts?
Even the after market stuff can fail. All it takes is one inclusion. If the after market bolts aren't any larger diameter or stepped for stress distribution. I would live with what the factory installed. A higher hardness is not always a good thing. Do both styles have cut or rolled threads?