6bolt/7bolt Madness!

[JdotRez]

WARNING: The story to follow is both convoluted and indicative of my own idiocy. I am already aware of this. If you, however, feel compelled to offer affirmation of the aforementioned qualities, I will understand.

So I'm building up a 7-bolt. (Yes, I know: moan, groan, blah blah crankwalk blah.) Anyway, I bought what I was told was a set of wiseco .20 over pistons and eagle rods for said 7-bolt. Long story short, the guy I bought them from lied. I, being a complete and utter dumbass, failed to recognize this until after balancing the assembly, boring the block to match the pistons and ordering new gapless rings, wrist pins, locks, and accompanying hardware. Upon attempting installation, I discovered my mistake, kicked my own ass and spent the past hour researching the most appropriate fix. Thus, I pose to you the following questions:

1: Can I simply buy a set of 1g Big Rods from the classifieds section, recycle the 21 mm wrist pins, locks, and pistons from the 1g set (yes, I know about the lower compression) and bolt them right up to my 7-bolt crank?

2: Will the diameter of the wrist pin journal of the 1g big rod match the 21 mm journal of the 1g Wiseco pistons I have (pt # 6560M855)?

3: If I do the 1g Big Rod swap, can I use the set of 7-bolt rod bearings I ordered or will I need to order a new set?

4: If I buy a new set of 1g Big Rods, will the entire assembly need to be rebalanced or just them?

5: If I can acquire a set of 1g Big Rods for $50, what other expenses can I expect? Is there a cheaper alternative?

6: Is there a substantial detriment to using 1g pistons and big rods? i.e. those symptomatic of the lower compression ratio

NOTE: The engine in question was pulled from the car that nearly killed my brother when he was my age. This sentimental value is the only reason I have not, am not and will not consider a 6-bolt swap.

Thank you so much. While this is only my 3rd or 4th post, I have learned so much from this forum over the past year simply by searching its archives.

Jason

 

[dsmgrimreaper]

why couldn't you be normal and do a 6 bolt swap, and im not saying that because of crankwalk, there are things you can do to a 7 bolt to make it less likely to walk, but that just seems like your tieing alot of time and money in to a 7 bolt.

 

[2gAWDTalon]

why couldn't you be normal and do a 6 bolt swap, and im not saying that because of crankwalk, there are things you can do to a 7 bolt to make it less likely to walk, but that just seems like your tieing alot of time and money in to a 7 bolt.

I guess you must have missed this part of his post:
NOTE: The engine in question was pulled from the car that nearly killed my brother when he was my age. This sentimental value is the only reason I have not, am not and will not consider a 6-bolt swap.

It sounds to me like he dosent want to hear about a 6 bolt swap...
JdotRez:So what were the rods for? Are they for a 6 bolt? If so you should be able to use them in your 7 bolt...

 

[Syndicate13]

There are 2 different sets of rods and pistons for a reason. You need the set for a 7 bolt. Simple as that. 6 bolt rods can be narrowed on the piston end to fit 7 bolt pistons but the crank end is larger. I'm not sure if you could narrow them enough for use on a 7 bolt but I wouldn't want to. Sell the 6 bolt rods and buy a set of 7 bolt rods and be done.

 

[JdotRez]

This is exactly why I am so confused. It seems some contend that the swap is possible, while others imply that it isn't. Can anyone please clarify this for me?

Thanks,
Jason

 

[Syndicate13]

This is exactly why I am so confused. It seems some contend that the swap is possible, while others imply that it isn't. Can anyone please clarify this for me?

Thanks,
Jason

It's simple. The rod bearing surface are on a 7 bolt crank is smaller than a 6 bolt crank. 6 bolt rods won't fit on a 7 bolt crank. The piston end of 7 bolt rods are smaller than on 6 bolt rods, hence why 6 bolt rods have to be narrowed to accept 2G pistons. Finally the wrist pin bore is larger on a 7 bolt piston. To make everything really simple, sell what you have and buy 7 bolt parts. IMO I would not build the 7 bolt, I know you don't want to hear that but it will more than likely come back to bite you in the ass later on. *puts on flamesuit, waiting for repsonses from angry 7 bolt builders*

 

[niddydsm]

if you do build this 7 bolt make sure you get bigger rods heres a good and affordable place

Lightning Motorsports - H-Beam