Longer Rods w/ Stock Block & Crank

[xlr8ngn]

Anyone running longer rods with a stock block and crank? Doing some calculations, I should be able to run up to a 6.6" rod. I am considering this to take more stress off the bottom end and run a lighter piston. Will the off center stage rods drop in to do this?

 

[Chris McDade]

Why are you trying to re event the wheel. The stock rods and crank are good to low tens. I think GM did there homework before they built these motors.

 

[xlr8ngn]

I am not trying to reinvent the wheel. Please explain how a 6" rod and heavy piston is better than a 6.6" rod and lighter piston. I have a set of new TRW pistons with polished tops and balanced, but I am going to sell them because they are still pretty heavy. I also have a set of stock rods that have been lightened and beams polished. If I end up not going to a longer rod, I am at least going to buy a lighter set of pistons. Improving your stroke/rod length ratio and reducing reciprocating mass takes alot of stress off of the crank and block. I would like to consistantly run 11.0 and not have to worry that I am going to break the main webbing and drive over my crank. Everyone here has me scared to death and I guess for good reason. I will be willing to dish out a few extra bucks to make my engine more reliable.

 

[86brick]

I would get JE forged pistons (much lighter than the TRWs) and use your stock rods. Also get the billet center main caps and if you want it to be really bullet proof get a billet steel girdle. Running low 11's shouldn't be pushing it too hard at all IMO especially if the car is a bit lighter.

 

[xlr8ngn]

My 86 GN has all the options I guess. It is a heavy car. I have already put in the center main caps with studs. I have also polished all of the main webbing. I had the block baked in an oven overnight to reduce internal stress. I have considered JE pistons. If I can find the right rods, I may have them make me a set. Thanks for the reply. Other advantages to a longer rod is it slows down the piston. It will stay at TDC longer building more chamber pressure, and will help with flow on stock heads with small ports.

 

[KendallF]

One option is to use rods from a 3.0 FWD motor of 80-85 vintage. Don't get the later 3.0s, as they were short deck motors. The early 3.0 rods are 6.35" length and are cast rods very similar to the stockers (they're so similar I can't tell the difference visually unless they're side by side). I was planning this for a budget 4.1 production motor (.035" overbore, SBC 383 stroker pistons). I think I still have 5 of those rods in the garage somewhere.

 

[xlr8ngn]

Kendall, that is some really good information. Thanks for the reply. That would definitely save some money over steel or billet rods. I was talking to a friend and he has a book with rod dimensions. He said there is a pontiac rod that I believe is 6.635" long that may work. I would have to machine out the big end just a little and narrow one side for the offset. I will have to check into it a little further to see if it will work.

 

[Steve Wood]

I am not sure how far up into the rings a 6.6" rod would put the pin boss, but..a longer rod should allow you to run a little more boost for a given gasoline as well as the other reasons you have pointedf out.

I was thinking that some had used rods approaching that length made by Carillo in the past. I think cost is the main reason on stock blocks...