SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: enginedoctor on March 30, 2008, 05:01:58 PM
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1. clean/glass bead conn. rods and inspect for cracks and flaws such as stress risers which could result in failure. grind off stress risers and debur rods as needed.... detail and extensive rod work in this area can make the difference.
2. in this i will use stock lenth chevy 350/383 rods as an example: lenth...5.700.
3. check rod lenth from center to center..[center of rod eye/small rist pin end and center of big end, rod bearing end....do your math and achieve the rod lenth that you need , the purpose of this is to have all rods the same lenth .]
4. inspect the rist pin ends for proper I/D.
5. before having rods machined have new high quality rod bolt assy's installed prior to machining!
6. in this case the rod bore on the big end will be , [2.224 7/10 to 2.225 2/10].
7. you only have .000 5/10 tolerance and this is critical !!!
8. try and find a set of rods that weigh close to the same before you invest .
9. make sure that you balance the rotating and reciprocating weights of all of your parts!
10. proper sizing and pre-assy. will result in crutial oil clearances , which is an absolute must to check during pre-assy.
11. if you decide to buy a new set of rods and are going to assume that everything is correct, you are mistaken.... someone made the rods and someone machined them, wether on cnc. or conventional equipment.. double check the work. this is not being critical , just careful!!
12. this is only basic rod work stuff and it is up to the engine assembler to check the work.
next time we will go into "CRANKSHAFT WORK"....... hope this helps you guys....see-ya.
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Many shops prefer to shot abrade the rods, as glass bead is extremely difficult to completely remove from parts. Also shot abrading strengthens the rods slightly, while glass beading weakens them. If you are installing new rod bolts and nuts(and you should), oil the threads and torque and loosen, then retorque the hardware a total of 3 times before the rods are resized,this burnishes the high spots and results in more consistant torque, whether you will finally torque them or if a rod bolt stretch gauge is used. Also tell your machinist whether you will just torque the bolts or if you have a stretch gauge so he can duplicate the method that you will use during final assy. There won't be a lot of difference in the big end distortion, but there will be some. It takes no more time to do this the best way. If ARP bolts are used, use the supplied moly grease on the threads.But DO NOT use anything but motor oil on stock or stock-replacement bolts, useing moly lube on stock bolts will result in an over torque situation and failure will result. Simply weighing the rods may not help since you don't know where the weight is, two rods can weigh exactly the same amount, but have the weight distributed differently between the large and small ends. We have seen two identical weight rods be off by more than 12 grams from end to end to each other. You must also maintain .012"+ between the rods as installed to allow oil to escape from the bearings, mock-up and check this before balancing is done, and don't forget to number the rods too so you know which journals the side clearances were checked for. Aftermarket crank balancing from some companies is a JOKE!!! Most factory balanced rotating/reciprocating assys. are not usually within 12-15 grams. They don't balance the rods end to end or balance the pistons either. They just weigh one rod and one piston in the set, and then use what typical rings and bearings weigh, not yours to figure the bobweights. Did they get the light or heavy piston or rod to use to make up the bob-weights? This is why race shops charge more to balance than the factories, it takes longer to do it correctly, and time is money. A street motor lives its life typically under 2500 RPMs, a drag motor usually runs at high RPM for 10-12 seconds, not full throttle across the lake, like we do. Thats why car engine builders aren't as picky(anal) as the better boat engine builders, they don't have to be. One full throttle lake blast lasts longer than a drag motor sees all season. Sorry about the length of this post, but I have a reputation for being picky. TIMINATOR
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... Sorry about the length of this post, but I have a reputation for being picky. TIMINATOR
I should have had TIMINATOR build my engine. :banghead:
;D J/K hdriderth :D
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I should have had TIMINATOR build my engine. :banghead:
;D J/K hdriderth :D
The wife and I are going to have to hook up the boat and take a trip South and meet some of you folks. Arizona is nice and hot during the summer. LMAO!!! ;D ;D ;D San Diego is nice most all year except when it rains. 4th of July on the Sliver Strand is nice too!
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We currently have engines "visiting" from Florida(2), Missouri, Washington state, Nevada, Mexico(2), and quite a few from elsewhere in AZ. Past "visitor engines" from: Oregon, California, Texas, Alabama, Utah, New Mexico, and Colorado. Jet pumps also from a whole bunch of places too! Yours could be next! Pumps usually go by Greyhound bus (way cheaper than UPS), engines by truck. Since I am in Havasu quite often, some peeps pickup/deliver their stuff to me there, or leave it with one of my friends there. Some customers just make it a quick weekend drop off of their engine here, and return with their boat when its finished, we can just set it in for free, and they finish it at home, or we can do a quick installation. TIMINATOR
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thank 's for reading "BASIC CONN.ROD WORK'. :)
you might add that bushing rods for floating pins,rod lightening, cap and rod
chamfering,deburring @ parting lines before mating ends need to be done.
drilling for pin oiling, etc. but some of this is not basic stuff.
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Thank you engine doctor. I have 2 engines I'm working on right now, and the info you gave will help me a lot.
I'm at a point where I need to balance my pistons. How would you recommend removing/adding weight to the pistons to achieve consistency?
Thanks for all your tech talk, keep it coming.
M&M Racing
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M and M racing. i will give you a call. thanks!