Iv been looking into rebuild kits for 7.3l idi most kits I see are for 83-94 7.3l idi except turbo model. As far as I know the only difference is the wrist pin size, is there any other difference? I have an 88 non turbo good rebuild motor and a 93 turbo motor with a window in the oil pan. I was going to use the 88 to replace the 93 and use the turbo set-up on it. Is there any (better) parts on the 93 turbo motor than the 88 n/a. I also have access to a 94 7.3l n/a motor, any better parts there. (I know your going to say how can it be a 94 n/a, it's from a ambulance so it was a E-350 c&c.) all opinions welcome please.
Turbo vs. na
- Thread starter racin460
- Start date
That 88 will be fine ,especially if you can get the .010 topped pistons. Save the good rods out of the turbo engine. Although I have seen many more factory turbo blocks windowed than turbo conversions. Wonder why that is.
racer30
Full Access Member
I think I know why....all three of the turbo engines I have taken apart have had rod bearing failure. The rods are 120grams heavier, the rist pins are 110 grams heavier. My engines pistons where 8 grams out of balance. The rods where about 6 grams out. 7 grams out of balance 4" from crank center at 4000 RPM is 28 lbs of force. It may not sound important to some poeple but balancing a engine is verry important for longevity. When they changed the design of the engine to have heavier guts I dont think they thought it through all the way. Having 230 grams more weight on the same size rod bearing added with a little oil change neglect and low RPM lugging adds up to a windowed block. Thats why I stayed with NA rods and then lightened them 100 grams.
icanfixall
Official GMM hand model
The above is basically the truth but let me add this. Never heard of any differant rod bearings for a turbo application. Might be because the turbo rod bearings are the only ones available tody. Less parts to stock. The turbo engine had a better oil cooler bundle with more fins per inch. Now thats all we can find. Same thing about stocking only one part on the shelves makes for less inventory stock. True the rods in the turbo engine are 33mm pins where the non turbo engine pins are 28mm so pistons are differant too. The turbo engine got inconel exhaust valves where the non turbo engine did not. Still they will fit any head turbo or not. The turbo block has the 1/4 inch drilled and tapped oil galley ports where the non turbo engines had the 1/8 inch oil galley ports. Now is any 94 engine be it turbo or not going to be a turbo application less the turbo... I really can't tell you that. Only opening up the bottom end and looking at the pin size can you really know if thats got turbo rods in it. About the inconel valves... I can't indetify those for you. They are really tuff to tell apart from non inconel valves.. Its a trust thing when buying them or looking at them. I do know my oem 89 engine ran fine for hundreds of thousands of miles being a non turbo engine with a Banks sidewinder turbo on it. Now pin damage or valve damage either. Just wore it out is all.
racer30
Full Access Member
Yes, I said the same size rod bearing. The 7.3 PSD got wider rod bearings giving it more surface area for the heavier rods and pins allthough the psd has a depression in the piston top for the fuel to spray into witch I'm sure made the piston lighter. My point was someone at Ford or international got the bright Idea to put a heavier rod and rist pin into the mix and didn't do anything to the bearing size. Just my thoughts on the weight of the rotating assembly being partly responsible for IDIT's having more rod problems than NA engines. This is because I have personaly seen three Turbo engines that lost rod bearings and None of the NA engines I disasembled had any rod bearing problems. Just my 2 cents..
icanfixall
Official GMM hand model
I really can't explain why the turbo engines you have seen apart all that rod bearing issues. I don't dought what you saw and I believe what you saw.. Its just the reasoning that got me wondering. I will do some research and post what if anything I find. I'm on a quest now for information.. Its a good quest...
racer30
Full Access Member
Well it just the fact that the rod and pin combo adds 230 grams more weight swinging on the same rod bearing size will put more stress than the bearing than a NA rod and pin combo. I'm not saying there bad or anything I'm just pointing out what I have seen and giving my opinion on what I have seen. I Know there is alot more to it than just the added weight the added compression from boost and more powerful thrust down on the piston from a little more fuel. I have seen 750 HP 550 torq on a rod that was 600 grams spinning at 8200 rpm with even smaller bearings so its not a easy question to answer. It just shows how important it is to balance your engine. Like I said before when I measured my engines parts I was 8 grams out on the pistons and 6 on the rods so I know it was out of balance. I had my stuff balanced to inside 1 gram and sent out the crank and my guy got it to .4 on the front and .8 on the rear Thats got to be better than it was so I'm pretty happy.
icanfixall
Official GMM hand model
Years ago I had what I felt was an issue with my new mahle pistons. They were so far out of weight balance between the 8 I was told it could not be fixed. So I called and talked to a mahle engineer named Eric about it. His beliefs were we couls run as far a 14 grams out of balance and not have any issues because we only turn 3600 to 3800 rpm...
Well I had to raise the BS flag on that one no matter who and what degrees he had. I sent back my set and they hand picked my new set off the production line. Then I balanced those 8 pistons till the differance between any one piston in the set was between 1/4 and 1/3 gram. Then al htis was sent to the balancer and spun balanced. Like I have posted before. You can hear my engine running but you can't astually feel it running. Thats a really odd sensation too.. Each cylinder must be the same right down to making the same hp. If compression is down on any cylinder then that cylinder wil not be making the same hp as the others. That will create a balance problem along the crank. It will become a vibration that ruins the hp and torque out the end of the crank. To get the best power from an engine all cylinders must be producing the same hp. We probably can't feel the slight differances but think of it this way. Kill one cylinder and have the engine drag that cylinder along with the other 7. Thats a feeling to the most extreme. We want the same power pulses from eash cylinder for smoothness. Years ago I worked on stationary 727 jet engines at a power plant. We called them paeker power because they got used only when we needed an extra 180 meggwatts. Those Pratt Whitney engine spun around 8800 rpm. The burners were very sensative too. If just ont burner was out it sencing would see that ahd shut it down. The hot side of the power section turbine blades needed to stay the same temps. If a burned was out that would drop the temps for a micro seconds. then as the blades moved on they wiould heat up and cool down. This was creating cracks from the excursions of 50 degrees up and down. Times 8800 times per minute. Blades would throw and ruin a nice engines plus it was really dangerous working around them too... Power pulses in the crank needs to be constant for best power and smoothness...
Well I had to raise the BS flag on that one no matter who and what degrees he had. I sent back my set and they hand picked my new set off the production line. Then I balanced those 8 pistons till the differance between any one piston in the set was between 1/4 and 1/3 gram. Then al htis was sent to the balancer and spun balanced. Like I have posted before. You can hear my engine running but you can't astually feel it running. Thats a really odd sensation too.. Each cylinder must be the same right down to making the same hp. If compression is down on any cylinder then that cylinder wil not be making the same hp as the others. That will create a balance problem along the crank. It will become a vibration that ruins the hp and torque out the end of the crank. To get the best power from an engine all cylinders must be producing the same hp. We probably can't feel the slight differances but think of it this way. Kill one cylinder and have the engine drag that cylinder along with the other 7. Thats a feeling to the most extreme. We want the same power pulses from eash cylinder for smoothness. Years ago I worked on stationary 727 jet engines at a power plant. We called them paeker power because they got used only when we needed an extra 180 meggwatts. Those Pratt Whitney engine spun around 8800 rpm. The burners were very sensative too. If just ont burner was out it sencing would see that ahd shut it down. The hot side of the power section turbine blades needed to stay the same temps. If a burned was out that would drop the temps for a micro seconds. then as the blades moved on they wiould heat up and cool down. This was creating cracks from the excursions of 50 degrees up and down. Times 8800 times per minute. Blades would throw and ruin a nice engines plus it was really dangerous working around them too... Power pulses in the crank needs to be constant for best power and smoothness...
racer30
Full Access Member
I totaly agree balance of power output per cylinder is dificult but not imposible. All you can do is try to be consistant on anything you do to your powerplant so that it is has the best chance of having even power distribution. I once had a rod break on my sprint car engine while racing, It broke at the base of the rod beem leaving the piston and most of the rod at TDC and the engine still ran with one hell of a out of balance shake you could feel in the seat. I dropped to the bottom of the track and drove half a lap on the apron then enterd the pits drove to my pit stall and the engine shot its guts out in my pit stall with a verry expensive Crunch..Bang..Pow..Smoking Mess...
I know at least one of racers turbo engines had a spun rod bearing , he got it from me, and I never thought about the heavier parts, makes perfect sense. also I bet the turbos and other things were eating oil so it got low,hot and thin, a disastrous combination.
racer30
Full Access Member
Ya that engine had three spun bearings and ran long enuff to throw a bunch of metal onto the cylinders scratching four center cylinders pretty bad. The heads have worn exhaust guides as well. It will make a good rebuild for my future Truck, HOPE.. HOPE.. I found another block that had good bores for my MH build. I am having some trouble finding a cam bearing install tool to rent in my local area so assembly is held up till I can find one. I have modifyed the oil pressure regulator in my Van style cooler head. ( Industrial engine mounts give me room for it) So I hope to get 10 psi more oil pressure to keep things cool and lubed. Thats another reason why Im changing the cam bearings.
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icanfixall
Official GMM hand model
How much shims did you add to the oil pressure regulater spring... I fabricated stainless steel shims to equal 70 thousands. Cols engine I see 75 lbs at about 1800 rpm all the time...
I sometimes feel that too much because I never checked what the filter bypass spring opens at. Still unfiltered oil is better than no oil on startup.
I sometimes feel that too much because I never checked what the filter bypass spring opens at. Still unfiltered oil is better than no oil on startup.
Knuckledragger
blowing chunks and grabbing porcelain
I have read this thread with some interest. Although the rod bearings will be affected by the extra weight of the wrist pin and heavier rod, I would suppose that damage is more likely done by the imbalance than extra weight. Like you said, 8 or 10 grams being thrown around is a lot to be dealt with dynamically. My engine is probably not as smooth as Gary's, but I notice just how smooth it runs on the road, unlike a former truck with a factory engine and no special internal balancing.
Racer30, did you remove the forging lugs to lighten your rods? I have been thinking about doing that to a set.
Racer30, did you remove the forging lugs to lighten your rods? I have been thinking about doing that to a set.
racer30
Full Access Member
I Have two shims that I was thinking of using, ( havent staked the regulator back into the head yet) .034 stainles washer and a .020 brass shim. I was thinking .034 would be enuff but if you used .070 to get 75psi then I might change my mind...I will be running a turbo as well as a air compressor for my air brake system on the MH and I don't want to be low on Oil pressure...I measured all the springs from the three oil regulators I took apart and the lowest miles unit was .026 longer than the other two... so I'm using the longest spring and a shim to be on the safe side. On the rods I removed .220 off the .550 thick cap end then rounded as needed to balance the big end it was about 80 grams removed. Then I removed 20 grams off the little end by reducing the size of the balance block and smothing out the casting flash. Then balanced them to about .5 gram each total weight. ( And thats not easy) I have pics of everything I have done on my engine up on a flickr page along with coments on each pic. I will be posting the site when I'm closer to putting the engine in the MH so I can update in real time as the swap is done. It has taken me Far longer to do this swap than I had planed. I just put a bid in on a cam Install tool on ebay so now I have to watch that too. One day at a time.....
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Got a buddy with one if you were closer, I am going to machine one just for these cam bearings.
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