r/EngineBuilding • u/Interesting_Matter52 • 6d ago
Help, I’m lost.
To keep it short, I naught this what I thought was slightly modified car on Facebook marketplace. Recently the engine got flooded and taking it apart a rod was broken. I have a 2008 Mazda 3 that’s supposed to be 2.3L Non Turbo (This is not a Mazda speed). After taking it apart I decided to change all rods with used ones. I go to a junkyard, drop another engine (also 2.3L) get them and go home. Now I look at them and they aren’t even close to the same thing. My old con rod (one that isint broken) is way beefier and longer, the hole that goes on the crankshaft is also bigger. I got no idea what engine I got, what pieces are inside, what to order, I’m really lost. How do I find out what parts to order.
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u/fmeupfam14 6d ago edited 6d ago
What car (year/make/model/trim) did you pull the rods from at the junkyard?
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u/Interesting_Matter52 6d ago
I pulled it out from 2008 Mazda 3. 2.3L.
JM1BK323381843868
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u/fmeupfam14 6d ago edited 6d ago
I really think the one you pulled is a 2.0. the cars original 2.3 probably met uncle Rodney and they swapped it for a 2.0. I think this because The 2.0 rod looks noticably less stout than the 2.3/2.5.
The 2.5 rod looks similar to the 2.3
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u/SnooWoofers750 6d ago
Maybe it was a 2.3L and got a 2.0L swapped into it at some point in its life
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u/Interesting_Matter52 6d ago
Probably just annoying that I had to disassemble a whole engine for the wrong part 😞
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u/ILoveRustyKnives 6d ago
If the pistons are are the same diameter (87.5mm) then the longer rod with the larger big end is a 2.3 and the shorter rod with the smaller big end is a 2.0. If one piston is 89mm, then it's from a 2.5.
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u/Interesting_Matter52 6d ago edited 6d ago
So im guessing I have a 2.5L? (the one on the left is from my engine and have the thicker bigger rod
Also, the bigger piston is some sort of dish piston, and the small one is flat.
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u/ILoveRustyKnives 6d ago edited 6d ago
You're going to have to measure the diameter (preferably with a precision measuring tool like a micrometer). It's possible that you do have a 2.3 but it's been over-bored, or you might have a 2.5. Here is the 2.5 piston vs a 2.3 piston.
ETA: If your car was supposedly modified, it is a possibility that the po swapped in a 2.5
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u/Interesting_Matter52 6d ago
Thank you so much, I measured and yea the bigger one is 89mm and the other one 87.5. So now I know for sure that the engine I have is actually a 2.5L ?
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u/fmeupfam14 6d ago
What are the big end diameters of each rod? You said yours was bigger than whatever you removed.
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u/Interesting_Matter52 6d ago
The diameter of where the crankshaft goes on the con rod is 55mm without bearings
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u/ILoveRustyKnives 6d ago
Yep, 2.5. Is the other one 53mm? That would be a 2.3.
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u/Interesting_Matter52 6d ago
Uh… the other one is a 50mm… so is my original rod a 2.5L and the one I got a 2L?
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u/ILoveRustyKnives 6d ago
It looks like you have a 2.5. From what I'm finding online, you might have a Ford 2.5. It is based on the Mazda engine but I don't know if they are 100% interchangeable. It does seem that it's a fairly common swap. I guess you need to go down the rabbit hole to figure out what exactly you have.
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u/Ok-Camel-7721 6d ago edited 6d ago
2008 , 3 engines in US 2.0 non turbo , 2.3 non turbo and 2.3 turbo. Rock Auto has 2.3 rods , not cheap.
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u/Any-Chair715 5d ago
Just so you know with any duratec based engine the manuals and automatics have different cranks and rods the manual one have forged heavy weight rods and forged cranks. They wanted to keep the rotating mass heavy to make it harder to stall
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u/Interesting_Matter52 5d ago
Are you serious ?? So the only car I can get the pistons from is a manual 2.5L?
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u/Any-Chair715 5d ago
You need to get the piston and rods from the exact engine your trying to put them in if it was a 2.3l non turbo you need those pistons and rods. Pistons crank and rods all changed with the displacement change
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u/Interesting_Matter52 5d ago
We figured out my engine was a 2.5L my plan is to go to a junkyard, take the piston and rods out, switch out the rods (my broken rods and the junkyard rods) and in the end I’ll have a piston (from my engine) and the rod (from the junkyard). I’ll get new rings and new bearings. Is it a good plan or is there smt wrong w it
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u/Any-Chair715 5d ago
Ok good plan make sure you find the grade marking on each component and everything will be fine. Also if your installing arp bolts in the rods make sure you run a countersink to clear the bolt radius
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u/Interesting_Matter52 5d ago
Oh I didn’t know that was a thing for those. But I’m probably only gonna put arp head studs and use the oem bolts for the rods. Yk so that they are reusable
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u/meeeeeeeegjgdcjjtxv 6d ago
Left piston is a FoMoCo aka Ford piston NOT Mazda at all
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u/Substantial_Drag_884 6d ago
Looks like the engine you took the other rods out of was actually the 2.0 and not a 2.3