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| Edjumacate me on the 2.8-3.4 (Page 1/3) |
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shemdogg
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APR 23, 11:42 AM
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Are they the same block w diff pistons n heads or a totally different motor. Tried some google searches, but everything was coming up for the 3.4dohc. I taking a motor to get assembled and am wondering if I should beef the motor out a bit. I have emissions to pass, so its gotta stay relatively stock. I know some folks on here have the 3.4. Looking for idears n knowledge pwease 
shem
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BillS
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APR 23, 12:58 PM
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The 3.4 is a stroked engine (longer stroke, same as the 3.1) with larger bores and still with cast iron heads. The following generation switched to better flowing alloy heads.
This is an original generation 3.4 installed in an old British car of mine.
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cvxjet
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APR 23, 02:31 PM
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The original 2.8 was expanded to 3.4 liters....The ones in the F-bodies are the same as our Fiero 2.8 and (Basically) interchangeable....Later, GM updated the engine with wonderful aluminum splayed-valve heads...These are not directly interchangeable with the Fiero engine; Our intake manifold will not mount to these aluminum heads because the intake ports are completely different.
I swapped in an F-body 3.4 back in 1999....And it has passed smog tests ever since....Although it has killed a CAT- but that may have just been a ICM or such going bad (The engine started running bad in 2012, so I started replacing parts before finding which one was bad- never very distinctive... but it did start running properly)
I am passing smog tests just north of you a bit in the east bay.
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FormulaGT
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APR 23, 09:39 PM
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shemdogg
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APR 23, 09:52 PM
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Thanks for all the replies fellas! So I have a brand new crate 2.8 shortblock( side of crate still attached) w no cam, and the old 2.8 that came w the car to the machine shop tomorrow. I guess what im getting at is could the shop just bore it to 3.4 and change the pistons? Or does the 3.4 have a different crank, rods, n heads? What would you do in situation? Not trying to go crazy power here, but an extra 20-40 hp would be nice
ty ty
shem
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Patrick
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APR 23, 10:17 PM
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| quote | Originally posted by shemdogg:
I have a brand new crate 2.8 shortblock... and the old 2.8 that came w the car to the machine shop tomorrow.
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There will be members here who know a lot more about this than me... but as of '88, the 2.8 had improved lubrication compared to the earlier 2.8 engines. Before putting any money into either block you've acquired, see if you can determine what versions of 2.8 you have. Odds are, that the "old " 2.8 you have is the original '88 block (which is good), and it's also possible that the 2.8 crate engine is the newer style as well. Both engines you have may be the superior style (which means you have nothing to worry about), but it would make for good peace of mind to know for sure.[This message has been edited by Patrick (edited 04-23-2023).]
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olejoedad
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APR 24, 07:54 AM
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The 3.4 has a larger bore than the 2.8, and the same stroke as the 3.1.
Heads are the same as the 2.8.
The 3.4 has the starter bolts on opposite side of the crank centerline from the 2.8.
The 3.4 uses the 88 style 2.8 oil pan / front cover interface, but the front cover is different than the '88 2.8.
The induction and exhaust are interchangeable with the 2.8 Fiero bits.
I was not aware of any new 2.8 crate engines being on the market.[This message has been edited by olejoedad (edited 04-24-2023).]
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fierofool
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APR 24, 08:52 AM
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MarkS
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APR 24, 09:31 AM
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My understanding mirrors above. Different crankshaft & pistons. Rods the same. Boring the 2.8 block to 3.4 dimensions is dicey. A 1.5mm oversize on a 3.1 piston will get you close.
ARI does do it but I'm thinking a significant amount of sonic testing on cylinder wall thickness is part of the process. They won't sell a stand alone kit for this reason I believe.
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fierosound
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APR 24, 11:57 AM
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2.8 to 3.1 to 3.4
Two different blocks, two different cranks for the 3 combinations.
2.8 - standard bore block, standard crank
3.1 - standard bore block, longer stroke crank
3.4 - larger bore block, longer stroke crank
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My World of Wheels Winners (Click on links below)
3.4L Supercharged 87 GT and Super Duty 4 Indy #163[This message has been edited by fierosound (edited 04-24-2023).]
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