I have read that the pistons in a v8 350 are the same size as the iron duke has any one don this and can give me advice on it . thanks

I heard that they were the same if from a 300...all GM did (supposedly) was chop the 300 in half...hence 151 CI...i'm not sure though...i aslo heard that you can use the roller rockers from a 300

Fieroman

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A.I.M: FieroMan500
ICQ: 146262049

300?

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Raydar

From the Department of Redundancy Department.

Actually, I think it's the 302 or 305 V8... a.k.a. 5.0 liter. I believe the engines (5.0 and 2.5) have the same bore and stroke. Not sure about the location/size of the connecting rod pins, though.

[This message has been edited by Blacktree (edited 01-16-2002).]

Modfi,I sent you an Email, Im copying it here and adding alittle to it: They are not the same size because the pin height is alittle different, about an 1/8th inch. But the bore, and pin diameter are the same. if you can find 4 2.5 rods that are about .125" shorter, you can most likley use the 350 pistons, or you can get a set of 350 pistons that have the same pin height, I am looking into doing this to my Indy's 2.5 since I found that the side skirts on the 2.5's pistons are too short and cause the piston to slap the CYL wall, another thing you can look into is the rods, the early small blocks (1967 or older) use a 2" rod journal just like the 2.5 and there may be a possibility of that rod fitting, and if it does, that will open up some rod options. Just keep in mind that this is only an Iron duke 2.5, nothing special or high performance about it. But you can improve its reliability and or durability. Yes, the Iron duke is the exact same size as a 302, both the bore and stroke are the same, If they made them before 1967,(I dont know for sure) than the internals MIGHT not need any modification to fit right in. I know for sure the deck height on the Iron duke and a chevy 350 is the same, and probably is on all the small blocks, so if you can match the crank pins, and width too, then have a 4" bore, in theory it will work.

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Matt D
1984 Indy Fiero (auto)
1985 2m4 V6 DIS 3.1 Auto

thanks every one for the info

Don't know anything bout which pistons but I do know that the 350 rockers will fit. they work good too, I just had to check them to make sure at every oil change (hmm that was once before the car went bye bye )

I'm having to bore a 2.5 30 over due to cylinder wall scarring, so I'm ordering a set of oversized hyperuetic(sp) pistons for it. Also trying to find a head that I can dremel(sp) out the oil flow on to match my grand am's head.

The 302 was basically a bored 283. It had a 4" bore and a 3" stroke. It was only in production for 2 years, and only offered in the Camaro with the Z/28 option. All of these had steel cranks (as did 283s). I do not know what the center to center rod length was, but the 327 and 350 have a rod length of 5.7". All 350 rods are large journal, but 327 (pre '69) and smaller SBCs had the small journal rods.

If you run across ANY original SBC 302 parts, don't waste them on a Duke. Sell them to some Camaro nut for gobs of cash (very rare) and do an engine swap.

Just my thoughts...

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Timothy E. Smith
1986 SE V6
1984 Coupe
1996 Ford Probe GT
1999 Chevrolet Silverado Z71
1975 Chevrolet ElCamino SS

[This message has been edited by tesmith66 (edited 01-17-2002).]

the fiero rod length is where the difference is between the small block chev and the 2.5. fiero uses 6.057 inch rod, so pin height will be quite a bit different than small block chev piston.

Well, fieroman 5000 wins the prize. It's actually a 301 pontiac engine, used from 1977 to 1981 in Bonnevilles, Lemans, GP, Firebirds, RWD Phoenix. The pistons and rods are exactly the same in the 301 as in the 151. Hope this helps. Btw, nothing from the 305/350 will work on this engine.

Phil

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GTDude 87 Fiero GT 3.4
25 years GM experience

[This message has been edited by GTDude (edited 01-17-2002).]

SO if this 2.5L is the same as a pontiac 301, can the rocker arms fro a 301 fit a Duke? The Duke stock ratio is 1.75:1 ('84). I would like to change to a 1.70 ratio to move the power band and torque to a lower RPM. Will this work. Also I belive the BBC rockers fit but the head must be modifird to accept studs and longer push rods are than nessesary. What is trouth?

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Peace and Happiness
Frank and his fotoflash, an '84 SE
Member NIFE

quote Originally posted by Blacktree: Actually, I think it's the 302 or 305 V8... a.k.a. 5.0 liter. I believe the engines (5.0 and 2.5) have the same bore and stroke. Not sure about the location/size of the connecting rod pins, though. [This message has been edited by Blacktree (edited 01-16-2002).]

Actually it would be a 305, the 302 is a ford engine.

quote Originally posted by roadwarrior: Actually it would be a 305, the 302 is a ford engine.

Yes 302 is a ford engine but chevy also made a 302 this is way ford came out with the 302 boss to be able to stay up with the chevy 302

Be careful when changing heads on a 2.5...they made several diff types from 84 thru 88......and they are not interchangable. Some are thicker...some thinner...some bolt holes diff. But a 301 rocker arm will work on any of them. They have several diff length pushrods too.

Phil

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GTDude 87 Fiero GT 3.4
25 years GM experience

quote Originally posted by GTDude: Be careful when changing heads on a 2.5...they made several diff types from 84 thru 88......and they are not interchangable. Some are thicker...some thinner...some bolt holes diff. But a 301 rocker arm will work on any of them. They have several diff length pushrods too. Phil

I plan on useing the same head just going to do a mild porting and CC it and having it rebuilt

What is the stock rocker ratio for a Pontiac 301?

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Peace and Happiness
Frank and his fotoflash, an '84 SE
Member NIFE

I have my 2.5 completly stripped down to just the block, Visually, I can see no real strength issues with the block, It has a solid wall of cast iron in between each of the 4 different sections of the crank and looks like it could handle some good horsepower, The main caps are all 2 bolt, and there is 1 on each side of each cylender supported by the wall, This combination usually means that the block can take some serious power. This engine's layout is one that is best suited for a hell of alot of power. It is simular to 4G63's and other high performance engines. However I noticed the one quality this engine does not have, There is only 1 counterweight per cylender. This is ok for the application that this engine is intended for. But when you have 1 counterweight pulling on only one side of the crank it will cause alittle flex, the engine is not really in a balance, and will fail at high rpms. I am just curious if a new crank with 2 counterweights on each side of the crank will lighten some of the loads on the crank and bearings and open this motor up to some performance possibilities. (the SD4 has this crank that Im describing)I just wonder what you think about this. Or is there some other reason that this engines block just can't make any good power (150 - 200 horses)I know what a superduty block looks like. I have seen the extra webbing and reinforsements that they have put on it. The SD4 can make 400HP or so. But without all the reinforcements, is it still ONLY strong enough to make maybe 120 horses reliably?

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Matt D
1984 Indy Fiero (auto)
1985 2m4 V6 DIS 3.1 Auto

Both the SBC and Chevy II 4 cyl (153) were designed from the Chevy I6. In the 70s GM needed another 4 cyl. Pontiac took the old Chevy II I4 and revised it. Many parts from a Chevy II engine will still fit a Pontiac 151. Regardless of what some one tells you it is not 1/2 a v8, although you can look at it this way when planning mods. As far as 301 parts enterchanging, GM probably used some of the existing I4 parts to cut cost. The 301 may even be designed after the I4.

Actually the 151 isn't half the 301...just a simple way to explain it. Almost all of the parts from 301 will work in a 151. And the 151 has no connection to the chevy 153 whatsoever.

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GTDude 87 Fiero GT 3.4
25 years GM experience

It is a popular misconception that the Pontiac 151 and Chevy 153 have nothing in common, but it is just not true. Pontiac made significant changes to the engine, however many of the features from the 153 are still there.

Erik-

quote Originally posted by GTDude: Actually the 151 isn't half the 301...just a simple way to explain it. Almost all of the parts from 301 will work in a 151. And the 151 has no connection to the chevy 153 whatsoever.

The 151 and 153 are more closly a like than people thank. This is off one of GMs parts sites

347056
Four Cylinder Performance Head
$354

This cast-iron performance head is designed to be used on 151ci or 153ci four-cylinder engines.