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  1. #1

    3100 heads vs 3400 heads

    I wes reading up on the differences on the 3100 and the 3400 to see where the biggest differences are because i wanted to do a 3400 top end swap. I found that the bore is different. the 3100's bore is 91mm and the 3400 is 92mm, so wouldnt that make the heads not fit on the 3100 block? i didnt get as far as the intake manifold differences but are the port sizes dif? I jus was wondering before i go oout and actually spend the money on a 3400 top end and i wont be able to use it.
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

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    Re: 3100 heads vs 3400 heads

    After '00 the heads are identical. before '00 the only difference was the port size. I don't think the combustion chamber was different at all between the two.
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    Re: 3100 heads vs 3400 heads

    Quote Originally Posted by 95 BLKDOUT Drop Top
    I wes reading up on the differences on the 3100 and the 3400 to see where the biggest differences are because i wanted to do a 3400 top end swap. I found that the bore is different. the 3100's bore is 91mm and the 3400 is 92mm, so wouldnt that make the heads not fit on the 3100 block? i didnt get as far as the intake manifold differences but are the port sizes dif? I jus was wondering before i go oout and actually spend the money on a 3400 top end and i wont be able to use it.
    sounds like the engine block bore...

    the heads are cloase enough they could be interswapped... I actually took the intakes off a 3400 venture van... which had one 3400 and one 3100 head!

    I think the valves have changed size slightly??? but even then... if your engine is fine and you are just doing the topend swap the benefit of swapping the heads is not worth doing IMO, unless your existing heads will not accept roller rockers.


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    Re: 3100 heads vs 3400 heads

    FYI: the 3100 bore is 89mm and the 3400 is 92mm. The only difference between the two was the port sizes. The valves where the same, 1.50intake and 1.70exhaust ( although dont quote me on that exact sizes )
    Jay

    1994 Oldsmobile Cultass Supreme SL
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  5. #5

    Re: 3100 heads vs 3400 heads

    so could i just do the upper and lower intake and throttle body swap? or would i have to do the heads too? i dont want to waste any money and if the 3400 heads wont be worth the swap them i dont want to do it unless i really have too. Ive heard of ppl doing just the throttle body swap, and just the upper and lower intake, and gettin a small power gain so i figure if i grab the upper, lower, and TB off of a 3400 and throw it on my 3100 i should gain some power. Nad Im also lookin for the UDP but thats another thread
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

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    19Cutlass94's Avatar
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    Re: 3100 heads vs 3400 heads

    Well if you put the 3400 heads on as well, youll see more of a gain in performance than that of just the UIM,LIM,TB.
    Jay

    1994 Oldsmobile Cultass Supreme SL
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    1995 Chevy K1500 350c.i. 5spd Z71
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  7. #7

    Re: 3100 heads vs 3400 heads

    well i figured that much but im tryin to figure out the Power VS Price ratio.
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

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    Re: 3100 heads vs 3400 heads

    Then just drop in a complete 3400...
    Jay

    1994 Oldsmobile Cultass Supreme SL
    3400/Getrag 284 5spd
    1995 Chevy K1500 350c.i. 5spd Z71
    350/NV3500 5spd
    2014 Chevrolet Malibu LS
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  9. #9

    Re: 3100 heads vs 3400 heads

    well that would be th eideal thing but im tryin to save as much money as possible
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

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    Re: 3100 heads vs 3400 heads

    You can get a complete 3400 for like $500!
    Jay

    1994 Oldsmobile Cultass Supreme SL
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    1995 Chevy K1500 350c.i. 5spd Z71
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  11. #11

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    Re: 3100 heads vs 3400 heads

    I did my first 3400 topend swap for $35 plus the cost of gaskets ie $80 for high quality perma-dry. and even if you bought a $500 3400 you would want to do the gaskets before install, plus the cost of installation or time and equipment if you do it yourself.

    if your engine is fine.... do not bother changing the heads... as long as your heads can accept roller rockers.
    I will be investigating whether the non-roller rockers can be used with the 3400 topend for my 94 CS. It cannot take roller rockers. theoretically you have to grind off material from the lower intake... but how much and will the required amount for clearance leave a hole through the intake????

    My ass-dyno tells me..... enough of an increase in high end power to make a difference... I have had two hard throttle instances where I totally free-wheeled from too much power... something the 3100 could never do no matter how hard I tried!






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  12. #12

    Re: 3100 heads vs 3400 heads

    I mean im sure a 3400 swap would be beautiful, ive researched that for years now but i just dont have the time, money and patience to completly swap in a 3400, Its more to it than jus 3100 out 3400 in... not much more but it aint that simple. and the money... well im a college student, enough said. so the UIM, LIM, and TB are all i can do at this time if it will work, that was the whole purpose of this thread.

    so in order for a 3400 intake to work on my 3100, its gotta be able to accept roller rockers? OK so if my 31 didnt come with RR's (wich im not to sure about, ive heard different things about this and since ive never opened up my 3100, im not to sure) the heads would have to be swapped out?

    im goning to make a new thread about the 3100 to 3400 intake and TB swap and what will and wont work
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

  13. #13

    Re: 3100 heads vs 3400 heads

    LA1 and LG8 heads have 1.76in intake valves............L82's are only 1.72in.

    Then there are the port size differences as well..........not to mention the completely redesigned rear exhaust manifold that actually has a semi-decent collector on it.

    Finally............there is the roller rocker issue (as in......you not having any on your 95 L82).



    With those three things in mind, I WOULD do the head swap in addition to the big port IM's and larger 56mm LA1 TB (LG8's and L82's are only 52mm).

    I bet there is an easy 10hp if you do ALL of the above...........and probably a bit MORE past the power peak (~5K)..............such a pity the stock shift logic will limit your ability to take advantage of the top-end gains.............
    1999 Dodge Neon R/T: Is MINE now.........WTF?? Maybe I DO have a working car for autoxing after all!<br /><br />1997 Honda Prelude SH: Still going tap-tap, and still being abused......8000rpm is good for it, I SWEAR.<br /><br />1993 Nissan Sentra SE-R: The parts and organ donor has appeared but has yet to be used.<br /><br />1992 Nissan NX2000: Rusting quietly while I try to figure out if a Bluebird long-block is really worth it.<br /><br />1991 Pontiac Grand Prix: Currently in 4th gear due to a shift-cable malfunction, but I&#39;m so lazy it may NEVER get resurected AGAIN.

  14. #14

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    Re: 3100 heads vs 3400 heads

    1.76 vs 1.72 seems like a minimal change. so I'll call it as I see it, it seems minimal

    port size differences may slightly restrict flow but seem to not have harmed my swap

    if you utillze the 3400 exhaust manifold you will have to change the downpipe. ask Brian P.


    95 3100's may have notched heads beneath each rocker. if it has the notched pedestal, it should accept the roller rocker.

    I'm running with 95 3100 heads with added roller rockers. If you can run with roller rockers I would do that


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  15. #15

    Re: 3100 heads vs 3400 heads

    well i guess i gotta open her up and check, i was on 60degreeV6.com and it says that 3100's didnt get roller rockers till 96 so with this in mind should i even bother?
    Current Cars: 1995 Olds Cutty Convertible, 2004 Chevy Blazer 2door 4wd, 1996 Dodge Stratus- Turbo SRT4 engine swap

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