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I'm getting ready to do my 3400sfi build in my z24 and im going allout on it i have the top-end pland out and ordering parts(its getting boosted) and i have a question about bottom end.. i know the stock 3500 crank will work and someone told me that there forged... is that true? and for connecting rods i know you could use the ones from a chevy 305 but have to be machined to work with a 3500 crank... is there any aftermarket cranks for a 3400sfi... thanks for all input...Billy
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the block will need to be clearanced alot to use the 3500 crank.
there are no aftermarket cranks for the 3400, GM made a slightly better 981 casting crank for the old turbo 3.1's but that'll be extremely hard to find. The stock crank is good for over 400 HP. -
Originally posted by 94z24cavy View Post
Who told you the stock 3500 crank would work? Look at the differences between the crank shaft main journal and rod journal sizes between the 3400 and 3500 cranks.
You'd have to use an entire 3500 block, or do a bunch of machining to use a 3500 crank in a 3400 block. The rods and pistons are different too. There was a thread on here somewhere about the 3500 cranks... some were supposed to be forged and some weren't. No one knew exactly what cars with 3500's got the forged cranks so it's hit or miss and the only way to tell was from a stamping on them. There is also the issue of the different internal timing ring on the 3500 crank which requires you to use an external crank trigger on cars with 3400 PCM's.
More trouble than it's worth IMO. The 3400 crank is plenty strong. You could send it out for shot penning and micro polishing etc, have it balanced and cryo treated... you aren't going to break it. Get some modified small journal SBC rods and forged pistons and call it done.'97 Grand Prix GT 3800 (sold)
'00 Grand Am GT 3400 supercharged
13.788 @ 103.73 mph, 320whp 300 ft/lbs
Gotta love boost!Comment
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yea im looking to be in the 400-450 range cuz my friend bought a motor and its had a 3500 crank and 305 connecting rods so that was all machined.. so you think ill be fine running the stock bottom because i dont granny my cars
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i missed that second post.. thanks for that info when we tear my buddies aprt again(getting ready to boost his to) i take pictures of the crank... wonder how much that cost the other guy to do.... i hope one day ill know as much as you guysComment
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Learned it all here... and still learning.
'97 Grand Prix GT 3800 (sold)
'00 Grand Am GT 3400 supercharged
13.788 @ 103.73 mph, 320whp 300 ft/lbs
Gotta love boost!Comment
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The 3400 and 3500 mains are the same, it is only the connecting rods that differ (and the 58x trigger wheel on the 3500). You can notch the block for the 2.25" journal rods, or have the crank machined for 2" journal rods (stock 3400).Ben
60DegreeV6.com
WOT-Tech.comComment
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why not run a whole 3500 or atleast bottom end?Comment
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Believe me I learned the hard way about the 3500. I probably spent near a grand putting a 3500 back together after buying the short block (previous owner took the top end for his 3400) and within the past 6 months the price of a complete 3500 is about 1/3 the amount of money I have spent. Unless someone is tossing out a 3500 crank and you are salvaging it, it probably isn't worth the money to buy one and have work done to make it fit.
The clearance on the 3500 block and oil pan is to make room for the connecting rods. If you grind the rod pins down to the 3400 stroke and journal size, and have the small block rods machined to fit then there may or may not be need for clearance. You would have to get the machine work done to the rotating assembly first then try to check for clearance around the rods. If you do go this route DO NOT forget to clearance the oil pan or you are going to end up with some shiny aluminum in your oil.
However for that amount of money you could probably buy a 3500 and a crank trigger from WOT-Tech and still have a few bucks to spare.Comment
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Originally posted by SappySE107 View Post
Ah, gotcha. Things aren't listed in the same order on those two pages and I was looking at a different number. I found it further down the list.
I agree with Wrath though. More work than it's worth IMO. Either just use a complete 3400 or 3500. Aren't the the stock 3400 rods stronger than the stock 3500 rods though? I thought I read that somewhere here, that the 3500's weak point was rods. Plus the 3400 you can use the SBC rods but 3500 ones would have to be custom made? Is that correct?'97 Grand Prix GT 3800 (sold)
'00 Grand Am GT 3400 supercharged
13.788 @ 103.73 mph, 320whp 300 ft/lbs
Gotta love boost!Comment
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If you are to use a 3500 crank, easiest way is to have the rod pins ground to 1.99" and use the 3400 rods. 3400 and 3500 has the same throw, and the same main size. I have pics floating around here somewhere of me bolting a 3500 crank in a Gen1 3.4 motor
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