3500 crank

[kwhauck]

Ok, so limited on time, I searched for 2 hours tonight on a 3500 crank swap and couldn't find a difinitive answer.

1. Is the 3500 crank forged steel?
2. What is needed to put it in a 3400 block
3. Can SBC rods be used if the 3500 crank is ground down
4. Will it affect my stroke or compression ratio?

[wasas9]

1. No. There are 2 versions. 1 is cast iron and the other cast steel, with the # 7484 on the crank itself you can see after the pulley is removed. Not many people have snapped 60* cranks so it's going to be able to handle 300 HP pretty easily.
2.

It's the bore, stroke is the same.

The crank is different, with larger rod pins on the 3500 than the 3400.

There has been lots of talk about re-grinding the 3500 crank rod pins, to stroke the 3500 or 3400.

The 3400 block will have to be clearanced to use the 3500 crank and matching rod journal sizes, unless the offset grinding was done in a way that the outside of the rod journals were in about the same spot as the 3400 crank, though I can't see the stroke being increased much by doing this.

Boring is not going to gain you much power, maybe a HP or two. Just bore enough to clean up the cylinders, nothing more. You want to keep the cylinders walls as thick as possible, for reliability and if you do make more power, there will be increased cylinder pressures, that will have to be controlled.

[Monzsta]

On a 350 Chevy, you can gain 5 ci by offset grinding the rod journal .050", ending up with a large journal -.060" under stock crank. the .050" raises the pin centerline, and thus the piston .025", usually negating the need to deck the block if zero deck is required.

On the subject of the 3500, the rod journal is a monster 2.249", vs the 1.999" of the 3400. A full 1/4 inch. That would give you an increased stroke of ..250" if offset ground for a displacement of 220 ci, or 3.6l up from the 204(calculated)ci of a stock 3400. Now you have to shorten your rod/piston combo .125" or your piston will be hanging out the top of the bore 1/8".

Now, if a bone stock 3400 is rated at 185 hp, that means each ci is producing .90 hp. If you stroked the 3400 to a 3600, doing nothing else, you'd see a theoretical gain of 14-15 hp. Plus a nice helping of torque with that.

If you applied this to the 3900, you'd get a 255 ci 4200! Hmmm...

[El_Diablo]

but the question is, is it still possible to do a "3600" stroke using existing off the shelf parts such as the small journal SBC rods? i suck at remembering the measurements of such things... thats why i always kept a lil cheat book handy at the machine shop, lol

also, i remember some guy on GAGT talking about a 3.7l stroker? anyone remember the guy and how he achieved this?

[Monzsta]

On the subject of the 3500, the rod journal is a monster 2.249", vs the 1.999" of the 3400. A full 1/4 inch. That would give you an increased stroke of ..250" if offset ground for a displacement of 220 ci, or 3.6l

His math may differ a bit. Maybe he rounded up.

[El_Diablo]

and sorry but i dont have all the numbers here in front of me but what would that same offset grind porvide with the 3500 block instead of the 3400?

[kwhauck]

wasas 9 - i have already made almost 300whp on the old supercharger setup, i hope to make around 500whp on the new setup.......

diablo - i am pretty sure the person you are talking about is my buddy John from colorado springs, he ditched that build, and i am getting a lot of parts off of his ditching it........

[El_Diablo]

i remember he also had another set of pistons built for an even larger engine aswell? 3.9 after the overbore IIRC? same guy? last time i heard about this was atleast a year or more ago

[sharkey]

but the question is, is it still possible to do a "3600" stroke using existing off the shelf parts such as the small journal SBC rods? i suck at remembering the measurements of such things... thats why i always kept a lil cheat book handy at the machine shop, lol

also, i remember some guy on GAGT talking about a 3.7l stroker? anyone remember the guy and how he achieved this?

.250" longer stroke and .040" overbore gives 3.72L.

[bszopi]

Guy I am thinking about with the 3.7L is a guy on GAGT (not John) that had an engine built by either RSM or JBP. Many people have disputed his engine though...

[silvergtjrad]

Guy I am thinking about with the 3.7L is a guy on GAGT (not John) that had an engine built by either RSM or JBP. Many people have disputed his engine though...

Ive never even heard of this guy or rumors of this engine before and I spend quite a bit of time on GAGT. Interesting.

[bszopi]

http://www.grandamgt.com/forum/showthread.php?t=62278&page=3

Babalouie is the guy's name. Although I guess there is still some questions on his motor. I thought he used a reground crank, but others say the 3.7L was accomplished with the bore. And of course, he never really comes clean to explain it.

[ForcedFirebird]

I'm very interested in stroking now. If the 3500 crank will fit in a 3.4/3400 block 3.605l would be had with a stock bore.

Was was done for rod length?

[Joseph Upson]

From the literature the GM tech on the Fiero forum posted the Steel crank is forged steel;

"The crankshaft is forged steel with deep rolled fillets on all 6 crankpins and all 4 main journals. Four steel-backed aluminum bearings are used. The #3 bearing is the end-thrust bearing."

also;

"The connecting rods are made of forged steel. Full pressure lubrication is directed to the connecting rods by drilled oil passages from the adjacent main bearing journal."

I don't know if a rod swap is justified, especially not for older refurbished chevy rods.

Sense you are dealing with a circle you can't offset grind a total of .250" from the crank and end up with a 2.00" journal, you have to divide the .250" oversize which will give a .125" offset increase in stroke since you are dealing with the stock 3.31" stroke. The big end of the rod is centered, otherwise you'll have to have metal added to accomplish the .250" stroke and I provided a source in another thread that would do it for $400, without metal added $200.

I believe clearancing of the block will be required for the 3500/3900 crank in the 3400 block. When you get right down to it the cost effectiveness to retain the 3400 block and modify the 3500 crank to fit probably borders on or exceeds the cost of using the complete engine and having the room for future stroke increase that GM already stated there is room for in the newer motor.

http://www.flatlanderracing.com/crankshaft_services.html#weldedstrokers

The larger journals are a benefit to rod bearing durability so you may want to consider added metal to keep the journal size and using custom pistons with the stock 3500/3900 rods, the parts in these motors should be better over all than the earlier stuff.

[Monzsta]

On the subject of the 3500, the rod journal is a monster 2.249", vs the 1.999" of the 3400. A full 1/4 inch. That would give you an increased stroke of ..250" if offset ground for a displacement of 220 ci, or 3.6l up from the 204(calculated)ci of a stock 3400. Now you have to shorten your rod/piston combo .125" or your piston will be hanging out the top of the bore 1/8".

By offset grinding (0 off the top, -.250 off the bottom of the journal) you raised the effective center of the circle 1/8 of an inch. Now X2 because you're swinging it in a circle. 1/8 up + 1/8 down = 1/4 total stroke. Do the math. I used to do this for a living..