Piston talk...3500 style

[bszopi]

The numbers in the CR calculator are calculated values, not measured values. They were determined by taking the standard deck height, rod length and pin height (I think that is it).

[Joseph Upson]

The 3500 rods are forged powder metal, most machine shops go belly up knowledge wise regarding the later V6 engines, I would think the appearance is due to the pressure and heat process used to make the rod rather than shot peening. Shouldn't you be concerned about potential intake manifold sealing with a .060 thick gasket? I have read in the past where shaving 2.8 heads (iron) could cause sealing trouble at the intake due to the narrow "v" angle, I would think going in the opposite direction might have an adverse effect as well possibly by spreading the intake ports a little further away from each other as they move upwards, the manifold ports will remain the same distance apart. Just a thought.

[ForcedFirebird]

The 3500 rods are forged powder metal, most machine shops go belly up knowledge wise regarding the later V6 engines, I would think the appearance is due to the pressure and heat process used to make the rod rather than shot peening. Shouldn't you be concerned about potential intake manifold sealing with a .060 thick gasket? I have read in the past where shaving 2.8 heads (iron) could cause sealing trouble at the intake due to the narrow "v" angle, I would think going in the opposite direction might have an adverse effect as well possibly by spreading the intake ports a little further away from each other as they move upwards, the manifold ports will remain the same distance apart. Just a thought.

I agree on the machine shops. I'm lucky to have the mentors where the shop is. We have a classA areospace/medical welder two doors over, and several 30+yr veteran machinists between the two buildings in our parking lot

The .060" gaskets are the stockers for Dave. He is using Camaro (.040") gaskets causing a .020" quench.

Best thing to do IMO is to have the heads milled and the manifold to match and use the correct gaskets, or to use different pistons to gain the CR. It's cheap to have heads milled (one the mill is set, takes ~5min), and many shops have head planers that are even faster.

[Superdave]

I could have the heads milled but the power difference between 9.8:1 and 10:1 isn't drastic enough to warrant the money spent. 9.8:1 is still plenty for now.


I was going to put the bottom end together tonight but it's like 5 degrees in the garage and i don't have enough kerosine to warm it back up to working temp.

and yes, my stock gaskets are .060 so if anything they'd allow the ports to line up better than before. I'll probably order up my pre-99 timing set tonight as well as a new 3500 gasket kit.

[ForcedFirebird]

Got an electric space heater?

Just call tha machine shop and see what they charge. Shouldn't be more than $50 for just a shaving on the heads. Your call

[Joseph Upson]

The 3.6L rods sound like a winner for the pushrod VVT motors which also have floating pistons. From the specs posted you would only need to bore the big end .030 over to accept the 3500 bearings. I hate the fact that no one really knows how strong the stock parts are a side from speculation based on factory set limits. I just can't rationalize them being weaker or equivalent to previous parts while at the same time supporting greater loads.

[SappySE107]

Yup, floating pins are nice. I still have brad's piston and rod for the 3.6. Should I send these somewhere? hehe, im done using them for testing for a while. I gotta pull my rings off the piston.

Double roller timing chain isn't too far off from being done.

[Joseph Upson]

Yup, floating pins are nice. I still have brad's piston and rod for the 3.6. Should I send these somewhere? hehe, im done using them for testing for a while. I gotta pull my rings off the piston.

Double roller timing chain isn't too far off from being done.

If I had a set I certainly would, GM specifically refers to them as "Sinter Forged Steel" instead of Forged powder metal.

Perhaps looking into the VVT 3500 with the short stroke crank would be an idea for a high revving option with the flow the heads have over the non VVT 3500 if the pistons are where the slack was taken up for the stroke decrease. I bet an on off function of the VVT module could make a high rpm cam very practical at idle and WOT. Wonder how a 60 degree motor would sound at over 8000 rpm.

[Superdave]

I'd still like to get ahold of a gen4 top end.. that would be a fun swap onto a 3500.. Even with the slightly offset bores it should still work.

[Joseph Upson]

I'd still like to get ahold of a gen4 top end.. that would be a fun swap onto a 3500.. Even with the slightly offset bores it should still work.

Not sure what to say about that, The heads would over hang the outer edges of the deck a good bit if my trial fit of the iron heads on my 3900 block are any indication, Then you would have to make sure the valves were not going to interfere with the bore and possibly get creative for coolant return from the heads due to timing cover differences. Also if the combustion chamber is to wide it may leave an area of the gasket uncovered allowing build up of combustion contaminants.

[Superdave]

Not sure what to say about that, The heads would over hang the outer edges of the deck a good bit if my trial fit of the iron heads on my 3900 block are any indication, Then you would have to make sure the valves were not going to interfere with the bore and possibly get creative for coolant return from the heads due to timing cover differences. Also if the combustion chamber is to wide it may leave an area of the gasket uncovered allowing build up of combustion contaminants.

That's something i'd just have to test in person... iirc CNCguy posted some pics a while back of the 3900 heads in various comparisons.

[ForcedFirebird]

Not sure what to say about that, The heads would over hang the outer edges of the deck a good bit if my trial fit of the iron heads on my 3900 block are any indication, Then you would have to make sure the valves were not going to interfere with the bore and possibly get creative for coolant return from the heads due to timing cover differences. Also if the combustion chamber is to wide it may leave an area of the gasket uncovered allowing build up of combustion contaminants.

Joseph, were thos 3900 heads in your post? I haven't seen them in person, but I was under the assumption that they were modeled after the GenIII SBC's (LS6 etc), but those ports have no resemblance...

http://www.carcraft.com/techarticles/general_motors_gen_iii_engine_cylinder_heads/photo_01.html

They still look like the general 60*V6 shape GM has been using.

[Joseph Upson]

Joseph, were thos 3900 heads in your post? I haven't seen them in person, but I was under the assumption that they were modeled after the GenIII SBC's (LS6 etc), but those ports have no resemblance...

http://www.carcraft.com/techarticles/general_motors_gen_iii_engine_cylinder_heads/photo_01.html

They still look like the general 60*V6 shape GM has been using.

No, the heads in the picture are cast iron heads with the typical area of the 3500 and below engines to show SuperDave the difference in deck area and the likely problem he would have were he to mount 3900 heads on a pre 3900 block, not to mention that the cylinder heads deck surface is not symetrical, the coolant holes are different in size from one end of the head to the other meaning he would have to match the gasket holes to those found on the 3900 gasket.

[ForcedFirebird]

No, the heads in the picture are cast iron heads with the typical area of the 3500 and below engines to show SuperDave the difference in deck area and the likely problem he would have were he to mount 3900 heads on a pre 3900 block, not to mention that the cylinder heads deck surface is not symetrical, the coolant holes are different in size from one end of the head to the other meaning he would have to match the gasket holes to those found on the 3900 gasket.

Sorry for the confusion. The link I gave is pics of LS6 ports, and was saying the 3900 ports look more like 3x00's than LSx's.

I'm all too fimiliar with the iron heads as I couldn't wait to get rid off them

[Joseph Upson]

Sorry for the confusion. The link I gave is pics of LS6 ports, and was saying the 3900 ports look more like 3x00's than LSx's.

I'm all too fimiliar with the iron heads as I couldn't wait to get rid off them

I believe what GM meant by comparison is the tall roof on the intake port of the 3900 which is higher than on previous heads. Unfortunately the valves are shorter on the LS1 heads so they are not candidates for swapping into the V6 head. I'm still interested in a combination offset crank and 4" bore on my extra block though. I'm still amazed at how Fiero members are still favoring naturally aspirated iron head V6 motors over the aluminum head motors.