3900 headgasket on 3400 head and other lz9 info

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3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

You can see that the center of the bore between engines is different. The fire ring on the 3400 head is obvious of where its location was. Yes all the bolt holes do line up so technically the gen 3 heads will bolt to the gen 4 motor. I circled two holes at the bottom. You can see that because on the gen 4 motor the bores were moved outward, the coolant holes on the gen 1-3 do not line up. Basically no coolant can flow from the block to the heads at these locations.

Any more pics of anything else I can take just ask.
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Last edited by Shaun41178(2) on Wed Jun 10, 2015 12:30 pm, edited 1 time in total.
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Re: 3900 headgasket on 3400 head

Post by The Dark Side of Will »

Cool! Thanks for the info. I think I've occasionally mentioned putting iron heads on an LZ4 or 3900 block, that's nothing but a nod to the guys who absolutely MUST have iron heads for "originality".

The only realistic reason I can come up with to mix offset bore with centered bore would be to run 3900 heads on a BowTie block.

As long as the builder is aware of this, matching coolant passages can *likely* be drilled into the deck surface of whichever component needs them, even if they have to be drilled at an angle.
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

The Dark Side of Will wrote:Cool! Thanks for the info. I think I've occasionally mentioned putting iron heads on an LZ4 or 3900 block, that's nothing but a nod to the guys who absolutely MUST have iron heads for "originality".
Not worth it
The only realistic reason I can come up with to mix offset bore with centered bore would be to run 3900 heads on a BowTie block.
Using lx9 heads would be a wiser and easier option. Ported lx9 heads will flow what Gen 4 heads flow and the ported lx9s are being flowed on a smaller bore
As long as the builder is aware of this, matching coolant passages can *likely* be drilled into the deck surface of whichever component needs them, even if they have to be drilled at an angle.
I wouldn't do this as the holes would be very close to the edge of the head. I suspect there might be problems with proper sealing. After seeing it up close tossing the idea out of earlier gm heads on a Gen 4 is the best idea
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Re: 3900 headgasket on 3400 head

Post by The Dark Side of Will »

Shaun41178(2) wrote:
The Dark Side of Will wrote:Cool! Thanks for the info. I think I've occasionally mentioned putting iron heads on an LZ4 or 3900 block, that's nothing but a nod to the guys who absolutely MUST have iron heads for "originality".
Not worth it
Depends... A 3900 shortblock topped with the Falconer heads and throttle per cylinder intake would be a LOT easier to drive on the street at 300ish HP than a 2.8, 3.0 or even 3.4 would be.
I agree that a 3900 with stock heads and a Fiero manifold is NOT a performance build... but some people do silly things in the name of "originality". Fieros aren't mid-year Corvettes and never will be.
The only realistic reason I can come up with to mix offset bore with centered bore would be to run 3900 heads on a BowTie block.
Using lx9 heads would be a wiser and easier option. Ported lx9 heads will flow what Gen 4 heads flow and the ported lx9s are being flowed on a smaller bore
And what do ported 3900 heads flow on a 94mm bore? :P
I wouldn't want to spend the money on a BowTie block unless I had a REALLY solid idea that sleeving it large enough (and OFFSET!) to take advantage of the later heads would work.
As long as the builder is aware of this, matching coolant passages can *likely* be drilled into the deck surface of whichever component needs them, even if they have to be drilled at an angle.
I wouldn't do this as the holes would be very close to the edge of the head. I suspect there might be problems with proper sealing. After seeing it up close tossing the idea out of earlier gm heads on a Gen 4 is the best idea
Do you mean close to the edge of the block deck? A 3900 gasket would be used with the 3900 heads, making it only necessary to drill the block... but if that's risky, then it's risky.

Other than the above "reasons" for iron heads, I don't see why earlier heads should go on a 3900 block.
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

The Dark Side of Will wrote: Depends... A 3900 shortblock topped with the Falconer heads and throttle per cylinder intake would be a LOT easier to drive on the street at 300ish HP than a 2.8, 3.0 or even 3.4 would be.
I agree that a 3900 with stock heads and a Fiero manifold is NOT a performance build... but some people do silly things in the name of "originality". Fieros aren't mid-year Corvettes and never will be.

And what do ported 3900 heads flow on a 94mm bore? :P
I wouldn't want to spend the money on a BowTie block unless I had a REALLY solid idea that sleeving it large enough (and OFFSET!) to take advantage of the later heads would work.
"Not worth it" as in the possible issues with the cooling jackets in the earlier style heads.

With a bowtie block, you can probably have it resleeved, with an offset bore, however the deck on the gen 4 block is wider to fit the later heads. The gen 4 heads will overhang the deck of any non gen 4 block. Ill get some pics of this and post them up. The gasket on a engine making any real power prob won't seal well towards the outside of the block and might even constantly leak.

No idea what the gen 4 heads will flow on a 94mm bore. They would probably lose flow. If that is the case, then why install them, when ported lx9 heads on a 94mm bore can flow 240 cfm on the intake which is about what gen 4 heads flow on a 99mm bore.
Do you mean close to the edge of the block deck? A 3900 gasket would be used with the 3900 heads, making it only necessary to drill the block... but if that's risky, then it's risky.

Other than the above "reasons" for iron heads, I don't see why earlier heads should go on a 3900 block.
No I mean the earlier heads on the later block will need to be drilled to allow coolant on the outside of the heads. The heads will need the drilling. the holes being drilled are very close to the edge of the heads. At this location, I for see possible issues with sealing of the gasket and very well could see coolant leaks.

Thats what I mean by not worth it. I guess if you found a cheap enough 3900 like I found, and slapped some used iron heads on it with a fiero intake, and fired it up to see then yea I guess you could give it a shot. any performance build I might object to. Ill get more pics and then we will know for sure.

I will say I don't think its a real issue having the earlier style heads on the later block as far as the combustion chambers not being "centered" Its a wedge head afterall with dished pistons. One could always modify the quench pads to make the chamber "centered"
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

I made simple marks of where a 3900 gasket sits on the earlier heads and marked where roughly holes would need to be drilled. It appears the iron heads that might be a tad more meat.

Iron.
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IMG_0339.JPG (100.73 KiB) Viewed 19572 times
Aluminum 3400 heads
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Re: 3900 headgasket on 3400 head

Post by The Dark Side of Will »

Yeah, that's pretty close to the edge. However, a little mill work on the block deck and head deck to meet half way and modifying the head gasket to match should probably make that work fine. The cooling system only has 15-18 psi in it, so it's not hard to seal. Use RTV on both sides of the head gasket if you're concerned about the width of the sealing interface.
Shaun41178(2) wrote:With a bowtie block, you can probably have it resleeved, with an offset bore, however the deck on the gen 4 block is wider to fit the later heads. The gen 4 heads will overhang the deck of any non gen 4 block. Ill get some pics of this and post them up. The gasket on a engine making any real power prob won't seal well towards the outside of the block and might even constantly leak.

No idea what the gen 4 heads will flow on a 94mm bore. They would probably lose flow. If that is the case, then why install them, when ported lx9 heads on a 94mm bore can flow 240 cfm on the intake which is about what gen 4 heads flow on a 99mm bore.
Has no one ported LZ9 heads yet? You are talking ported LX9 heads vs. stock LZ9 heads, right?

I'm not going to throw the cost of a BowTie block at "probably" unless I have a serious backup plan.
The loadpaths through a "conventional" block with the head bolt threads in the deck put the bore liners in tension from combustion pressure. This means that sleeving such a block can be very detrimental to the block's strength.

This is not the case with LS and more modern engines which have the head bolt threads in the outer wall of the cooling jacket. This puts the bore liners in compression at all times.
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

The Dark Side of Will wrote:
Has no one ported LZ9 heads yet? You are talking ported LX9 heads vs. stock LZ9 heads, right?

I'm not going to throw the cost of a BowTie block at "probably" unless I have a serious backup plan.
The loadpaths through a "conventional" block with the head bolt threads in the deck put the bore liners in tension from combustion pressure. This means that sleeving such a block can be very detrimental to the block's strength.

This is not the case with LS and more modern engines which have the head bolt threads in the outer wall of the cooling jacket. This puts the bore liners in compression at all times.
Yea a set of lz9 heads were ported and from what I read, not much was gained. Prob not enough to justify the cost.
taken from this thread
http://60degreev6.com/forum/showthread. ... post423322

Lift_________[0.100]_[0.200]_[0.300]_[0.400]_[0.500]_[0.600]_[0.700] Avg CFM_ Max CFM
stock(int)____62.4___128.6___186.8___218.9___232.1___238.5___NA______177.8___238.5
stock(exh)____52.6___100.0___138.2___150.1___154.7___155.8___156.5___129.5___156.5

ported(int)____67.1___131.9___191.1___236.0___250.0___257.3___261.1___199.2___261.1
ported(exh)____52.6___101.3___134.1___155.7___166.6___170.3___172.0___136.0___172.0

Oh yea forgot to mention, the lz9 heads on a 3400 block will not work. which means they won't work on a bowtie block unless you had a much larger bore than 94mm. the combustion chamber of the heads is larger than the bore in the 3400 block. The valves do clear cylinder walls however. So you might be able to install the large lz9 valves into the 3400/3500 heads for more flow. Not sure though.

By comparison here are my ported gen 2 heads on a 95mm bore with smaller 1.72 intake valve
Lift______[0.100]_[0.200]_[0.300]_[0.400]_[0.500]_[0.600]
(int) ____64.6___122.0___173.0___204.0___217.0___223
(exh) ____58.3___104.0___148.0___167.0___168.0___168
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

Anyone have a fiero v6 timing cover laying around? I need a measurement off of it.

I need to know how deep the timing cover is measuring from the mating surface at the block. I need to know how deep it is at the cam location. Thank you.
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Re: 3900 headgasket on 3400 head

Post by Shaun41178(2) »

Shaun41178(2) wrote: Oh yea forgot to mention, the lz9 heads on a 3400 block will not work. which means they won't work on a bowtie block unless you had a much larger bore than 94mm. the combustion chamber of the heads is larger than the bore in the 3400 block. The valves do clear cylinder walls however. So you might be able to install the large lz9 valves into the 3400/3500 heads for more flow. Not sure though.
The lz9 heads have a combustion chamber that is 97mm wide. if your block has a bore smaller than 97mm then the combustion chamber of the head will be larger than the bore. just measured this today so posting it up.

bore a bowtie block to 94mm and use ported lx9 heads. You should be able to make 300 crank hp on pump gas and be less than a 300 lb engine
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Re: 3900 headgasket on 3400 head

Post by The Dark Side of Will »

The ported LZ9 heads gained 18 CFM at .500 lift... that's significant. Further development will make them better.

The stock LZ9 heads are also 15 cfm over your ported gen II's at .500 lift and the ported LZ9's are 33 cfm ahead. Soo... yeah, I don't see why a body would put early heads on the 3900 block... unless said body just got a smokin' deal on a 3900 short block.

The Jeep 4.0 is an example of the silliness that occurs when the chamber overhangs the bore... Build ones can't run 9.5:1 on premium.
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

normally the dots line up on the crank and cam gears with #1 cyl at TDC. This is the location of the timing marks when the engine is off. From what I have read, the vvt is in the fully advanced position. In order to get the dots to line up, I had to disassemble the housing, then turn the gear. This essentially retards the timing when the engine is assembled and running. Its almost full retard to get them to line up.

I am going to get a cam degree wheel and see what the numbers look like at full advance and full retard or at least to where the dots line up.
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

some vvt info here for the v8s which gm probably had similar number for the v6

http://www.hptuners.com/forum/showthrea ... 2-With-VVT
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

http://60degreev6.com/forum/showthread. ... ec-dilemma

Taken at .050" Lobe Lift
IN open relative to ATDC 1 19
IN close relative to ABDC 30 48
IN Duration 209
EX open relative to BBDC 59 41
EX close relative to BTDC 29 11
EX Duration 210
LSA 120.5


Im gonna have to try to confirm that


Stock 3900 was 6.168EX and 5.878IN
Stock 3400 was 6.075EX and 5.750
3900 base circle is 1.395
3400 base circle is 1.273
New ones are 6.250EX and 5.960IN.

http://www.v6z24.com/jbodyforum/also-gr ... t,360.html
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

The Camshaft timing gear has 50 teeth on it. Which equates to 7.2 degrees for each tooth. Lets say I wanted to retard the cam. Cam timing is in relation to crank rotation so since the engine turns clockwise, if I wanted to retard the cam events, I would turn the crank clockwise, while not moving the cam correct?

Research says that the cam is advanced around 7-9 degrees when the vvt is deactivated. I am guessing that equates to 14 degrees at the crank. For some reason however this just seems like too much advance. I can't seem to get a straight answer on the links I have found. Lets say however it is 14 degrees crank advance with vvt off. By retarding the cam by one tooth, that equates to 14 degrees at the crank which will now have the cam in the straight up position or at approx 3.5 degrees advanced pending on if the default is either 7 or 9 degrees.

thoughts?
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by ericjon262 »

FWIW, here are some pics of the cam phaser.

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Re: 3900 headgasket on 3400 head and other lz9 info

Post by Shaun41178(2) »

I was going to post pics of the phaser but yours are much better.

Thoughts on the cam timing and moving a tooth?
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by ericjon262 »

Shaun41178(2) wrote:I was going to post pics of the phaser but yours are much better.

Thoughts on the cam timing and moving a tooth?
I hadn't really given it much thought, if I ever go gen 4, I'd just keep the VVT active so it wouldn't really be an issue. Have you considered taking the lower gear to a machine shop and having them cut new keyways into it? basically making is an adjustable gear.
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Re: 3900 headgasket on 3400 head and other lz9 info

Post by The Dark Side of Will »

Shaun41178(2) wrote:The Camshaft timing gear has 50 teeth on it. Which equates to 7.2 degrees for each tooth. Lets say I wanted to retard the cam. Cam timing is in relation to crank rotation so since the engine turns clockwise, if I wanted to retard the cam events, I would turn the crank clockwise, while not moving the cam correct?

Research says that the cam is advanced around 7-9 degrees when the vvt is deactivated. I am guessing that equates to 14 degrees at the crank. For some reason however this just seems like too much advance. I can't seem to get a straight answer on the links I have found. Lets say however it is 14 degrees crank advance with vvt off. By retarding the cam by one tooth, that equates to 14 degrees at the crank which will now have the cam in the straight up position or at approx 3.5 degrees advanced pending on if the default is either 7 or 9 degrees.

thoughts?
Are you thinking of this because you want to do a VVT delete? What's wrong with using the stickshift G6 GTP program in a 58x ECU. Doesn't HP Tuners support that?
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