Swapping series II heads onto EV6/LN3/SI tall deck shortblok - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-15-2005, 11:38 PM   #1
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Default Swapping series II heads onto EV6/LN3/SI tall deck shortblok

OK fer the fellow psychotic gearheads out there....
on the rear 90 3800 LN3 engine in the twin engine 94 Olds Cutlass 442 (ordered the Jegs 10pt cage a few days ago... backorder)
has anyone tried to swap the later SII heads onto a LN3 vin C before?
They seem to have the same bolt pattern, but diff accesory mounts-no big deal there rear engine has crank, WP, alt, and tensioner only
the series II heads also having the factory roller rockers and smaller bolt retainers, better ports etc.

I see two things that have to be acounted for, the 90 LN3 block has a taller deck height which with using the series II Lwr intake manifold will require spacers, this is also an easy fix as I have acces to a bridgport mill and alum stock of varrying thickness' and tap for bolting to intake with paper gaskets and flush head screws.

the cam lifters are hydraulic roller for both engines but the series II has shorter pushrods for the lwr deck height, there is a possibility the stock LN3 pushrods will work but custom length pushrods arent too bad....

Now the 3800 WILL be getting Turbocharged at some point maybe this winter and get a MegaSquirt EFI setup (90 non PCM controlled trans....) and we have already swapped to the delco ignition. and there are plans for an intercooler.

I see several bennefits from doing something like this, factory roller rockers, less friction. symetrical, port and chamber design with bigger better flowing valves. and better exhaust manifolds for us toi turn into turbo headers.

not I have another idea that goes along with this, if I get the supercharged 3800 L67 heads with the injectors in the head and use the NA intake I can run 12 injectors that will help deliver the extra fuel required the MS EFI can be programmed for this (batch or new sequential) and delay/shutoff the second set of inj for better idle and proper mixture at WOT full boost. we have peak and hold (low impedance) type Quad 4 injectors that will flow 30lbs each at 50psi (boost refrenced/rising rate) and 12 would more than handle the fuel requirments

a fabricated Upper intake manifold is not out of the question with me, I have access to a TIG welder and have an alum mig so I can mockup and do final welding, and because there might just be a better TB / location and from the look of things I can make the roller rockers a different ratio with the bridgport and a 300 amp TIG welder.

Just curious if anyone knows if this has been try'd, Al and I'* next run to the Upick a part I will be doing some "research" with a 90 LN3 and a 96 NA/SC, and if everything checks out we will be going home with the parts....

we are still looking for a front 3800 drivetrain but we have the rear 3800 to play with fer now... let me get some feedback... Dr Jay, Wilwren

Regards, James
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Old 04-15-2005, 11:59 PM   #2
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we compared the LN3 and a SII in a post here, I believe it was 95nSTA, and he compared the pic of his block w/o head wih another LN3 with no heads, there were some major differences
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Old 04-16-2005, 12:10 AM   #3
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LN3> L27 will work, but not series II. The ports aren't even the same sequence intake and exhasut.
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Old 04-16-2005, 12:21 AM   #4
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1993 sle, do you know where that post is I have searched but I got nothing with the keywords I could come up with

I will be doing research on this at the Jyard as there was a SII and a Vin C LN3 right next to eachother, also to look at the supercharged heads is a couple of cars over.

BonneMeMN, The ports dont matter, as I would be using the SII lwr intake and manifolds the intake will just need spacers
here is the best case scenario, on the LN3 block, supercharged SII heads with the SC fuel inj rail and a NA L36 Lwr intake with it'* injector rail with a fab Upper intake manifold with a N* or equiv TB

When I am at the Jyard I will have my CCing stuff and all my Micrometers to take measurments of all the parts involved.

James
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Old 04-16-2005, 01:13 PM   #5
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Ummmm....upper intake won't matter, bud. The VALVE sequence is different. WAY different. Coolant ports are too.

I believe you're in for a rude surprise and a waste of money.
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Old 04-16-2005, 01:57 PM   #6
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Coolant bosses from the block into the heads isnt a big deal... at least the SII isnt reverse flow and have differences like a reg sbc vs LT1/LS1

the valves arangment is different ie. the cam lobe timing events are tailered for the I-E-I-E-I-E valve positions of the SII and not the E-I-I-E-I-E of the LN3, this is one of the only things that I have found different between the cams besides the sleeve bearings that got changed from roller bearings on the balance shaft (dont think that the balance shaft bearings changed anything with the cam bearings.

like I said we will be doing some research in a Jyard and comparing/measuring parts and iff it still doesnt look good we wont be doing that but I will be taking the roller rockers as I am sure that I can machine and tap the fat stud that the LN3 L27 uses for rocker arms with the smaller metric thread of the roller rocker pedestals and still get them on this engine.

Lowbuck redneck hotrodding lol
I am still planning on some stuff fer the 3800 when the turbo goes on, if the cam differences turn out to be more than a lathe and bridgport can work with, then Oh well but you never know till you try I am still determined to use the * I supercharged heads with their own inj ports and the NA (Series I) lwer intake with it'* own inj ports, 12 inj will be possible and with MS EFI tunable....the rest is easy lol
a new fabricated uper intake with a TB (N* or Ls1 etc) located at an angle would improve IC plumbing....

this would all be so much easier if you could find a chiltons that listed cam journal sizes etc....like you can on my 68 F250/74 Nova, but it still will be fun to rip into them at the Jyard.....

James
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Old 04-16-2005, 09:11 PM   #7
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I posted that up not too long ago, i'll go look for it.
Looks like i'll be able to see if it'* really possible afterall.
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Old 04-16-2005, 09:15 PM   #8
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Old 04-16-2005, 09:53 PM   #9
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95naSTA if you could look for it, does it have pictures as all the info I get is specs and not detailed exploded diagrams.

Merlin, yeah I have seen that post and thats no problem even with using the SII headers/Exhaust manifolds no problem the heads are farther apart on the taller deck LN3 SI 3800 but since we will be cutting the Xover pipe for a turbo flange thats not an issue, besides we have a really large rear engine bay....plenty of room..

My main issue with this swap right now are the diffrences between the SI hyd roller cam and the SII hyd roller with it'* different I and E lobe patern cam I can use a SII cam gear if needed as the cam/ crank centerline wasnt changed from SI tal deck and SII short deck.

I am curious about the supercharged heads and the NA intake if I can use the factory rails and make em work....

All will be found out on a nice sunny J yard day! you dont have to be nice to a Jyard car.....

James
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Old 04-16-2005, 11:44 PM   #10
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http://www.bonnevilleclub.com/forum/...php?p=338530&h
no specs or anything but theres some pics/ideas
Shameless Plug:
I've got a series 2 cam(x2)/camgear/crank gear/exhaust manifold set in my garage i'd let go fairly cheap if you can't get it at a junkjard for some reason.
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