Swapping DOHC for 3X00

[jmgtp]

Well, we have already established I'm crazy for pulling a perfectly running LQ1 out of the car so this should be no surprise. My real motivation to pull the heads is because this is essentially a junkyard motor: I want to see the cylinder walls before turning it over, clean the heads, and maybe do some really light head work. What I consider light headwork would be me removing casting flash and that is probably not even worth the effort...?

I suppose I can always change my mind. If I pull the rocker covers off and everything looks clean and sludge free then I may not pull the heads.

According to the power plot GM has on that site it looks like it should be making ~180 ft/lbs at 1000 rpm. That is impressive. I like the overall torque curve, pretty flat. Certainly will be different than the dohc, especially mine since it is modded for top end and lost a bit of low end. Torque is what is really important to a DD. Having some high rev horsepower to back it up just makes it fun when you want it to be.

[jmgtp]

Forgot to mention... I plan on making the 3500 exhaust manifolds work - I'll have to build a custom crossover. Though it looks like some Impalas came with an LX9 and the crossover is the over the trans type, unless I'm mistaken and the Imp motor is a vvt. My engine is from a G6 and the headers available won't work in a W car. They might work if I built a modded xover for them too but I can't justify the cost of the headers expecially if they dont bolt right on.

[IsaacHayes]

The ones with the cross over are standard 3400/3100 style logs......... Only a few had those. I think the impala ones are VVT, as it went from 3400 to VVT IIRC.

Forced_Firebird had the flanges for the 3500 manifolds at one time...

[jmgtp]

Okay, so basically for an existing crossover to work I would need to use the inferior 3400 style manifolds rather than the better flowing header style 3500 ones.

I don't think I'm willing to downgrade to the 3400 style so I'll probably be fabbing a custom crossover to reach over the trans and then use a Y pipe to merge the 2 before the cat. Hopefully I can find the flanges somewhere, otherwise I should be able to weld it up pretty easy. Only part I don't like is this means there will be no heat sheilding on the 'crossover' part.

Isaac... you have been very helpful, along with everyone else, in this thread - I do appreciate it!

[CNCguy]

You can get the flanges here.

http://www.britishcarconversions.com/component/virtuemart/?page=shop.product_details&flypage=flypage.tpl&product_id=93&category_id=26

[gpse3400]

Oh crapola I missed this thread.... You can use your rear lower mount and use the 3X00 main lower mount in tandem, upper torque struts, w-body flexable fuel lines for a 3X00, wbody 3X00 TB linkagne, a rear exhaust manifold from a '97+ wbody with down pipe, you need to lengthen the IAC, alternator and DIS wires, a 3.1 power steering pressure and return line is the easiest to deal with, on the return line, you will need a piece of angled hose, Throttle cables, you may need a '91-'93 3.1 A/C compresor line, that should do it.

[jmgtp]

Thanks for the posts...

CNC those flanges look just like what I need. Doesn't fit the rear manifold though?

gpse... I was really hoping all of my existing a/c stuff would bolt up without a problem. Reason being I have the original R12 in there and it still blows like ice.

[CNCguy]

They are strictly for the front manifolds since everyone seems to use a front manifold in place of the rear one.

[IsaacHayes]

I think the older AC will bolt up, at least the top 2 should.........

Front manifold goes more down than straight back... Later year GM cars the downpipe shoots out more straight back instead of angled down. That's the reason for using the front on the back as well for older car swaps.

[jmgtp]

CNC... Are they usually stocked? I don't need it right this second and would like to see what I will end up doing with my setup before buying. Going from the dohc to the pushrod I think I will have lots of room to figure out my exhaust setup... I'd like to make the existing manifolds work if I can. This is somewhat of a budget minded swap.

I do need an external crank trigger. I had asked Ben about it a few days ago but I don't think he got back to yet or I may have missed his message. I want to get that as soon as possible if you have them in stock. What about the 3x00 FPR relocator bracket?

[IsaacHayes]

The FPR bracket is not needed, but if you get it, you don't have to do anything.

I just angled the FPR, and bent the lines (just with my hands just to change the angle a little more) so that it would sit back down in the bracket that holds them down. I ground a little on the TB neck too to clear it, but in the wrong spot (was doing all this off the car then swapped over all at once. It's a DD)..

I also loosened the fuel line hold down bracket, and rotated the rails so that the FPR side was further away from the neck, then tightened the bolts down to hold it there. There is some play in the bolt holes of the bracket that allows it to slide around some then you tighten it down.

[gpse3400]

The front mounting tabs will bolt up but the rear bosses might not be clocked right....you might be able to get one bolt in there.

[jmgtp]

That's good to know I can get away without that piece. The small odds and ends are beginning to add up. I don't want to cheap out on anything but if I can save on something I plan to.

I'm also trying to get the alternator figured out. I've heard a few different things. One being that the 3500 uses a specific bracket and also that after a certain year he alternators and brackets changed. Going in to this I assumed any 3x00 alt would work and maybe the connector would be different than what is on my 91 harness. I'm still at a standstill on this one.

While I'm posting I may as well ask... Will any 3x00 fuel rail work so long as it is not a returnless system or are certain years preferable? Same question about injectors (3400 inj I'm assuming are adequate) and will my stock dohc injector harness work?

[jmgtp]

Ordered the crank trigger, metal intake gaskets.... and FPR relocator - decided if it makes like easier for $30 its worth it.

Things I have or are on the way:
-lx9 engine
-crank trigger
-intake gaskets
-fpr relocator
-have an assortment of TBs at home and will look into making an adapter to use stock dohc TB
-stock dohc air filter but no airbox for it

Things I know I still need:
-alternator (see above post - not sure which to use)
-fuel rail / injectors (also see above also)
-power steering - heard I could use my dohc pump with a diff reservoir?
-dogbone mounts and dogbones - assuming 3.1 w car stuff will fit?
-airbox - is the 91-93 3.1 airbox the same as the 91-93 dohc one?

I will likely look to ebay for a lot of what I don't have since those items seem to go cheap there but if anyone has them lying around shoot me a price.

thank you everyone for continuing to put up with me! I know all of my questions cannot be answered since I may be the first one doing this swap on an OBD I DOHC car but I'm trying to soak up any preexisting knowledge that is out there.

[gpse3400]

Ordered the crank trigger, metal intake gaskets.... and FPR relocator - decided if it makes like easier for $30 its worth it.

Things I have or are on the way:
-lx9 engine
-crank trigger
-intake gaskets
-fpr relocator
-have an assortment of TBs at home and will look into making an adapter to use stock dohc TB
-stock dohc air filter but no airbox for it

Things I know I still need:
-alternator (see above post - not sure which to use)
-fuel rail / injectors (also see above also)
-power steering - heard I could use my dohc pump with a diff reservoir?
-dogbone mounts and dogbones - assuming 3.1 w car stuff will fit?
-airbox - is the 91-93 3.1 airbox the same as the 91-93 dohc one?

I will likely look to ebay for a lot of what I don't have since those items seem to go cheap there but if anyone has them lying around shoot me a price.

thank you everyone for continuing to put up with me! I know all of my questions cannot be answered since I may be the first one doing this swap on an OBD I DOHC car but I'm trying to soak up any preexisting knowledge that is out there.

If the mounting bosses are the same, you can use GEN 3 alternator braket, and if you do I highly recommend getting the 140 AMP alternator with matching bracket from a 3400 minivan. The connector is different but the wires all do the same function, P I L S. The P/S pump you will need a 3X00 reservior and pulley. the only air box that will fit approriatly to a '93 and earlier W body will be the Coffee Can filter set up from a RARE '93 3100 Culass supreme, but since I am sure you will have a hard time finding that car you can get an air filter assebly from a '90 or might be 91 3800 buick w body, dont forget the plastic snorkle extension that is mounted to the body. You can use an intake duct from a '94 3100 Wbody. The 2.8/3.1 filter box is the same as the TDC but it is not usable with the 3x00 as the tb is mounted more centrally. For torque struts I would use the '95+ ones, but the older GEN 2 ones will work. Keep in mind that if you use the rear lower TDC mount with the 3x00 main lower mount, the engine will be hard to push back to get the torque struts on, dont let that deter you. You may have to drill an extr hole in the body for an extra mounting screw. To mount the AC you will need a '91-'95 Iron AC bracket. To make things easier use the old red band 3400 injectors and get a '91-'94 VIN T 3.1 wiring harness, it ll plug into your car harness just fine and operate, you will need to lengthen the IAC, TPS, and Coolant temp sensor wiring. If you decied to try and use the tdc hraness keep in mind that you will have to secure it from the serpentine belt. Also a '96 3 wire coolant temp sensor you will need as it will also operate your gauge, 3 wire connector like the TPS. The gauge wire you can run down below the crossover pipe to your connector on the car. The heater pipe on the passenger side, you will need a heater outlet from a 3100 Cutlass Ciera and a heater hose/pipe from a '91-'93 3.1, you will find this above the water pump. Chop your existing metal pipe before the elbow that bends up to the firewall. Take the 3.1 heater hose/pipe and chop the metal pipe after the elbow that leads to the firewall. Run a heater hose to connect the water pump to the heater pipe at the firewall that was chopped. I dont think I explained that one well enough.... but you will see when you see it....