Doom86

I have a 72 3/4 ton chevy with a freshly rebuilt 350 in it and we are going to put it im my 86 Z28, LG4.

One thing i need advice on is the intake manifold. The 350 has a broken 2 barrell carb so my 4barrel qjet will be used. In order to do so we have to swap the intakes. Will my intake bolt up to the 350's heads? We're still getting the casting numbers off them (for the second time) to be sure exactally what heads they are, they look like they have had machine work, what ever they are. Will the LG4's intake reduce power over the stock 350's intake?

Next issue is the LG4's rediculous exhaust. I have to say i was amazed to see a 2.25" Y pipe, im assuming the rest is the same. Do IROC's have better exhaust? Im broke as a joke right now and have a friend who has a IROC factory exhaust he may part with. I dont mind a "temporary exhaust", its an easy swap if its already fabbed.

If there is any other "tips" any of you can think of please enlighten me..

many thanks..

nsimmons

As for the iroc measure the pipe

diameter = 2 * (circumference / 6.28)

five7kid

iTrader: (14)

Unless the 350 heads have been shaved, the LG4 intake manifold will bolt up to the truck engine. It is in fact a much better manifold than the factory put on the typical 350.

Being an "IROC" doesn't guarentee anything about the exhaust. It is what engine was in it that determines whether that exhaust is any better than what you've got now. If all you can afford is a factory take-off system, look for an L69 (VIN code G), or '86-'90 LB9 or L98 (VIN code F or 8) set-up.

Doom86

thanks for the middle-school math refresher, nsimmons. I was actually trying to see if anyone knew if they were bigger then LG4 cars, before i drove over there. all jokes aside thanks for the help

five7kid, she is getting a proformance upgrade come "income tax" time. i just want to have something to put on there before then thats cheap and more effective then the straws on there now. Someone told me the Y-pipe on the L98 IROC's were 2.75", im hoping its true, even though it is an "odd" size. thanks again for your help.

Anything else i should know about this swap? Should everything match up?

five7kid

iTrader: (14)

The dipstick will be on the driver's side on the 350. LG4 cast iron exhaust manifolds didn't assume that, so they interfere with the dipstick tube. Headers solve that, but until tax refund time (file early), you can either bend up the tube to get it past the manifolds, or spring for a Lokar flexible dipstick set-up.

The '86 LG4 has a one-piece rear main seal crankshaft. The way the flexplate mounts to the crank is different than the way the 72 350 will be. You need a 153-tooth (12-3/4") flexplate for '85-earlier so your 3rd gen starter will work.

Doom86

thanks again five7kid you are always a good help.

Sorry if this is an ignorant question. But will the trucks flexplate work?

Will the distributor off of the LG4 work ok on the 350? its the factory distributor with a Accel "Super coil", id like to keep it if i can. The trucks carb isnt computer controled so its a vaccume dist.

Im kinda rushing this project now because my LG4's head gasket seems to be leaking. I drive the car hard a lot so i dont like driving it with leaky gastkets.

im hoping this is a decent upgrade, he (my father-in-law) tells me that the 350 makes his truck scoot.

five7kid

iTrader: (14)

The truck flexplate should work as long as you use the approriate starter. Most likely it is a 168-tooth flexplate. The starter will sit farther out than the LG4 starter does, which has been known to cause exhaust/starter interference issues.

Everything from the LG4 should bolt up to the 350 except what I already mentioned.

nsimmons

I didnt answer the question directly because like five7 said it doesnt matter what the car came with.

Btw my irocs pipe is 3", who knows if its original

86iroclamarque

good question. what is the stock size of exhaust pipe on an IROC?

SLOWFIVEOH

iTrader: (2)

Another option would be to get a y pipe made, I put headers when I did my LG4 to 350 swap, but thats not much different when it comes to making a y-pipe. A local shop only charged me $60 to make a 3 inch y pipe, and only $175 to make a custom made 3 inch catback, of course I bought the muffler and cat but thats still not bad! Def. worth it, especially when the alternatives are trying to break off rusty exhuast bolts to get a used y-pipe thats only going to be temporary. You could get a shop to make a nice 3 inch y pipe to hook up now, then a few bucks to modify when you get headers!

Doom86

Thanks for everyones help here, you all are always cool.

There has been slight change in plans with this install, any comments or help is welcome here.

We are not sure what has been done to this truck motor, but the info i got about its power was, "if i nail it the ***-end slides side-ways" (this doesnt sound like the smogger 190hp factory setup).

Given this info and my long-term goal of a 12 second car im going to change the transmission to the TH350 that is also in the truck. i've read, and heard, a lot of people say the 86' 700r4's cant handle a lot of power.

We've measured the tail-shaft of the TH350 and it is 9", so my 700r's drive-shaft should make it bolt up to the rear-end, correct??

What we're hoping with this install is that we can slide the motor and trans in together, with the 700r's drive-shaft on and bolt it up. The only thing we're changing on the trucks motor is the intake and carb, we're planning to use mine.

The only thing i can think of that will give us a problem is the torque arms not mounting. I have a friend who's a welder, couldnt we just fab up a bracket or something for the torque arms? Would this cause any problems?

Good news, i scored some hedman shorties for the new motor, they are in transit

Thanks again you all :hail:

ljnowell

You would be much better off buying the bracket kit, but yes, you can fab up a bracket for the torque arm. I know people that have done it before. You may find a picture here if you search.

Doom86

thanks, ljnowell, i'll keep that in mind.

Any other comments or sugestions here?

Doom86

could someone answer my questions?

Thanks

five7kid

iTrader: (14)

In a pickup it does.

Doom86

I was looking at the heads on the truck motor and they are indeed the 333882's that probably came on the truck originally.

These heads seem to be considered garbage to a lot of you folks, do you think i should swap them for my lg4's when i have the motor's out? My 86 has the factory installed heads on them which i think are 416's or 601's. There is a good junkyard here, i can pull any heads for 30-40$. There was a few 3rd gens there last time i went, one was a 350 91-92 transam if my memory serves, heads still intact.

thanks for all of your help everyone.

five7kid

iTrader: (14)

Either your LG4 or those L98 heads in the yard would be better than those 882's.