Is this system a direct bolt-on for my 1985 LG4 with stock exhaust manifolds? If not please feel free to make a recommendation.

Magnaflow Manifold Front Y-Pipe 86-89 Cam/Fbird V8 16450

 

By the picture, it looks right.
Are you still going to use manifolds?
The reason I ask is that I have an SLP stainless
Y-pipe for my 84 LG4, if you might be interested.
It has a 3" outlet, so you will probably need to make a
conversion at your cat converter. The stock cat is VERY restrictive,
get rid of it if it's still in there. Replace it with a hi-flow unit.
Shipping might be expensive, though.
The joints are tig welded, so it is 1 piece.

I see that you can get it for $205 on eBay. Go for it.
Upgrading the exhaust on these cars is the single
greatest improvement you can make. You WILL notice a difference.

 

spoon has a nice setup headers and ypipe for these cars if you arnt running cats I love it with my borla cat back system.

 

Not even close. That Y-pipe is intended for HO manifolds. Aside from being larger diameter exits, HO manifolds don't dump in the same place as low output manifolds. To make it work you'd need 86-up HO manifolds. Then there's about 1/2" diameter difference in the cat, and the cat-back exhaust...

 

He said LG4, not L69.
I believe you are talking about the TPI manifolds.
He has a carb.

 

Yeah, he has an LG4 low output 305. The magnaflow 16450 fits 86-up TPI cars with HO
manifolds. The passenger's manifold will be about 2" short and at the wrong angle to bolt up.

I never said anything about the L69. I said HO manifolds. Some TPI cars have the restrictive TBI/LG4 style manifolds, and some have HO manifolds. GM refers to the LB9 in some cases and the L98 in most cases as High Output engines.

 

The magnaflow 16450 fits 86-up TPI cars with HO
manifolds. The passenger's manifold will be about 2" short and at the wrong angle to bolt up.

Drew -I take it you are 100% certain about this???

If so, then I have the correct SLP y-pipe he needs.
But I also have a set of blasted and hi-temp black coated HO manifolds.
No air injection tubes, though. Not used since painted.
JA85Z28 - I have what you are looking for, whichever way you decide to go.

 

Well, I can read the Magnaflow website and deduct that if it fits 87-89 5.7L cars then the 86-89 5.0L cars they're saying it will fit use the same manifolds as the 5.7.

 

Here's a comparison of standard and HO manifolds. The middle pair are LG4/TBI, top and bottom are L98. You'll notice the very different outlet on the passengers manifolds. It really sucks when you figure this out while laying under a car and spending money on parts that dont fit.



Also if converting to HO manifolds, you need this EFE delete spacer.

 

Pretty sure this piece is no longer available from Magnaflow.

I bought one with a complete Magnaflow in 2015 and was told there was no more stock then. Maybe they've made some more?

 

I genuinely appreciate everyone's input. Last weekend, a friend and me laid down a 25 hour thrash from Friday night to Sunday evening. We installed a set of Aerohead Racing prepared 601's complete with bowls blended and gasket matched intake ports, Summit 1103 cam and lifters, Comp Cams roller tip rockers/ push rods, Melling timing chain, Fel-pro 1 piece pan gasket, and Cometics gaskets for the remaining sealing surfaces (zero leaks). Cometics gaskets are a little pricey, but viton rubber over a metal core makes for excellent sealing.

The exhaust system is really killing the little 305 and needs addressed asap. Again, I appreciate everyone's hard earned knowledge. Here's a few pictures from the thrash. Tear nearly complete


Idles excellent at 750 rpm with only a slight attitude.
In 1985, I was a young buck Sargent in Germany, and bought this almost exact car new through the PX. The only exception is that this Z28 is a 5 speed!

 

Looks great!!! Keep us posted!

 

The TPI manifolds and the L69 manifolds are interchangeable, as are the y-pipes. the early TPIs actually used the L69 y-pipe. Drew is correct that the LG4 manifolds will not fit the TPI or L69 Y-pipe, at least on the right side.

be that as it may, the only true HO was the L69.

 

Very NICE z28!

 

Somebody better build a time machine and go back to tell GM...

This is from the 1991 Firebird sales brochure.

 

 

if you look deep down, into the recesses of your soul, you'll come to agree with me.

 

I don't go poking around down there, the horrors that lurk within my soul are best left undisturbed.

The brochure that scan comes from refers to the LB9 and L98 as "H.O." or "High Output" every time they're mentioned. To say otherwise would be pure blasphemy.

 

That y-pipe was discontinued over 2 years ago - I sold quite a few of them and even bought the last few before the warehouses were cleaned out.

Like others have said, it is for TPI manifolds - which by the way will bolt up to LG4 or L69 heads and then you can use the y-pipe (if you can find one).

I had an 84 LG4 and to get around most of the restriction I had gale banks make up a y-pipe to use both the LG4 manifolds and also a 3" TPI cat and cat back. Added over 30hp just by that one change - back in 1990.

 

The catch is that not all TPI cars got the good manifolds. Single cat 90-92 LB9s often got the TBI style manifolds, with matching Y-pipe, cat, catback, etc. That's why Magnaflow lists it only fitting up to 89.

 

Gutting the cat today. I will probably end up having a custom y-pipe.

 

The Camaro's Had The Same Engines,They Were Never Refereed To As High Output,I Think That Was Just A Marketing Ploy Used By Pontiac Back In The Day.

 

Cleaned out the "cat" ... ...MAJOR IMPROVEMENT!!!

 

You Mean Like The Marketing Ploy Chevrolet Used When They Stuck "H.O." Stickers All Over The L69?

Are you callin' my Pontiac Motor Division a liar?

I suppose you could look at it that way. Or you could look at it and recognize nearly all the things that made an "H.O." were incorporated on most TPI engines. Given that LB9 and L98 engines put out higher HP than the L69, wouldn't it be logical that they're "H.O." engines by definition?

I love a good debate, but you guys are stuck on the minutia.

 

Paul - it is listed on Summit, and a few Ebay ads as well. It is possible they made another run of them.

OP - I recommend this swap on your LG4. I swapped out the LU5 stuff which was the same as the LG4 manifolds and Y pipe and added a better cat, and a Dynomax exhaust for an L69, as well as the manifolds. It definitely woke the car up a bit.

Check around the net. I think Magnaflow might be stocking it again. It is a well made y pipe and fits great.

 

SLP LG4 Y-pipe

 

HO manifolds.

 

Just in case anybody on here is trying to get ideas for a custom y-pipe, here is what my new setup looks like. Small block 350 mated to D3321-R headers and Borla catback exhaust.

 

That fits nice.
How about a side view pic showing how low the collectors hang?

 

Wheb i go back to my car tomorrow night I'll snap a pic, but to give you an idea its about an inch lower than the front LCAs.

Shouldn't have to be too concerned about scraping, however i plan on metal-ziptie-ing a couple round pieces of metal around the collectors to prevent ripping off the header wrap when i DO scrape. I am open to better suggestions for preventing rippage though...

 

if you dropped your car and are running long tube headers avoid train tracks curbs and speed bumps just saying and if street driven use extreme angles to navigate those situations...

 

Metal zip-tie = large hose clamp.

 

So wrap them with a bunch of hose clamps to help prevent ripping the wrap off?

 

Can you tell by looking at the manifolds whether or not they are the good ones?

 

Use your semi-circular metal shields. Good idea.
Just use 3+ inch SS hose clamps to hold them in place instead of the SS zip ties.
They will hold much better.

 

I suppose that if you know exactly what you are looking for, you could tell the difference.
When they are laid side-by-side, you can see that the outlets exit at different angles.
The casting number is the only other way to tell if they are still bolted to an engine.