Please don't cry out loud I know I will choke them down a good bit. just wanted to know if these manifolds will bolt up and work. Also are the manifolds for the LB9 and the L98 the same? Thanks Pat

Yes they will bolt right up. I think the 5-speed LB9 and the L98 got the same manifolds. the auto Lb9's prolly got the crappy TBI logs.

No they won't Vortec has a different bolt pattern and port design.

The 1st answer applied to the exhaust manifolds and is correct; the 2nd answer applies to the intake manifolds, and is also correct.

Which "manifold" are you asking about?

ahh, sorry

I mean the exhaust manifolds!

for the background: I want to drop a crate engine in my car and was looking at the vortec tpi-engine from sdpc. and because we have some stupid laws witch doesn't allow us to run headers, I'm stuck with the stock exhaust manifolds...

I am unaware of any such law forbidding the use of headers. I do, however, know of a law that says that the AIR tubes must be in tact as well as a bung for the o2 sensor. In which case, there are such things as those. For example, I have SLP headers that are 50 state emissions legal. They have the AIR tubes and a sensor bung in the driver side header.

I am curious, I want to see this law in writing.

believe me, we have other laws that are even more stupid than this.
If you have heard about the TÜV in Germany, forget it. Here in Switzerland its even worse...

for example performance: I'm only allowed to add 20% to the 230hp stock, this means legally i can take my car only to 276hp...

for example exhaust: any changes made to the stock exhaust system have to be approved. if they are too loud you can forget it...

Its hard to change anything on the car, especially when its a car that was not sold in thousands over here...

probably I should move to the USA...

You had asked about the LB9 and L98 exhaust manifolds and whether they are the same. From what has been posted here the L98 manifolds are larger.

If someone could confirm this it would be helpful.

The other thing to do is to port whatever manifolds you end up using. Just like an intake there are gains to be had in porting the exhaust manifolds.

RBob.

The Stock Echaust Manifolds on the L98 will not fit Vortec Heads. The Passenger side Manifold has an elongated bolt hole to that will only fit the L98 Heads. Plus the ports on the head will not match the ports on the old exhaust manifolds.

350 TPi Vortec 1989 GTA

Well, I ran into that same problem with the bolt on the passenger rear side of the manifold... However, I just left the last bolt out . So far, I'm about 8,000 miles and no leaks or problems so far. I did use a Mr. Gasket Ultra-Seal header gasket though and torqued the bolts evenly. I've got L98 exh. manifolds on Edelbrock E-tec heads.

Oh, and I thought I would have to port my manifolds to match the cylinder head ports, but my e-tecs have the same size port opening as the L98 manifolds!

you could always port and grind the hell out of the stockers. I feel for you, living in a header hating country.

Never heard anything of the sort. But, I don't have either, so only going on internet pictures and internet chatter. (I'm certain about the "elongated" part, though - it's "relocated", not "elongated".)

LB9 and L98 manifolds are the same, with the possible exception of the '91/'92 single cat LB9. But, like said, port/clean up what you've got - if it's 230HP, you've certainly got the "good" manifolds.

The few that I've seen recently the only difference is at the flange opening, 305 is under 2", 350 is over 2"

I'm swapping in a dual cat in place of the single and was told I also needed to change to the L98 manifolds for better flow.

Edit: The Passenger side manifold outlet is also extended an extra 1 1/2 in.

Don't rule out Canada!

The exhaust manifolds will not be a direct bolt-on, although they will work. See below.

This is correct, although the head exhaust ports will match the L98 exhaust manifold ports. You will need either an adapter plate (this is how I did mine) to properly fit the exhaust manifold, or do like thirdgen88 and hope that whatever sealant you use holds up. Personally, I'd spend a few bucks for the adapter plate.

- 89_IROC

Could somebody post a picture of this elongated bolt hole? And adapter plate?

The factory has done so many wierd things in other areas, it's probably not wise to make blanket statements about exhaust systems.

If you have a 230 horse L98, though, I don't see how you'd have a problem using those manifolds on Vortec heads.

Unless there is an elongated bolt hole I don't know about...

Regrettably, I don't have a picture of this. I understand the value of a picture, which is why the following may not help.

The passenger L98 exhaust manifold is more oblong on the foremost end - this is easy to see when comparing the two exhaust manifolds. The Vortec heads don't have this bolt hole asymmetry, which creates a problem when using L98 exhaust manifolds. All the bolts will fit, but the foremost manifold bolt hole will extend approximately 1"-1.5" past the bolt hole in the head. I suppose that one could seal it up and hope for the best, but I felt better after spending $25 for an adapter plate.

I hope I'm not coming across as condescending - after all, I don't know anything at all about engines other than pulling one and putting a few things back on it. This is just the best way I can think to describe it without a picture.

If you'd like, I'll take a picture of my L98 heads and show you what I'm talking about with the bolt hole asymmetry.

- 89_IROC

Please do.

I'm not trying to be condescending, either. This just doesn't sound like anything I've seen or heard.

I understand, and it certainly threw me for a loop when I was bolting the manifolds to the heads! I wracked my brains for hours, thinking that I'd missed something, so I finally took the situation to my local dealer and found that I needed an adapter plate to properly mate the exhaust manifold to the head on the passenger side.

I know that I keep talking about this "adapter plate"; I'm Googling for a picture as I type. Unfortunately, I haven't pulled my engine yet (I'm preparing for a complete restoration), so I may not find a picture of the adapter plate. Hopefully the pictures of my L98 heads will help once they're compared to Vortec heads. I'll see if I can get those pictures on CD by tomorrow morning sometime (unless someone else gets the pics before I do).

- 89_IROC

This is what is being discussed.. The L98 manifolds will only completely bolt up to a "light weight" cylinder head casting. On the passenger side rear of an L98 cylinder head, there are three bolt holes for the number 8 exhaust port (two of them are next to each other at the rearward side of the port). The L98 manifold bolts to the outermost of that pair of holes. Therefore, when you have a cylinder head that has the standard (only) bolt hole configuration, you won't get to put a bolt in that last hole..

I think "elongated" has confused a lot of people... "Relocated" (I think someone already mentioned it earlier in the thread) would be a better descriptor.

Having said that, I've had zero problems (I think due to the rigidity of the cast iron manifold) with my L98 manifolds on my E-Tec heads. Heck, I even went to retorque the bolts only to find that none of them had even loosened (big surprise after owning headers on my last bird).. Oh, and Mr. Gasket Ultra-Seal header gaskets rock.. :-D

thirdgen88, this is EXACTLY what I was talking about - thank you! "Elongated" was probably a poor choice, I'll admit

five7kid, does this picture help or would you still like me to take pictures of my L98 heads? The adapter plate (that my Google search still hasn't found) allows for a proper exhaust manifold fitment.

- 89_IROC

edit: thirdgen88, the black plenum and runners rock

The end port has a "3rd" bolt hole - I understand that. The stock exhaust manifold uses the rear-most or outer-most hole - understood.

I guess my confusion was I thought the Vortec heads had that extra bolt hole - but again, I don't have Vortec heads (just seen pictures and taken quick looks at the dealer).

Hey swisscheese--what does the law specifically say? Perhaps you could go with some different exhaust manifolds if its just a matter of looking stock.

One option may be LT1 exhaust manifolds. Because they use a 3 bolt flange at the outlets there may be some fit issues with the chassis, but worst case it should be easy to grind off the ears and add a flange made from 1/4" steel that would "collar" the outlet (similar to the loose flange on the ball end of the exhaust where it attaches to the catalytic convertor). You may also need to move the air divertor box on the passenger side, but these manifolds have air injection ports and oxygen sensor tap. I don't know if these manifolds flow any better than the TPI logs, but they sure look like they would. Just my opinion though, I have no facts to support this.

Another option may be using Sanderson "cast headers." Since they're cast iron they don't look like headers. Unfortunately they don't have air injection or oxygen sensor provisions, but these can be added--the trick would be to make them look like a factory piece--maybe grind off the name & the ribs, and be careful about adding the taps. Again, I have no idea if these flow better than TPI logs either, and the fact that these are show car pieces isn't encouraging, but its one more thing to look into.

Good luck.

True or false image of Vortec heads?

http://www.sdpc2000.com/images/produ...75_9826016.jpg

Looks like a mix: No center intake bolts, but does show exhaust cross-over.

The iron vortec heads I've seen have this feature--it looks like an exhaust crossover but its just a relief that goes nowhere. No idea what the point of this feature is.

edit: corrected some horrendous grammar

Okay, what about the 3rd exhaust bolt hole on the #8 exhaust port?

That I didn't look at--once I saw the EGR was a fakeout I was no longer interested (I knew vortecs used 'divorced EGR' but this feature made me do a doubletake).

Hopefully a vortec-headed member can run out and peek under the hood?

This is a true image of Vortec heads. That looks like my 350 HO crate motor, actually.

It's 11:46am central time and I'm headed to work, so let me know exactly what you're looking for and I'll do my best to check tomorrow morning before work.

As an aside, that exhaust crossover looks familiar but I wasn't paying any attention to it when bolting up the intake.

- 89_IROC

Are there 6 exhaust manifold bolt holes per side, or 7?

(The link is to SDPC's picture of a 350 HO crate.)

There are 6 unless they've changed the exhaust manifold bolt pattern since the summer of '03. I say this because I would definitely have noticed if there were more; I spent several hours studying the manifold and the head trying to figure out how to solve the problem.

The head in the picture does look like it has 7 bolt holes, but I'm going to guess that there are only 6 based on my limited experience.

- 89_IROC

Something wacky I saw on SDPC2000.com: The new big port vortec heads show 8 taps on the exhaust side. This is weird, and of course it may be a generic picture.

see here:

http://www.sdpc2000.com/cart.asp?act...129&pid=229034

bump

Well, I was thinking of putting on some Vortec heads over the winter.

Since the stock manifolds won't work, I assume that headers and the Edelbrock TES design for our cars will have the same problem with that last bolt hole?

Considering this is my only car, but not exactly a daily driver, I still need to maintain factory ground clearance (potholes in NYC are a bitch). What headers can I go with that won't compromise clearance, and fit in the compartment like a set made for our cars?

The stock manifolds will work.

The Edelbrock TES will work.

The extra bolt holes in the heads won't keep either thing from working.

All of the usual SBC headers will fit Vrotec heads.

Ya know, rereading my post, I see my mistake. I shouldn't have said the manifolds don't work. Just looking at how the rearmost bolt was left out when using the stock manifolds led me to believe I'd have a leakage problems with a TES or headers if I had to do the same.

Thanks for your reply.

All off-the-shelf 3rd gen headers use the "traditional" SBC six exhaust bolt arrangement.

is there a fresh post on this for a solution?

I am helping my brother in law install a freshened up L31 engine into his 86 with a carb intake and there is no seventh hole on the heads. It just has the 6.

GM may have added the extra hole later on L31's for crate motors but this truck engine has none.

The 3rd gen pass side manifolds I have are from an 86 305 and an 92 350, that would cover the whole gamut of applications in 3rd gens, and both sadly have an "offset" rear bolt hole.


for those of you still misunderstanding I have diagramed the issue for further examination.

I have never seen a vortec head with the seventh bolt hole. My own set of 062 castings don't have it either. Here's a pic of part #12558060 from gmpartsdirect.com ~>

here's a pic of the HT383 which comes with vortecs ~>

Also, those 'large port' vortec heads on sdpc that 377Z posted are not production vortecs, they are the bow tie high performance version of the vortecs

is there a manifold which will work (other than headers) for the passenger side?

a guy at the dealership said he could get a pass side manifold which had the proper spacing for $120. I told him that the guy would order him the wrong one because I dont't believe there is a 3rd gen manifold that has the proper bolt spacing for the rear on the passenger side.

I'm STILL running without the last bolt hole... Just put a good gasket in there and torque the bolts down to 30 ft/lbs and all will be good... Its been over a year now...

Most headers use the inside bolt hole as opposed to the outside one like the manifolds.

If you want to use manifolds you might want to try a set of pre ’96 LT1 (f and b body) manifolds. They are drilled like the earlier f-body manifolds with the outside bolt hole drilled, but there is room to drill the inside bolt hole. The problem with them would be that the LT1 cars used a 3 bolt flange to connect the manifold to the y-pipe, where the 3rd gen manifolds used a 2 bolt flange, but the flanges are in roughly the same location, they do fit the chassis.

thanks man, that is the kind of constructive answer I was looking for.

interesting topic to ressurect,
my guess is that gm added the extra hole on the drivers side(where mine is)for a stud to hold an accessory bracket.i don't remember the passenger side of my original manifolds having an extra hole over the older ones.
i think mine had the p.s. bracket attached there??????????
Eric

Mark,
The passenger L98 exhaust manifold is more elongated on the foremost end - this is easy to see when comparing the two exhaust manifolds. The early heads don't have this bolt hole asymmetry, which creates a problem when using L98 exhaust manifolds. All the bolts will fit, but the foremost manifold bolt hole will extend approximately 1"-1.5" past the bolt hole in the head.
cap-10

cap-10,

I moved your original question here http://www.thirdgen.org/techboard/ex...der-heads.html (Exhaust manifolds for older heads and emissions) because it is a different topic.

Known as "thread high-jacking".

Thank you,
Did not mean to High-jack anybody. Just wanted to get some info to resolve problem. The reason I am not going to headers is because I have most of the stock exhaust parts and funds are real tight.

cap-10