1996-2000 truck stock Cast iron exhaust manifold on 1985 C10

[Geoduck]

I've installed vortec heads on my 1985 305. I'm aware the 85 stock exhaust manifolds don't fit correctly.
My question is; will 1996-2000 Chevy GMC Truck Exhaust Manifolds fit my 1985 C10? Has anyone done this?
I'd like to retain cast iron manifolds. As I understand it headers would add very little to my 305 with a mild "RV" cam.

 

[jh86]

Headers or manifolds for 86k10 350 w/ Vortec heads?

Hello, Anyone have experience with headers or manifolds for 86 K10 350 with Vortec heads? I’d prefer manifolds over headers. Not looking for high performance. Have scoured internet but can’t find a straight answer.

www.gmsquarebody.com

 

[jh86]

What is your emission setup?

 

[bucket]

I've installed vortec heads on my 1985 305. I'm aware the 85 stock exhaust manifolds don't fit correctly.
My question is; will 1996-2000 Chevy GMC Truck Exhaust Manifolds fit my 1985 C10? Has anyone done this?
I'd like to retain cast iron manifolds. As I understand it headers would add very little to my 305 with a mild "RV" cam.

You will probably find that they are too wide and interfere with the frame rails.

With a little bit of cam and the better heads as well, long tube headers would likely provide a large enough bump in mid range torque to probably be noticed by the 'ol butt dyno. Quality headers and gaskets will greatly lessen the chances of experiencing the types of header issues that people tend to b!tch about.

But if you want manifolds, that's fine too. I believe mid 80's L69 or LB9 manifolds would be nearly a direct replacement. I don't remember them having the oddball bolt spacing.

 

[Geoduck]

What is your emission setup?

Jon, I removed all emission equipment. But do have PCV connected of course.

To answer your question. Headers by Summit (SUM-G9006) will fit our truck perfectly with Vortec heads I know this for a fact.
As you know Vortec heads are slightly different than Gen 1 heads. Vortec exhaust runners are about .100 or .125 taller than Gen 1 heads. Gen 1 manifolds will congest exhaust scavenging. Although they would work its far from ideal. Also the Gan 1 right (passenger side) exhaust manifold and head far rear bolt spacing is about an inch farther than on a Vortec head. There would be a serious exhaust leak.

1996-2000 SBC truck exhaust manifolds are made specifically for those heads. Those trucks are very much like our C10. From viewing pictures of those manifolds driver side looks like an easy fit. Passenger side may interfere with firewall.
If you have those manifolds I would be very interested to learn how they fit your C10.

Andy always has good advise. It maybe better to simply go with headers. Jon, your 350 would gain more from headers than my 305 although the 059 heads I have are darn good.

 

[Geoduck]

Thanks Andy, aways appreciate your input.

 

[jh86]

Jon, I removed all emission equipment. But do have PCV connected of course.

To answer your question. Headers by Summit (SUM-G9006) will fit our truck perfectly with Vortec heads I know this for a fact.
As you know Vortec heads are slightly different than Gen 1 heads. Vortec exhaust runners are about .100 or .125 taller than Gen 1 heads. Gen 1 manifolds will congest exhaust scavenging. Although they would work its far from ideal. Also the Gan 1 right (passenger side) exhaust manifold and head far rear bolt spacing is about an inch farther than on a Vortec head. There would be a serious exhaust leak.

1996-2000 SBC truck exhaust manifolds are made specifically for those heads. Those trucks are very much like our C10. From viewing pictures of those manifolds driver side looks like an easy fit. Passenger side may interfere with firewall.
If you have those manifolds I would be very interested to learn how they fit your C10.

Andy always has good advise. It maybe better to simply go with headers. Jon, your 350 would gain more from headers than my 305 although the 059 heads I have are darn good.

I shared that thread because there is a link to another thread that used 8525hkr manifolds and shared pictures. Seemed promising enough that I’ll be ordering to try in about a month.

 

[bucket]

Jon, I removed all emission equipment. But do have PCV connected of course.

To answer your question. Headers by Summit (SUM-G9006) will fit our truck perfectly with Vortec heads I know this for a fact.
As you know Vortec heads are slightly different than Gen 1 heads. Vortec exhaust runners are about .100 or .125 taller than Gen 1 heads. Gen 1 manifolds will congest exhaust scavenging. Although they would work its far from ideal. Also the Gan 1 right (passenger side) exhaust manifold and head far rear bolt spacing is about an inch farther than on a Vortec head. There would be a serious exhaust leak.

1996-2000 SBC truck exhaust manifolds are made specifically for those heads. Those trucks are very much like our C10. From viewing pictures of those manifolds driver side looks like an easy fit. Passenger side may interfere with firewall.
If you have those manifolds I would be very interested to learn how they fit your C10.

Andy always has good advise. It maybe better to simply go with headers. Jon, your 350 would gain more from headers than my 305 although the 059 heads I have are darn good.

Didn't the earlier '91-'97 LT1 heads have a very similar port design? I haven't had any in front of me for many years. The F-body or B-body manifolds could possibly be a decent choice without killing as much power.

 

[joseph_bruce]

A lot of good advice in all of the above. Several things to think about:

If you've got the engine in the truck and some manifolds; give them a try. No better way to see if they fit the chassis.

Even though a manifold has the same casting number; it might have emission fittings and y-pipe flanges such that other things won't fit or you need a lot of plugs.

If the flange/gaskets don't line up with your y-pipe; you're going to need a lot of "custom."

Headers "might" be your best option for ease of instillation; but unless you're spinning over 5000 rpm; don't expect them to "help."

The odds of finding a used set of manifolds that aren't rusted to the point that the studs and any efe valves or extensions are removable is getting lower every day.

Lots of plus and minus to either choice. Just pick what you're happy with and find what will fit.

Most all of us have been in a similar situation. Good luck!

 

[bucket]

How is it that so many people think that headers only provide gains at high rpm? The fact is, it's quite the opposite.

 

[Ricko1966]

Dyno sheet 2.5 rams horns,2 inch rams horns,headers on a 383. Before all the rush to buy 2.5 inch rams horns,they won't fit our trucks,the 2 inch angled ones will,but aren't very good.If I wanted manifolds, I'd look at some lt1s . Look at the difference the headers make at low rpm

 

[CalSgt]

GMT400 Vortec exhaust manifolds fit just fine, I threaded a pipe plug in the EGR port and ground it smooth before painting them.

ETA: There are a ton of these manifolds available for cheap that are still in great condition

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