Inlet manifold bonanza...

[1990Z71Swede]

When gathering parts for a mild upgrade I took a dive into my own parts bin, mainly just to assess the greatness or lack thereof of the stock TBI inlet manifold. (just by eyeballing it, so not very scientific really ) While doing so I took some pictures. Maybe they can be of use to someone else doing something similar?
What I had to work with was:
#1 A generic 1968 Q-jet Cast iron manifold, found on for example 275 Hp Camaros.
#2 A GM/Winters Z28/LT1 factory replacement aluminium High Rise, similar to a performer RPM, this is the one with the oil fill tube.
#3 A Holley 300-36 Again a High rise comparable to a performer RPM, but slightly larger (not taller) overall.
#4 The odd one out a Weiand X-celerator Single plane Low rise.

Now, I'm personaly either going with a cleaned up Stocker or a non RPM Performer Q-jet manifold plus adapter.
The runners of the Stock TBI manifold are pretty much identical to the old cast iron Q-jet lump, so that part I guess is just fine for what I'm doing, but the "plenum" is a different story altogether.

The TBI manifold has some quirks. Apart from the obvious 87- onwards angled center bolts, the entire plenum has coolant in a water jacket around it. The exhaust heat riser port appear to be used just for EGR and does not pass through. The underside part of the plenum water jacket connects with the open rear water passage, and exits through the port used for the heater core. The pics of the underside shows the difference. All of this could influence which way to go, when choosing a manifold that suits your specific needs. Old news maybe for most people, but take it for what it is.

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[Schurkey]

The TBI manifold is almost exactly the same height as the "ZZ" aluminum manifold 10185063 as used on the various performance crate engines--ZZ4, for example. When not using TBI heads with the goofy center bolt angle, this manifold requires no mods for throttle, Cruise, or TV cable attachment other than to adjust the TV cable. Even stock fuel hoses can be used with a little adjustment at the frame bracket. The ignition coil mounting, and the vacuum pipe for the power brakes can be relatively easily adapted. A little trickery can also allow the OEM-style heater-hose quick-connect to be used. A thin TBI-to-Spread-bore adapter plate is needed.

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The ZZ manifold also has a provision for EGR; although the valve style is different and too far forward--interferes with the IAC on the throttle body. This can be dealt with, but it's not easy. EGR and a lack of attachment point for the brace coming off the A/C compressor are the biggest issues with using the ZZ manifold.

Chevrolet Performance Parts - 10185063 - ZZ4 Aluminum Intake Manifold- 1955-1986 Small Block Chevy With EGR - Spread Bore Or Square Bore Carb Flange

Chevrolet Performance Parts - 10185063 - ZZ4 Aluminum Intake Manifold- 1955-1986 Small Block Chevy With EGR - Spread Bore Or Square Bore Carb Flange

paceperformance.com

 

[1990Z71Swede]

I'm tempted to try the similar to the ZZ4 manifold, Edelbrock 3706, if I cand find one on the cheap.

Edelbrock 3706: Performer Small Block Chevy EGR Intake Manifold for 1987-95 Cast Iron Heads - JEGS

Designed for street Chevy 262-400 with 1987-95 cast iron heads that have canted centerbolt holes

www.jegs.com

But if that fails, a stocker opened up to 50mm with rounded entry to the runners is probably just fine.

 

[HotWheelsBurban]

Back in the day, that GM LT1 aluminum intake manifold was the hot setup for a built 350/383. I have one that I got reasonably priced in 1988 cause it had a couple of corner holes broken. Had a friend who could weld aluminum fix it though! I had another one that we found on a van in the old pick your part yard east of downtown Houston. Cleaned it up, carried it to many swap meets, finally got $200 for it at a meet in the DFW area a few years later.....
Technology has improved so much since the early 70s when these were the hot setup. I guess with the square bore carb base, you could put an aftermarket TBI type injection system on it? Presuming one has the funds to acquire said system and the pieces to make it work.....

 

[1990Z71Swede]

Back in the day, that GM LT1 aluminum intake manifold was the hot setup for a built 350/383. I have one that I got reasonably priced in 1988 cause it had a couple of corner holes broken. Had a friend who could weld aluminum fix it though! I had another one that we found on a van in the old pick your part yard east of downtown Houston. Cleaned it up, carried it to many swap meets, finally got $200 for it at a meet in the DFW area a few years later.....
Technology has improved so much since the early 70s when these were the hot setup. I guess with the square bore carb base, you could put an aftermarket TBI type injection system on it? Presuming one has the funds to acquire said system and the pieces to make it work.....

Nah, that one is reserved for the 327 in my Camaro. it is going from a terrible mismatch of components installed by the PO to a stockish but faster period correct aperance. 1967 had no vents in the valve covers, and that oil fill tube is part of my plan to create that look but without the road draft setup.

Also I'm under the impression that the 4bbl aftermarket TBI's work better with single plane manifolds, and I also think that those setups might become way harder to keep running when they become of age.

 

[HotWheelsBurban]

Nah, that one is reserved for the 327 in my Camaro. it is going from a terrible mismatch of components installed by the PO to a stockish but faster period correct aperance. 1967 had no vents in the valve covers, and that oil fill tube is part of my plan to create that look but without the road draft setup.

Also I'm under the impression that the 4bbl aftermarket TBI's work better with single plane manifolds, and I also think that those setups might become way harder to keep running when they become of age.

That's kinda what I figured.... can't be a proper replacement for a carburetor w/o some of the same problems eventually, could it?

 

[1990Z71Swede]

That's kinda what I figured.... can't be a proper replacement for a carburetor w/o some of the same problems eventually, could it?

It's difficult to predict the future... (duh )
But It would be foolish to expect the same reliability and parts availability as an OEM factory installed system. A guy just have to take into account that eventually it gets obsolete and needs replacing with the latest and greatest...

 

[HotWheelsBurban]

It's difficult to predict the future... (duh )
But It would be foolish to expect the same reliability and parts availability as an OEM factory installed system. A guy just have to take into account that eventually it gets obsolete and needs replacing with the latest and greatest...

I'm just trying to decide if I want to keep this manifold for "future projects" or try to monetize it. Both my 400s are Vortecs, and my GMC is probably getting the Cadillac motor eventually to replace the stock six. So I don't have any pre fuel injection small blocks in the fleet right now....
I bought this one for a 70-72 Monte Carlo with 350 that I had many years ago; car rusted out before I could ever get it running right.

 

[1990Z71Swede]

I'm just trying to decide if I want to keep this manifold for "future projects" or try to monetize it. Both my 400s are Vortecs, and my GMC is probably getting the Cadillac motor eventually to replace the stock six. So I don't have any pre fuel injection small blocks in the fleet right now....
I bought this one for a 70-72 Monte Carlo with 350 that I had many years ago; car rusted out before I could ever get it running right.

For a serious 400 build in a car the GM LT1/Z28 would not be my first choice unless I was after the Bowtie/Winters oldschool coolnes. I do actually HAVE a 400 block & crank and a pair of AFR 195's. If that ever gets done, I'm planning to top it up with the 300-36 and a Frankensteined Holley "950". If the AFR's where 210's I would go for a Single plane, like the Holley 300-25.

But For a stump puller 400 truck build the Z28/ LT1 manifold would do juuust fine, I guess.

 

[98 Nitro]

I like the Holley 300-36, used it on 2nd gen camaros and some Novas with 307/350 motors. Holley used to have an EGR medium rise too and both manifolds had an 87-95 heads version as well.