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Page created by MRHZV8 Jan 26th 2005:
Data contributed by T and other named contributors:
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Brock inlet manifold. Click to enlargen. Photo by MRHZV8.

The term Manifold describes the collection of a number of pipes connected to the engine.
The Inlet Manifold is responsible for directing the air and fuel mixture into the Engine.
HQ SS' Shed
The Exhaust Manifold is responsible for directing the exhaust away from the Engine.
Small block Chev inlet manifold. Click to enlargen. Photo by old_skool_kid.

Exhaust Gas Recirculation, even when working perfectly, can be a cause of warped inlet manifolds. Early Fuel Evaporation vanes and Hot Spot vanes can stick in the cold start position
and cause exhaust to be continually blown under the bottom of the inlet manifold. The result is a warped and heat stressed Inlet Manifold.
Blue Motor Inlet Manifold showing burnt edges. Click to enlargen. Photo by Merc9112006.

Nuts, bolts and washers used on Inlet and Exhaust Manifold sets can be critical. Thermocycling (the process whereby a stud expands under heat, allows the nut to rotate, then contracts on cooling to leave the nut loose) is an issue that is addressed by the manufacturer during
Blue Motor Exhaust Manifold where it couples to the Inlet Manifold. Click to enlargen. Photo by Merc9112006.

Replacing the specialised items with after market items can have a deleterious effect since the
factory supplied unit is designed to stay tight irrespective of the temperature of the manifold
Std Early 6cyl red single barrel Inlet Manifold. Click to enlargen. Photo by HQ SS.

HZ, UC and VB 6's used special square shaped dimpled washers to hold the Hot Box together that prevented the bolts from working loose.
EGR valve on Pollution Inlet Manifold. Click to enlargen. Photo by HQ SS.

Gaskets need retightening after their first run. It's imperative that they be retightened otherwise leaks will result.
X2 HD/R Inlet Manifold. Click to enlargen. Photo by HQ SS.

In the days of leaded petrol, exhaust manifold leaks were easy to fix by pulling out the choke
and flooring the accelerator. Any holes would be plugged with lead ash and then the lead ash would become burnt into place by normal driving.
Now in the days of unleaded petrol, this is no longer possible.
6cyl, red, two barrel Holley Inlet Manifold. Click to enlargen. Photo by HQ SS.

6 Cyl VK Commodore Exhaust manifold, wire brushed, checked for cracks, and painted in Hi-Temp black paint. Click to enlargen. Photo by LMH.

Underneath the Blue/Black motor 6 cyl Carbie Manifold. On the left is the mildly warped flange and on the right is the re-leveled one. Luckily this was only mildly warped so a flat block and 180 grit wet & dry brought it back to level. If you don't they can leak exhaust at these joins. Click to enlargen. Photo by LMH.

Have installed the Gaskets for the EGR and have used some Hi-Temp silicon as an insurance policy against exhaust leak. I hate exhaust leaks!! This is ready to be mated to the Carburettor manifold. It will be tightened lightly only until it is installed to the motor ensuring they both "adjust" themselves and pull into the head. I do a light tighten of the manifold to head nuts, then tighten the 4 nuts that hold the manifolds to each other, then go back to the nuts on the head again. Click to enlargen. Photo by LMH.


Submitted by MrHQGtS on Sat, 14/07/2007 - 03:04.

both are pollution manifolds, turn em over and they have 2 barrells for the carb then they are for a 253.

iirc, the top manifold is pollution hj (rectangle shaped EGR port) (HQ had no EGR Ports), bottom manifold is hx-hz.(U shaped EGR Port)

Black motor inlets had a square port for the EGR. Click to enlargen. Photo by Dusty Dirt Roads.


Submitted by MrHQGtS on Sat, 14/07/2007 - 07:50. They would be HZ manifolds used with HQ Heads. Click to enlargen. Photo by Dusty Dirt Roads.

202 UC showing the dimpled type exhaust manifold. Click to Enlargen. Photo by T.


===253 Inlet Manifolds:=== 

If I am not misled I have been informed that the 253 V8's had humps in Runners # 7 & 8 to slow Fuel down because these two Cylinders run rich when fitted with a 308 Manifold, which I am told does not have the humps in the Factory Manifolds as it does not affect the 308 motors, but to be honest I have never stuck my finger in to see if this is true or false, my Mum taught me well... ;{D


Pig (OINKS308)


Not sure T, but if I recall correctly this was on the pre-Pollution 253 and 308's and am only going by what I was told by Mechanics over the years in regards to 253 versus 308 as to which Engine makes the better engine, but I have seen an old mate's 253 backed by a Toploader 4 Speed and a 2.9:1 Diff from a Tank Fairlane pull 13.9 over the Quarter in a fully decked out Panel Van in Street trim and drop to 12 seconds flat in a Ute with Ladder Bars and Slicks with 3.7:1 Diff and no Tailgate at the old Surfers Paradise Drag Strip, so a 253 can wear a lot of its big brothers hot up gear and not suffer as a result as many would have us believe...

I have seen quiet a few Blue 253's fitted with the 4BBL Manifold and Rochester from later 308 Commodores and they ran trouble free for many years after I had relayed what I was told about the humps in the Manifold, never seemed to have affected them so maybe I was informed wrong or maybe it doesn't really have that big of an effect if the Motor has been mildly worked with bigger Cam and Exhaust etc?

If it works who are we to argue otherwise? :{D

Pig (OINKS308)




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