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I'm installing the original exhaust setup in my 74 HQ 350 and I cant understand exactly what this heat-riser valve does.
Does it just restrict the exhaust gases a little and makes the RH manifold heat up faster?
Just seems like one big restriction to me.
Thanks
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Rig Hi,
If the system is complete and working, what the heat riser valve does is restrict gas flow out of 1 bank whilst cold.
The restricted gas flows thru the ports under the inlet manifold and then into the opposite cyl head where it then exits out of its manifold.
When it passes under the inlet manifold it also does some preheating to help drivability in cold extremes.
Also this is where in later smog engines exhaust gas is introduced into the fresh air fuel mixture for emission reasons (EGR) EGR wont be on yours. Oily
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Thanks Oily thats all news to me I never realised they did that.
So I guess early chev heads and intake manifolds didnt have these ports in them?
Mine seem to be all the right numbers for a 73-74 HQ so should be ok.
Thanks
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quote:
Originally posted by RigPig
So I guess early chev heads and intake manifolds didnt have these ports in them?
Not so ! Another reason for the heat crossover was to operate the auto-choke. I believe that SBC V8s have had this system since 1955. Dr Terry _________________________________________ When calculating a car restoration budget, be as accurate as you can & then double the final figure. It will be closer to the truth. |
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As Terry says. Almost all standard SBC's had the crossover ports in the heads. The only factory heads i've ever seen without them are 292 slant plug "turbo" heads.
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learn something every day
Thanks guys
"I would never want to be a member of a group whose symbol was a guy nailed to two pieces of wood" (George Carlin)
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