Hate to sound like a newb, but...

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65LoveAffair

65LoveAffair

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Okay, I was reading about upgrading intake and exhaust manifolds at various locations, and I kept coming across a recurring theme. A lot of what I read said that some "aftermarket" manifolds will cause you to lose intake manifold heat. What exactly does this mean? Thanks, and sorry for the newb question.
 
Aftermarket intakes and headers are not cast iron like factory pieces are. Cast iron holds heat better than mild steel or aluminum. Only time intake manifold heat matters for our cars is cold weather running. As far as warm weather goes with factory stuff, cooler fuel/air mixture equals more power. Thats where aluminum intakes come into play.
 
Manifold heat is the crossover of the exhaust gases in the intake. Better know to some as the center port. Some after market intakes do not have this cross over. It is eliminated for performance. It keeps the fuel charge from getting heated.
 
I've had a few aftermarket manifolds cross my work table that had the heat cross overs blocked on purpose. Others were blocked with years of gunk. :-D
 
can you run a set of headers with the stock intake manifold without a problem??
 
Yes,, it just takes longer to warm up. Again only pertains to cold weather driving say below 50ish degrees. The colder the longer,, You may or may not experience any drivablity problems.
 
There are several Aftermarket Manifold that have heat provisions. Our Aussie Speed manifolds have a heat provision (as a add-on option). You pipe your heater hose through it and it uses water to heat the manifold. Others like the Offy have manifold heat on the bottom like the factory heat.
Frank
 
65LoveAffair said:
Okay, I was reading about upgrading intake and exhaust manifolds at various locations, and I kept coming across a recurring theme. A lot of what I read said that some "aftermarket" manifolds will cause you to lose intake manifold heat. What exactly does this mean? Thanks, and sorry for the newb question.
Click to expand...
No problem. On the /6, the intake manifold bolts onto and is heated by the exhaust manifold. This heat is very useful when the engine is very cold and it is hard to maintain the flow of fuel vapor to the engine. Most aftermarket manifolds to not have the provision to bolt up to the heat riser on the exhaust manifold, though some do.

No intake heat

Pro:
  1. Denser fuel/air charge introduced into cylinder (more power).
  2. Possible to run slightly leaner jetting on carburetor.
  3. Less tendency to "lean out" when engine is running hot.
  4. No EGR.
Con:
  1. Takes longer for engine to warm up and run smoother.
  2. Less fuel mileage, especially on short runs.
  3. Automatic choke less efficient.
  4. Increased harmful emissions.
Since /6 carb heat depends on the exhaust manifold as a source, similar things happen when an aftermarket exhaust system is used. The only exception to this are the Dutra Duals and manifolds with a hot water provision. The Dutra Duals twin manifolds are based on the stock manifold and retain the heat riser for use with a manifold that is compatible.
 
2 Darts said:
No problem. On the /6, the intake manifold bolts onto and is heated by the exhaust manifold. This heat is very useful when the engine is very cold and it is hard to maintain the flow of fuel vapor to the engine. Most aftermarket manifolds to not have the provision to bolt up to the heat riser on the exhaust manifold, though some do.

No intake heat

Pro:
  1. Denser fuel/air charge introduced into cylinder (more power).
  2. Possible to run slightly leaner jetting on carburetor.
  3. Less tendency to "lean out" when engine is running hot.
  4. No EGR.
Con:
  1. Takes longer for engine to warm up and run smoother.
  2. Less fuel mileage, especially on short runs.
  3. Automatic choke less efficient.
  4. Increased harmful emissions.
Since /6 carb heat depends on the exhaust manifold as a source, similar things happen when an aftermarket exhaust system is used. The only exception to this are the Dutra Duals and manifolds with a hot water provision. The Dutra Duals twin manifolds are based on the stock manifold and retain the heat riser for use with a manifold that is compatible.
Click to expand...

you are correct in saying that the intake depends on exhaust temp for helping to heat the intake BUT you have never felt my under hood temp with unwrapped/coated headers...
 
2 Darts said:
The only exception to this are the Dutra Duals and manifolds with a hot water provision. The Dutra Duals twin manifolds are based on the stock manifold and retain the heat riser for use with a manifold that is compatible.
Click to expand...

I thought the Dutra Duals "twin" manifolds were 2 3 into 1 manifolds that were completely divorced from the intake? The hybrid Dutra front and Modded rear stock manifolds retains the heat riser to the intake. Just an observation. Water heated I suppose could be done by bolting a gasketed plate to the bottom of the intake and running the water through the EGR port?
 
i'm going to jump on this with a small mod project i've got.

so how about modding a stock manifold to achieve duals like this (from Waggin):
attachment.php


i'm starting to chop up a stock manifold to try to recreate this, and here in Australia we just don't get as cold as you seppo's so the heat-box isn't a big worry..

this is to run with a speco dual carter BBS intake (so two stock single-barrel carbies)

but, my main question would be about the auto-choke on the stock carbies - can i retain the auto-choke on the pair of BBS's, given there will only be one choke-riser thingy on the exhaust manifold, and that's ideally not connected . . .

(edit - i forgot to click the 'notify of responses')
 
yeah, the only problem is the cost of shipping to Australia - means Dutra Duals are just not an option.

hence i'm looking modding up a set myself using what i have available . . .

chris.
 
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