lascelles

Folks I noticed a few threads on how to block off the coolant from the manifold.

Why block the coolant passages in a stock manifold?
Why is there coolant in there anyway?
Does that apply for both 12A +13bA? FYI - I have an 85 12A


Can I gain 10%HP or 20MPG by sticking in a couple quarters??

RX-7 Chris

iTrader: (19)

It is there to help warm the car up faster. By having a hot manifold the fuel does not atomize as well.

pinoyremix

coolant runs through the stock intake manifold to warm up the the manifold faster and make the car warm up faster...especially on cold days...one reason i sealed them.up is because with aftermarket manifolds the ports are actually welded shut..and you could put new o-rings...but i just optioned to bounce the coolant back sooner..by installing freeze plugs from pineapple racing...

flight_of_pain

you can get the freeze plugs from any auto parts store, I used 20mmWx12mmD IIRC.

i blocked them off personally so i can change manifolds, without losing coolant/making a mess.


isaac

Jeff20B

iTrader: (13)

Quarters don't work that well. Get freeze plugs.

flight_of_pain, I hope you blocked off your ACV port too. Or hopefully you are using an aftermarket manifold. You do NOT want hot blasts of exhaust pulsating up into your manifold with no way to cool it. Yes, that is the other reason why Mazda has coolant flowing through the manifold, to keep it cool!

I will not block off the coolant ports if the ACV port in the intermediate plate is active. You can shove a bunch of quick steel or devcon in there but it's a good idea to clean the carbon off first, which can be done with the engine in the car.

If the car ever has to pass emissions, don't block anything.

Box_Man

Another thing that the coolant passages do in the intake manifold is prevent intake icing. Ever notice how on piston powered planes they have a carburetor de-ice mechanism? this is because of the Venturi effect cooling the intake charge down below the freezing point, which at altitude can ice up the intake and choke the engine. I blocked mine because I hate the mess I make taking off the intake manifold with the ports enabled, and because I live in florida, where I'm always at sea level and it's hot as ***** 24/7.

Jeezus

iTrader: (4)

I beg to differ... Quarters worked well for me, and used slicone sealant to hold it in place.

Granted I took them off a year later (after I went through a wrap-around side draft, to lake city side draft, to holly downdraft) for a nikki stripped and prepped carb.

If given the choice between the two, definitely get the freeze plugs. Only reason I didn't was because all the shops around here didn't carry 20mm freezes.

flight_of_pain

yep, that was taken care of before the engine went together


isaac

lascelles

I wasn’t asking how (there are several threads) as much as Why or why not.

So far we have:
Plus Side
Warm the car up faster. To help vaporize the gas
Prevent freeze up of the carb.
Needed for ACV

Minus Side
Change manifold quicker easier

There has to be a power gain or something for it to be common on the racetrack.

AverageJoe

iTrader: (1)

You might want to do some re-reading because RX-7 Chris said the hot intake mani DOES NOT atomize the fuel as well. Also, how is being able to quickly swap manis a minus?

Hyper4mance2k

iTrader: (40)

Pros of blocking:
Colder air intake tepms make more power
less mess

Pros of leaving it alone:
Faster warm up
no carb icing
needed when you have ACV




That's all there is to it.

lascelles

I meant minus the coolat.

If he meant that the coolant helps warm up the manifold but stops it from getting hot. Ok
But the coolant is adding heat to the manifold after the engine warms up. So I think he mis-typed

Crit

iTrader: (6)

Regarding racing, a lot of folks do it because of protests. If you're in a class that requires stock porting and you get protested, you're going to have to remove the intake manifold in the pits, same day, and might have a race soon-after. Freeze plugs make the day MUCH easier.

mjm4jc

RX-7doc or Addict,

I wish you guys could chime in and give your opinions on this one :-)

Mike