BBC manifold gasket questions

[beached1]

When I blew my 454 a few months ago, I noticed that the maifold gaskets had block off plates in the center. This blocked the exhaust ports that would run through the bottom of the intake manifold. I don't know much about 4 strokes or V8's but this lookes like it could be used to heat the fuel/air that is coming into the intake. I went to change my manifold today from a performer dual plane to a Torker single and noticed that the enginer rebuilder used a gasket that didn't have this blocked. Does anyone know weather it's better to have this blocked or open? The engine builder said it's better to run it with them open. To quote him "Heat is Horsepower son" Now I don't want to keep asking him the same stupid question cause he's the kind of guy that will skip a wrench off of my head if I sound like I didn't listen the first time. But where I ride is usally very hot. Blythe, CA in July/August is always around 110/120. I would think my motor is getting plenty of heat or "Horsepower" If anyone has any info on this, I would appreciate it.

[Gerrit]

Unless i'm mistaken. The cooler(more dense air) the intake air temperature, the more expansion you will get in a hot cylinder, therefore creating more power.

[Riley]

Someone correct me if I'm wrong here, but I would block it off. Unless you have a heat stove type choke that sticks down in the passage, then you need it open. If you have an electric choke then I think it would be ok to block it off. I think the exhaust crossover allows for quicker warm-up times in cold weather, and most people don't boat during cold weather. Just my opinion.
Riley

[froggystyle]

Block it off. Most really high performance manifolds don't even have anything to go into anyway. The open gaskets are just cheaper. Some come with a small metal plate for the purpose of blocking it off. Most high performance gaskets don't even have the provision for it. You are right, Blythe is already providing you with plenty of "horsepower". I believe he is talking about the atomizing effect of a warm manifold. It keeps the fuel from condensing on a cold manifold, like in a blown application. That is why, to a certain degree, a warm-soaked manifold will produce power on a supercharger. And I think it is most apparant when running alcohol or nitro, which always run dramatically cooler. So much so, that at operating temp on my old IMCA modified, the alcohol caused the manifold to be cool to the touch, with beads of water on it. This phenomenon is not applicable on a normally aspirated gasoline engine though I don't think. PonPon, Racing Ray? Whatdaya think?

[Racing Ray]

If I am not mistaken the intake flange on a Torquer already blocks it off as it has no provisions for an EGR valve?

[froggystyle]

Ray, I think you are right. It's been a couple of years since I ran a single carb, but I remember the Torker having advertised "not EPA approved". Am I right about the atomization vs. heat discussion???

[spectras only]

Most boats have an electric or a manual choke installed by the builders,there's no need for the heat passage to be open.The seventies tarantula manifolds and offy's never had them.They ment for cars for faster warmup.I use a phenolic spacer [a one inch and a two inch on my boats] between carb and manifold to keep the carb even cooler.

[beached1]

Thanks for the input guy's. This Edelbrock Torker II does have the passage in it that would allow for the exhaust to pass through. I'm going to get the gasket that will block it off however. Hopefully these changes will help. My boat is a tank! Thanks again guy's! I've learned so much using this forum than I have anywhere else.

[Racing Ray]

I thought it was the old style Torker not the new one. As spectras only said the heat riser passage is to help heat the intake faster.
It also helps reduce emmisions by heating the intake and making sure more of the fuel is burned by better atomization. Thankfully our boats don't need smog checks yet!
The cooler the intake charge the more power period. Thats why innercoolers, Nitrous and even cool cans are used. That is also why the same combo on alcohol will run about 3 tenths quicker in a quarter mile run.
A phenolic spacer or one of mircarta usually only 1/2" is a good idea too. Any taller and you start to affect the vacuum signal sent to the carb. In some cases good, in some not so good. Stay away from an aluminum spacer as it will indeed transfer heat to the fuel.
Before the newer materials were put in use Moroso made a carb heat sink. Essentially a stack of alternating gaskets and thin aluminum plates. I havent seen them in awhile not sure they still have them.

[ponponracing]

Plug it or block it buddy! You want the mixture to be as cool as possible. You are in the hi-perf business here. Street application is different. Take my word.

[beached1]

Thanks again. I feel vendicated. My experience racing two stroke PWC's was making me suspicious. The "heat is horsepower" is sort of true. You want your cylinders to run at a certan temp consistantly. But in two strokes anyway, your carbs want cool dry air. Hot air robs horsepower. Four strokes shouldn't be any different in that respect.