Vavletrain instability small Block

[Duke W.]

Re: Vavletrain instability small Block

Your heat riser is already effectively blocked off because there is no crossover port in the FI manifold adapter.

I think what Clem is suggesting is a good idea- fill up the entire head riser port in the head and blend the outside end into the exhaust port geometry. I don't know anything about "high temperature furnace cement", but it needs to be something than can withstand, say, 2000F to give some margin for 1500F EGT.

It also needs to bond well to cast iron and have a similar thermal expansion coefficient.

Maybe Clem knows of a specific product name.

Duke

[Clem Z.]

Re: Vavletrain instability small Block

Your heat riser is already effectively blocked off because there is no crossover port in the FI manifold adapter.

I think what Clem is suggesting is a good idea- fill up the entire head riser port in the head and blend the outside end into the exhaust port geometry. I don't know anything about "high temperature furnace cement", but it needs to be something than can withstand, say, 2000F to give some margin for 1500F EGT.

It also needs to bond well to cast iron and have a similar thermal expansion coefficient.

Maybe Clem knows of a specific product name.

Duke

i used a furnace cement a friend got me from the steel mills. tech inspecting at drag strips is were i saw bill jenkens using poured in lead. the head is water cooled so the stuff you use will never see the melting point of lead. the shape of the passage keep the filler from moving even if it does not bond to the cast iron

[Joe C.]

Re: Vavletrain instability small Block

I wouldn't use lead, or furnace cement unless I knew that I'd be tearing the engine down frequently and making inspections.

I had forgotten that you have a fuel injected engine, so of course what I did is essentially very similar to what you already have.

For peace of mind, and especially if you don't tear your engine down frequently, I'd remove the heads and have the passages brazed up. Filling and blending the passage down low in the pocket near the valve involves adding quite a bit of bronze, which you can then shape with a bur and a die grinder. The less than ideal exhaust port shape has a negligible effect on exhaust flow. You will not see any significant flow improvement, if any, on #4 and #5 exhaust ports if you blend them to match the other six.

I don't see any harm in having the exhaust fill those blocked passages. If there's no flow through them, the chambers will be almost stagnant and the temp of the gas in them will stabilize to that of the surrounding cast iron.

[Ken A.]

Re: Vavletrain instability small Block

Boy, you guys make this complicated. Bill Jenkins used melted pistons-just like every racer I knew back then. Who in the world would pour lead in an engine when you're trying to cut weight?

[Clem Z.]

Re: Vavletrain instability small Block

Boy, you guys make this complicated. Bill Jenkins used melted pistons-just like every racer I knew back then. Who in the world would pour lead in an engine when you're trying to cut weight?

the engine i checked was a jenkins built cast iron head BBC and it sure looked like lead to me. pouring 1200 + degree F molten aluminum would be interesting deal.

[Ken A.]

Re: Vavletrain instability small Block

He's still around, so you can ask him-but he will probably charge for the advice. Every shop I knew of had way more scrap pistons than lead laying around & it's easy to do with a torch. Just break up a piston and use the head as a bowl & start melting.

[Duke W.]

Re: Vavletrain instability small Block

Lead melts at about 620 deg. F, so even with the cooling jacket pulling heat from the rear, exhaust gas would probably melt the lead surface in the port.

Aluminum heads don't melt even though aluminum's melting temperature is below peak EGT because high temperature exhaust gas only heats the exhaust port about 25 percent of the time while the cooling jacket removes heat 100 percent of the time.

The same applies to piston crowns which are exposed briefly to 4500 degs. F.

Duke

[Joe C.]

Re: Vavletrain instability small Block

Why not fill it with asbestos?

Why............just grind up some of your old pipe insulation sleeves, or, better yet, use the powdered stuff that you used to use to seal the firebox in the oil fired boiler with. It works great and is good to very high temperatures. The fibers that will be shed during engine operation will continually work to give a nice, finish honed surface to your engine's cylinder walls. If you have a high overlap camshaft installed in your engine, the scouring action will be very fast, and your cylinder walls will be clean as a baby's ass, lickety-split! Hey.............they used Bon-Ami in 1955.

[Ken A.]

Re: Vavletrain instability small Block

Joe, back in the day, we used a special alloy called unobtainium. Wherever you used it on a race car it made a huge difference- more power, lighter weight, & guaranteed a win at any race. I used to have a huge stash of the stuff but lost it all the day the car became airborne and floated off never to seen again. We had just filled all the tires with helium and we theorized that it reacted with the unobtainiumn & caused a negative weight.-It was a 63 with a factory 409 engine.................