Tired of cracking cylinders!

[A.J.Towers]

You need good gas and a wideband and make sure your A/F is right. If you still crack cylinders then you either need to back off the timing or turn down the boost. Thats it. Guessing at your A/F and using mystery gas will always result in broken parts.

[Jeremy_Owen]

Thought I would pull this post back up and see if the OP found a solution.

Also  MY dellorto will flow 103 gallons per hour of fuel throught it at 7psi AT the needle. Fuel pressure at the pump is 9 psi. It will flow 60 gallons per hour at 3 psi at the needle and 6.5 at the pump. My pump is a holley black and it flows 130 gph out of the hose that goes to the carb with the needle un hooked at 6 psi at the pump and 0 at the feed hose.  Full free flow the pump is doing 180 gph. All this is at 17.4 volts at the pump. Max pump pressure is 14 psi.

The needle will flow EXACTLY the same at those same pressures with ANY pump, assuming the pump is capable of providing the pressure. Note that a holley red would NEVER match those numbers even with no regulator AT ALL. The pump just simply isn't capable of it. Ultimately the flow is detemind by pressure and area, a given pressure will provide a given volume on a fixed given area. BUT if the pump can't flow the volume, it won't build the pressure, which is then determined by the area given to flow through.

So it's simple really. IF you have fixed needle and seat size you will always increase flow if you increase pressure to the needle and seat. IF your pump can't supply the volume you won't see the pressure at the needle and seat.

YOU MAY still see pressure at a regulator with a pump that provides inadaquite volume if the regulator is not a return style because the regulator then becomes the "area" (restrictor that causes the pressure) and the pressure will drop again when it hits the "area" of the needlewhich is bigger than restriction provided by the regulator to cause the pressure. This is how ALL non return regs work. By creating a variable restriction to controll pressure. So with a non return style regulator you may have less pressure at the needle and there for lower flow than indicated by a pressure gauge that is not after the regulator near the needle and seat.

Also you will have head losses, drops in pressure, which is a drop in flow, from pump to carb. This is indicated clearly in the first part of this post. The smaller the feed line the higher the head loss will be. The more bends, the longer the line, the more expansions and contactions, the rougher the line, the more head loss you will have. So dont forget that the pump will have to over come these head losses.

[jeff denham]

you can take this into consideration or not. so your running end castings i presume? if so did you ever take a good look at them down the sgl hole of entry. can you see your spliter if you cant then that could be your problem. we went throug that many years ago. some people said it dosent matter when its under presure but i feel it does. it that radicul turn that it has to make under boost were 2 clys starve for gas. better design end casting or pletuim style. just my two bits . jeff d.

[Dean N]

jeff, a lot of people dont think design makes any difference on either intake or exhaust.....

mo boost cures all.....................
 

[Chip Birks]

Well, the car went to junction last year to run at Madson's race.  It did well, except that after the first pass we noticed that the block was cracked.  We epoxied it up and managed to finish the event in 2nd place.  That was nice, no cracks on the cyls.  Car is still apart waiting for a new case.  My father has lost motivation something serious and really hasn't touched the car since the week after the race last sept.  Hopefully I can kick him into gear soon enough. Thanks for checking up on us.
Chip 

[markvo]

What Jeff Denham said! Do you have trick ends? Carb probably not the problem.