Howdy Folks, I´ll Need Yha´lls ideas out there. I´m losing power around 5500 rpm. The engine is a cross ramed wedge, all **** and blow and mechanically all set for 7000-7200. It hooks good but then stalls gradually....like it´s running out of gas probably. I just put it together and I only made a Basic Setup for now. Timing is set to 32° at the Moment. Big Cam, heads and a "mystery" cross-ram sould be able to handle 6500-7000. First I thougt the 12.1 cr blows of the spark. But Mondello or Nicholson didn´t have Computers on board back then. So I think I can dump that thought. Any ideas......? Thx in advance, chris
Could be a weak ignition system, weak valve springs, fuel starvation, breathing problems with the intake or exhaust, etc. Like he said, more details would help folks help you. Pictures, and a complete description of ALL the parts, is a good place to start.
Fuel flow (volume ) needs to be checked......NOT pressure....possible restriction at a line kink or fitting
1/2" fuel line but stock pipe going into the gas tank. There might be the problem. Spring pre***ure should be alright (420 lbs./in.), gross valve lift (static) around 0.620" solid flat tap and 12.1 for the bang in high gears. Slugs are Ross and heads are Victors with MW windows. The whole setup is all out. A&A Cross Ram is hopped up by Rick Allison. MW iron manifolds are special tuned by myself for better flow and are going into 3" long tube headers which are mounted into the factory 3" MW style exhaust system (Could the block off plates be the problem....fumes need to travel backwards for about 1 foot??). Carbs are stock 4150´s 600cfm with mechanical secondaries. I will tune the mill as soon as the streets are clear of snow again. All in all the engine is thought trough very well but I agree the intake and fuel issue could be the limiter. But not around 5500 rpm..... Thx for any thoughts.......chris
1/2" fuel line but stock pipe going into the gas tank. Stock pipe into gas tank Well that pretty much limits the entire fuel system to what ever the stock line capacity is. You could run a 8" sewer pipe up there but you'll only flow fuel at the capacity of the stock tank outlet. If you need 1/2" fuel line to feed both carbs I'll bet they drain it faster than the stock pipe can fill it
A fuel pressure gauge, mounted where you can see it when driving all out, will help diagnose fuel starvation issues. If the pressure drops at higher rpm, you need to fix the supply problem. I have 1/2" tube going into the bottom of the tanks on my hot rods, and 1/2 line all the way to the front, where it Tees at the pressure regulator to 3/8 to each carb.
wedges like more timing. your running timing like a early hemi. 36-38 with good gas. 40 makes them sound nice and snappy in neutral but under a load hp suffers.
that makes sense to me, the old design big block Chevys also like 38-40 degrees. Although having it backed off a little just makes it lose a little power, it doesn't keep it from revving
no it probable does not address the problem. but the timing still needs to be upped a bit. there is a lot to be gained there. when ever i have had rev problems it has almost always been the springs in a other wise good running engine. and its magnified even more in a blown engine. I'm such a firm believer in it i regularly check them with a on the head checker. lms makes several different versions based on the application. if any one needs their contact info i can post it. they cost about 200 dollars. costly but easier than pulling heads.
OK thanks to Yha´ll - I´ll increase Timing and take care of the fuel Problem. One more question. I bought the Sun Retro Tach right down at the Summit Racing store: We figured out that the Tach show´s about 300 rpm less than the engine runs. It is set right....what´s the cause. Is Sun just cheap trash? I didn´t check the tach at 5500 rpm. I´m sure I was not in the 7 area but it could be that the tach failure is not going linear.
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