Jim, My cam card claims my cam is a 288-94H. The advertised duration is 288 and 294. OK. But it is identical in every other way to the 288-96H. The lift is .515 and .525 with 1.6 rockers and it is ground on a 116 LC, just like the 96H. The duration @ .050 is the same for both cams, so that point is moot.
Also, I was content to leave without a printout because my question was answered... there is a flat spot in the power curve right where I claimed, so we figured it is either heads, intake or cam. I'm pretty sure Kenne Bell Stage3 heads wouldn't be the cause. It COULD be the intake, but we're thinking more like cam. We'll know more next week.
Bring me up to speed here Jeff.. Is this the same motor I put the cam in, in your garage, back about 01 or 02, or something new? is it the same cam, if it's a different motor? Are you absolutely sure as to the install location of the cam? ?? JW
Jim, I'm logged on with Nick's PC. Same cam, different short block. Same heads. New Edelbrock B4B. The engine you worked on was the numbers matching 430 with the KB Stage3 heads that I'm still using. 1971 455 +.030 forged Speed Pro 10:1 pistons. Cam is installed exactly like you did it on the 430... on a 108* centerline (6* advanced). Yardley
And it never did this in your 430? I recall driving it, and it didn't do it, if I recall correctly. JW
Since you said the flat spot is not there when the car is cold did you try covering the intake with lots of ice for one run to see if that made a difference? You never know what'll happen. That doesn't look like it shoots up at 5000. It pretty much looks like it levels off at 4500 and just hangs around. Has the cam been degreed lately? Maybe it is advanced too much? I'd try degreeing it once just before you pull it out. Should only be +4 or so. Maybe it is at 12 or more. Maybe there is some kind of reversion going on in the intake because of the cam timing causing the fuel to puddle up in it which would cause the low F/A readings and when the car is cool(ice on the intake) it leans out the mixture to a more reasonable ratio thereby restoring the power somewhat. I don't know if somebody ever asked this but has the engine been doing this since day one or did it appear after driving the car some miles? Did you look at the pushrods to see if every one is coming up about the same as the others to make sure there are no lobes going away?
The info I posted really doesn't show it like on a graph. It literally flattens out for 800 RPM or so than pulls up to 5500. Like I told Jim, it has been doing it so long that I just accepted it as part of the car and lived with it. The cam was degreed when the engine was built and was degreed to a 108* CL. We'll confirm that this week when we swap cams. No, we didn't ice the intake. I'm confused on that too. Some runs in the car it didn't flatten out and pulled all the way to 5500. So we just don't know. Could the new B4B have some weird thing going on with it? Like I said, we'll take an old B4B with us and use it if we need it.
Oh here's something I forgot to mention: The temp probes in the headers showed that the B4B runs lean on the driver's side and therefore the jets on the PASSENGER side of the carb should be 2 sizes higher. (the pass side feeds the driver's side and vice versa). Just FYI. In fact, Nick Serwo already knew this and always jetted his carb's that way. This just proves it.
I have a TA timing chain in my engine that was mismarked. Everything was off 1 tooth. If your cam was installed based on the crank gear markings and not actually "degreed in" with a wheel and an indicator it might cause your problem. Some things I'd check if I was in your shoes at his point. Has the outer ring moved at all on the damper. Have you checked the timing with a timing light throughout the rpm range. (check for timing bouncing around or dropping out at higher rpm).
The intake doesn't flow from op. side to op. side. It is more of a double X pattern if you draw it out on a paper. I'm pretty sure the driver side of the intake sends the mixture to 1,7,4,6 and the pass goes to 2,8,3,5. This keeps any one cylinder from pulling mixture right after another. Follow the normal timing pattern: 1,8,4,3,6,5,7,2 Usually #1 runs a little lean because of the length of the runner so you jet that side up some on the primaries. Engines vary though. Wouldn't hurt to try cooling the intake with ice just to see what it does when you get back to the dyno even if it is running better.
Well, my race season is officially over. Looks like some debris has been circulating through my engine and the thrust bearing is really scratched up bad and the crank needs to be polished on at least that main journal. The #4 main has worn to copper only in one corner, not the whole thing... odd. A couple rod bearings are pretty scratched up as well. Looks like I'll have the line bore checked, and hope the crank can be polished without going beyond 2.5 thou on the rods or mains. I have another crank, but that will require all new balancing again... not in the budget. sigh...... is this supposed to be fun?????
Man, that sucks and was unexpected. I suppose the only saving grace is that your quest to find what was causing the flat spot led you to finding this before the motor grenaded on a pass. It's a small saving grace, but trying to find a little silver lining. If you need anything I have that 455 sitting in that Riv that can donate parts.
Thanks, budnik. I think I'm going to have that other crank I have cut .010/.010 and then align hone the mains. And balance everything again. I don't think this crank can be saved without opening up the clearances too much.
I was changing the leaky rear neoprene seal. I figured that as long as I was loosening the main caps I'd just lift a couple and check the bearings. Imagine my surprise. Well, actually it wasn't really a surprise. When I saw all the gold dust in the bottom of the oil pan I knew there was a problem.
I have followed this thread every day , In my mind I felt the camshaft was not the problem based on the fact that the engine would rev through the flat rpm spot & pull strong to the upper rpm ranges. This was not saying that there was not a problem with the valve train it self. Do you feel that this crank & bearing problem may have been the reason for the flat spot ? You don't hear much about the effects of these types of problems on preformance engines because it's hard to be aware of them when they just start to happen , I have heard oval track racers comment on flat spots in the rpm range "it seems to dwell @ " on their engines before a major failure . Well Yardley I think you came out better than most , you still have a good combo to work with & that new Scott Brown cam to look foward to ! ick
