Ok here its the scenario I have a 4.3 V-6 chev, Nitrited crank, Steel straps on the mains, Speed pro 9:1 blower pistons, Eagle rods, crane hydraulic roller cam HR-230/352-2S-12, Crane Gold rockers and Vortec heads, BDS 4-71 Supercharger with a Holley 4150 blower carb, MSD billet distributor and a 6A-BTM with iridium plugs. I have what sounds like a ping in it when I get into the throttle below 2300 rpm. I have had the distributor checked for curve they tell me it is bang on. I have tried initial timing from 5 to 20 degrees and all in timing at 3000 rpm up to 38 degrees. I have changed the pumps on the carb to 50cc units thinking it might be a lean ping. I have even gone as far as buying an LM-2 air / fuel ratio tuner guage. For the most part I am to the rich side at 11 and under throttle I am at just under 14. I run it mostly at 3200 ft above sea level. It is 10% over driven and it makes 8 psi at the most. I have even gone as far a swapping the pulleys to go 10% under driven and to no avail. I am out of ideas, Is there something I am missing? Help Russ
What are you running for fuel? With 9:1 static and 8 pounds boost is around 13.5:1 for a final comp ratio. Did you degree your cam in?
I have been running 92 octane for the most part on the street and have even tried some 108 with no difference....Degree in the cam? I have no idea what my engine guy did there. Thanks Russ
just because you put "9 to 1 pistons" in it, doesn't mean you have 9 to 1 static compression ratio. Did you MEASURE it? Did you compensate for altitude? how's your quench area? what fuel are you running? EDIT---whoops- I see you answered that while I was typing
Builder said that because of altitude here it is equivalent to 1 atmosphere and that it was really at 8:1 like which he builds a ton of turbo motors at. We have no air up here! As for measuring it I have no idea. How would I measure it? Russ
38* is a little high on the timing, especially if your pistons are the design with the slit half way around the oil ring groove. Do you know for sure what your static compression is? Also check to make sure the TDC mark on your dampner is REALLY TDC. Also what condition is your 4-71 in and how loose is the belt? If need be I can send you my helper she has a few years under her belt now...
Here are a couple pictures.....these are of the parts from the builder The blower was new from BDS. I run the belt with 3/4" play each way or 1.5" total. I know that might be a bit loose but when it is hot it is at about 3/4" total. Russ
get rid of the plugs, theyre glowing .get som regular old acs that are cold and non projected. 38 is too much timing also, try backing it down to around 30 under boost
Your getting some good advise here, I question and wonder where your builder stands on this.... Looking at your bottom end pic and pistons brings some questions to me but to keep the subject at hand with the engine this is what I would do. Get rid of the plugs your running! I would lock the timing at 29* MAX no advance. Make sure your dampner is marked correct. Now these are things I would do for starters on the engine your running does not mean this is the noise your hearing, but looking at your combination I would do. Why I asked what condition the blower was in and belt tension you have you could actually be hearing a parasitic noise from belt to blower and drive in unloaded force. For fun you might put a timing light on it turn the lights off in your garage shine the timing light on the upper pulley bring the rpm up to "the" noise on the engine you will be amazed at what you see!!! Watch to see if the pulley chatter matches the noise your hearing. On all my big HP deals I always do a final dyno pull in strobe, you can do this with a simple timing light in your garage it puts time still you will be amazed what you can find by doing this.
Thanks for all of your knowledge guys. My builder has no I dea what the noise is from what I have explained. He does build quite a few turbo 4.3 chevy engines. I have often thought the noise could be belt or drive. It is really noticable when you drop to passing gear right at the first the rpm jumps or jump on it causing it to pick up rpm fast, but you have to be under 2300 jumping up to hear it and it only raps for a few times. But I take my foot out of it right away when it happens. What do you guys think of these E3 spark plugs? It all looks good on paper. do you think they would work good with a supercharger? Thanks again, Russ
Try swapping in Autolite's coldest standard plug for your application, and take some timing out of the distributor advance, not the initial. You can start out around 6-8 and be all done at 25deg and 2500rpm. You said you are at 14:1 A/F on the throttle? That is seriously lean for forced induction. Does the carb still have power valves in it? You may need to raise the closing vacuum on them.
you should be aiming for 11.5-11.8 air/fuel ratio- go with a cheaper plug-I've run AC plugs in boosted applications- they're cheap and act as a fuse should i have a problem-rather eat plugs than pistons, right? You've got way too much timing, boost an compression-all three for running around on pump gas, jumping on it at low rpms. back your timing down and spin the blower slower- or switch to E85 and wick it up, lol... rick
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