went to the 1/8 mile today in Elgin. Good news/Bad news. good news 1st..went a best ever 6.72 bad news ..#8 spark plug got shut by something during the run. the mph was best ever at the particular track (100) but the speedtrap is spaced wrong so mph on the timeslip shows about 3-5 mph off ( from what we can tell between our cars). On a 6.7x pass mine usually goes between 105 to 108. Thats beside the point. Havent yet tore into the engine yet because it got dark. What I can see is the ground strap bent down over the electrode with a tiny mark...kinda triangular shaped on the middle of the strap. Not much other damage is evident around the rest of the plug..and the other 7 only have peppering on the porcelain. We were using a pretty safe tune with 46 squared in the crossbar and 6 lbs of fuel on the 1st pass ,then dropped it to 5.5 lbs when we saw the outer ring was chalky with soot. I really didnt hear any nasty sounds coming from the side so I cant be sure what knocked it shut. The oil hasnt gotten dark or shiny from metal like a bearing went or anything. I know hypereutectic pistons tend more to break up than burn unless a small piece got pulled off and rattled around. During the pass , I heard like a psst noise in 2nd gear,stayed in it, it made the noise again near the end and it surged some. The mph matched the pass prior to it so I dont think it lost power. Bottle press. was between 900 to 925 on both passes. Used good 110 racing fuel and autolite 134 racing plug. It didnt do anything to the head gasket either and they are regular fel pro gaskets. I figured if anything they would go 1st. I reckon I'll have to dig into it when I get a chance,and see if I need pistons...fish
When you said "peppering" on the porcelin, is it shiny, like aluminum? Sounds lean if there's peppering. How big a shot was it? I think I'd do a compression check, Hyperuthetic pistons and nitrous is a bad combination, high silica in the pistons, they are prone to shattering, I'd guess #8 piston has damage. I've had problems with #8 burning the ground strap hitting a 200 shot, but the 2 times this happened, something else went wrong causing a lean condition, I'd also guess that #8 cylinder may be the "lean" one all intakes have at least one runner that'll be "leaner" than the rest, I could be wrong,#8 is in the back, and under acceleration you'd think it would be OK. Good luck, keep us informed. Gary G.
BadBuick...here is the diagnosis..i think... Had to have been a momentary lean condition.I pulled the head off this a.m. and found it had lipped off the top of the piston on the front about 1 and a half inches woth was gone where you can see the top ring in there.The chunk floated around some before leaving coz it made marks on the rest of the piston and shut the plug. The rest of the pistons on that bank were just fine with some carbon on the centers and clean around the edges but not hot spotted. I had the intake ported and balanced by a reputable engine guy in Colorado so I hope it doesnt have a lean runner. I know the ford guys have problems with the back runners going lean too,who knows. I am ordering a set of 12:1 pistons thurs so I can have it back together soon. I probably wont use alot of n2o until I get the stage 2 heads on it with larger chambers. I guess I know the threshold of the hypereutectics now :spank: Thanks for the help guys..fish
I wonder if you need to look at the exhaust valve seat, from when the piece finally left the motor. Gary G.
Ouch! Do you know if you were up against your fuel cut-off switch which could have been responsible for the surging? By the way, I did the math and 8psi fuel would have been right-on with the 40 fuel/ 46 nitrous jetting. I actually came up with a .039 jet for the fuel but 8psi would have been close enough to be pushing it it you didn't hold to 8psi. Yeh, those pistons you had are brittle and can't take cylinder pressure. Congrates on the 6.72. Thats Movin' for a street motor.What kind of 12.0 compression pistons are you ordering? You could be "buying" yourself another problem if you don't keep the nitrous in mind. You need tappered pins and lower top ring lands. .300" down. THis will ensure a happier future. FYI, I ran 5's with only 11.6 compression and a 180HP shot. :Brow: More compression will just be harder on the Buick block when you spray it. How much cam are you looking to go with? I found this link today to do math with for the fuel jets. Just remember, its a reference. It should work for NOS, Compucar, Nitrous Works, and most others that are setup for low psi. The only one that I wouldn't use it for would be Nitrous Express since it appears they drill there fuel bar on there plate different which might not agree with the conversion. :bglasses:
Oh Yeah..... http://www.coldfusionnitrous.net/calculator.html I ment to post it. But here it is. Don't get into too much trouble.
Fish ho is the Guy that did your intake i live in Colorado just wanted to no if i no him. Ricks right on pistons need to movie that top ring glain down that nitrous loves to burn that spot on a piston with a stock ring heigh have done it with 200 HP before not a good deal. Let me no i can get you some pistons at fare price for what you are trying to do.
Jeff,Rick,Bad... Jeff: Paul Klyczek did the intake Rick:I was looking at the wiseco's that Burek sells. Yer definitely right about the lowered lands,I figured it was a custom piston anyway by looking at their website, so i could specify dropping it some.Wasnt going to change the cam till I get the stage 2's. let me know what yalls opinions are on what Im about to do. Thanks again fellaz I need all the help I can get...fish
About that "surging" what size bottle do you run, what shot, and how many nitrous passes did you have before the surging? You may have been just about out of the "sweet nitrous", like 33% of a full bottle is the "sweet stuff". I'm pretty sure with my full 10 lb. bottle, and the 200 shot, I can for sure get 2, maybe 3 good nitrous passes, and then time to change the bottle. I'm sure that different brands are alittle different, because of the jet map, I run a NX plate. Unless the surge was more of a miss when the spark plug got stuffed. Just guessing since you mentioned that you don't run a fuel cut-off switch. Gary G.
Yo Bad... It was only the 2nd pass of the day and it was my blue bottle ,NOS bottle with regular HI Flo valve. I try not to put more than 2 passes on a bottle but I only have 2 so if there is a 5th pass I'll go for what I can. I have been taking a bathroom scale to the track w/me to monitor the wt. of the bottles as I use em. I dont use the fuel switch cuz I really really trust the pump,wiring and relay. Ive thought about it but I always hear about the switch causing 1/2 the problem with a tuning situation,maybe Im nutz. Cya ...fish
What are running for compression now? I think since you still have the iron and stock block that you should just keep it simple. Change the pistons, balance it and press on. Go with a good balancer if you don't have one yet.
Hay Fish i no Paul lives about 15 minutes from me. Rick that is a good site on the Jetting i was doing Nos Big shot Jetting Nos runs there Fuel jets real fat they want n 47 f 53 5.5fp I put 53n 47f at 7psi worked out good i saw these on 6 Jetting setups at 7 psi flowing fuel pressue
Jeff, are you sure that the jet numbers are the actual hole size that is needed for that formula? I know that my NX stuff is different, I have "99"s in my kit, and when I plug that in it doesn't even come close. I'm not farmiliar with everybodies jets, just be sure you know what you have before assuming that your "fat" and make changes because of that formula. Gary G.
Rick.... Ive got the dished and double eyebrowed silvolite hypereutectics in it now. I am kindof at a crossroads at what my future intentions are. I know I am getting the Stage 2 TE heads so Im thinkin more about how I'll be setup for them. I figured since I killed the pistons, I would put in there what would be right for the TE's,and since they have larger chambers,the 12:1 plus the heat shedding characteristic of aluminum I could make the most power. BUT ...you guys have done this and I want to use the best advice I can. What is the happy medium for what will be a .038 or .040 overbore with good rods, TE headed,N2o using iron block engine? I will be changing the cam with the TA heads and I know the new pistons wont take advantage of em. I know I could probly dig in the archives to find out what the non-girdled blocks give up at ,but what do you reckon it will happen at? I would probly feel better buying a done block from a member who is going to the new blocks than trust the shops around here. I know Im asking a helluva lot of questions and I seriously appreciate the knowledge yall impart to my program.Thanks again...fish
Gary i am not shure on yours are you plug in the two nitrous jets try these here are some stock Nos jetting for a big shot plug the numbers 1000 bottle pressure 1 nitrous jet N 47 f 53 n 55 f 61 n63 f 71 n73 f82 n82 f91 n93 f 102 they say 5.5 psi flip the jets flow at 7 psi
Fish if you go .38 that is a 4.350 there is a 4.360 those are the two sizes in a wiseco that they have for stock rods with the 1 inch wrist pin. 4.375 is as big as you should go need block fill at that point
If you are looking for a good strong setup not super pricey have your stock crank turn down to BBC rod journal Order a set of eagle h beam rods 6.700 or 6.800 the rods have to be side dressed to wide stock you will also have to side dress the bears down as well
