I also put a new cap and rotor on Saturday (MSD stuff) While in there, I checked the centrifugal advance by hand, and it was kinda stiff, as in not wanting to spring back to initial when advanced. I know that's not normal, but when I check my total, it advances (36 deg) when its running, the timing always returns back to initial (18/19) So I'm thinking its NOT stickingo No: I'm going to pull the distributor ( MSD Pro Billet) this weekend and see whats up. I want the advance working properly, I don't know if its advancing all the way everytime, plus its free to check:laugh:
Mark, Also try to make your runs with the same engine temp when testing. 20 degrees will make a significant difference. Log that in your book also. Gary, I said it before I think the Q jet on the single plane is not good due to the huge secondaries being biased toward the rear. I know others with 455's have not seen an issue with it I still think a square bore would be better suited. This intake has a purpose, we just have not built the right engine for it yet. Mart might be the closest.
I would try a 81/90 on the jetting Get it down to 11.8 on the AFR I am surprised you can run 36* I can only run at 32* I would try to come up on the motor to 1500 rpm I launch at 2000 rpm I agree with Steve you need to get to the track where you can make several runs Dragway 42 used to be so great for this. You can probably make about 4 maybe 5 if you are early at Quaker on a Friday. They run a gamblers race so it takes up time. I was told on Wed. you can make a lot more. Plus you need to start at 32 on the timing and work your way up till the mph falls off like Steve said, it's the only way you are going to get the timing correct. You will more than likely along with the ET do the same thing on jetting the carb. Mostly you change the back two since the front are used for normal driving, but that does not say you can't do that at the track also. Takes about 5 minutes. You just start to write everything down in your log book and you will see the trends of the car getting faster and getting a little slower as it gets older like mine is. That was how I found out the car will run its fastest letting it cool down no lower than 150* That seemed like the magic temp to start the engine from, by the time you get up to the line you are at 180*. It is on its way up and not already there getting ready to hit 190. More runs you get the more you figure it out.
The secondaries being open is simply a measure of tension against them. The size of the carb and how far it's open isn't a direct indicator of cfm ingested. Engines don't 'breathe' cfm in a linear manner. The relationship of what the cylinder needs to what the induction can provide is changing as the piston travels, with the piston speed varying along with the rod angle's change. Max piston speed is when the rod and crank are at 90*. You don't have enough valve opening or CSA in the port to exceed the cylinder's needs at that point. As an example...a longer stroke/shorter rod or with a lower rod ratio can utilize 'more head' at the same rpm (with same displacement), without suffering a loss at the bottom end of the powerband. Another way of viewing the same thing is when a power increase is observed via more rocker, more radical cam profile, etc. Inversely, if the induction were capable of more, then much less cam would be needed to match the power output. The engine's torque and power peaks are controlled by the restrictions...in most cases that's going to be the intake port (and cam if it restricts the intake much more than staying SLIGHTLY behind the cylinder's needs...enough to keep a slight pressure differential needed to hasten the initial movement of the intake tract) IF YOUR previous intake was already exceeding the engine's needs (the port's capability), then adding more intake and carb would not change much. I'm making assumptions about your combo but I know I can very effectively feed a cylinder only 5 cubes bigger with a 315-330 cfm port, without loss of bottom end (with a similar rod ratio). Better heads properly matched to the overall combo will absolutely be a game changer.
Keep taking the car to the track. Finish the season out with the sp3. You'll definitely make up the ET as you dial in the tune and get your shift points nailed down. Try and aim for cooler days (although you can correct for DA like Larry and others have mentioned, it's still nice having a quick time on the time slip itself) If you still don't reach your previous best time I think you would be better off looking at your combo, seeing what reasonable changes you can make to improve it, and then deciding which intake suits your engine best. I probably say it a lot but I've run a 14.18 at 94, 1.96 60ft on a bone stock low compression 72 350 with just an 800cfm qjet, 3.73s, 27" slicks and 1 5/8 headers. Until I had the car dialed in I was runing as much as half a second slower. I always managed to have a run with a botched shift or a poor footbrake launch. I'm not sure how you leave the line but if you footbrake it that leaves more room for error as well. With that and the self shifting it can take a while before you are consistent. After a dozen or so passes I made big improvements just trying different minor tweaks in the pits and keeping track of it. You have much more work done and I know you'll get it to consistent mid to low 13s with what you have. It's all about dialing it in. I just don't want to see you beat yourself up over the intake or your drivetrain combo because there is so much more you can do before making any big changes.
I'm going to keep plugging away with the SP3 I suppose, before I change back to the Stage 1 (if I do) I'm also going to get the app. for the weather that Larry linked. I have a book I've been keeping track of all the changes since last year. In a perfect situation, I'd rent a track for the day, to test both intakes, Q-jet vs AED on the Stage 1, different timing, AND enough passes to get some consistent results on the same day, and same weather, but who has the time or money for that, LOL
You said you had 80/88 jets in now, I said to go up to 81/90 jets that would richen it some. Did it 60ft ok or was it better than before. What happened at the 330 ft mark. If the shift did not happen out of 2nd till almost 7 grand you need to fix governor so you can shift it yourself or have Vince fix it for you to shift with it in drive. I had to do that on my 2004r since the nitrous would hold the engine/trans longer. You take 2 tenths for bad air day and take 2 tenths off for the over rev to 7 grand and you have 1/2 second improvement, and that is without much tuning yet. You have not even used a spacer yet, I am looking into a Wilson Taper spacer, This may compliment my K&N Flow Control air cleaner. I have a 1 inch with a 1/2 inch nitrous plate on the DP intake so there is some room to add a spacer with SP3. After all the other tuning to go faster with jets and timing you have to play with the shooters and that timing to get the car to 60 ft better. That alone will make it faster. Ever see what your rpm is in the traps? I was at 4 grand with the convertor locked up on the motor and at 5 grand with the nitrous running and the convertor locked up.
LOL, sorry Guy, I mis-read what yah wrote, damn I'm getting bad! I have the governor set for 6 grand or damn close to it. What I do is start with the shifter in second, let it auto shift to second @ 6 grand, then manually shift to third at 6 grand(except for the last time:shock For some reason, it doesn't seem to hold second gear to 6 grand automatically, so I hold it manually. It did this before Janis rebuilt the trans alsoo No: I do have a 4 hole spacer, its less than an inch tall tho, nothing fancy, I've had it for years. I cant find my time slip, it may have gotten thrown out with my receipts in my wallet, I'm kinda pissed about that! I do remember my 60 foot was bad, something like 2.1, I could tell on the go, the front end lifted, but the slam in the seat wasn't as strong (is that like a butt dyno?)
LOL yeah kinda, that is where the tuning will come in for accelerator pump tuning on both primary and secondary shooters. That is why I said to launch at about 1500 or so, this might get your 60 ft quicker and then the ET will be better. You will get yur best ET by lighting up the second bulb on the tree and not moving up any more, this way you will have some roll out before the timing clock starts. The car will be moving already before the timer starts. Which is after your front tire unbreaks the light beam on the track. (the second bulb you lit up in staging) Believe me, this aint much but it gets the car ahead of the beams. Might be 5 inches of movement, enough to get the engine off its stumble before the clock starts. You have to do all of this and stay consistent with it to get your best time. what ever habits you start with good or bad get rid of the bad ones keep the good and you will run a good consistent number. You will make your best runs around here in Sept. and most of Oct. with that nice COLD SP3 Intake with Cooooool air just wanting a Ton of gas rammed down its throat, you will make your best run then.
Just noticed that you wrote that you were leaving at idle! WAY to low of an RPM! If you suspension is up to it with good sticky tires, brake torqueing at higher RPM can reduce your 60 ft time considerably! Leaving at idle is not only bad on the drivetrain from shocking everything for zero to hero all at once is how things get broken. At the minimum, brake torque to 1,000 RPM just to get some preload on that drivetrain so you don't break anything.(well not as easy anyway) Brake torqueing helps preload the drivetrain to remove the shock from a dead start to WOT. Brake torqueing right before converter flash should help a lot to get moving off the line. You definitely want to try different RPM at the line to see what your combo likes best! That is if you have your traction under control, can't remember what tires and suspension mods if any you have to help launch? Getting that 60 ft time down is one of the best ways to reducing you QM time. My brakes are so good that I can brake torque at WOT without the rear tires breaking loose, but is to much when the brakes are released and the tires break loose slowing my 60 ft time down. I had to find that happy medium where I could hold the RPM before launch that when I let off the brake and hammered the gas the tires would hook, which is around 3,000 RPM for my car, I have a 3,000 stall converter if you were wondering.(I hope this helps, GL) Derek
mark, you will have numerous issues to dial in with any changes in h/p. 1st; dialing in the engine. carb, headers, gas, cooling, etc 2nd; the converter. my engine doesn't kick in till 3500. think it needs a 4-4500 stall. some dragsters leave at idle, others at stall. 3rd; the transmission 4th; tires. too big is no good, too small is no good 5th; gears 6th; suspension. this is a big one. every change in h/p will change the working chassis/suspension. chassis/suspension constantly changes itself. all these are items that make or break your improvements in time and mph. john
Not all combos like to be pushed up on the converter , some do work better leaving at a little above idle, just depends
Excellent info:TU: Thank you!! Derek, I just remembered now that you mentioned about leaving at an idle, last season I WAS leaving at around 1000 rpm, or a bit more, that's when I would get a 1.9 60' I do remember someone saying that leaving at more than idle with a Q-Jet your into the pump shot a bit, then when you slam it WOT, a portion of the pump shot is used already, and it can cause a slight bog, so I stopped doing that. Now that I have a DP carb, is that situation a moot point? John, my gear is 3.42, since this is not strictly a track car, I chose my MT DR's based on my rear gear and my 245-60-16 BFG size which is why I went with 275-50-15 MT DR's I wanted to keep the overall diameter very near the same so as not to kill my 3.42 ratio. I think 275-60's would have been too tall. No traction problems that I can tell on a prepped starting line. Last year at Super Summit, they didn't prep the starting line, and I was spinning the DR's My suspension is stock GS, front sway bar (thick) rear bar, boxed lower arms, new rubber bushings well, 1991 or so new. Urethane bushings up front. Suspension feels fine, tight, no issues. Damn theres soooooooo much to learn AND remember from last season. I'm determined to get my 350 GS as quick as I can for what it is, a full weight (38/3900 lb) GS 350
I still say you need to blow a little gas thru it, a 75 shot would put you well in the 12's and wouldn't come close to straining anything. Best case scenario is you fiddle around with tuning and it MAYBE goes a 13flat, where as you could spend $450 and go to the track and have a blast. Only other option is to dig back into it with more cam ,Comp and heads to net the same results, ID have a plate on that thing and giving it hell
my gear is 3.42, since this is not strictly a track car, I chose my MT DR's based on my rear gear and my 245-60-16 BFG size which is why I went with 275-50-15 MT DR's I wanted to keep the overall diameter very near the same so as not to kill my 3.42 ratio. not a f/t racer; 10" wide tire maybe too wide which will so you down. nhra stocker is 9" wide. and your not full bore race engine/car. No traction problems that I can tell on a prepped starting line. Last year at Super Summit, they didn't prep the starting line, and I was spinning the DR's what watch the class racers are doing. they make things happen with nothing. My suspension is stock GS, front sway bar (thick) rear bar, boxed lower arms, new rubber bushings well, 1991 or so new. Urethane bushings up front. Suspension feels fine, tight, no issues. suspension tuning is an art with old metal. again look at the stock/superstockers. there should be some tips for your tight chassis. I'm determined to get my 350 GS as quick as I can for what it is, a full weight (38/3900 lb) GS 350 here is where you lose the benefits of the above info. 3900 w/3.42 w/350 s/p, you are going to struggle. you can't make it move quickly and deftly off the line with that combo. you will have to work on the 3500-4000 & up rpm to push the car down the track. I feel your pain doing this. I had my 350 s/p in a 73. no slicks, junkyard trans w/2500 stall. times were 13.5 to 15.5, but mph was ALWAYS 103. top end was crazy. go figure.lol
:eek2: LOL you and Foxes Den said the same thing, SPRAY IT! I do have my original block (with windage tray) another good crank, capscrew rods, TA billet 9 keyway timing set, main bearings, and a few other things. I WAS entertaining the idea of putting together another engine, 11 to 1, roller cam, my roller rockers, the aluminum heads when they come out, SP3, blal blah blah,
At 3,000 RPM IIRC was under 1/3 throttle so the secondaries aren't open yet so there is the full shot of the rear pumper and maybe a 1/4 shot left in the front. You're not running a one pump shot wonder now so you can launch with more RPM because you now have a rear shot you can dial in. A Holley type carb is WAY more adjustable than a Q-Jet, and once you get the hang of them much easier to tune as well.(unless you're Cliff Ruggles that is) Would be cool to add a pump shot to the secondaries of a Q-Jet! They sell pump shot cam kits so you can make your shot happen at different throttle angles if you want to play with those, as well with bigger shot pump diaphragms; https://www.summitracing.com/search...-pump-cams?N=4294951509+4294949628+4294921485 "These Holley accelerator pump cams will allow you to "tailor" accelerator pump performance to the engine's actual requirements. They include cams that have a different shape or profile to give different results. Cam "lift" directly affects the accelerator pump stroke, and, therefore, pump capacity. Ramp profile or shape controls the "timing" of the shot. A steeply-rising ramp shape will give a fast, heavy fuel shot right off idle. Conversely, a gently sloping ramp will spread the pump action over a longer period of time." Copied and pasted what they wrote in the description page of the first kit. The link is for multiple kits because I wasn't sure what carb you have, just that its an 850 DP. Looks like the gentle sloping ramp pump cam for the front and an more aggressive ramp for the rear or somewhere in between? Test, test, test, have fun, you can have that dialed in, in no time. If you start losing traction you can step up your rear suspension with a set of adjustable upper control arms so you can set your pinion angle to -1.5*(if its not there now? measure first). When doing this you need to measure your trans angle and call that zero, then make the pinion angle point down 1.5* from zero. For example if your trans is pointing down 2* then the pinion angle needs to point down 3.5*. Also, if you disconnect your front sway bar links at the track that will make it easier for the front end to come up and transfer the weight to the rear tires at launch. Leaving at higher RPM can cause you to lose traction but if you can control your traction at higher RPM then you can get your 60 ft times down because you're now launching higher in your power curve. A few things to consider, I hope this helps. GL Derek
Thanks Derek! It seems I have the pieces, I just have to learn how to tune them to work together now:Brow: With everybodys help and advice here, I'm going to keep at it:3gears: I'll admit I'm green at this track tuning stuff, its COMPLETELY different than "it feels strong on the street" stuffp
