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Street N StripPost your vacation driving stories, day at the track, breakdowns, safety issues, driving techniques, unique driving conditions, etc. STREET RACING STORIES ARE STRICTLY PROHIBITED.
"Can't do that in my garage, especially with open headers."
Well, you may but by risking the neighbors good relationship and your garage windows.
Nice work. Looking forward to see if it has cured that noise.
Went to the track last weekend. No luck - electrical noise is still there, especially at full throttle and high RPM. Next to try a different box. Daytona Sensors sent me a replacement box some time ago on a RA that I avoided opening (so far). I really thought the capacitor was going to cure the problem......
About the race.... Was a very nice sunny cool day about 70 degrees out. I did have my best 60' and best 1/8 mile ever (just by a touch). 1.50 sec and 7.07 sec, respectively - so that was very good! Still can't get below that 11.1 seconds and past that magic 10.99. After 2 time trials, I got lined up with the track points leader first round. Fortunately he broke out by 0.01 sec and lost! Second round I happened to get the light just right and ran right on my time - legitimately won that one against a much faster car! After my second round run, my race buddy I hang out with in the pits blew the 406 in his 85 Blazer. He pulled the heads in the pits. Rod came loose, broke the camshaft and a piston and the block and put holes in the oil pan - bent a bunch of valves - oiled down the track pretty good. He said this was the 7th year of racing for his short block, so I guess it lasted pretty well. After waiting about an hour to get things cleaned up.... third round I red lighted and on the trailer I went.
Nice getting close but it's always a pun to miss by just that little.
Next time!
Electrical noise can be a nightmare to cure, especially dealing with sensors. They are built sensitive, but also the cabling is prone to pick up signals and if the box is sensitive it may interpret noise as a signal and store it. Good luck on that one.
Doesnt' look like tens are in the cards for this year. Might make it to the track this weekend but it's supposed to be high 40's for temp so traction will be significantly down.
I installed the new CD-1 box (separating power and coil primary wires from signal wires), and believe there might be a little improvement with the noise - but hard to tell in the garage. I'm done chasing noise. Guess the AFR and RPM logs well enough to be used. The box still functions as a 2-step rev limiter for using the trans brake, and I can program timing changes without turning the distributor. Guess that will need to be good enough.
Starting to collect parts for off season upgrades. Going to go with a much stouter cam - get rid of my Comp Cams XE274H and into a race-type cam, but staying cheap because my existing short block will never be upgraded (will start from scratch with aftermarket block and bigger heads if bottom end ever gets improved). So I'm 95% sure I'm going with a Crower 00307 solid flat tappet. I've been agonizing over it for a week, checking out others, and keep coming back to it. It's a 106°LCA High Rocker Ratio cam on a P55 core installed at 102° intake centerline. Lift with 1.6/1.5 rockers will be 0.554/0.540. Duration @ 0.050 is 248°/256°. If a lobe hits a rod (and it may in a 383), I'll send it back and get a small base circle cam made of the same. I've been reading and supposedly (at least according to Vizard - my favorite condescending automotive author) the 106°LCA is much more correct for a 383 and should boost the upper midrange torque a lot over my current 110°LCA cam (as much as 30-40 ft lbs) but the torque curve will be much narrower with less on the bottom end. Vizard has a lot of ego, but I find he also has the education, reasoning, and experience to back up his claims. Also, piston/valve clearance decreases with decreased LCA (increased intake/exhaust overlap) and increased lift - so that may also be an issue (I suppose I could always keep 1.5 rockers on both intake and exhausts if necessary). Peak torque for a 383 with this cam is supposed to be at 4500, so that will be up from 3900, peak HP at 6000 (same), and should rev to 6500 (same). My TC stalls at 4100 and I shift at 6500 or so with drop-back to 5000. Hope my engine will respond favorably at all pertinent RPMs. Shouldn't go much higher than 6500 because of my cheapo hypereutectic pistons, and I'm already right on the recommended horsepower limit of my aftermarket connecting rods (hoping they are both over-engineered). Already bought some Howard's lifters with the EDM oil hole in the face to keep the flat tappet cam lobe lubed. Of course I'll do what seems to be my annual leak down test to see how rings are doing, and then pull the engine and remove oil pan and heads for bearing/piston/cylinder inspection/cam installation and degreeing/cam lobe interference checking - put the heads on and go back together with the mix of rocker ratios and original pushrods, check piston to valve clearance, select the best pushrod lengths, and get those sourced. Put together with only the outer valve springs, install engine, and break in the cam - then finally put the inner valve springs in and button things up.
But before the teardown I want to get it on a Mustang dyno I found (sorta in my area) for a "before" reading. This dyno should be an order of magnitude better than the Superflow Inertia dyno I had it on last year. Been talking to the operator and he said I can even start in 3rd gear on the trans brake with roller stopped if I want - then just tell him how fast I want to ramp the speed and where I want to stop increasing speed - he can hold the roller against the engine while ramping to any speed (or holding steady) and measure up to 900 horsepower. With the (Superflow) inertia dyno, power is measured by how fast of a rate you can increase the speed of a heavy roller - speed increases so fast that accelerator pump shots were still happening during half of the dyno run (works OK to get a peak HP, but not for carb tuning). The Mustang is an eddy-current design where it uses (adjustable) electrical power to work against the engine. This should be so much better. Then after the cam change and break-in, take a half day of dyno time and look at the ignition timing as well as dialing in the carb using the AFR gauge.
That's my plan! There's always hope for 10's next year! My converter may not be quite optimum for this cam, but it should hopefully be net positive horsepower for most of my RPM range. Bet I'm going to need to use the trans brake to get into the power sooner and to get rid of that power brake booster. Smaller LCA = more overlap = less vacuum. Should really have a nasty but powerless idle and run very poorly when cold!
Thanks! That one was 11.23/119 with a 1.52 sec 60'.
RT was horrible (still trying to get used to the trans brake) - think it was around 0.3 sec. I kinda freak out when my foot isn't on the brake pedal, but pushing on the accelerator - and the trans is holding it there. I end up late getting up to the 2-step RPM and then subsequently late letting off the button. The first one of the day was RT=0.7 sec!!
In eliminations later I just went off the foot brake. I can get down around 0.05-0.07 using the foot. Hopefully that will tighten up to even less when I get the trans brake down. Times seem to be pretty much the same either way, but wheels come up a little more with the trans brake.
From the (before cam upgrade) Mustang Dyno session. 386 RWHP at 6100 RPM; 365 torque at 4700 RPM - both uncorrected. This is about 15HP less than what I saw on the Superflow Dyno last Winter. This is typical as I understand it when going from an inertia dyno to an eddy current dyno.
Took cranking compression and leakdown rates on warm engine before pulling out for teardown. Seems to still be OK after 4 seasons of racing. No evidence of detonation on the pistons. Ended up buying a Lunati 401B1 camshaft which is nearly the same as a Crower 00307 (106° LCA) but designed specifically for 383 and 406 Chevy engines with 10.5:1 compression running in the RPM range where I am at (100° intake centerline - 6° advance ground into the camshaft!). Should be an entirely different animal than my little XE274H street hydraulic cam (110° LCA, 106° intake centerline)! Engine is disassembled down to the short block and I'm ready to try out the new cam for rod clearance tonight!
Interesting thing is that the lift/duration on the XE274H with my 1.6 rockers is similar to the lift/duration on the 401B1 with 1.5 rockers (what I will be running). It's the valve timing that is WAY different! The lower LCA valve timing should make the torque peak much bigger, but in a narrower range. The intake centerline of 100° (full 6° advance) should help bring that peak down a bit in RPM (for the lower RPM limits of the stroker motor). Apparently this is why the 401B1 cam is specified for the 383/406 with the 3.75" stroke. Should idle extremely poorly, but really come on like gangbusters when it hits the RPM where it can take advantage of the greatly increased intake/exhaust valve opening overlap! The exiting exhaust starts to pull in the intake charge even before the exhaust valve closes - why race engines can have greater than 100% volumetric efficiency. I don't care about the idle, because my converter stalls at 4100RPM and I'm not trying to drive it on the street anymore.
One other thing I will need to check when going back together is the piston to valve clearance. It won't really be opening the valves much more than before, but it will be opening them at different times.
09-25-2018, 08:17 AM
