Not really. Just an assumption based on general terminology is all. "Valve float" is just the general terminology used to describe the end result. It can occur due to insufficient metering within the lifter itself(your assumption here and you may very well be right).. or physical separation/lofting the lifter off the nose of the cam(too little open pressure for the weight of the valvetrain).. spring surge.. bouncing off the seat(too little seat pressure).. all of which is typically the result of the spring not being up to the task at hand(rpm/valve-train weight). All of these events result in the lifter pumping up during periods when the metering can't keep up or extra clearance/slack between parts is occurring. This obviously allows the lifter to pump up all the way to its full plunger height(whatever pre-load heights you previously set them at multiplied by the rocker ratio being added into the mix) and stands the valves open and overtaxes the already limited metering of these OEM lifters to play catch up. Only way to pull everything back into line, regardless of what started the chain of events, is to reduce the engines rpm. I would most definitely try to figure out if the pre-load amounts you have most recently used will improve on matters in the slightest. If the motor is bouncing against the rev limiter.. how do you know if the valves are floating at the same rpm as they previously did, right? Maybe try raising the limiter by 200 rpm and see how it sounds and feels compared to before? As I've mentioned several times already.. the tighter/more you reduce the pre-load depths.. the lessor the valves will stand open when things get out of control from a metering standpoint(less pump up height = less valve seat standoff height after rocker ratio multiplication is factored in). So, let's say you previously had the preload set to 3/4 turn(might be an exaggeration but bear with me here). Full plunger height gains x rocker ratio = a BUNCH of standoff height. IF tightening up the preload to say 1/8 turn makes a substantial difference(this is about .015" preload height/what I prefer).. in reducing how quickly/badly the valves float(how quickly/badly the motor breaks up and falls over during over-rev)?.. then you have likely narrowed it down to a metering related issue(related to an insufficient OEM bleed rate). But if it only makes a slight difference in how quickly/badly the motor breaks up and falls over?.. then you may instead have a valve control related issue that your new reduced travel lifters may not completely cure. Keep in mind that it can often be a mix of both(improper metering AND spring control) so this troubleshooting technique is not foolproof and without error.. it only shows trends to help you narrow down the underlying issue before you go tearing into an engine and needlessly start tossing parts at it. Took me forever to write that little bit due to other projects going on outside but I hope that helps. PS. not sure if we ever discussed spring spec's for your cam(roller, IIRC)?.. but you should have not much less than about 150 on the seat due to a roller cams more aggressive ramp rates(faster lifter rise and fall rates), heavy assed OEM lifters, and the stouter 1.7 RR. A Ti retainer would lower that requirement by about 5lbs or so but not much more. 125-130lb cookie cutter "one size fits all" springs will not sufficiently do the job here.
Greg, the cam is a COMP XE282HR. 35-522HR-12, Hydraulic roller. 232/240 at .050. Advertised lift of .565/.574. Actual valve lift measured with soft spring was .606/.615, LSA 112*. Rockers are Comp CCA-1332-16 Pro Magnum advertised at 1.6 but measured at actual 1.7. The springs are AFR and have 150# on the seat and 355# at 1.240" with coil bind at 1.16". I talked to COMP tech about the cam and they said that that was the best cam for the engine with the compression I am running (9.7). They also said that their spring wasn't any better and I had a lifter problem and I am getting as much RPM as I could expect with the stock lifters. They recommended the short throw lifters. I already have a set, but I don't want to pull the heads to install them. They also said that even with the short throw lifters I may not be able to get 6500. IOW, that's the best I'm going to get unless I bump the compression and go to a solid roller. Pretty much what I expected. We have a double-header this weekend. I will be running both days. I should get a bunch of runs on the car. It's also supposed to be cooler also so I should be able to get some good comparisons from my earlier in the season runs.
Thanks for the follow up, Jim. All that rings a bell now. And yeah.. those roller style springs should be fine a bit past 6,500 even without light weight components. I'd still try a quick rev limiter adjustment(if you have the required chips) before you load it on the trailer just to see if the lifter preload settings did anything for you. Even a minuscule 100-200 rpm improvement is better than nothing at all. As for the cam itself not being able to pull to 6,500 and beyond?.. take their input with some added salt. They design em' amd make em" but they don;t test them in every combination known to man so there's some wiggle room still left in their advice. The things you have going for you in this combo of parts are the cam being ground on a wider lobe sep angle.. which hurts max torque a tad but raises the peak power rpm up higher in the rev range. Then the biggest factor that you have changing the typical rpm limit expectation(based on duration and lift figures alone) is the simple fact that this cam's sitting smack dab in the middle of only 302 CID's. I had that exact same grind/lobe design(#12-432-8 ground on a tighter 110° LSA) in my 383 Chevy and it quickly went to 7,000 before it started falling over. Took lots of valvetrain mod's and manifold/head work to get me there.. but even before all that hubbub it went straight and cleanly to 6,500 without breaking a major sweat. No doubt that the grind is good for your lighter chassis combo. Trust me here, once you get those lifters swapped over?.. that little short stroke motor will pull really nicely up top and reach out WELL past 6,000 rpm. Good luck with it next weekend.
It is a real shame you can`t get more than 6200,you`re not even getting full potential from your cam.Good luck to you & have fun,you will eventually iron out the bugs.
I'm definitely having fun. My winter project will be fixing the shortcomings of this engine/car. For sure, I'll install the short stroke lifters, probably mill the heads to get the compression up, increase the stall in the converter, go to a spool and new axles, and change the gears. But, for now, I'm going to try to win some rounds!
Miserable weekend of racing. Fought the weather all weekend. Wind caused us to have to go to 1/8 mile on Saturday. That was after time trials at 1/4 with temps in the low 80s. So, I took my 1/8 split and dialed 7.96. Waltzed through first round when other guy broke out. Second round, the dreaded 'red light of doom'. I left on the second yellow. Don't know why I did it, but I did. We also tried to get my '66 Nova in to the street car Quick-8 13.0 index. The car runs 12.70s with the exhaust uncorked. So, with my son driving, we went 12.92 through the mufflers. Too fast. I took 2* timing out and he went 12.97 the second pass. Didn't make the field. There were 40 cars trying to make the 8 car field. The bump was at 13.12 for the second run. He was pretty disappointed. So were 32 other drivers! Drove to the strip today in the rain. Sat in the truck for two hours until it stopped raining. Took them an hour to get the strip dry enough to run. Back to 1/8 mile. I reset the timing to 38* and ran 7.88 for my first and only run. Rain came down again and washed us out. We got 3/4" of rain last night and today. That's unheard of in Boise in July. We normally don't get any rain after June 15 until September 15 other than a rare thunderstorm. This was an almost continuous soaking rain. 5 passes in two whole days.
Must be a perspective sorta thing. Because after not driving down the strip for a few years now.. I'd be happy to get 5 passes in even if it was snowing out. Better luck next time.
Three weeks with no racing. Won't get to race again until the August 30th. I'll have to retrain myself again!
Decided to replace the aging EquaLok posi. It was not spinning both tires in the water box. I installed a 28 spline spool. Not my first choice, but I got a deal on a bunch of 28 spline 9" stuff so I used it. Only got to make one run but it hooked perfectly. This was at the Midnight drags that Firebird has a few times a year. It's oriented toward street cars and you have to have mufflers, so I put a pair of header mufflers on it. The car did not like the restriction and went 12.81. But, 282 cars showed up to run and I gave up after one run and put it on the trailer. It was a zoo. I race again Friday night. The weather has cooled off and I'm looking for some faster ETs and more consistency with the spool in it.
all the little changes add up in the end. Have you ever tested and tuned towards optimum collector lengths on this combo? Anywhere between 12" and 20" should increase peak torque and spread it over a bit wider rpm range.
I had 18" header extensions on it. I painted them so I could tell where the paint burned off with the intention of cutting them off at that point. I have always read that that is the technique for getting the best combo of torque and horsepower. But, I didn't get a clear burn line. I have them off now since I ran it with header mufflers last outing. I intend to run it without mufflers or extenders Friday to see what difference it makes, if any. After Friday, I'll try a different type of paint to see if I can get a clear burn line. I used high temp engine paint last time.
yeah.. that's a decent enough method to help you dial it in. No high temp paints.. defeats the whole purpose.. use white lacquer based paint. It burns in yellow/brown witness marks much quicker. I've said it before and I'll say it again.. your 3" headers collectors are too big for this little motor.. ESPECIALLY with that converter.. and there is power to be gained with reverse cone style collectors. Probably so much torque gain that your tune will change(due to better exhaust scavenging/less reversion) and the converter will stall another 100 - 150 rpm higher. http://www.headersbyed.com/hc_ventext.htm Easy to make reverse cones with these two parts. Then slip a 3" extension into the big end of the flowmaster venturi's(they're ID sized for slip-on) and test/adjust the lengths for an optimized torque curve. https://www.summitracing.com/parts/pte-h7243/overview/ http://www.flowmastermufflers.com/a...uri-reducer-cone-300-in-id-to-250-in-od-pair/ Or.. design it closer to what the pro's use. Slightly more money but even better results. I'd go merge style with 2 1/4 outlet and cone it up to around 3" final outlet size with whatever length of 3" straight works best for your combo. Your 60's WILL pick up and the system will still work well with your new lifters higher rpm potential and better stall speed once you get it all back together. http://www.coneeng.com/exhaust_system_kits.html Most don't understand that too big pipes cost far too much average power in trade for peak horsepower only. Calvin Elston is building systems that are putting 595bhp+ through a single 3" tailpipe with a 2.25" choke merge collector. 1.625" off the head. In-car: http://www.exhausting101.com/ PS.. forgot I had this saved link too. Cheap china based stuff but the price is tough to beat. I may be using these myself with ends chopped off for connecting a reverse style cone. http://www.ebay.com/itm/CXRacing-4-...ash=item257d2ad4dd:g:OsIAAOxyLN9Sp82A&vxp=mtr And these too. Works already done for you.. just add the extensions. http://www.ebay.com/itm/OBX-Univers...ash=item281801dc27:g:93oAAOSwZJlXMi94&vxp=mtr
Good for you. Hopefully not too abrupt a transition and steep an angle? What choke size?.. 2 1/4?.. ding ding ding!.. or 2 1/2?.. better than 3" by a country mile. Any pic's? Some fun math. 3" pipe sq/in = 6.49". x 2 pipes = 12.98 sq/in flow area. Enough for about 680 horsepower of exhaust flow. 2.5" pipe sq/in = 4.43". x 2 pipes = 8.86 sq/in flow area. Enough for about 460+ horsepower of exhaust flow. There's obviously far more to it than that(a small/short constriction in a longer section of larger diameter pipe doesn't take the same hit in flow area).. just look at the video above for proof of that. You just lopped off about 33% of flow area from your secondaries. Got torque? lol
