I'm defeated. I've done all I can think of and I am no closer to fixing this than when I started. This problem has plagued me for at least 3 years. When the Riv is just getting warmed up, when I do a WOT blast it pulls hard all the way to 5300 RPM and the 1 - 2 shift is instant and hard. After 2 or 3 more full-throttle runs (basically after it gets to operating temp) it begins to lay over above 4000 RPM. It just won't pull any more and seems to labor to get from 4000 to 5000 RPM. Even the 1 - 2 shift becomes lazy. It doesn't fall on it's face like it is running out of gas; I've had that before and it doesn't feel anything like that. What I've done (each mod has had no affect on this problem): * replaced external Carter electric fuel pump with Aeromotive 140 GPH pump * replaced every inch of fuel line from tank to carbs with push-lock line and -6AN fittings * tried 3 different fuel pressure regulators all set between 7 and 8 PSI * removed first the pre-filter from ahead of the pump, then both pre and after filter so I had no restrictions from tank to carb * installed a distributor and Stinger S4 setup that was all ready to go from another car, thus eliminating my MSD and conversion distributor/trigger * replaced my Pro Systems Holley 950HP with a stock Holley 950HP * jetted up my 950 to real fat and confirmed float levels are dead on * 3 different coils... a NAPA IC12, a used MSD Blaster2 and a brand new MSD Blaster2 What is left? I was told to try adjusting my roller rockers. I suppose I can do that, but why would that have this effect on full-throttle runs? I'm open to all ideas here. My cam is a TA 288-94H Duration at .050" is 230/240* Lift at .050" is .515/.525 with 1.6 rockers Ground on a 116* Lobe Center Installed 6* advanced on a 108* CenterLine Stock B4B Ported and polished iron S1 heads Shorty headers TA 1.6 roller rockers No sock in gas tank and no electric pump in tank either 90AMP 1-wire alternator Runs flawless when cold! HELP!!
If anything, the valves are on the loose side. They tick pretty good. I was told to readjust. I suppose that is next on the list. Again, why would this only have an impact after warmed up?
Do I really need to give you a lesson on the tensile strength of metals at different temps? I'm just saying what I would check first before I spent any more money on sh!t that ain't fixing it. It's easy to remove a couple springs and check their lb rates. If they are weak the motor will not rev under load.
There's that Gay Dave charm. Hard to believe you're still single. A simple statement explaining that under warm loads the spring rates change would suffice. That being said, how do I check the spring rates?? Or do I need to take them to a shop and have them checked? For that price and level of aggravation I'll just buy new springs. $130 would be the least I've spent this month on this. And do I need to ask TA what each spring rate should be (inner and outer)? Or are the rates listed somewhere? And why would my springs fail after less than 10,000 miles??? Seems like so few miles to get from street driving and track blasts 5 times a year. But the way it runs makes it sound like springs.
You've pretty much eliminated everything else besides an internal engnie problem. I say valve springs are the culprit as well. I use the old clothes line trick to hold the valves up. Works like a charm
Had The Same Thing Happen To Me With A Set Of Poston Springs They Were Only 2 Years Old And Not Double Either, So I Put A Set Of Iskys And Wow What A Difference It Was, Like A Different Car .
There is a "claw" that fits on the rocker and has a guage on it so that you do not even have to adjust the rockers. I have also used the tool so it can't be to hard. Just make sure that the piston is at or near the bottom of the cylinder.
You could always throw in a new set to avoid some of the hassle, but as far as checking them goes, the cam card will have recommended spring poundage listed; lbs at installed height, and lbs at full lift. An automotive machine shop can compress the springs in the proper fixture w/gage at these heights and you can compare the numbers to what is recommended for your cam. I'd test a few springs from both I & E and both banks, just to get a better feel for the variation in numbers. Devon
That sounds slick. You'd only need a dial indicator to watch spring height and record the numbers at both heights. Devon
Had one of these years back. Its not as actuate as bench testing. But you can test the spring on the engine cold. Then go cruising around when the car acts up take it home and re-test it hot. Its a quick way without much hassle and without removing the valve spring, and a pretty good tool to have. Its made by Moroso.
I have a removal tool and the compressor fitting. Will take me longer to move the AC compressor out of the way than to swap springs. I'll call TA in the AM and order another set of 1125 springs. Like J says (and I've said a lot this week), I've ruled out everything but mechanical failure. I'm rather surprised that TA Dual valve springs would fail after so few miles with a relatively mild engine build.
I am too, Yards. I run over 0.600" on mine and have had them in for something like 15 years. There's always the possibility of a quality issue with the heat treat on a particular batch here & there, I suppose. The engineer in me hates the thought of not testing yours, but I realize it is a lot of work and they're not a high dollar item, after all. Devon
I put the same cam in with new ta alum heads done by J W. Always been noisy, I was told that cam can be noisy. The other research Ive have done on here supports the claim. It has always run well no changes in noise no matter what my preload was. I have set preload a dozen times already and will do it again tomorrow just for peice on mind. Good luck Matt:beer
I think everyone is on the right track with valvetrain. Springs are inexpensive, I consider them a wear item and swap them out every year or 300 passes depending on how lazy I am at the time. If the guides are too tight, it could cause the valves to bind when hot. Verify your preload with a dial indicator, guessing is not an option. I like .030 +/- .005 on a flat tappet cam, everyone will have their own preference. Always wait until the engine/oil temp is over 160 degrees before revving past 3k RPM, valvesprings will last a lot longer that way.
