T and D rockers coming loose?

im running a conventional headed bbc with T and D shaft rockers and have had great success up to this point but attended and won a no prep race New Year’s Day but had 3 intake rocker nuts come loose and fall into the motor so far I’ve found 2 and 1 is somewhere still in the motor but I found a piece of it in the pan, also I use the Recomender LSM torque wrench for the rocker jam nuts? Any ideas on why they possibly came loose? Possibly valve float even though I didn’t rev it over 8100 rpm which is the usual rpm I turn it unless the springs are going away? I run a Manley severe duty valves with 340 lbs on the seat and around 880 on the nose with just over .800” lift! Also I’ve got 60% leak down on number 7 cylinder and it’s going past both the intake and exhaust valves like I may have tuliped the valves which number 7 is one of the intake valves that came loose? And number 7 wasn’t burning any cad off the plug like it was rich so I don’t know how it would tulip the valves??? Any ideas would be greatly appreciated ! Also I had the blower slowed way down and plenty of fuel for the conditions! Anyhow thanks for your

 

Seat material. good video from matt at MBE on this. Good Luck

 

also replace the studs and the cross shaft on the rockers that came loose or you will be repairing it again !

 

Do you have a pic of your rocker setup. I know how mine was fixed and all the issues went away

 

Hi mike and sorry it to me so long for a response, the reason I believe my fuel curve was ok is I’ve been running this combo successfully for awhile and it’s a conventional headed 555 ci bbc with a static compression of 10.5 with a max advance of 28 degrees and a HH 14/71 OD @ 14% and a enderle 990 pump with a105 main and a 65 high speed the blower at 8000 rpm makes about 32-33psi but the spark plug on number 7 cylinder which is the one that the valves are leaking looks like it just came out of the box, in fact only 3 of the 8 plugs are burning about 40% of the cad around the plug so I think my tuneup is pretty safe?

 

If I were lean or detonating wouldn’t you see some heat on the plugs?

 

If that’s the case how do you tune that if your not getting a reading off the plugs and nothing looks alarming on the data logger??

 

How old is all this stuff. Age and fatigue play a major part in t&d stuff. Been there done that.

 

Well I should mention that my rockers are almost 9 years old with a lot of runs and a lot of street driving on them and I will admit that I meant to pull the valve covers and check the lash after the first run but didn’t because typically they don’t move but even though they show no signs of wear and the trunion and roller tip still feel tight and smooth maybe it’s just time to replace them? Let me ask this question what spring pressure do you think is necessary for this combo? 55 mm large base circle cam with .904 lifter specs lift .819 int .810 ex. Dur@ .050 280int 290ex 114 LSA 2.30” stainless int valve 8200 rpm with 40-43lbs boost???

 

I forgot to mention that those lift numbers are with a 1.8 rocker ratio!

 

I totally respect you’re abilities and experience but I gotta completely disagree based on my experiences. On a normal tuneup I can read a plug that went about 2 seconds. It won’t be full color but if it looks “out of the box” it was fat.

If it’s hot in low gear it’s going to take some cad off. That cad isn’t going to heal itself if I fatten it up out back.

That’s one nice thing about reading blower v nitrous. A nitrous motor could be dead lean until 1000 ft and then color up the porcelain at the stripe. On alcohol, if you Lean it out somewhere, the plug is going to tell you about it. Downside is that the alcohol is way harder (I would say impossible) to differentiate timing from fuel.

 

I run a little more cam, same or more rpm, maybe less boost (you said 33 and 43 in different posts, which by the way, is a badass blower for 14% on a 555). I used to run double Nexteks that were about 270 on the seat installed, replaced around 250. Probably 850 open. No real problems but switched to triples that are low to mid 300s on the seat, ~900 open.

 

Yes that day @ 14%OD around 7800 rpm I was Seeing 33-35 lbs boost and with the blower @39%OD I’ve seen 43 lbs with intake temps never more than 100 degrees at the end of a run , I’m very impressed with TBS XR-1 blower , I’m curious on the specs of your cam bjs 344 and if your running titanium valves ???

 

SS intakes and inconel exh. SS would only last 10 runs on the exh. I’ve had a few different cams, forget exactly which one I’m running now, but generally .855/.840 285/305-310 on lsa of 115-116 in at 111-114. I ran one with shorter exh and tighter lsa because somebody said it was better; definetely wasn’t better, pretty sure it was a few hundredths slower.

All std base circle and stock size lifter bore. Short deck block. 7/16 pushrods. I think .165 on exh maybe thinner on intake.

I ran Harland sharp studs for a few years with 3/8 .083 pushrods then all of a sudden they wouldn’t work anymore. Crower stainless shafts now and they’ve been perfect other than when I pulled the top of the cylinder head off.

 

Do you guys ever look at and measure the rod bearings?

 

Fat and over timed can detonate pretty easily. Fat is not always safe. Personally to me i think there is too much timing in the engine. This is not a hemi. id take 6-8 degrees out and lean it out till they are burning 1/2 to 3/4 on all the plugs at the 1/8th. Also i would start playing with the nozzle jets to even the burn out.

i also think you're probably a touch light on valve spring with stainless valves. People dont think about how the boost on the area of the backside of the valve reduces seen valve spring pressure by the valve.