Valve Spring Pressure

We run a KB526, fuel heads, Superman 35 over, Bruno/Lenco 2 sp, shift @ 8300, 1/8th mile, 2900lb outlaw 10.5 car. We broke an exhaust valve last weekend on #7 (atleast we think that was first), and on the intake side the keeper/lock was missing. They are titanium valves. Cam is .4778 lift, stage V 1.7 intake rockers, cluff exhaust rockers. EGT's show that cylinder getting cold .5s into the run then dropping off halfway into the run. After pulling both heads off, you can see every intake valve is hitting the pistons, very little, but they are definately touching. Running .040 head gaskets but are going to switch to .064's. We checked the springs, they are all about 375-380 @ 2.050. The are manley triples, they have 26 1/8th mile passes, no over rev's. Any thoughts? Do we need more like 450lbs?

Josh Long

 

I run 400 to 450 on the intake never any problems shift at 9200 through the lites at 9500 to 9800..dave

 

As above, we chuck them out at 400 intake 380 exhaust pac doubles 1360 intake 1355 exhaust,..... last forever if treated right

 

What's coil bind on those springs? Are you checking lift on the actual head and not just computing lift (rocker ratio x lobe lift)? You may find that you have more than the computed .812" lift; may find less from deflection but always a "must check." I also think that on the hemi you need more like 475# min on the intake side, on the exhaust it's not as critical but I'd still say 400# min. You should put some clay inside the cylinder, on the ex. pocket/int. pocket/dome/squash area. Put your head back on and turn the motor over with rocker system on, once you turn it over a few times you can take the clay out and get your clearances. Depending on comp. height and v.r. depth, a .040 gasket should be fine. The .040 doesn't seem to last very long since it's so thin, you'll see chatter marks on the edges of the o-ring impression around the cylinders. You need min. 080" clearance on piston to head....the piston to valve maybe .130 int. and same for exh. to be safe (<- exh. could be a bit less perhaps). Perhaps Noel will chime in, he'd know a bit better than most. We run a 1361 on the int. and then swap them to exhaust once they go below 475#. Ken @ Motorsports Unlimited is the guy get your springs from, he's a sponsor of this site.

Brandon Booher
NHRA TAD #34

 

Cam Timming

It is possible that the camshaft has been installed incorrectly. As the camshaft is advanced, the closer the intake valve will come to the piston.

Noel

 

It's possible Noel, in fact we were just talking about how we need to double ck it. What's confusing is last year the cam was advanced a couple degrees...I believe it was at 38. This year we retarded it and set it straight up how the card said to @ 36 to give us a little more top end power.

 

Just to follow up...we checked the camshaft last night. It is advanced from 36 to 67 degrees Can this happen? or is it installer error

Good call Noel.

Josh

 

cam

It's dangerously easy to have our cam move a tooth with a KB geardrive when the fuel pump extension is removed. Make some reference marks or get a lift #at the rocker arm so you can verify where you're at with the timing marks.

 

We run a casale gear drive. We'll take it apart this weekend and let everyone know what happened. I would think if it was that far advanced when we raced a month ago the bottem end power would be hard to control on 10.5's.

Mike, you going to wichita next weekend? We thought we'd try to get this thing together and go out. Can't beat free entry.

Josh

 

don't see how it would even run that far out?..you better check and re check..you checking at .050 dave

 

Dave, yeah we ck'ed at .050...suppose to be 36??? and was 67. Not sure what's going on. Appreciate the help. Had to go to BAE for the inserts & guides.

Josh

 

wichita

We'll be there Josh. Could use cars for sure.
We tested there last weekend and the track was maybe a little better than normal.

 

only thing you need to watch at wichita is the sand that blows on the track..dave

 

i run the higher spring pressure now just my thoughts it seemed harder on the parts i used to run 380lbs on both intake and exaust and when lower than about 345lbs i repalced them and the car ran fine 3.90s in the 1/8 and 5.90s in the 1/4 in a 2380lb funny car 526 with the fuel heads and wasnt killin parts just prelubed every thing real good i know guys run a lot of pressure these days i had my first valve train failure while runny with spring pressures over 400lbs when it pulled a valve into could of just a part failure remember its not always a monkey see monkey do deal just because they run doesnt mean you will run faster with it good luck

 

Jim you are so rite I run more pressure and now more problems

 

Just to follow up, cam was definately in at 67 degrees at .050. Nothing broke or moved that caused the cam to move, we just accidently set it up that way I guess. How it ran as good as it did (personal best time last race) is beyond us. I thought 2 or 3 degrees made a difference...on bottom end or top end. So why didn't we see something major on 30??

Josh

 

Is this the 114x Crane style cam?

296/300
.4778 int lobe
.5100 exh lobe
114 centerline

BAE sells a really nice bridge setup to degree a cam with, if that'd work for you I'd get one as they're relatively cheap. We've put them in a puff-teenth off when it got installed off the wrong "0" on the degree wheel...that always makes for a fun day. With it retarded that far youd be tagging every exhaust valve in the thing but advanced that far???, I'm sure Noel will chime in here. Do you know what your piston to valve clearance is?

Brandon Booher
NHRA TAD #34

 

Peacemaker-Are you related to WJ Burmingham?

Brandon, that sounds right on the cam. I don't have it w/ me but I was thinking it was like a 486x grind? We checked clearence after setting the cam in right. Playdough was about .100" thick and it never touched...w/ .040 gaskets.

Josh

 

valve spring

No im not related to him never heard of him.

 

Spring Pressure

I have an idea! If every one here that thinks less is better!!!!!!!!!!!! How about each one of these people have a contest. We will see who can get away with the least installed pressure!!!!!!. Where is the rate addressed?

Let me know how Opinion, vs Logic works out. There is some simple math to answer the question, and 300 lbs of seat is not the answer.
Please let all of us know how the less is better contest works out.

Noel