hrcslam

What was measured is almost dead nuts for what they should read. 150-155 on those springs at 1.740" is not accurate.

Here's the math. 125 on the seat @1.800". 372lbs per inch.
So, 125/372=.336".
0.336" compression of the spring will give 125 lbs of pressure which is the installed height of the spring or 1.800".
1.800-1.740=.060".
0.336+.060=.396".
0.396*372=Seat pressure of 147lbs at 1.740".

Springs vary so this is an estimate based on the rated spring pressures. You won't hit 155lbs on the seat with those springs until your installed height is 1.720". If you go to that, you'll have less than .050" clearance from coil bind with your cam. I'm not sure how the harmonics of the springs would tolerate that clearance.

Anyone using 918's with less than .050" clearance from coil bind.

Maybe you need to look at different springs all together. With how aggressive those lobes are and you not experiencing the symptoms of valve float until 6K, plus the recommendation of 155lbs on the seat. I'd look into new dual springs. Lloyd spec'd a set for me @ $450 for the set with retainers, locks, etc.

IIRC, those Patriot Dual Extreme springs are 155lbs @ 1.800" and 410lbs @ 1.150 Coil bind at 1.090". But, they are expensive.

Howards Cams 98118 also meets your recommended specs, but they are designed for LSx engines and I'm not sure they'll fit on the LT1. Anyone know?

v8vette84

What I don't understand is there are other people using the same springs with no problem. So you think I don't have enough seat pressure for a 232/240 .578/.574 110 LSA Cam? (Those numbers are with 1.6 rockers.)

hrcslam

There's more to the cam than just those specs, in fact those specs are almost useless for this topic. The ramp rates that Lloyd sells are very aggressive. You'll need at lot of spring pressure to prevent them from bouncing on the seat. If he says you need 150-155 on the seat I'd shoot for the higher end of that.

v8vette84

Well Lloyd said in his emails that 145lbs. on the seat at 1.740" is good so anything over that I think is better.

hrcslam

But you are there and you're getting valve float. What did you set your lifter preload to?

flame

iTrader: (13)

Another thing to check is valve guides. I ran into this with a motor I bought years back. It hit a brick wall at 6000 rpm I thought maybe the springs were worn out so I went to change them. Put air in the cyl to hold the valves up and could hear the throttle plate whistling. Turns out there were 5 intake guides so loose the valve was cocked on the seat and leaking. Something else to check if you have a data log is airflow and map when it happens. Had a WS6 last summer that was running out of air around 5800. Removed the baffles in the hood and it screamed to 6500.

v8vette84

Makes sense. I will have to data log again to see if I can find a problem. Also when I put air pressure in teh cylinder it does leak out a little bit. I thought this was normal but maybe its not. When I pressurize the cylinder am I supposed to hear nothing? Is it supposed to seal completely? It leaks out slow but it still leaks down. I figured that was normal because of the piston rings not being a 100% seal. I've only tested one set of valves but air does leak out. If you lean close you can hear a little hissing of the air plus see it on my compressors gauge that it slowly goes down.

v8vette84

Well I never confirmed it was valve float, it just has some of the telltale signs of valve float. The machinist I talked to the other day seemed to think it was a fueling issue or it could be that I didn't degree my cam. (Was very set that my cam was so far off it was making the power drop off early.) I don't feel it could be that far off but idk. I set my preload to 1/2 half a turn past 0 lash. (Sometimes a little more) Lloyd said i should be setting them around 1/8 a turn past zero lash. Just enough to take out the play. Otherwise your springs are going to battle the lifters. That machinist told me to go a full turn or more past zero lash. His reasoning was that the oil in the lifter makes the engine never even get close to its full lift. He was also telling me on occasion he preloads all the plunger travel out of the lifter so the car essentially acts like a solid lifter. Not too bright to me.....

hrcslam

The reason I bring it up is because you could be experiencing lifter pump up... 1/2 turn is about .020-.025" IIRC. It's easy to to check, set your preload to 1/8 turn spin it up.

v8vette84

Some I did 1/2 a turn others I did 3/4 of a turn. I will try 1/8 of a turn and see what happens. I'll be tackling this tomorrow as its rainy here and ever since I moved I lost my garage use. (Which sucks)

hrcslam

I know the feeling. I recently had to cut bills temporarily for short term disability. I had to move all my storage stuff into my garage. Sucks.

joelster

I ran the XFI468 cam which was very aggressive, 242/248 with .584/.579 lift, with the 918 beehives. Never experienced valve float. Ran them with stock lifters, and slightly heavier valves with the TFS heads 2.02/1.60 valves. The only lightweight parts in the valvetrain were the pushrods which were chromoly. I adjusted the preload to roughly 1/16th-1/8th of a turn past zero lash. Basically set the lash to zero and turn the wrench a tiny bit, no more. Install height was critical and I had to buy special locks to get the springs higher and into spec. Ran that motor for years and shifted it at 68-6900 hundreds of times with no issues. It's still sitting here waiting for a home. Everyone will have their own method of setting preload and their theories and reasoning behind it. Some will do it like I did, while others will swear to go 1/2 turn or even 3/4's of a turn.

hrcslam

The ramps on the XFI cams are not nearly as aggressive as the ramps Lloyd sells. The XFI ramps are fast for a shelf grind. But Lloyd sells cams that have lobes that are damn near squared, not egged or oval like yours and mine.

What did you set your seat pressure too? Our cams have about the same ramp rates, I've spun mine to 6700 RPMs on the dyno without valve float with 128.6# on the seat. If you're set up with the 918's at the 1.800" setting and spinning to 6900 I may be inclined to up my redline to 6850.....

I set my lash to 1/4 to help prevent pump up, which I didn't see on the dyno either. 1/8 should help with pump up even more so.

flame

iTrader: (13)

You will hear some past the rings.But should not in the intake or exhaust

v8vette84

So my day was cut short by my 4 day old Harbor Freight compressor dieing. So I will be getting a better compressor in the next few days to continue my work.

v8vette84

So I FINALLY got the car back together and I think I preloaded a lifter wrong or maybe the pushrod was never seated correctly in the cup to begin with. I was driving around and it was running good, I got on it and was running up to around 6k and was not cutting out yet and all the sudden I hear a clanging/banging noise. I get home after nursing her home and I thought for sure I dropped a lifter into the piston and would need to pull the head and check all that stuff. Basically I broke a lock or broke a spring I also thought a possibility. Anyways I pull both valve covers and find the driver side rear-most rocker arm sitting sideways and the push rod sitting sideways. I checked the lifter and it was still in place and the pushrod is not bent. The rocker is chewed up a little bit so I will be buying a replacement. Here are some pics. Seemed to be running good until the rocker fell off the valve. The valve and retainer seem to be ok. The paint on the retainer was scraped off but its not damaged.

v8vette84

That rocker was the first one I set so its very possible I screwed it up... I double checked all the rockers but I don't remember checking that one again...

v8vette84

I might clean up the rocker and reuse it until I get a replacement. The roller tip and center bearing are in good shape. It's only banged up on the outside. I think I just set the preload incorrectly or set it while the lifter was partially on the cam lobe. I just don't remember checking it thoroughly like I did the other rockers.

hrcslam

Use extreme caution with that idea. It may look like only gouges, but there could be cracks that you can't see with the naked eye. Personally, I wouldn't run it again. Not worth the risk.

That sucks man.

bufmatmuslepants

iTrader: (3)

There's your danger with SA rockers. You are VERY lucky it was still holding onto the pushrod, had it slid the whole 90 degrees you would have a pushrod sticking out of your hood. Right there tells me that you don't have enough spring pressure to keep the tip with the little fingers around the valve at high rpm and you are losing contact with the valve. I know it sucks to shell out the money for NSA rockers but your cam needs much more rpm than 6000, and if you almost lost a rocker at 6000 you'd be screwed at 7000 where that cam should be shifted.