Changing valve springs on GN1s

[toomanymodz]

Well, as some of you know, I've been chasing down a gremlin with my engine. It basically stops pulling at around 5400 rpm. It has PAC 1200 valve springs and according to the Weber Power Products website, those are intended for mild roller cams running low RPM's and street boost. They only have 350# open pressure. Those springs probably will work fine on ported irons with the small 1.7x valves and say a 206/206 cam and 1.55 rockers. But since I'm running GN1's with the heavier 1.90 valves, a 218 cam and 1.6 rockers, valve float starts occurring pretty early.

So today I have begun the task of swapping the springs in the car. (fun let me say). I'm installing the PAC 1201's, which have 410# open pressure and are designed for larger billet rollers, street/strip use.

I have finished the driver's side. Next is the passenger side, which is going to be lots of cussing. Does anyone have any tips/tricks for the back two valve springs? The A/C box is right there.

 

[Paul Lohr]

This might help.

Instructions:
http://turbobuick.com/forums/threads/changing-valve-springs-with-heads-on.370757/#post-3005686

The spring compressor:
http://www.cottonsperformance.com/proddetail.asp?prod=VST&cat=70

 

[toomanymodz]

My heads use a stud setup, just like a Chevrolet small block. Luckily I already had a lever-type tool that I've used on Chevy's, and it's working great. That A/C box on the passenger side is so close however, I'm going to save those two springs for last.

 

[turbofabricator]

Oh man........always.....ALWAYS do the hardest proceedure FIRST. That way it's all down hill from there.

Ya, those rear springs are a challenge to get to. I've had to cut and weld the compressor to get to them at times.

 

[turbo nasty]

Oh man........always.....ALWAYS do the hardest proceedure FIRST. That way it's all down hill from there.

Ya, those rear springs are a challenge to get to. I've had to cut and weld the compressor to get to them at times.

Second that had to mod mine as well

 

[bison]

With the spring compressor slightly modded and some patience those springs aren't too bad.

 

[toomanymodz]

Ok, the job is done. I'll do a quick pull tomorrow and see if this fixes my RPM problem.

 

[toomanymodz]

Major disappointment. It helped, but only by about 300 RPM. Now the float occurs at 5700 - 5800 instead of 5400 - 5500. I was hoping that the float wouldn't happen until over 6k.

 

[bison]

Major disappointment. It helped, but only by about 300 RPM. Now the float occurs at 5700 - 5800 instead of 5400 - 5500. I was hoping that the float wouldn't happen until over 6k.

What lobe # are you running?

 

[turbofabricator]

What is the actual seat pressure? Not advertised seat pressure. You can add shims to get the seat pressure up as long as it doesnt cause coil bind over the nose.

 

[toomanymodz]

Not sure what lobe #. It's the billet roller cam that Weber sells. 218/212. They originally setup the heads with the PAC 1200's. The PAC 1201's have the same installed height so I didn't re-shim them. I wonder if titanium retainers would give me any additional RPMs. I'm only needing another 200 or so. This engine probably peaks at around 5500 or 5600, so ideally I'd want the shift points to occur at 5700 - 5800. I don't plan on taking it past 6k...really no need to. Shimming is a possibility, I just hate going through this whole dang process again. It took a few hours to swap those springs..argh. Another option would be to run solid lifters and lash them to .006

I'm just going to take this step by step. The car doesn't hook very well on the street. From a roll the tires will start spinning as soon as the boost hits and they don't stop spinning until over 80 MPH (MT drag radials 255/60). My pump-gas goal is high 10's. Right now it's ran an 11.18 short shifting at 5300, so it has some more potential if I can get this valve float issue resolved. I'm not gonna even think about adding an alky kit or race gas until I get this float problem (and traction problem) resolved. Oh yeah, my drivers seat is still broken so I need to fix that (i'm hanging on the steering wheel with both hands!).

 

[bison]

Im not convinced its a valve float issue at this point. What is the valve lift? Id call Weber and ask what the lobes are. There is a 218 hyd lobe that requires more spring than what you just put on but ive never seen it coupled with a 212 lobe. You likely have 3313 intake and 3312 ex, 110 or 112 LS. Neither requires any crazy spring and will rev past 6000 easily with what you are running. For a 93 octane only application id be running a solid grind with more duration to take advantage of the extra mass flow with the extra rpm. You will have a big trade off down low when doing so though.

 

[toomanymodz]

I'm wondering if its an issue with the lifters pumping up or something.

 

[bison]

...

 

[jpwalt1987]

You have the morrel lifters don't you??

 

[qws2000]

Toomanymodz.... Can you PM me when you have a min, Having the same problem. thanks AL

 

[toomanymodz]

These are rated at 140 on the seat. I'm running the Morel lifters with a little less than 1/2 turn pre-load. I read somewhere that the comp 885's have a better design. There is a new lifter that Weber sells that has a redesigned plunger that only has .020 of travel

 

[bison]

Id be interested in the result with a set of the lifters from weber.

 

[turbofabricator]

Bison, there has been alot written about the new Comp low travel lifers and they seem to work well. Not many people are getting big gains, but if it stabilizes the vavltrain at RPM then why not. Magazines seem to all have articles written about them, but magazines are there to support thier sponsors. (yep, I know....what a SHOCK!!) In theroy they make alot of sense especially with over 150 lb.s of seat pressure.

I too wonder if valvetrain is your issue. Are you sure you are setting the pre-load correctly? I had a guy years ago call me after installing a set of my heads on and said I did a LOUSY job!! HE said the valve seals were ALL leaking bad and now his car smokes. (this was from a guy that assembled his engine on a 4'x8' sheet of plywood on a gravel drivewayon start up it wouldn't make oil pressure because there was a piece of gravel in the oil feed gallery) But after talking with him for about a half hour I asked him to explain in detail how he adjusted his pre-load. He was using T&D 1.65 rockers and he had tightend them until it bottomed out the plunger then added another 3/4 turn. He said it wouldn't make any compression and that I had given him wrong instructions on how to adjust the valves. I had told him to tighten slowly until there wasn't any clearance between the push rod and lifter/rocker, then add 1/2 turn more. Well to him it took tightening the adjuster until the plunger bottomed out. That meant adding the additional 1/2 turn kept all the valves off thier seats. (and meant crashing the retainer into the seals, too) So, not saying you are doing it that bad, but if the pre-load isn't right it can do what you are describing. Or you have an ignition break-down. What is your plug gap? Need to run about .030"-.032" at high boost. Good plug wires. Try swapping coil packs and ignition modules with someone else for a few runs. Also how are you grounding the engine grounds? Grounds are VERY important on these cars.

 

[toomanymodz]

I am positive the pre-load is correct. While we were in there we performed a leak-down check using a dual-gauge Tavia and all cylinders were under 4% except #2, which was still within acceptable limits. Plug gap is .028 Plug wires are Magna-core. I know there is debate as to whether this is float or not, but what I find interesting is that changing the valve springs provided a confirmed 300 additional RPMs. With the old springs I never saw anything above 5550, ever. This time I saw 5850 rpm. I am holding 2nd gear and watching the tach before I shift into drive. I have both a recall memory tach and a laptop recording the runs. I have checked my coil pack ohms and they're perfect. The engine doesn't miss at all. Even when hitting the RPM limit, it's not missing. All factory grounds are there. I have a complete spare engine on a stand. I guess I could try swapping the coil and module.