26 lB Springs with BM cam?

[Craig B]

I am running a Black mamba cam with 26 lb springs. If I switch to a 1.2 rocker do I need dual springs or a heavier spring? Looking to pull close to 8000. Thanks

 

[TheDullCarbide]

I would say 36 or 37 lb large single springs at least. At 26 lb you're asking for valve float.

 

[Craig B]

I would say 36 or 37 lb large single springs at least. At 26 lb you're asking for valve float.

Thanks. Do you know if the 37 lb. springs are the same diameter?

 

[OND]

I believe you can pull close to 8000 rpm's with a set of 26# springs , and yes the 37# springs are a bigger diameter....your head will need to be cut to fit the 37's in there .

 

[TheDullCarbide]

The 37 lb is a large diameter spring. I'm not totally sure about the 32 or 36. The 26 lb is a "small diameter" spring which means it has the same diameter as the stock spring. Large and dual springs require different retainers and a modified spring pocket.

 

[osu1978]

I am running a Black mamba cam with 26 lb springs. If I switch to a 1.2 rocker do I need dual springs or a heavier spring? Looking to pull close to 8000. Thanks

I run 37lb with my MBJr and 1.2 rockers. What MAX RPM are you at now? Depending on other mods the regular BM should easily be able to get to 8000 rpm so go with the bigger springs.

 

[Craig B]

I run 37lb with my MBJr and 1.2 rockers. What MAX RPM are you at now? Depending on other mods the regular BM should easily be able to get to 8000 rpm so go with the bigger springs.

I haven't had a chance to bring it up to the Max RPM yet. The head is moderately ported with 28mm / 25mm valves and 1.2 rockers.

 

[ole4]

I have run a BM with 28.5/25 1.3 raceeng rockers with 26lb springs to 7500. ran great never had it higher. I also do not remember what my installed height or seat pressure was but I normally set them a bit tighter than the .850 installed height. A BMjr would require the 37 lb springs as its a more aggressive cam as far as lift per degree. For a new build I would go with 37lb springs just to be sure. There were a few people that had the red stripe 37 lb springs break and NR now sells a new one. I ordered it and got the green stripe duals and it is much stronger than 37LBS installed so I am guessing if I just check the outers it will be around 37. I have not had time to test it yet.

 

[Craig B]

Thanks everyone for the replies. I will order a set of 37 lb. springs

 

[Craig B]

What 37 lb spring should I get? I see NR has 37lb red and 37 lb green

 

[ole4]

I ordered the 37lb greens as some people had breakage issues with the red striped springs. What I received was the green striped duals. I think if you only run the outside spring it would be 37lbs but I did not check it yet. If I have time I will go measure it .

 

[ole4]

So the green stripe duals at .850 are 52Lbs with the inner spring removed at .850 the single green outer was 36lb. So I guess he sends the dual spring but just calls it a 37lb spring.

 

[Craig B]

Thanks Ole, I will order them up.