Massive drop in valve spring height ? .BSA B33

Hi , I thought something was not right on my Bsa B33 ( modified to 597 by previous owner )when riding it would go surprisingly well up to ¾ throttle , but felt like it was slowing at full throttle, and it had a lot of reversion or fuel stand off at the trumpet , i thought the cam timing might be wrong ,anyway the magneto died and while the cover was off , i checked the cam timing wrong , I found the intake cam , 1 tooth or 10 degrees retarded , the engine never really felt like it had any compression but did have with full throttle and a good boot , so i reset the cam and thought I should recheck the piston to valve clearance and found the intake valve spring was a light finger push for seat pressure ! Actually about 10lbs , took the head off and found that intake spring was 13mm shorter than the exhaust valve spring , like it wasnt heat treated correctly ? the heads have been nicely modified with 5/16 stems , with excellent ports , ex valve 45mm intake 47mm , port to carb 35 mm , springs appear to be Terry's VS345, stock cams I think , going by lift , intake cam only had .280" lift , i replaced it , it also had two barrel spacers and piston was down the bore about 2mm , i removed the 1.5mm spacer and the shallow dome piston is now about .75mm from the top, squish was tight and i had to make a squish band on the head , it has 1.0mm now , PV was ok but as it passed by the pocket was close , so have clearanced the pocket edge and have 2.0mm clearance now , just trying to get the valve springs to a reasonable seat and over the nose spec ,new stock springs are not too flash at approx 60lb and 110lb if these are shimmed they are too close in the coils at full lift I swapped out the inner spring for another and get 115lb and 175lb which I think is just a little too much for the old girl , I'm sure closer to 80lb and 140-150 would make it last longer , I'm not going to be over revving it . Any thoughts please comment . Cheers.

Up date on this popular subject , I got a hold of some second hand inners and bumped up the seat pressure to 86 lbs and over the nose to 140 lbs , which im going to try, I have some other inners that give me 115lb on the seat and 175lb over the nose but I think that might wear the pointy bits off my cams , i found on another forum post that someone checked their new springs at , 60lbs on the seat , but as the bsa ran with 10lbs on the inlet valve so I will see how she goes , just have to wait for my rebuilt magneto. Cheers

After rechecking my compression the 600cc b33 , it had two barrel spacers a 6mm and a 1.5 mm piston down the hole about 2mm
And the domed piston was from a shovelhead, initially I thought it would be nice to have a squish band, so I took the 1.5 spacer out , I think this was how the engine was originally built , but found it nipped off the plastersene, I did a mod to the chamber edge and got a nice .040" squish band , but when I rechecked the comp it was 11.3:1 ! , way too high , after some research I bought a evolution piston 1340 +.030 same size but + 2mm in pin height , made a steel 8mm barrel spacer . I didn't want to lose my squish band so I welded on some eyebrow style mounds and machined them to suit my chamber , I'm around 7.4: 1 my flat top part of the piston was down 1mm , I reassembled it and got a cranking compression of 150psi cold , so I will see how it goes , I've swapped the phf30 carb body for a phf36 . I am sure it's going to be happier .
Cheers .

Shelby-Right said:

After rechecking my compression the 600cc b33 , it had two barrel spacers a 6mm and a 1.5 mm piston down the hole about 2mm
And the domed piston was from a shovelhead, initially I thought it would be nice to have a squish band, so I took the 1.5 spacer out , I think this was how the engine was originally built , but found it nipped off the plastersene, I did a mod to the chamber edge and got a nice .040" squish band , but when I rechecked the comp it was 11.3:1 ! , way too high , after some research I bought a evolution piston 1340 +.030 same size but + 2mm in pin height , made a steel 8mm barrel spacer . I didn't want to lose my squish band so I welded on some eyebrow style mounds and machined them to suit my chamber , I'm around 7.4: 1 my flat top part of the piston was down 1mm , I reassembled it and got a cranking compression of 150psi cold , so I will see how it goes , I've swapped the phf30 carb body for a phf36 . I am sure it's going to be happier .
Cheers .

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Post some photos if you can
I'd like to see that

Here's some pics , don't be too critical I didn't get a 100% clean up of my weld , which I don't think matters , I used 4047 which is 12% silicon , I got .040 with solder I'm hoping this might help the big hemi chamber , gain some tumble or help with a more homogeneous mixture for a complete burn , I also read that as the piston slows down on the exhaust stroke toward TDC it gives a last spurt of pressure to empty the chamber, any thoughts ? The old piston the second ring was stuck really bad so if you kicked it over at a medium speed it felt like it had no compression , but when you gave it a good boot the compression obviously pushed the ring out and sealed the valves good , it kicks over and feels and sounds like a normal motor now 150psi cold , hopefully it will go nice and stay together , I'm not racing it .

Some other issues I found were , the inlet rocker was coming in contact with the retainer first for about .020" , that's really bad , It has lash caps on the big oversize valves that were .053 thick , I've changed these for some .080 thick from a 426 hemi aftermarket 5/16 stem ones that's fixed it , nice oil hole to .