Valve question
- Thread starter OPdemigod
- Start date
briggscrazy
Member
Valve length depends on the spring pressure you want. Lets say you were running the stock clone class, and the limit is 10.8 lb valve springs. By shortening the valves you would get more spring pressure. But at the same time you would not meet the height requirement. Longer valves would allow you to run some custom valve springs. Like the old briggs flathead springs. They are longer and spring pressure would increase as the springs are compressed. Also if you wanted to run roller rockers and you needed more height for the retainers so the pushrods would match. A lot of variations here and I would leave it to the people who know what they are doing and have the tools to set up your head correctly. But of course experimenting is one way to learn but costly sometimes.
I am a single dude with a decent job... This is all about learning and fun for me. I am not racing, but I want to mod this engine and beat my friends moped. That being said, here are the parts I am running so far...
Predator (non-hemi)
black mamba jr
26lb valve springs
flattop piston
still need to measure to choose a billet rod
I was thinking as long as I am doing the springs, and have the head open, why not switch to stainless valves (etc)... However, I noticed there were a bunch of different sizes. I dont know what to choose. I guess I could put calipers on them and see what size I currently have, but should I make adjustments as far as valve size?
Predator (non-hemi)
black mamba jr
26lb valve springs
flattop piston
still need to measure to choose a billet rod
I was thinking as long as I am doing the springs, and have the head open, why not switch to stainless valves (etc)... However, I noticed there were a bunch of different sizes. I dont know what to choose. I guess I could put calipers on them and see what size I currently have, but should I make adjustments as far as valve size?
sneaks12303
Member
A longer valve with the shorter 26lb white springs will only make the situation worse. The long stem valves R usually reserved for Hemi heads that need more "Potential Lift" before "coil bind" occurs with High lift cams . And then the longer 32lb green or 36lb red springs R used . Your non Hemi head prolly has 5mm valve stems giving U less choices for aftermarket parts . The more popular 5.5mm clone valves gives U more choices.
DirtRacer7
Member
The valves that you have stock are pretty decent. I'd just put it together with what you have and run it. Just don't put dual valve springs in it. like sneaks said the 5mm stem throws a monkey wrench in it for you as far as finding easy replacements for a beginning builder. With that cam I'd run stock valves and 26 lb springs.
sneaks12303
Member
Sure , U can stack shims also there R 2 types of keepers . High groove and middle groove . The High groove with improve initial "seat pressure" on the shorter springs and more lash cap room . I like the 26 whites on my smaller 24/25mm exhaust valves . I don't usually have to shim but I don't usually make deeper seat pockets either.
One thing to keep in mind here is that your head most likely has 5mm valve stems, and most aftermarket valves out there have 5.5mm stems like the clone and hemi heads have, meaning you cant use those aftermarket valves without reaming the valve guide to accept those valves. You also dont want to just stick a bigger valve in a stock seat without cutting the seats so that valve matches the seat. Need to make sure you do your research and do things right to get the best out of your engine, you need to do it right. Just leave the stock valves and retainers in your head, get some 1/8" shims and put one under each valve spring if you are using 26lb springs, and that will put your installed spring height nearly perfect for those springs, valves and retainers that are in those heads. You could go with a bigger cam like the Dyno 308 if you want more torque and power, and a stock length billet rod with thin head gasket, or .020+ billet rod and a thick fire ring head gasket
Local hardware store has the shims....ask for machine washers, i believe they are 5/8 inside diameter but you can measure around the valve guide where the spring sits and just find some washers that are close to same size just a little bigger. 1/16 or 1/8 is usually the thickness of the washers at the hardware stores, some may have them thinner like the actual valve spring shims you can buy at kart shops but i havent seen any of those that thin at stores. I use a 1/8" shim under the 26lb springs