310 Cam

[One Fast Kat]

Yes
Be careful if you use valve springs with too much pressure it will destroy the compression release.
Without warning the next time you try to start the engine it will kick back, pull the recoil out of you hand and either the tendons in your fingers or arm along with it.
Trust me it can really hurt!!
If you continue to use it with a broken compression release the plastic parts in the recoil will eventually fail. Usually on the starting grid before the feature.

I see you sell a 310 cam for your Animal super stock class, does it have the compression release on it? And does it break with green stripe dyno cam springs?

 

[delray]

another method would be to make a valve cover with a lever that can keep the exhaust valve from fully closing while starting.

I would think you would have to control the movement at the tip of the valve,so the device would have to be on top of the rocker tip,but then you would run into the push rod jumping out of place. not to mention how you would support the device in the valve or underneath it and all the other things that jimbo mentioned. I think designing a compression release in a billet cam would be a lot easier.
freeze your ideal sounds neat. flick of lever/switch and off you go. now you just got to build it.

 

[delray]

I wasn't really implying installing a Tecumseh style compression release setup. just showing how simple of a design it was. for your little release valve for harley and chains saws that would take little work also to fab into a animal head. just no room without machine work and welding involve. maybe just no room at all. have you look at a animal head before? for me if i deside to build a animal stroker i would have to have a rope start for my application.

took another real good look at my intek head(only head I have in front of me) and assuming it is casted the same as a animal head in that area.
there is a area on the side of the head i could mill flat and tap into for threads and drill a hole that would lead right into the chamber and it doesn't have to be right where my green line is. just a reference point.

i'm sure if you had to run the tin work you could easily punch a hole in the tin for the compression button.

 

[Jimbo]

I see you sell a 310 cam for your Animal super stock class, does it have the compression release on it? And does it break with green stripe dyno cam springs?

Yes it has a compression release on it.
I don't use green stripe springs so i'm the wrong guy to ask that question.
I'm guessing they will work for a while but i can't say how long.
There are things you can do to adjust the installed height and therefore, the spring pressure.
Someone from Dyno cams would be the best person to ask.
The 206 engine with the stock springs has somewhere around 20 pound of seat pressure.
The WF comes with a set of Briggs dual springs and i believe they are somewhat less than 30 pounds of seat pressure.

 

[Jimbo]

took another real good look at my intek head(only head I have in front of me) and assuming it is casted the same as a animal head in that area.
there is a area on the side of the head i could mill flat and tap into for threads and drill a hole that would lead right into the chamber and it doesn't have to be right where my green line is. just a reference point.

i'm sure if you had to run the tin work you could easily punch a hole in the tin for the compression button.

That's the last place i would drill a hole in an Animal, LO 206 or Intek head.
If anything i wish it had more material there and was stronger in that area.

 

[delray]

That's the last place i would drill a hole in an Animal, LO 206 or Intek head.
If anything i wish it had more material there and was stronger in that area.

why would you say that jimbo. looks to be very solid and thick in that area(all aluminum) and from the looks of some of the aftermarket compression release units they look to be very small in thread size. for example lot smaller then a spark plug.

 

[delray]

here is a Husqvarna Decompression for a chainsaw and looks to be less then .400 in diameter and in length. that's a small hole and I just don't see how that can distort the structure of the front head. also have picture a plug with the decompression built into it. don't know if they make the right plug for a briggs or even if they are any good use?

 

[delray]

one other design to look at.

 

[CarlsonMotorsports]

here is a Husqvarna Decompression for a chainsaw and looks to be less then .400 in diameter and in length. that's a small hole and I just don't see how that can distort the structure of the front head. also have picture a plug with the decompression built into it. don't know if they make the right plug for a briggs or even if they are any good use?

I've used the style on the right with the JR billet heads. I would think you would be fine tapping the front of the 206 head, honestly I've not tried it as most builds of this type use a remote electric starter and are not concerned with a compression release.
Jimbo's concern (I think) is that between the top/front two bolts on the animal/206 head is typically where the head gasket fails due to the cylinder head pulling down closest to the exhaust port.

FWIW, I like the Dyno green stripe springs with our .310" lift cam and 1.3:1 ratio roller rockers.
Compression releases won't live with the green stripe springs, but I'd also be concerned with the extra rpm that you'll likely be turning with a 310 cam as well.
If you absolutely insist on pull starting and a compression release, I'd suggest staying smaller on the cam (255 outlaw or WKA stock) and the stock Briggs springs, (better yet Dyno AN-2 springs) will handle 8000 rpm all day long.

-----
Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com

 

[Jimbo]

I guess i probably sound pretty negative about some of this. I apologize for that but there are a few things i have learned that i will pass along to you and then hopefully you can make a more educated decision.

The hottest part of the head is where the exhaust port is. Aluminum melts at 1270* F
It gets softer the higher you heat it. The softer it gets the more easily it bends.
The higher the head temp gets under the head bolt by the exhaust port the more it compresses and you loose head bolt torque.
That's why the heads have come with the heat disperser for several years.
If you machine .100" off the head gasket surface to build more compression it make the head considerably weaker.
More compression puts more stress on the head gasket and repeated stress on the head bolts and threads.
Using gas for fuel will substantially raise the head temp.
The reason i make a domed piston is so you don't have to weaken the head to make more compression.
The most common place for the head to blow a head gasket is between the top 2 head bolt holes.
Bore the engine to X.XXX" requires better head gasket integrity.
Even ignition timing plays a role in this.
Drilling a hole through the head where we need the most strength is probably not the best idea.
It will work for a while depending on all of this and more.
You have to determine what you are ok with.

I will tell you that i don't use a compression release valve in the head.

I will also tell you that big steel valves are heavier than stock steel valves and higher rocker ratios with big cams increase valve opening rates tremendously. It takes a pretty stout spring to control that acceleration rate. In my opinion 30# of valve spring pressure will let you down at high rpms.
Search the net for a high speed video of valves out of control from using the wrong valve springs.
Ti valves are 1/2 the weight and twice the strength of the same size steel valve.

You can probably do what you want to do by making compromises but in racing the people with the best stuff make fewer of those compromises.

I could write a doctoral paper on this but i hope you get the point with out me doing that.

Best of luck
Jim

 

[delray]

another problem you can get with running a release mechanism on a cam is when you let it idle real low. that can trigger compression release and could cause havoc on those parts too.
thanks again jimbo and others guys on your input with this type of engine we are talking. there just wealth of good info about this to find on this web site and guys. two weeks ago I had no clue about in's and out's of this type of engine and the only thing that I new about them was in the pass when I would beat them with my Tecumseh engine. wasn't that they where pooch engine or down on power. guys just didn't know how to setup there drag bikes correct. at the end of the day i'm still very interested in this stroker engine and potential power this small block can put out.

 

[One Fast Kat]

After reading all of this I think I have come up with a simple solution. I bought an engine from someone that Jimbo had converted from a used 206 to a stroker animal.
I had the opportunity to buy a 310 cam with compression release real cheap. That is why I asked. Just a simple question. Got complicated real quickly. As often happens on here.
I think Jimbo made it very plain that it will not last. I build mostly flatheads, Limited Flatheads and open flatheads. Their stock cams have a compression release that is built into the cam lobe as a ridge on the exhaust lobe. Not a mechanical device like the clone or the animal compression release. Just installed a 308 dyno cam without compression release. End of story!

 

[flattop1]

Question , why can't the little bump be added to the cam .
I know that its claimed to be a power loss . How much would you actually lose ?
Even if it cause valve and seat wear, how long is a modified really staying assembled . Part of a year , maybe a short season .

 

[Jimbo]

One more thing.
I use a die grinder and put a very small radius on the leading edge of the compression release so that when it hit's the lifter it's easier on things.