Cylinder Head guru's please!!!

[nostrixoxide]

Hey guy's,

I got my 6.5 clone motor all short blocked. I'm just waiting to decide what I wanna do with the cylinder head. I have a couple questions some of you may be able to help me with.

1st) What is a safe amount to deck the head when using the AGK flat top piston / aluminum rod combo along with a stock thickness head gasket & still be able to run 91 octane???

2nd) I ordered the stainless valves, retainers & keepers for this thing. But AGK is recommending the use of 26lb springs with the stainless valves. I already have brand new 18lb springs will this be ok??? Why would they require using 26lb springs just because the valve is constructed out of stainless??? Shouldn't spring rates be determined based on the demand of the engine? I can only assume that if they say the stainless valves are "lighter" & stronger then a stock valve, then the lower rate spring should actually be able to control the "lighter valve" that much better??? The only reason I can come up with is they want more spring tension to apply more pressure on the keepers so not to drop a valve by having a keeper come loose or something???

And finally,

I plan on porting the cylinder head, but I would like to see any pictures that might be floating out there before I start playing with the head. I see alot of area for improvement, but at the same time I don't want to smooth something that might be a critical shape for a specific reason. So if anyone has some DIY porting pic's that would b a huge help before I just start cutting away.

Thanks,
Nos

 

[minidragbike]

You don't want to just start porting anywhere. There are certain area as you may already know. But even when you know the areas it still has to be done right. I have pictures, but no pictures are gonna show you every point in the head, and everyone ports a little different. I mostly port for HIGH RPM. Mainly because more RPM is more speed.

Now milling the head, or what you call decking the head is done to create more compression. More compression is needed to make more torque. Making more torque is sometimes better than making horsepower. Or that is what most people want when they describe what they want to feel when they ride. Now being limited to 91 octane isn't gonna allow you to do much. If you are running a stock chamber head you can mill a good amount of material before you run into problems. The only thing that limits this is octane your gonna run, and valve lift you are gonna run. I would take .100" off if it's a stock chamber head.

The valve springs are another story and are very important if you are planning on reaching higher RPM. The 26 lb springs are pretty much the limit with a stock cam. Basically any stronger and it will flatten the lobes. Now there are other things you have to look at. heavier valves, heavier locks, and retainers. This all also plays into the big picture. The stiffer spring will compensate for the extra weight, and close the valve faster once the motor begin to turn higher RPM and the weaker 18 lb springs can't close the valve fast enough. That's when you run into a thing called valve float. Some have even ran the 1.2 ratio rockers with the #26 lb springs with success.

To save yourself a lot of time just go by what the person with experience is telling you. This person has already tried this with great results. You are still trying to get there and trying short cuts can sometimes be fatal to your project.

 

[nostrixoxide]

You don't want to just start porting anywhere. There are certain area as you may already know. But even when you know the areas it still has to be done right. I have pictures, but no pictures are gonna show you every point in the head, and everyone ports a little different. I mostly port for HIGH RPM. Mainly because more RPM is more speed.

Now milling the head, or what you call decking the head is done to create more compression. More compression is needed to make more torque. Making more torque is sometimes better than making horsepower. Or that is what most people want when they describe what they want to feel when they ride. Now being limited to 91 octane isn't gonna allow you to do much. If you are running a stock chamber head you can mill a good amount of material before you run into problems. The only thing that limits this is octane your gonna run, and valve lift you are gonna run. I would take .100" off if it's a stock chamber head.

The valve springs are another story and are very important if you are planning on reaching higher RPM. The 26 lb springs are pretty much the limit with a stock cam. Basically any stronger and it will flatten the lobes. Now there are other things you have to look at. heavier valves, heavier locks, and retainers. This all also plays into the big picture. The stiffer spring will compensate for the extra weight, and close the valve faster once the motor begin to turn higher RPM and the weaker 18 lb springs can't close the valve fast enough. That's when you run into a thing called valve float. Some have even ran the 1.2 ratio rockers with the #26 lb springs with success.

To save yourself a lot of time just go by what the person with experience is telling you. This person has already tried this with great results. You are still trying to get there and trying short cuts can sometimes be fatal to your project.

Thanks MDB,

I already ported & decked my cylinder head. I didn't go to radical with the port job just got rid of all the rough edges & blended the area around the valve guide to have alittle less drastic of a step & tappered the area just above the valve seat. I didn't really increase chamber volume, but I did port match the manifolds to the cylinder head. And I had the head milled 65 thousanths. The chart I had said that would be good for somewhere between 11.5:1 - 12:1???

After I worked the cylinder head, I just kinda said F the whole pump gas deal. I figured worst case senerio I could always just carry a little bottle of some octane booster with me incase I ever need to fill up at a gas station on a long ride. Or some moth balls :^)

Oh MDB one last question. What do you suggest I use for a clutch on this thing? I figure it should be in the 13-15hp range. Should I just go ahead and use a multi disc style clutch? And what do you think of those SMC Vortex clutches?

 

[Stang]

Your ignition timing is also gonna have a lot to do with what gas you need to run along with the compression.

 

[minidragbike]

Well if you tossed the whole pump gas limitation of building you can make more power.
You still haven't told me if you have a stock 22cc, 18cc, or 14cc head to start with?

The ignition timing is another thing to play with too. For higher RPM you will want more ignition timing. But doing this will make your motor slightly harder to start up. Like Stang said playing with it will alter the fuel you need to run just like the compression. The more compression and timing, the more Octane you will need to have.

I prefer a multi disc clutch for best performance. But it also depends on what your using you motor for, and distance your gonna be running. The Tomar is one of the best clutches to get. Mainly because you can always find someone seller the parts at a deal compared to almost every other clutch except the Horstman Grease Lighting. The Tomar Stellar clutch is basically the same clutch as the Horstman GL, but it's just built tougher.

 

[Stang]

If you gonna go through the bother of building a high performance engine which costs $$$, you're really going to want to run at least racing fuel. I run 110 octane in my 390. If alcohol was more widely available around my area I would have probably used that instead, like alot of MDB's bikes.

 

[nostrixoxide]

Thanks for getting back to me about this guy's I really do appreciate all the info & advice. Sorry I didn't state more info about my build. First of all the bike is gonna be used for some pretty good power rides. Were talking probably some 20 mile rides with some chill out moments in between. Basically from one side of town to the other? To put that into perspective for you MDB that would be like going from Strawberry Square in the CPT to Mansville and back like 10x's or so???

Here is my build list: all starting with a stock Harbor Frieght GX200 clone!!!

Stock 22cc head Milled 65 thousanths / Ported & polished. Left the intake side alittle rough but the exhaust side looks like a mirror inside the chamber.

1.2 ratio rockers
18lb springs
Stainless Valves, Retainers & keepers
Moly Push Rods

Block: Govenor & oil sensor were removed. Block is stock deck Height...
Stock camshaft
AGK Billet rod w/ bearing. Clearences were massaged alittle to promote smoother rotation
Flat top piston w/ file to fit ring set. I went alittle wider on the ring gap incase I decide to squeeze this turd :^)
All grade 8 bolts & studs were utilized in the build.
Stock head gasket also

22mm Mikuni carb (still needs to be jetted properly)
AGK manifold with pulse fitting (figured that would be were my N20 nozzle would go)
Manifold has also been port matched to the cylinder head
AGK 2 stage header (also port matched to the cylinder head)
Uni air filter
Basically all the standard after market items, I just took the time to make sure all the tolerences were more to my liking. I've built several full scale engines before so I have a higher then average mechanical knowledge & ability.

I am also using not the AGK billet flywheel, but the lighter aluminum flywheel with a stock timing key. I believe the flywheel I have advances the timing around 4 degrees over the stock iron flywheel. I didn't want to go nutz on the timing strickly to keep her an easy starter. My pull start arm gets enough exercise already if you know what I'm saying???

I figure she should be good for somewhere in the 13-15hp range. I could run alcohol since we have a few places locally here that sell it, my only problem is it's not yet readily available at the pumps :^) This isn't going to be so much a race bike as it is a nice cruiser that can get out of it's own way if need be. I plan on puting this thing into one of those larger Baja Heat mini bikes. So I don't think it will be a wheelie monster or anything like that unless I got this thing engaging at peek torque. (hence the clutch questions)...

Maybe my next build will be a Mansville killer, but right now I just want something decent to putt around with my boys on. Once again thanks you guy's for all the input. Maybe I have overlooked a few things that you can fill me in on.

PS, one last thing I did was modify the stock guide plate & I shimmed the rocker studs to keep the geometry for the rockers the same. Quite a bit of material came off the head & I didn't want to have to go and machine some new push rods. So I thought this too be the best way to keep that stuff the devil invented (coil bind) from occuring...

Another idea I've been tossing around is using a smaller smog pump as a supercharger of sorts & I don't think it would be to hard to convert the Mikuni to a blow thru style to accomidate the fuel delivery. I rebuilt a few of those in my life time & they are pretty simple in design compared to a Holley HP double pumper. Alot less moving parts & seals. Only real issue would be the float, but I don't think it would generate enough pressure to crush it like a stock brass float in a holley???

 

[minidragbike]

I have seen the smog pump setup before, but for some reason it didn't make the power the guy wanted. It ran pretty much like a stock motor.

That's a nice combo, but I would reduce the compression more. The extra compression will make more heat internally. And running those kind of distances isn't good with that kind of heat.

 

[nostrixoxide]

I have seen the smog pump setup before, but for some reason it didn't make the power the guy wanted. It ran pretty much like a stock motor.

That's a nice combo, but I would reduce the compression more. The extra compression will make more heat internally. And running those kind of distances isn't good with that kind of heat.

So do you suggest I put the stock dished piston back in it or maybe have alittle milled off the top of the flat piston? Another idea might be to run it alittle on the rich side to combat the heat factor correct? More fuel should help cool the combustion chamber down slightly wouldn't you think? Or would I just be wiser to run a larger fuel tank & just go ahead and convert to alcohol? That should keep this puppy cool right?

So what do you think this combination should be worth power wise & where do you suggest I set the stall speed of the clutch at? I read once that you suggested gearing these OHV clones alittle on the long side because of the amount of torque they generate. Is this correct or did I misread that material?

Thanks again for your quick response & suggestions. Any carb jetting info would be greatly appreciated also. I know I will have to take some plug readings, but a base line would really help. I'm about 3K ft. above sea level.

 

[Stang]

You will need a large gas tank to run alcohol for long distance trips. Personally I think TAV's make for great riding bikes. If you plan on racking up the miles and riding it a lot, you may want to look into a torque converter. I wouldn't want to stall the engine too high, you dont want to to stay fully engaged when your just cruising, unless you plan on just blasting around @ 50mph then your good to go. I forgot what my brother has his set up at but maybe he'll get a response in here soon.

 

[nostrixoxide]

Thanks Stang, I'm just not sure if the TAV will be able to support the output of the motor. I guess I could always be a little easier on the throttle?

 

[65ShelbyClone]

So do you suggest I put the stock dished piston back in it or maybe have alittle milled off the top of the flat piston? Another idea might be to run it alittle on the rich side to combat the heat factor correct? More fuel should help cool the combustion chamber down slightly wouldn't you think? Or would I just be wiser to run a larger fuel tank & just go ahead and convert to alcohol? That should keep this puppy cool right?

More fuel can help reduce ping up to a point. After that it starts costing power and wasting fuel.

A stock .010" gasket with a 22cc head milled head and a flat top piston should get compression around 11.4:1. That is around the ragged edge for most 91 octane engines, but I would keep the compression where it is and manage any pinging with the ignition advance if necessary.

I don't know where you live, but if E85 is hard to get, then my advice would be to cut the pump gas with something like VP StreetBlaze 100 or whatever Sunoco has. Both are usually available at the pump and a gallon of 100 costs about the same as a little bottle of octane booster. The 100 will also raise your actane a lot more. Rockett Brands has a pump gas/100 unleaded blending chart that tells you the final octane after mixing in different proportions.

 

[Stang]

Thanks Stang, I'm just not sure if the TAV will be able to support the output of the motor. I guess I could always be a little easier on the throttle?

It should be fine, I think they are underrated, or you could step up to another model. I use a model 40 for my GX390 and I'm pretty sure its well over it's rated limit.

Also if you feel you need to lower the compression get a GX160 head gasket they are .045" thick instead of .010", that would lower it to about 9.9.

 

[minidragbike]

Copper head gasket, and stock dish piston

 

[nostrixoxide]

Shelby:

I live on Ave. N & 60th west in P-dale. I know that little gas station/Dairy next to White House on Division sales 100 street blaze. I can get good stuff from R&E too. I just wanna have the option of hitting any gas station if need be & it's alot easier to carry some booster or just buy some at the gas station then lugging around a gas can on my rides. Once I get this thing all together we should meet up sometime. My boy Lunch owns the carb shop over off of Trevor just south of Ave. I we usually putt around the back alleys & such over there.

Stang:
Isn't ur GX390 a 1" crankshaft? Don't those TAV's support a higher output then the one's designed for the 3/4" crank? I would love to put the TAV on my engine, so if your positive it will work just fine then thats what I will purchase.

MDB: Where can I locate these copper head gaskets? Or do I have to contact SCE here locally & have them make one special for me?

 

[65ShelbyClone]

A local huh? :thumbsup:

I know about that VP station/drive-through dairy too; I got some 100 there a few months ago when it was "only" $4.80. A month later it was $8.00. :thumbdown: I turned around and walked out of R&E when they wanted the same price for methanol.

I would say just give yourself some cushion and use a bigger fuel tank while running better gasoline. That, or use a thicker 160 head gasket like Stang said.

 

[Stang]

Shelby:
Stang:
Isn't ur GX390 a 1" crankshaft? Don't those TAV's support a higher output then the one's designed for the 3/4" crank? I would love to put the TAV on my engine, so if your positive it will work just fine then thats what I will purchase.

Yes, I run a model 40 but I've seen people with blockzillas run a TAV2 heh. I'm not saying that's the best choice for that use, but to me they seem to be underrated. I can't guarantee anything I'm just telling you what I've seen.

 

[minidragbike]

I have seen that before also, but I wouldn't recommend it.

I might be selling one of my racing GX200 heads soon.

 

[nostrixoxide]

Shelby:

Yeah R&E can be alittle pricey at times. But my boy Cuda runs the show over there & he takes care of me. I got another hook up over at Riders Choice also for fuel supply. And my boy Kelly's folks own the Napa Auto Parts over off of Sierra Hwy. He can order 55 gallon drums of whatever octane at cost. I just don't know if I want a huge barrel of explosives sitting anywhere around my water heater :weld: So where abouts are you located here in the wonderful AV?

Stang:

I think I've decided to just go ahead with the triple disc clutch like MDB suggested. I've been reading up on this company called SMC they make a clutch called the Vortec. It has a different design that allows you to use the same springs to play with RPM engagement. Pretty trick little piece & there doing something different then the standard. Another clutch I really like is the X5 make by Horstman. That clutch really looks like a killer piece also & it has less mass & moves the bulk of the weight in towards the actual crankshaft. I can see how that would be a benefit when considering unsprung weight. After reaserching the X5 alittle I've determined most of the other clutches on the market are kinda like have a full tube chassis 6 second race car but on 24's rims? More rotating mass to get moving...

MDB:

How much are you looking to get for your race head? My friend has a clone motor & he might be interested in purchasing it from you. Also, when do you guy's meet up down in the CPT? We would like to take the drive, meet some new people & see those screamers you guy's are running. Oh yeah, any word on that copper head gasket?

 

[minidragbike]

ARC carries the copper head gasket, it's thick about 0.045".
The head I have has the biggest valves you can fit for a stock bore setup. Fully ported, Polished, and milled. It's used so I will let it go for maybe $200 plus shipping.