Head advice

T_Dub wrote:

Yep, I'm sort of leaning that way now. Maybe I'll get him to port her out, that way I know I'm not going to have issues. He's actually not as expensive as some I've seen, for a Stage I port its $750 and that includes a valve job and a head resurface.

See what he says, stage one or street cleanup. It will be the best money you can spend..............

yes i definately listen to what Larry has to say.i remember around a 100 years ago it seemed like anyway!:laugh: i was building my 1st bigblock chevy for my 67 el camino had a laundry list of what i wanted in my motor and was too smart to listen to anybody so the wiser guys decided to let me learn the hardway and off to the machine shop i went.boy did iget a fast education from the best engine builder i ever met and he still is as far as im concerned!anyway he proceeded to tell me i didnt need a 4 bolt main block,i didnt need big rods,i didnt need rectangular port heads and monster camshaft just because we ran a lot of that stuff in the bigblocks he built for our boats didnt mean it would work in my el camino and i came to find out he was absolutely right!so listen to some of these older guys we have made all the mistakes in the past alredy!:laugh:

PLUMMEN wrote:

yes i definately listen to what Larry has to say.i remember around a 100 years ago it seemed like anyway!:laugh: i was building my 1st bigblock chevy for my 67 el camino had a laundry list of what i wanted in my motor and was too smart to listen to anybody so the wiser guys decided to let me learn the hardway and off to the machine shop i went.boy did iget a fast education from the best engine builder i ever met and he still is as far as im concerned!anyway he proceeded to tell me i didnt need a 4 bolt main block,i didnt need big rods,i didnt need rectangular port heads and monster camshaft just because we ran a lot of that stuff in the bigblocks he built for our boats didnt mean it would work in my el camino and i came to find out he was absolutely right!so listen to some of these older guys we have made all the mistakes in the past alredy!:laugh:

amen to that....and have the scars to prove it.

Well, Larry told me my 650 head will flow just fine, but that I should get rid of my BS34's and get a set of 29mm carbs. So I'm cuurently saving for a set of 29mm Keihin CR's. They're only $650, anyone wanna buy a set of 14 year old BS34s?

T_Dub wrote:

Well, Larry told me my 650 head will flow just fine, but that I should get rid of my BS34's and get a set of 29mm carbs. So I'm cuurently saving for a set of 29mm Keihin CR's. They're only $650, anyone wanna buy a set of 14 year old BS34s?

Well, listen to the guy that has the tools and equiptment to prove what he says. The GPZ head is an easy swap, but may not be best for your performance needs. It's easier to pay now then to keep rebuilding your motor, looking for more power. Tyler I know you are listening, I hope this may benifit others as well. If one of Larry's heads don't work for you, I will find a way to bolt it on my 900, and fly like the wind.......................John

kzz1p wrote:

I just saw pictures of a 650 head, that LarryC just finished. It is for a 700cc kit and will use 31mm carbs. It had D port intakes for mid range flow. This head flowed 120 cfm, thats more then a stock GPZ1100 head. Heres a picture, it has stock valves. Most guys wouldn't need that much flow, this bike will also be used at the track. Save your pennies and have Larry do you a street clean up. If Larry only gives you 80 or 90 cfm, thats equal to a stock GPZ1100 head. If you can ride, a head like that would be the real deal.

To clarify this a bit. The CFM reading is at 28" of test pressure. To convert to 10", multiply by .598. To go from 10 to 28 multiply by 1.67.

120 * .598 = 71.6 CFM [Stock was 58CFM at 10"]
A stock GPz [83] is 82CFM @10" > 136.9 @28"
A stock Kz 1000 is 68 CFM @10" > 115.2 @28"
A stock J 1000 /1100 is 74@10" > 123.5 @28"

I test at 28" for several reasons.

1 - what happens at 10" can change at 28". You might not see turbulence at 10" but it can show up at 28". You hear it when it happens. The port gets real noisey.

2 - I prefer to probe the port for velocity at 28".

3 - My formulas for required CFM and CSA are tied to 28".

Local velocities on this head are NOT what I would use for all out drag racing. They are specific for the intended use of this particular motor with 5mm larger than stock carburetors.

The floors are filled in. They are not "jammed full of epoxy". The ports were all cc'd for volume. Measured for centerline and Average CSA calculated and set to the intended peak HP RPM for the engine.

Formulas for all that are feely available on my website if you would like them. With a good small increment tape measure and a 100cc burette, you can establish your current values for average CSA.


Larry C

aint he cool ? :laugh:

He really is.