head porting

i'm just starting porting one of my extra gpz heads for one of my 1393 blocks i'm going after some big flow numbers on this one i'm using .507 lift cams and i'm planning on a big load of nitrous going thru this motor i'm aiming for low 8's possibly 7's on a 7 inch tire. i think i can do it to morrow i driving the guides out and going crazy on the head. i'm putting in shorty guides[another fine product from ape] i already have my nitrous ports set up and ready to go so that is figured out next i have to get some good epoxy so i can start raising the floors up i don't have over size seats so all i can do is go to oversize valves but it will work the intakes are going to be matched up to a set of 40 mm lectrons. as soon as that head is done then i start on another head for my little bike, one that will work on a 1197 block so that little 5.5 tire will be working hard. larry help me out what kind of epoxie are you using i used to use devcon but i'm having a hard time finding it.

i knew a guy here in omaha years ago whos name has been declared mud in my book,anyway he used to think he was a head porting guru .his answer to screwing up ports was to fill em full of devcon i converted a few heads to doorstops in my early attempts to port heads but could never bring my self to epoxy them up like he did so they became doorstops.ive still got the last couple heads i did that turned out reasonably decent but i told myself id never do another other full blown porting job myself,its too cheap for me to have somebody like Larry do it the right way! :laugh:

yes your exactly right mr.plummen dood if i didn't know what iwas doing and didnt have accsess to flow benches and accsess to an engine dyno and two 250i chassis dyno's id never attempt it but since i do i'm going freakin crazy i work in the worlds best place to be a motorcycle mechanic with the summers off it's incredable i feel like a little kid at disney land sometimes buddy it's awesome. i have ported quite a few heads for some the local smaller engine guys and more than a few for my self but i've never done a real go fast head so now's the perfect time to do it.and your right you can mess up real bad if your not carefull as for larry i have heard nothing but good things about his work and if i wasn't working where i am i would have absolutly no problem giving him my stuff to do the man is a pro and highly respected all over not just here. infact one day maybei'll get him to do one up for me as well just to see how i stack up it would be worth it.

timebomb33 wrote:

i'm just starting porting one of my extra gpz heads for one of my 1393 blocks i'm going after some big flow numbers on this one i'm using .507 lift cams and i'm planning on a big load of nitrous going thru this motor i'm aiming for low 8's possibly 7's on a 7 inch tire. i think i can do it to morrow i driving the guides out and going crazy on the head. i'm putting in shorty guides[another fine product from ape] i already have my nitrous ports set up and ready to go so that is figured out next i have to get some good epoxy so i can start raising the floors up i don't have over size seats so all i can do is go to oversize valves but it will work the intakes are going to be matched up to a set of 40 mm lectrons. as soon as that head is done then i start on another head for my little bike, one that will work on a 1197 block so that little 5.5 tire will be working hard. larry help me out what kind of epoxie are you using i used to use devcon but i'm having a hard time finding it.

If you're going to fill the ports, Joe Mondello has what you're after. 1-800-MONDELLO (666-3355)Spalsh Zone Pro Epoxy Kit

Get some Kay Rolls while you're on the phone with them. They're great to have around the shop for more than just porting.

IMO, you're ahead of the game if you have a J head to start with. Port volume / runner CSA is more appropriate for what you're building with a whole lot less grinding.

Larry C

timebomb33 wrote:

yes your exactly right mr.plummen dood if i didn't know what iwas doing and didnt have accsess to flow benches and accsess to an engine dyno and two 250i chassis dyno's id never attempt it but since i do i'm going freakin crazy i work in the worlds best place to be a motorcycle mechanic with the summers off it's incredable i feel like a little kid at disney land sometimes buddy it's awesome. i have ported quite a few heads for some the local smaller engine guys and more than a few for my self but i've never done a real go fast head so now's the perfect time to do it.and your right you can mess up real bad if your not carefull as for larry i have heard nothing but good things about his work and if i wasn't working where i am i would have absolutly no problem giving him my stuff to do the man is a pro and highly respected all over not just here. infact one day maybei'll get him to do one up for me as well just to see how i stack up it would be worth it.

you and larry are da man,or da men! :woohoo: :laugh:

some of the best time and money i ever spent was going to joe mondello's head porting technical school.me and my brother we're in the first class.i still have my phd(porting head doctor)certificate.that man is a wealth of knowledge.

leon holmes

just so people understand.flow benches and dyno's are measuring devices.they don't tell you what the secrets are,they do confirm when you have found or learned them tho :laugh: .
keep us posted timebomb,there seems to be lots of interest in portwork.

leon holmes

larrycavan wrote:

IMO, you're ahead of the game if you have a J head to start with. Port volume / runner CSA is more appropriate for what you're building with a whole lot less grinding.

Larry C

X2

it's not the grinding i'm worried about it's the filling back in when i've gone to far!

timebomb33 wrote:

it's not the grinding i'm worried about it's the filling back in when i've gone to far!

Lot's of material in those heads.

Probe it while it's on the bench at .400" lift @ 28" with the carbs mounted on the head. Need a good J bend pitot? Holler and I'll put you in touch with a guy. He's made several for me. He's a disabled veteran, super nice guy and all the extra work he gets really helps him out.

Larry C

you know that comment about going to far well i just punched thru the intake port on number two cylinder the old die grinder kind of got away but no big deal epoxy to the rescue that the kind of thing that happens when your trying to build a head setup for 40mm lectrons. if i don't go faster because i'm making more power at least i know the engine will be alot lighter it sure doesn't take long at 15,000 rpm for a die grinder bit to make a big pile of chip's so far every thing is going well and i have some heavy duty epoxie on order it should be here in a couple of days then the flow bench fun begins.

whats the thinking behind rasing the port floor? is it to decrease the angle of the port bend as it turns to the vale seat?
do you steer the airflow to one side of the port to create swirl into the chamber or just go for the best flow into the seat area.
i know what works on the vw aircooled heads i work on but the small high rpm bike heads are a new learning curve.
theres a lot of differance to getting a head to flow for 500cc per cylinder at 6500rpm than a 165cc cylinder at 10000rpm.