GlockLT4

I'm going to be porting my LT1 heads on thurs and friday. I have spent a LOT of time trying to find LT1 specific porting techniques, but I've come up empty handed. Anyone have any tips or sites that describe the technique on an LT1 well?

I have pictures of the cross section LT4 and LT1 heads and I see that I can open up the intake runner of the head a bit to try and match the LT4, that's about it.


[Modified by Glock'94, 4:09 PM 12/18/2001]

Chris@SD

Actually, that is exactly what you do not want to do. The intake runner should hardly be opened up AT ALL! The smaller, the better.
The basic design of the head is very good! Do not try and change anything, just expand on what is already there.
Good Luck,

GlockLT4

ttt

lcvette

Glock,
Chris is right, they are good casting designs from GM... A minor port matching and removal of casting flash from the port walls to have a smooth surface with no obstructions will benefit and be all you'll want to go your first time in. The bowl work is critical for making power on these heads and is where you should focus the long tedious work.. long and tedious not meaning big metal removal.. but smooth contoured work!!! concentrate on the smooth none "flat spot" finish always keep the tool moving. I can tell you now that if you have set only 2 days aside to port those heads you'll find yourself about 1/4 of the way done. There is a reason head porters charge a lot to do heads.. And you'll be able to testify to this by mid next week is my guess. I am sending you an email as i am just passed where you were in school so i will share a secret or two with you to help your cause... good luck and email is on the way!!

Chris :smash:


[Modified by lcvette, 8:15 AM 12/18/2001]

Nathan Plemons

Best thing you can do with a set of LT1 heads it just smooth them up. Don't make anything bigger.

The Blue Demon (friend's camaro with the 396) has heads from Total Engine Airflow here in BG. They are his stock castings that have been cleaned up on a CNC machine. Really it didn't make anything any bigger, but man are they SMOOTH. He's also got some huge valves, something like the biggest valves you can put in an LT1 head. They are awesome, I want a set but I can't quite find a way to cough up some $1000 for the work.




[Modified by Nathan Plemons, 8:24 AM 12/18/2001]

AquaMetallic94LT1

He actually means the area after the intake runner. I sent him the cross sections of the stock LT1 port and the LT4. I suggested that he should try to match the shape of the LT4 port from the point where it necks down between the valve guide and the short radius to the valve seat leaving the actual intake area alone.

GM deliberately enlarged the runner from the intake port entry to the short radius. Why did they do that if it kills low speed torque ?

GlockLT4

Yes, sorry I did not mean the actual intake... i meant the intake tubes OF the heads.

SPD DMN

Curtis, it took me almost 2 weeks to port my own heads (long since gone). Even going nonstop, expect it to take 2-3 days.

GlockLT4

hmm.... i'm thinking i'm just going to smooth out the blemishes and stuff probably... that shouldn't take too long.


[Modified by Glock'94, 4:10 PM 12/18/2001]

lcvette

That would be a NO NO..... on the LT4 heads the port floor is already too low from the factory.. that short turn is as small as i would want it to be! a gentle smoothing of it is the most i would attempt without a flow bench and a few scrap heads to try some new shaping and find a better configuration.. if he ground down the short side radius the air charge would not have enough radius to successfully make the turn and effectively make use of almost 1/3rd of the valve circumference opening under the short side. the air would miss the turn and bottle the air charge being directed down from the port/bowl roof.. not a good thing.. as the piston gets closer to BDC and the valve event has begun its second half (closing) the piston is not moving as fast.. this means that the rate of space becoming available for the new charge is slowed down.... this means that your velocity of the charge is what you rely on to continue a flow into the chamber.. kill the port design and velocity and as the growing cylinder volume is slowed by decreased piston travel the air will slow and become stagnant while there is still some duration and lift left.. this is wasted time for a charge to enter the chamber.
Now why do they make such big heads then..? well for high revving engines and bigger cubes. The faster you turn the more inertia the incoming air charge is going to posses and the bigger port acts as the smaller port did because now it is supporting a larger mass of airflow and the RPM that the engine is turning requires a high CFM of air to sustain the ability to make power. larger runners feed these engines air and don't choke it. this is why slapping 210cc AFR on a relatively stock 350 will lose more then gain results...unless your planning on turning in the neighborhood of 9000-10,000 revs.. Then they will work well in conjunction with the appropriate cam.. there is way more then shaving metal out of the way in this filed and everyday I read something new that captures my interest on the subject...... Its an ever learning art and a fun one at that.. And a critical point for making power... read all you can on it and absorb what you can from others.. !! that's what should be done before you start the work. With knowledge will come a much better understanding of the reasons you make each cut or remove what in head porting!! that alone makes the job a lot easier!

Chris

GlockLT4

this is why i'm thinking of not even doing it now (save it for later and pay someone to do it). aparently there is a lot more that i could do wrong than good, and i'd rather just leave it as it for now and worry about it when i've got the money to do so.

damn this is frustrating.... :crazy:

Chris@SD

There is a reason why we get paid what we do to port heads. :)

MDL-01C5

You're right my friend... It's amazingly easy to ruin a good set of heads if you don't know exactly what you're doing. I agree with Chris-- if you are going to try this yourself, then you MUST take the time to learn and understand what the airflow dynamics are within the ports, how they work, and why. Then you'll know how everything you do will affect those things, and come out with an improved set of heads:) :cheers:

GlockLT4

Very understandable.

h rocks

Glock, you can improve the airflow of the stock heads yourself. Now the question is, can you *maximize* the airflow for your intake, cam, throttle body etc. That answer is *no*. Were you planning on having the guides done and a 3-5 angle valve job done also? Flowed? If you have a friendly machine shop that will allow you to do the "donkey" work on the heads, then do the parts that take real expertise, you probably can save yourself a few hundred bucks. With the condition of your engine, I would be suspect just removing the gunk, porting them and slapping them on your new stroker bottom end. I wouldn't do that even with good heads that had low miles on them. You are going to end up spending a ton by the time you're finished, you might as well consider spending $1,000 bucks on a good head port and re-build. It's really crucial to maximizing the potential of your rebuild.
BTW, you may want to check out the Standard Abrasives website. Great tutorial on DIY head porting. They will tell you that anything beyond mere "clean up" is best left to the professionals.

R23HTC

I'm sure he would if he had the funds. Remember he's trying to do this on a budget and at LEAST get the bottom end done.

GlockLT4

Yes, I don't know why most of you guys can't understand that I'm in college, I had to replace the bottom end anyway, so I spent a few more bucks (actually probably less because of the parts deal i got) and got the 383 crank and better pistons. I don't have $1000 laying around to throw into my heads. The only way I can afford any head work right now is if i do it myself. I appreciate all the suggestions everyone has given me about doing the job myself. Since everyone was flaming and roasting me for not doing my heads, I felt it a duty to try and do them myself... SCREW it ... I'm not doing anything with them.. i've had it... sorry to get mad but this is really frustrating me. I will deal with the heads later when I have the money. end of story. If you want to pay for my heads to be done, go RIGHT ahead. Put yourself in my situation before you start tell me to go take a loan out for head work that I don't have to have done. My goal with my car is not a bazzillion horse power and I don't race it at the track, just street drive it. Please get that across in your heads.

jeez.. i feel like i just spun a bearing in my head... :crazy:


[Modified by Glock'94, 6:01 PM 12/18/2001]

mackeyred96

I would leave this to a PRO. If you don't know what your doing you can screw up a good set of heads fast.

ghall

If you could see the head porting job little Chris(lcvette) did on his dads head and the port job he is doing right now on mdl-01c5(matt's)--you would understand his point--he really knows what he is doing and doesn't mind taking the time to explain the concept to --us more challenged .I got a chance to see one of Matt's finished ls-1 heads tonight--all i can say is :cool: :cheers: :smash: :eek: --he's not just a redneck with a die grinder.

Geoff Hall

GlockLT4

yes, lcvette had some great tips! I'd love to see a set of heads he has ported.