lgaff

i am debating if i should go ahead and port my L98 heads at home. I have never done this before, but it seems from what i have read that it is not very difficult. Has anyoine ever tried this???? Any suggestions would be appreciated. I plan on just opening up the bowl, removing the valve stem support(in the bowl), and cleaning up the ports.

Lgaff
1990 coupe

95autoLT1

Go for it...If you F@#K them up more the reason to upgrade :cheers:

65Z01

Though you likely can't do as consistent a job as a good CNC shop it's a worthy project that will carry pride when done when done well.

You will need a manchine shop to do valve guides, new valves & valve job so maybe they can also check intake flow after your porting.

Get the Standard Abrasives video (Summit has it) and read David Emanuel's book on Small Block Chevy Performance. These have some good advice on building an excellent set of heads.

importeater

i second 65z01 in his oppinion the standard video is great, as long as you don't try to alter the shape you can do a wonderful job of smoothing the heads and increase flow yourself. same with the tpi manifolds, take your time, port slow..make sure it's bright and don't remove too much !!

XtremeVette

Importeater are you stock.....running what you sig says?...or have you done mods....are you auto or stick?


thanks jeff
1990 vette too

importeater

somewhat stock? i think..car has roller rockers, long tube headers, a true dual 2-1/2" exhaust with no cats. i spent about 10hrs porting the factory tpi plenum, runners and base..not much a guy can do with runners. 160 therm, hmm..what else..that's about it really, airfoil and foam air cleaner..did the pass with a 2.143 60ft time even, just wore out 300 compound street tires...i'm not sure if i have stock heads though as there are no egr ports like others i have seen. car is a 6spd with a 3:33 ring.

No Go

I wouldn't touch them. You won't know if you did any good or not-no flow bench.

Airflow is not something most can eyeball so would rather not put the work into it and have a 90% chance that you are ending up with a worse product

Now port matching would be fairly easy but many experts say there is little to be gained-but certainly not lost in this procedure.

Good Luck:)


[Modified by No Go, 2:58 PM 11/25/2001]

CORKVETTE1

if i was you i would not port my own heads esspecially with no expierence it could be worst than you think nothing to gain everything to lose unless you are willing to spend the $1000-$1500 to buy new heads if you mess these up

vettedreams

don't let anyone scare you away from porting them yourself . Just do some research andtake your time and the end result will impress & satisfy you . I was in your same shoes awhile back and i did it for the first time with noticable results, and now with theseL98 's i'm going to do the same thing, so good luck to you.

GRX

Have a pro do it. In the long run you will be better off. :smash:

Mez

You may want to contact a local auto machine shop to find out what they charge for a basic pocket porting and 3 angle valve job first. It may be less than you think. You can do some things, but there are some things best left people with the right equipment and skill.

Below is a link to photos of the before and after my porting work done a few weeks ago.
http://temp.corvetteforum.net/c4/tmezger/

I was like you and initially thought I could do it all myself. But quickly concluded I would be guessing where to remove material especially in the valve throat and combustion chamber area. Most people can do the gasket matching and port polishing but for many heads, the most gain comes from pocket porting consisting of opening up the port throat area just below the valve, short side radius smoothing, 3 angle valve job, and radius work in the combustion chamber around the valves. Simply making the ports bigger can cause a reduction in low RPM torque due to reduced port velocity.

You are probably facing a dilemma. CNC porting is very popular but relatively expensive. CNC LT4 heads costs $1800 to $2800 (plus shipping and insurance costs). Perhaps if the goal is to get that last horsepower possible, this is the way to go. In my case, I was not willing to pay $2000 for ported heads. So I visited a local head-porting specialist, Trevor Johnson in Rockwall, Texas and had him do a basic pocket porting and 3 angle valve job. As you will see, the ports did not get the sexy polish work. That’s because I did not want to pay for it. I am sure it would have been worth a few more HP but not at the additional cost. I did do my own intake manifold port gasket matching which was very straightforward.

I am extremely happy with the results. The intake ports picked up almost 20 CFM, which is a bunch. The total project cost was about $600 including new head bolts and gaskets. I gained 22 hp at the rear wheels while still using the OEM cam, ECM, air cleaner, and exhaust system.

john25

I ported and polished a set of heads using the kit from standard abrasives. The heads were iron 302 Ford. It it a time consuming tedious operation but if you have the time and patience go for it. The kit has an instruction packet that shows how to do the basics. I chose to have my aluminum L98 heads CNC ported. The porting job is also pretty messy and when you use either carbide bits or grinding stones on aluminum, it'll clog them up pretty quick. You have to keep them lubricated with WD-40 or something similar, so it gets even messier. Iron doesn't create this problem. That's one of the reasons I chose to have it done. Also the price wasn't bad. $400 for the CNC porting and hand finish, and another $40 for the thermal cleaning. That does not include the 3 angle valve job, but you can have that done at the shop of your choice. If you want to know where to get this done drop me an e-mail. Good luck.

Chris@SD

Mez is on the right track, but I do not hold the same views of CNC porting. I think hand porting is better in ALL cases for making power. You will NEVER see a race team use CNC porting on their heads. There is a reason for that. The teams that do use CNC porting use that process to rough the heads out (get them close to the desired shape) and them hand tune the heads to get the most power they can.
Every set of heads that we build go from the porting room to the flow bench MANY times! Every port is flowed MANY times. This is done to ensure that every set of heads and every port are up to standard and flow VERY CLOSE to the exact same volume of air. This is extremely important as you do not want some cylinders going lean and others rich. This is also the main reason it is dangerous to port your heads at home. You do not know if what you are doing is damaging the flow or increasing the flow.
JMHO,
Thanks,

Mez

Chris,
You and I have shared our views on this subject a couple of times. I share your views with regards to CNC porting vs hand porting. CNC is very precise to a point. I have been told by an experienced individual that he can port a set of heads faster and better without CNC. Perhaps I should have made myself clearer.

One more thing --- there is a difference in performance and price between various levels of porting. I.E. Stage I, II, and III. Generally, you get what you pay for but everyone has to decide the balance between cost and performance. If you want 450 rwhp, a basic pocket porting of stock heads is not going to get you the results necessary.

Chris@SD

I could not have said it better myself! :)
Sorry if I answer the same questions many times. I been on this board for almost 2 years. I have answered every question out there a few times, just for new people.
Again, what Mez said it 100% true. Not everyone wants to be the absolute fastest out there. Some are just looking for a little more kick and that is it. A good pocket port and gasket match will get you exactly that. We have been doing these with many satisfied customers, so yes, it does work. :)
Thank,

AquaMetallic94LT1

You should be able to pocket port (remove casting bumps etc) your heads yourself. Add a 3 angle valve job and some good flowing valves and you have whats called stage 1 porting. Summit racing sells a video on the pocket porting thats pretty good. Spreed pro puts out a book on heads and porting that you can get from Amazon or Barnes and Noble that is very good also.

Stage 2 and beyond porting should be done by an expert unless you are really interested in getting into porting heads as hobby. If you decide to attempt stage 2 porting , try to get access to a flow bench to check your work. Don't sweat the cylinder head cost. There are lots of used L98 heads around. You have 4 sets of ports to experiment with per test head. Once you get the porting down, do it on the real set of heads. Then have a machine shop do the rest of the work on the heads. The L98 head is pretty common so there maybe a book or magazine article that details how to do stage 2 porting also. There is a book on porting heads where the author shows you how to cast a copy of the port out of plaster so you can experiment without damaging the head as well.

Look into just buying a better set of heads too. Its usually cheaper than getting the heads ported and refurbished. AFR has a new head that has a 180 cc intake port that is supposed to flow close to their 190 head that would be perfect for a 350.

Good Luck. :)