HP Rebuild of heads

blksc

Registered User
To those of you who have rebuilt your heads for HP use id like to ask :

What type of valves did you use ? including stem diamter and who makes the valves ?

Roller rockers ?

did anyone go with the customer length pushrods ?


ps.. why do people who rebuild the sc heads have to 'weld' the exhaust port to further improve flow ?
 
hp rebuild for heads

When I had my heads done I got a lot of info from Tom Morana at Morana racing in Canada. He is a great guy and willing to share information. If I remember right 305 chevy valves fit. depending on what cam you have 1.80 roller rockers are a good upgrade, I got mine from Tom. Iused 4.3 chevy pushrods with special guide plates supplied By Tom. I have never of welding exhaust ports. I was told by Coy miller not to go to far on porting the exhaust ports. My intakes are gasket matched to the intake. I also portedout the intake in the back where the blower manifold goes into the intake. Last time I talked to Tom he was doing 2inch valves. If I were you I would give him a call.:D
 
I cant give you the numbers for stock sc valves size,but i will explain some things involved.
If you install a high lift cam.as (a example) .575 lift or higher you will need to use longer stemed valves.
so when the cam lob lift pushes the valve open, the spring pack around the valves will not coil bind.You
need to keep .050 + space between the coils of the spring. To fix, you machine the head directly under the
spring to lower the spring pack,and,or you install valve spring collor ,that has a deeper dish in the center.this will raise
the top of the spring pack to give the coils more space.so they do not coil bind.More rocker arm raito will add to
the coils binding.To find out if you will have coil bind you put a dial indicator afix to the top of the head with the dial indicator plunger on top of the valve stem.Then push down on the valve,at the same time watching the dial indicator
until you reach .575+.050=.625 .If no binding that part of spring pack set up is done.then you take it back apart and
measure for spring pressures you want.to due this you need a small type arbor press with dial indicator,Press the spring down .625 .the press will have a gauge to measure the wt. of the pressure that you apply this will measure spring pack pressure.When buying your valves you can get them with the same dia as stock from tip to valve head,or buy taper valves ,from the valve tip, to where stem just exit the valve guide,inside the port, it can be a smaller dia.for more flow.

ROLLER ROCKERS, If you purchase rocker with a higher rocker arm ratio ,this will push your valves open farther.If you
want more valve lift,and if you do not want to go to the trouble of installing a cam .

If you do the above you may have to change pushrod Legnth.You can find what lg.you need with a adjustable pushrod.

WHY WELD PORTS, EXHAUST OR INTAKE.Head ports drawn up on paper may look great.But buy the time the factory casts thousons of them the dies become worn and miss line,with inperfections,from air to ect.
When a head porter gets your heads to port .He will inspect them, and fine were the valve seat has been press in on the intake. There can be a large void in the port that meets the valve seat.If you look inside of the port (intake side) you can
see the bottom edge of the valve seat sticking out.The porter will remove the valveseat, and fill the void with weld,press the vavleseat back in ,and make a cut so the inside dia.of the vavleseat matches the inside dia.of the port .So the air can
pass from the port into the combustion chamber,with out hitting the back of the valveseat.Porters do build up welds,so
they can cut or grind back down to change shapes,fill voids ,raise the floor or top of port,or to taper port to raise air speeds.
 
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Lots of info!

Thanks guys thats a lot of info.

say tim: for my cam im gonna be right around 530 for lift. I guess i'll just have to wait til i get my heads to decide on what im actually going to do with them. I've seen some pictures of the intake and exhuast ports on our heads and they are awful so i feel like i have to do atleast mild port work to remove the casting bumps if nothing else.

As for the welding: Couldnt someone just blend the bowl area to remove the ridge from the seating area ?

Also how much software are aluminum heads ? I've ported iron before but im told aluminum is alot easier to cut so go at it with a lighter touch
 
If you can find a shop around you that has a serdi valve seat cutter.It will cut about
a 1/4in past the valveseat into the bowl part of the port ,and do the valve job at the same time giving you up to 7 angle
valve job .And the cut in the bowl will center the port to the valveseat and valve guide. this will give you a cut circle in the
port,then you just blend in the rest of the bowl and port to match serdi cut.
On aluminum heads you can blend with die grinder using sanding cones or round ones.For just blending aluminum
you dont need a carbide cutter if this it your first port blending.
 
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In addition to the welding Randy mentioned , there is welding being done on the exhaust ports to improve flow by changing the shape of the short radius.

In stock form it is very sharp and doesn't flow well suposedly because of turbulence. In order to smooth this radius out, aluminum is welded into the bottom portion of the port with a special tig welder (very small head) and the port is reshaped, resulting in a "D" shaped port with the flat part on the bottom. I recently had this done to mine for more exhaust flow, here is a picture.

exhaust%20ports%20110102.jpg


Stegimeier does this and also does some welding on the roof of the port for similar reasons. Here is a link to the Stegimeier heads that answer most of the questions.

http://www.apten-us.com/scheads/38heads.html

David
 
Thanks

These are sooo sweet ! Well i must admit im a lil discouraged. I bought my spair set of heads with the intent of building them for HI per use but just adding up the parts alone, it just seems to be alot more expensive than i thought.


ps.. any more great pictures of those heads ??? Also can i get a supstantial improvement in the heads without welding the bottom ?

If i removed the casting flashes, 5 angle valve job, polished exahust and combustion chambers and roller rockers.. any estimate on power increases ? Keep in mind i'll be running a dr fred 520 cam
 
Shops out there have 5 angle serdi type cuters they have them made,from 3 to 7 angle there is not much room for more
than the 7.I would go to the place David brought up or, Morana.These guys have many hours of R&D time in these
heads.but they cost.If you can go the serdi type cutter way,and gasket match every thing you will be very happy.and save a lot of money and improve the flow numbers.and get some good horse for street use. 300hp. plus with bolt ons.
And stick your chest out and say,DIY.A serdi type cut will be like following the dotted lines.
If you want 350 plus hp.And want to race alot .Get a pro for pro flow.Like DAVID N.
 
Hmm i'd like to get well over 400 to the rear, eventually. but right now im aiming for 300 at the wheels. I think what i'll do is do lite clean up on the ports, match port them to my intake and polish my combustion chambers.

And then with the heads i take off the car to bolt these on i'll go all out for my 400+ goal.

I figured that with doing the clean up myself i could do the heads with the 5 angle valve job, and stronger parts for about 800.

:rolleyes:
 
sweet!

Thanks. All this sc crap is new to me. I havent actually gotten my heads from the seller yet and its killing me. I cant wait to hot tank them and start working on the ports. I dont think picking up 70HP is too impossible.. or am i just dreaming ?

Between the UD pulleys, Double Intercooler(with nitrious cold plate) and bigger TB/MAF and raised top i should be at 300hp easy at the wheels.


BTW: In my humble opinion i would run a double IC with a Nitrous cold plate anyday over a damn front mount. Alot cheaper and packs on alot more power.
 
I don't think you will get 70 HP unless you do the heads with oversized valves and welded ports along with a very agressive cam and a dyno tune.

Ask Fred what gains to expect, I'm guessing 30-40 HP if your exhaust is flowing freely.

A double IC with nitrous cooling still won't equal a front mount IC. The front mount has much less pressure drop and flows about twice as much air.

A Coy Miller stage II with headers, 42# injectors, all the bolt-ons and a tuner or custom chip will generally pull around 300-315 hp at the wheels. That's enough to run high 12s. The only two SCs I'm aware of that are in the area of 400 rwhp are Coy Miller and Chris Wise.

Take a look at the dyno sheets in the "Top SCs" section and then click on the owners name to see their mod list. I've been working on my SC non stop for the last 2 years and just broke 300 rwhp a couple months ago.

David
 
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Way to burst my bubble !

Well i am going with a someone what aggreesive cam, but i thought..

35 from heads
15 from UD pulleys
15 from bigger TB and MAF
15 from dbl ic and n20 plate <-- way conservative:

total : 80hp

Also, yes the front mount has a lower pressure drop, but if you can cool the intercooler, thus creating a densor air charger you will be making comparable power for a third of the price. Advantages of the FMIC is location, and improved efficiency right ?

** Note **
I just wanted to say i dont think im a know it all, i love debating and learning. Part of my argument is for education. Dont take my posts to mean im a wanna be know it all.
 
the improvement of an fmic is not only the great cooling, but its like porting heads, it just simply flows a lot better.
 
I had a Double IC with 850 CFM fan along with an 1-1/4" raised top and a pair of ported and diffused IC tubes. Changing to the Magnum Powers front mount kit added 26 HP at the crank.

Even if you freeze the IC (might crack) is won't flow as well as a large front mount or an air to liquid IC like Chris Wise is using. Before buying the FMIC I looked seriously at a system to spray co2 on the IC for cooling (less dangerous than nitrous) and it just wasn't going to work nearly as well.

I even tried propane injection to cool the air charge and it has other problems that I'm going to try and overcome for use in the summer.

David

PS: I think you should add a raised top, MP plenum, a cold air intake and some rear end gears to your list before buying the double IC.
 
Good advice! I will follow that david. I still have a long way to go, with all the possibilities the mind couild go numb trying to figure out what to do!
 
I have seen several Coy Miller Stage II cars with all the bolt on's (including the double I/C) not hit 300RWHP. I'm sure some CMRE owners can chime in.

The welded exhaust is important if you want real HP. Chris spanel made over 300RWHP with a stock intercooler, stock 94 blower, and stock plenum on those heads.

IMO the heads can be the second biggest gain for the buck. Chris Spanel also gained about 80HP with the heads, cam, and a throttle body. Look at some people who just ported heads, they are seeing in the 25-40HP range gain.

What's the biggest gain for the buck? That would be the Magnum Powers Plenum and MPII blower porting, they cost less and give a lot.

If you did the Magnum Powers setup (including the FMIC), and the Stiegemeier setup, you would be safely over 300RWHP and close to the limitations of your stock bottom end.

Also, I am a magnum powers dealer, and I have access to some SC owners selling things like double intercoolers, liquid intercoolers, and other performance parts. Shoot me a message if you are looking for somthing.

Brian
bjherron@apten-us.com
 
Brian you raised a valid point.. at what point will i have to rebuild the bottom end of my motor to sustain the stress i'll be putting on it ?
 
depends on the tune. If you get a good tune with no detonation it should last a little above the 300RWHP level. But anything past 300 at the wheels is not going to last forever.

Brian
 
35 from heads
15 from UD pulleys
15 from bigger TB and MAF
15 from dbl ic and n20 plate <-- way conservative:



Well remember that is crank hp that you are estamating...

so around 64 to the wheels for an auto... 68 for 5spd or so.

Stock 94... 230crank 185rwhp... + 65 = 250rwhp.




Also, you might get 15from a tb and maf if you also upgrade the tube between the two..


Chris
 
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