devilfish

Could you clear som things for me?
Can you match port heads to a cam? How does that work? I thougt porting just whas to smooth things up for the air and exhaust?
And what does 1.6/1.5 rr stands for? What is the numbers? Enlight me about all this numbers and what they stand for. Lift/duration etc etc.

Thanks for your time..

:cheers:

vettmech

Lift is the amount that the cam will open a valve. There is lobe lift and net lift. The bobe lift can be multiplied by 1.5 or 1.6 depending on the rocker arm ratio you are using. Stock SBCs have 1.5 ratio rocker arms. Big blocks have 1.75. Duration is the amount of time the valve is open in degrees. Overlap is the amount of time BOTH valves are open . Port matching to a cam has to do with the optimum port volume and has to do with air flow. Hope this helps a little :seeya

devilfish

thanks alot, that realy helpt :) So If I tell my mechanic the spec on teh zz-9 cam He can match port my heads? And should I use 1.5rr with stock ported heads inbstead of 1.6?

Regards

65Z01

Port matching is (mostly) different from valve lift, though the heads should flow enough to support the valve size and net lift.

Go to Comp Cams web site for a nice explanation of valve train geometry; and to the Standard Abrasives wite for information on head porting.

If you read the specs on the ZZ-9 cam it shows int/exh=.483"/.520", based on 1.5:1 rockers. Since .520" is the max lift for single springs (with dampers) I would use 1.5:1 Comp Cams ProMagnum Roller Rockers. If you go to 1.6:1 RRs with this cam you will need double springs with more spring pressure and so more valve train stress and wear. Since you want to raise the RPM over stock, I would go with 7/16" studs, hardened pushrods and guide plates, Ti retainers, 10-deg locks and toss the oil shedders that were atop your stock springs.

I suggest you have your mechanic pocket port and polish your heads, install new valve seats along with int/exh=2.00/1.56 SS necked and swirl-polished valves, a 3 (or 5) angle valve job. And then he can port match the intake and exhaust as possible with the heads.

devilfish

ok... After read this 5 times i start to get it :)
I will check the sites you named, thanks :)

So I must leave the intake base to my mech so he can port match them?
And what is "oil shedders". Thanks again for your time..

65Z01

Yes I would have your mechanic match the intake and exhaust flow paths as much as possible when he does the head porting.

If your mechanic has done head porting he will know what to do; if not, take the heads to a good machinest who has done good head porting.

Oil shedders are tin caps that sit atop the stock later L98 valve springs. Their purpose was to limit oil travel down the valve stem; later (on the LT1) GM discontinued use of oil shedders, to lighten the valve train.

The stock spring + oil shedder + retainer + locks is much heavier than the Comp Cam #981 spring with Ti retainer and 10deg locks.

This extra weight (inertia) serves to limit top RPM before valve float.

devilfish

My mech has several years exp with head porting. He is one of Swedens best in this field, he even goes under the name "the caveman" due to his work in porting heads to both streetbikes and track cars hehe well... ;)

Do I need harder springs with the zz9 cam aswell?
Could you print down what I need to change on the heads when going to the zz9?
Thanks

65Z01

It sounds like you have a good mechanic for the job.

With the ZZ-9 cam I suggest you use the springs recommenced by TPIS (P/N 700-132)along with Ti retainers and 10deg machined locks. Valve spring shims may be required to attain the recommended seat pressure; see TPIS for that data. Get a copy of the TPIS catalog (or maybe their site) for data on those springs.

I would then install ProMagnm 1.52:1 RRs for 7/16" studs, ARP 7/16" studs, hardened pushrods and guide plates, new GM lower and upper valve seals.

Have your mechanic check the valve guides and install new ones if indicated.

He may need to grind some material from the drip tabs and the sides of the bolt posts inside your valve covers so that they will clear the new RRs.

devilfish

ok thanks.

I do I check the "recommended seat pressure", and how do I adjust that?

Thanks

vettmech

Seat pressure can be adjusted with special shims........ be sure to check for spring bind before you start the engine and also be sure the retainers clear the end of the valve guide and seal .......... :seeya

65Z01

Correct but your mechanic will know how to properly install the springs and all after he has ported the heads.

devilfish

ok .

Do Ineed new vavles? is that something you change or reuse?

65Z01

To go with head porting I would install performance valves.

devilfish

and what should I look for there? Is it just to get preformance valves for chevy 350 alu heads?

65Z01

Stock #113 castings come with int/exh=1.94"/1.50" valves. The stock seats will accomodate up to 2.00"/1.60" valves; I believe you can install 2.02" intake valves with larger valve seats.

Here Lingenfelter offers such performance valves and Manley offers performance valves.

A good valve (of the size chosen) should be SS, necked, swirl-polished and back cut for maximum air flow.

Ask your mechanic what is available and get his recommendations on installing new valve seats or staying with valves that fit stock seats.

gtsyellow

the manley pro-flo valve in the stock size is the best bang for the dollar in valves for the D-port casting. summit racing wants $152 for a set of intake and exhaust valves. they are necked down stainless steel, these valves and a bowl job + 3angle seat job will increase the cfm. also polish your combustion chamber while they heads are off. the swirl on this casting isn't the best & any help you can get to avoid detonating is worth it.

devilfish

ok...

You think this port job + zz9 cam or lpe219 with superram is good for 400 at the crank?

Thanks

:cheers: