scja heads

I have a set of the scja heads that is going on a 557 . Going to run 93 octane pump gas 10.7 to 1 compression.  they came with 2.20 intake valves. I have read that these heads do really good with back cut on the intake valves.  I talked to local machine shop and he recommend buy 2.25 intake valves that had back cut all ready and doing a good valve job. And little touch up. Said they would flow 380s. My questions are  does that sound right and would the increase of valve size from 2.20 to 2.25 be worth buying new valves. Vs doing back cut on my 2.20 valves and same valve job and touch up. He said he had never tried that. What would be your opinions on power difference / ....thanks

IMO you'll never get 380 with just a valve job and 2.25 valve.

Keep the valves and just do the backcut on them.

Mine went 381 with the 2.20 intake valve and porting. It really picked up the low lift #s with the 2.25 intake but hurt a little from .570 lift on up.

dfree383 wrote:

Keep the 2.200" valves and just do the backcut on them.

X2 ...

With doing the back cut on the 2.20.valves would it help to still get valve job and touch up as he called it. Or just do the back cut.

If one wants 380 cfm on the intake side....back cut the 2.200" intake valves and do a moderate amount of porting.

How much would the back cut on valves alone make them flow.

It pickles up the flow where you need it in the low and mid lifts.

380 is useless at .800 lift if you using a .600 lift street cam.

one of the cam profiles that was suggested to me was int.262 @.050 / ex.270 @.050 and int..635 and ex..657 on a 110. from what I read on these heads that they worked pretty good until 650 lift. that cam didn't sound to bad. I also read the 2.25 valves helped the lower numbers. that was why when the machine shop suggested 2.25 it and said they would flow 380s [ that's where I got that 380s number also read other people flowed them over 400]. t I thought all this stuff sounded like a good fit. but that's why I asked these questions. so am I understanding this right. there would be no useful power gains by porting or adding additional valve size in a application like this were rpm would be 6500 or less.

Bang for the buck is a back cut and a little blending.

If you want to spend a bunch more, the valve job (if the shop knows the right angles, not many do) and adding bigger valves. Will pick up flow and add some power. Got to watch the throat dia and such as you can add flow and hurt low and mid no's where you need them most.

I would think they should know the right angles. The name of the shop is.   ........  race engines. Lol but I don'tknow. Is those valve angles a secret thing. I wouldn't care to spend a little on the scj heads if it helped alot. He wasn't to high to do the 2.25 valve job. Just don't want to spend a whole lot to where i would have in them as much as i could have bought p51 or 325 trick flows that flow around 400 out of the box.

Do the back cut on your existing valves and have him bowl blend them, that's the biggest gain for the money spent.

Ok sounds good. What kind of numbers would that get them to. Ball park?. Would the cam work well with them that was mentioned or would something else be better ?

The backcut on the intake valves should be approximately .080" to .085" wide, and it should be at a 30* angle. The backcut can pick up the mid-lift flow numbers by 12- 18 cfm and it really helps the engine breathe. If "he", the shop owner doesn't already know that, then find another cylinder head guy. There is no need for a backcut on the exhausts valves.

Charlie Evans

He knows that. Think that was why he suggested the 2.25 valves that were back cut all ready. Would the bowl blending be needed on both intake and exhaust .

You are not gonna get 380 with just a bigger valve and valve job unless you port the that head. Ain't gonna happen.

Of course with just a correct back-cut and a bit of bowl blending, well over 300 cfm at only .400" valve lift is pretty normal.

At 650 lift would it flow 350 with back cut and bolt blend. Would it need blend on both intake and exhaust.

With these heads and valves back cut with bowl blending what would be the best intake. Victor or trick flow ?

garys gt wrote:With these heads and valves back cut with bowl blending what would be the best intake. Victor or trick flow ?

With a 557, probably the Trick Flow "Mafia" intake for a Dominator size carb..

garys gt wrote: Would it need blend on both intake and exhaust.

It surely helps to do the bowls on the exhaust but, not near as much as the intake side.

Are both mafia intake and victor designed for regular production heads. Would the ports on either or both  intakes  need to be matched to the scj heads.

garys gt wrote:He knows that. Think that was why he suggested the 2.25 valves that were back cut all ready. Would the bowl blending be needed on both intake and exhaust .

What you said above seems very confusing to me. Most new aftermarket stainless steel valves are NOT backcut already. The odds are that the 2.250" valve that he would order are not going to have a backcut, unless he specifies that they do, and he pays a little extra for the backcut. If your head guy has a valve grinding machine, then it's only going to take about 8 - 10 minutes for him to grind the 30* backcut on your eight 2.200" intake valves.

Yes, bowl blending is needed on both the intake and exhaust bowls.

Charlie Evans

He must have known where to get some valves that was back cut or he would not of said it. But it does not matter anyway i am not going to do that. Just going to get him to back cut the 2.20 valves that came with the heads. I have a question about the bowl blending.  Is blending just smoothing out the bowl area like polishing and getting rid of casting imperfections ? If so I could do that part myself.

garys gt wrote:Are both mafia intake and victor designed for regular production heads. Would the ports on either or both  intakes  need to be matched to the scj heads.

This kinda simple stuff is discussed all over the place on this forum ... have you done any "searching" at all...? Do you have any idea or prior knowledge about the actualities of available performance parts for the big block Ford...?

The Victor manifolds have smaller cross-section ports however, they are on Cobra Jet port center-lines; (regular production port type heads have different intake port center-line locations at the flange).
The "Mafia" intake is Cobra Jet port size on Cobra Jet center-lines. The regular Trick Flow "Track Heat" manifold is only available with a 4150 pattern carburetor flange and regular port size / locations.

Almost no intake manifold of ANY brand engine will match the cylinder head intake ports exactly.

this kinda simple stuff is discussed all over the place on this forum ... have you done any "searching" at all...? ......yes
Do you have any idea or prior knowledge about the actualities of available performance parts for the big block Ford...?....some
Almost no intake manifold of ANY brand engine will match the cylinder head intake ports exactly......that's what I was looking for.. ..so my question is would I need to port match ?