scj--vs--p51

557 ci motor...same motor..test 1 is p51 heads straight from the box...test 2 is scj heads straight from the box....which one would have more power--tq, looking to see if the extra 1000.00 the p51 cost is worth it over the scj heads..if everything was kept equal

725 hp verses 880 if both engines were 14.5:1 + compression and cam was right and the mafia intake.. (WITH OUT OF THE BOX HEADS). Do a light bowl blend on the SCJ's and things change considerably JMHO...........

1. In addition to what Blake said,,,,And,,,,,,,,,,backcut the intake valves on the SCJ heads.
2. Also, normally you can't run as much camshaft with the SCJ heads, (because of their valve spring installed height) as you can on the P-51 heads. The P-51 heads have +.100" longer valves.
3. The SCJ heads come (out of the box) with a steel retainer, whereas the P-51 heads come standard with a steel retainer, but can be ordered with titanium retainers.

Charlie

If you're looking to buy a set of heads to keep as you upgrade shortblocks along the way I'd opt for the P51s. They'll need less "work" over the long haul...

Not to hijack the thread........

But will the P-51s bolt right on where TFS or D0Ve head has been?


Russ Hood

Moodyblues wrote:Not to hijack the thread........

But will the P-51s bolt right on where TFS or D0Ve head has been?


Russ Hood

No different valve layout

The tfs street heads have the ex port raised .270.

IDT-572 wrote:

Moodyblues wrote:Not to hijack the thread........

But will the P-51s bolt right on where TFS or D0Ve head has been?


Russ Hood

No different valve layout

Dammit

But the raised port very rarely causes a problem.............

c.evans wrote:1. In addition to what Blake said,,,,And,,,,,,,,,,backcut the intake valves on the SCJ heads.
2. Also, normally you can't run as much camshaft with the SCJ heads, (because of their valve spring installed height) as you can on the P-51 heads. The P-51 heads have +.100" longer valves.
3. The SCJ heads come (out of the box) with a steel retainer, whereas the P-51 heads come standard with a steel retainer, but can be ordered with titanium retainers.

Charlie

Relative to "can't run as much camshaft".....
1] The same duration can be run on both cyl. heads.
2] If the P51 have an optional valve spring they can run more lift...I think that's what Charlie was speaking to.
3] Due to the flow curve of the SCJ they do not require a hugh lift so, it's a moot subject i.m.o.
4] Newer SCJB heads have a better spring than the orginal [more lift potential & pressure] .

IDT-572 wrote:

Moodyblues wrote:Not to hijack the thread........

But will the P-51s bolt right on where TFS or D0Ve head has been?


Russ Hood

No different valve layout

Blake....I think you have something to resolve than matter

Lem Evans wrote:

IDT-572 wrote:

Moodyblues wrote:Not to hijack the thread........

But will the P-51s bolt right on where TFS or D0Ve head has been?


Russ Hood

No different valve layout

Blake....I think you have something to resolve than matter

Yep just a hand drill and elbow grease..............

Be sure to put green oil on the valve guides before you start

IDT-572 wrote:But the raised port very rarely causes a problem.............

In a chassis where the headers were built around the street heads the P51 can be a problem.............tight clearance...............a generic header may not be an issue.

blake are you using and off the shelf header ?

bruno wrote:blake are you using and off the shelf header ?

Same exact header your running but coated..................

IDT-572 wrote:

bruno wrote:blake are you using and off the shelf header ?

Same exact header your running but coated..................

beats the crap out of paint...............

richter69 wrote:

IDT-572 wrote:

bruno wrote:blake are you using and off the shelf header ?

Same exact header your running but coated..................

beats the crap out of paint...............

Smart azz.......................

Just thinking out loud here. How would the SCJB's that are fully massaged work on a 557 work on a turbo application ?

With "green oil "


-John

I don't think that would be a very good combo imo. All of our OEM style CJ heads have a somewhat restrictive exhaust port to some degree, because of the factory exhaust port location, the need for stock style headers to fit and etc. In a high output turbo engine you want as good of an exhaust port design as possible, because the exhaust flow is going to be restricted with the addition of the turbos themselves. Therefore I would much rather see one step up to the A-460 heads (or bigger), which in ported form flow 320-330 cfm without a test pipe.

Charlie

Charlie, thank you kind sir

-John