questions on 1.3 break in rockers and 5/16 pushrods

[steve cowan]

hi guys,
building the 327 sbc junker that i have previously posted here
i have purchased some 1.3 ratio howards break in rockers with a 7/16 stud
my question is
how long do i keep the 1.3 rockers on the engine for - only for inital cam break in ?
run the engine for a couple hundred miles?
i remember randy running one of his engines down the track with 1.3 rockers and it still put a good number down
the other question is -
dart sportsman 2 heads only have provision for 5/16 pushrod
happy to run a thick wall 0.080'' - 0.120'' 5/16 pushrod
or can i or should i make provision for a 3/8 pushrod if the heads can be milled out to suit
i am only running basic flat tappet cam stuff on this engine
i have purchased 2 different off the shelf comp cams
12-648-5 grind # 270 xos
240 @ 0.050'' int
246 @ 0.050'' exh
adv 270 - 280
int lift with 1.5 rocker 510''
exh lift with 1.5 rocker 519''
108 lsa
lash hot 0.016'' int
lash hot 0.018'' exh

comp cam # 2
12-664-47 grind # xe282s-10
244 @ 0.050'' int
252 @ 0.050'' exh
adv 280 - 290
in lift with 1.5 rocker 520''
exh lift with 1.5 rocker 540''
lsa 110
lash hot 0.016'' in and exh
4/7 firing order swap

i also have a new set of scorpian 1.6 1.5 7/16 rockers
using std length milodon valves installed height 1.78''
i have springs and retainers to suit
i know the 327 likes to rev up a bit but i want to keep it max rpm at 7000 if possible
i will be trying both these cams in this engine
for me it is learning,and i have no problems about playing with rocker ratios,intakes,valve lash etc,i have plenty of parts IN STOCK ON THE SHELF
any feedback and suggestion appriciated
the sportsman 2 will only be getting a clean up and a valve job to start with and i would eventually like to try a set of vortecs later on

[Geoff2]

I have seen photos of Scorpion alum rockers where the there were cracks around the roller tip axle; the engine in question was only running a mild hyd rol cam & moderate spring pressure.
Have also seen pics of other Scorpion rockers with the anodising starting to flake off the underside of the trunnion area. This area is heavily loaded, & the flaking was an indication of flexing, so only a matter of time before there would be a 'bang'......
Better to be safe with steel or s/s rockers.

[pdq67]

Heck, a stock solid lifter 30-30 cam 327 will hit 8,000 rpm fine! Just like my old junk301 would.

I would install a good old Isky Z-30 and their needed valve springs and go!

BUT, BUT!! You might want to install a, "scatter-shield" and, "block plate", to protect your feet at rpm!

Suckers have a bad habit of coming unglued above 8,000 rpm!

I am buying SFI stuff here once I bite the bullet. Front damper and all on the clutch end!!

Can you say, 8,000 rpm and higher?? 4.155" x 3.00" = 325" engine..

pdq67

[Truckedup]

Heck, a stock solid lifter 30-30 cam 327 will hit 8,000 rpm fine! Just like my old junk301 would.

I would install a good old Isky Z-30 and their needed valve springs and go!

BUT, BUT!! You might want to install a, "scatter-shield" and, "block plate", to protect your feet at rpm!

Suckers have a bad habit of coming unglued above 8,000 rpm!

I am buying SFI stuff here once I bite the bullet. Front damper and all on the clutch end!!

Can you say, 8,000 rpm and higher?? 4.155" x 3.00" = 325" engine..

pdq67

There's quite a few 30-30 cam dyno test printouts on different engine builds available on various internet sites....All of them show the power falling off rapidly after 7000 RPM..Why rev to 8000 ?

[BigBro74]

Steve- if you want to leave the rockers on for quite awhile it is no big deal. Make sure the pushrods clear okay and are still held in place by any guideplates (this may be close). Also make sure that if you drive or load the engine that if it is higher compression there are no detonation issues as on a solid it may alter the running duration somewhat.
on iskys website the have a blurb about real long exhaust splits and Ron Iskendarian wrote about recommending a circle track racer to run break in rockers on the exhaust side for a race while they made the racer the correct cam...........and the guy did really well that way...

I have a set and they work nice
Jason

[BigBro74]

also- if u run 1.6 rockers on the sportsmans they will probably need the pushrod holes slotted for clearance(you probably know this) - J

[BOOT]

The purpose of break-in rockers is to reduce the load on the new cam & lifters similar as taking out the inner spring or just using less install height/spring rate for break in. After the initial break-in they are just reducing power, I'm sure some over camed combos or maybe an incorrect pushrod length with nonbreak-in rockers they work just fine.

As mentioned sportsman need the pushrod holes opened up, the exhaust is easy and intakes I mocked it up to see where it needed material removed.

[MadBill]

I've seen 10-12 hp gains with 1.6 vs. 1.5 intakes on near stock SBCs, but ~ nil effect on the exhaust side. I've also read reports of substantial gains from reducing excessive exhaust lift via low ratio rockers. One was some high hp Modified that picked up so much they had to change the gearing. Back home on the dyno, they found it was up 40 hp from replacing 1.7s with 1.5s.

[steve cowan]

I have seen photos of Scorpion alum rockers where the there were cracks around the roller tip axle; the engine in question was only running a mild hyd rol cam & moderate spring pressure.
Have also seen pics of other Scorpion rockers with the anodising starting to flake off the underside of the trunnion area. This area is heavily loaded, & the flaking was an indication of flexing, so only a matter of time before there would be a 'bang'......
Better to be safe with steel or s/s rockers.

Geoff,
thats interesting that they would fail like that,i figured with a lifetime warranty and they say they can go to 900'' lift and 950 lbs open spring load they would be acceptable for a mild solid flat tappet cam and 350 psi on the nose,i spose i will keep an eye on them and let everyone know the outcome over time.
steve c.

Steve- if you want to leave the rockers on for quite awhile it is no big deal. Make sure the pushrods clear okay and are still held in place by any guideplates (this may be close). Also make sure that if you drive or load the engine that if it is higher compression there are no detonation issues as on a solid it may alter the running duration somewhat.
on iskys website the have a blurb about real long exhaust splits and Ron Iskendarian wrote about recommending a circle track racer to run break in rockers on the exhaust side for a race while they made the racer the correct cam...........and the guy did really well that way...

I have a set and they work nice
Jason

jason,
thanks for the reply on scorpion rockers,
i think a cylinder head with a very good exhaust port a single pattern cam could possibly work well,that could be why pdq67 loves his old school isky cams

I've seen 10-12 hp gains with 1.6 vs. 1.5 intakes on near stock SBCs, but ~ nil effect on the exhaust side. I've also read reports of substantial gains from reducing excessive exhaust lift via low ratio rockers. One was some high hp Modified that picked up so much they had to change the gearing. Back home on the dyno, they found it was up 40 hp from replacing 1.7s with 1.5s.

bill,
i have read here on speedtalk where bigjoe,DV and yourself say good improvements with 1.6 rockers on the intake only,i will be testing myself so thanks for your feedback