Who has theirs installed and up and running on a near stick build? What did u use for rockers and pushrods? .506 lift with hydraulic lifters. Thanks. Kim
Speedmasters
- Thread starter oldkimmer
- Start date
-
dano
Evil Handy Man
Not running yet but I used Hughes 1.5:1 rockers and custom Smith Bros. Pushrods. I don't recall the length. Lunati VooDoo Hydro Advertised Duration (Int/Exh): 268/276; Duration @ .050 (Int/Exh): 226/234; Gross Valve Lift (Int/Exh): .494/.513; LSA/ICL: 110/106. Heads were ported and set up by MRL so these were purchased as bare heads.
The Comp Magnum (not Ultra Pro) rockers I had didn't line up well geometry wipe wise, a kit from B3 fixed that but the tunnels got in the way even after opening them. The Hughes fell right in with a small shim, but that was these heads.
The Comp Magnum (not Ultra Pro) rockers I had didn't line up well geometry wipe wise, a kit from B3 fixed that but the tunnels got in the way even after opening them. The Hughes fell right in with a small shim, but that was these heads.
Good info on the rockers. The Speedmaster rockers look like Comp copies and look a mile off. A buddy tried my Speedmasters on his Eddy heads and switched to Harlan Sharp for the win. I don't think he shimmed them at all.
dano
Evil Handy Man
Harland would have been my second choice but my dad did Hughes on his 440 with 915 head and they fell into place.
Thay could be the same rockers.
PRH
Well-Known Member
Hard to see the data...... printer was about out of ink.
Not a great build....... not our combo.
The short block arrived assembled(stock type rebuild, dished pistons way down the hole)..... they had some industrial heads to put on it...... told them that probably wasn’t a great option for trying to make power....... they bought some SM’s.
PRW rockers that needed clearancing, RPM intake, xe268 cam, Ede 750 carb.
331.5hp@5200
Not a great build....... not our combo.
The short block arrived assembled(stock type rebuild, dished pistons way down the hole)..... they had some industrial heads to put on it...... told them that probably wasn’t a great option for trying to make power....... they bought some SM’s.
PRW rockers that needed clearancing, RPM intake, xe268 cam, Ede 750 carb.
331.5hp@5200
Last edited:
PRH
Well-Known Member
Eh....... it’s kind of a dud imo.
I had tested one a few weeks earlier that had a better combo for a short block, bowl blended J heads(230cfm), LD340, same headers, another Ede 750, small custom solid cam........ just blew this thing into the weeds.
Made 86hp more.
We were thinking the SM combo would at least be in the 1hp/ci range(365hp)...... but iiwii.
Just goes to show it really is all about the “combination”, and that one “special” part(in this case, the heads) isn’t going to do much for you.
I think it would have made about the same power with minimally tweaked 1.88 valve 360 heads.
I had tested one a few weeks earlier that had a better combo for a short block, bowl blended J heads(230cfm), LD340, same headers, another Ede 750, small custom solid cam........ just blew this thing into the weeds.
Made 86hp more.
We were thinking the SM combo would at least be in the 1hp/ci range(365hp)...... but iiwii.
Just goes to show it really is all about the “combination”, and that one “special” part(in this case, the heads) isn’t going to do much for you.
I think it would have made about the same power with minimally tweaked 1.88 valve 360 heads.
Last edited:
dart_68
Well-Known Member
PRH
Well-Known Member
Should be an easy 1hp/ci cam.
355” Chevy, bowl blended 1.94 valve open chamber heads, stamped rockers, 9:1, RPM, 650 carb, headers....... xe268.......400tq/360hp.
355” Chevy, bowl blended 1.94 valve open chamber heads, stamped rockers, 9:1, RPM, 650 carb, headers....... xe268.......400tq/360hp.
PRH
Well-Known Member
340, 10:1, 587 heads, 2.02, very mild bowl blend, std Performer, 650 Holley 1.5 Mancini rockers, 1-5/8” headers...... old school 268H cam
Even that made 1hp/ci
Even that made 1hp/ci
PRH
Well-Known Member
Had one on the dyno recently....... 421” SBC.
Very nice rotating assy, but the pistons were way way down the hole.
I can’t remember what the cam was, but I seem to recall it was pretty lumpy(I’ll see if I can find the specs), but it had unported open chamber smogger heads(882’s), rpm intake...... 375hp, and all done before 5k.
Customer wanted to get a number on it before taking it apart for some upgrades.
Edit- the intake was a split single plane Holley SD, the one with the runner connecting cyls #7 & #8 together.
Cam was XE274.
My feelings about the SM headed 360 are that the zero planning resulted in a rather poor piston choice , which I think was the biggest “issue” with that overall build.
We didn’t build the short block, so who knows if it was set up with performance clearances, or stock rebuild type clearances.
It may have had piston to wall clearances that were costing a few hp.
I feel like the “same basic” combo, but with a better piston/CR/quench combo, done with performance in mind could have yielded 30-40 more HP(to get it into the 1hp/ci range), and then swapping out the hyd cam for a small solid would up it another 20-30hp, if for no other reason than the lifters wouldn’t be acting up, which would allow the curve to hang on longer.
Very nice rotating assy, but the pistons were way way down the hole.
I can’t remember what the cam was, but I seem to recall it was pretty lumpy(I’ll see if I can find the specs), but it had unported open chamber smogger heads(882’s), rpm intake...... 375hp, and all done before 5k.
Customer wanted to get a number on it before taking it apart for some upgrades.
Edit- the intake was a split single plane Holley SD, the one with the runner connecting cyls #7 & #8 together.
Cam was XE274.
My feelings about the SM headed 360 are that the zero planning resulted in a rather poor piston choice , which I think was the biggest “issue” with that overall build.
We didn’t build the short block, so who knows if it was set up with performance clearances, or stock rebuild type clearances.
It may have had piston to wall clearances that were costing a few hp.
I feel like the “same basic” combo, but with a better piston/CR/quench combo, done with performance in mind could have yielded 30-40 more HP(to get it into the 1hp/ci range), and then swapping out the hyd cam for a small solid would up it another 20-30hp, if for no other reason than the lifters wouldn’t be acting up, which would allow the curve to hang on longer.
Last edited:
I mocked up stock rockers. No go. Tried the old Hughes 1.6 Rockers. Need clearancing for sure. Likely a B3 kit also. Kim
What were the issues with the stock rockers?
They are to close to the inside of the valve stem. I’m gonna try them on my J heads and see what happens there. Kim
Last edited:
The Hughes are excellent on the Speedmasters. Kim
I'd bet they're pretty good on just about anything!
Did you have to clearance them and use a B3 kit?
I’m happy with the way they are. Just bolted them on and checked. Kim
These are the older Hughes rockers made by Probe exclusively for Hughes. If u wanted them u had to buy from Hughes, Probe wouldn’t sell them to anyone else. Kim
Ahhhh. Good to know. Thanks!
Wyrmrider
Well-Known Member
kim how did you check the geometry?
roller in the center or narrowest stripe
or both?
tks
roller in the center or narrowest stripe
or both?
tks
Definitely not a huge cam, but it's up there, A stock 340 268 cam is an entry level cam arguably just slightly milder than a xe250 cam, xe268 is 3 steps up from that, basically the last step before you start getting into more street strip cams. A xe268 you should be at 1 hp per cid level and definitely needs gears stall headers decent intake etc...
I used the 1.6 rockers I have just to see where they may end up at. The roller was almost centered and moved a hair to the inside. I never measured the width. This motor is planned out with 1.5 ratio so we won’t be using the 1.6s as it will be street friendly for his wifey. Kim
Wyrmrider
Well-Known Member
the stock 268 cam has about the same duration as a 274 comp
but it's so lazy, especially on the close that for power the duration is wasted
that duration together with the wide LCA close the intake late- killing your low end -dynamic compression
that's why the smaller comp feels better on the but dyno
lunati 262 out powers the 268 comp chevy design and gives more low end- compare the lifts
that said i do not know if either is right
just that a comp smaller than the 275hl is wrong
1.5 or 1.6 rocker does not change that you need a narrow stripe
1.6 on the intake
(one size smaller cam) works -and is street friendlier
1.6 on the exhaust not so much or hurts under max torque-not for you
but it's so lazy, especially on the close that for power the duration is wasted
that duration together with the wide LCA close the intake late- killing your low end -dynamic compression
that's why the smaller comp feels better on the but dyno
lunati 262 out powers the 268 comp chevy design and gives more low end- compare the lifts
that said i do not know if either is right
just that a comp smaller than the 275hl is wrong
1.5 or 1.6 rocker does not change that you need a narrow stripe
1.6 on the intake
(one size smaller cam) works -and is street friendlier
1.6 on the exhaust not so much or hurts under max torque-not for you
Last edited:
-
