|05-16-2013 08:39 AM|
ALL of the "large valve" 400 heads, including Ram Air II and IV had 30 deg. int. seats. The 455SD heads had a 45 deg. int. and some of the 350 heads.
In oklen times, it was "convention" that there is no need to "lift" the valve off the seat any further than where flow "peaked. We know better today ("average" is far more important than "peak"). But most Pontiac intake ports DO stop at around .410" lift, unported. Even the legendary McKellar series of factory "race" cams yielded only .408" lift with 1.5 rockers. Smoley Yunik was the ojne to put 1.65s on them and watched power JUMP. He and Harland Sharpe "teamed up" to develope the roller rocker for the 1960 Pontiac "Trophy" series of 389s.
The 041 (Ram Air IV) cam was the first one I recall from Pontiac that had higher lift. It was also the first "computer optimized" cam GM produced (1966).
|05-16-2013 06:47 AM|
1.65 ratio rockers were rarely used. Found on early SD (389/421) and the RA IV engines. But had the plug not been pulled on Pontiac performance, there'd have been a lot more head/valvetrain development than what was seen back then.
Pontiac Factory Cam Specs. You'll see the ICL were relatively retarded and the cams tended to use a relatively wide LSA to keep overlap in check.
|05-16-2013 03:18 AM|
|Nuck Chorris||seriously, mighty 400s ran around with only .408 lift from the factory? Did they have 1.65 rockers stock? Or was that just RAIV?|
|05-15-2013 05:36 PM|
I think you have the wrong specs for a 068 cam. The specs above are for a Pontiac 744 cam. 068 specs are in the middle of the following link:
Pontiac Cam Specifications
keeping the indian alive.
|05-15-2013 12:30 PM|
All the "goodies" for Pontiac engines are being reproduced, most in very high quality. Ram Air IV intake, 455SD carb, "long branch" exchaust manifolds, 041 cam, 47 heads with good valves and a little "cleanup" (big ports aren't required). This combo is good for near 400 HP and about 420 lb. ft.
We've found the Pontiac to have an advantage in racing classes where "stock" manifolding is required. they did their "homework"... (:-
Having done many different method of installing screw-in studs, we've also found the HeliCoil method to be the most reliable.
|05-15-2013 10:34 AM|
The problem w/the pressed in studs besides possibly pulling is the non adjustability of the bottleneck stud design. Yes I know some guys will use polylocs or SBC-sized lock nuts to get some adjustability, but the better route is to drill/tap for proper screw in studs and be done w/it. That will provide a more stable valvetrain as well as accommodate any length pushrod (within reason) that may be needed to set the geometry up correctly.
There are many things that can effect the pushrod length- the geometry has to be physically measured/checked and corrected as needed.
|05-15-2013 10:28 AM|
"Which parts" is a Ponti-yacker well kept trade secret since most of the factory parts have been discontinued.
It is easy to "over-cam" a 350 CI Pontiac engine since the bore is so small in relation to the stroke. A Melling SPC-3 Tri-Power / H-O camshaft is a nice little cam for a 350 CI engine with freeway-flyer rear cogs and a TH-350 transmission.
The Melling SPC-3 camshaft is the aftermarket version of Pontiac's #9779068 performance camshaft. That cam was installed in the 421 H-O engines,389 Tri-power engines, 400 Ram Air III (4-speed manual) engines, 428 H-O engines and the 455 Super Duty engines. You can use stock replacement valve springs and pressed in rocker studs with that camshaft.
Valve lift... .406" I / .407" E
Valve duration.....224 deg. int./ 236 deg. exh. @ .050" lifter rise
|05-15-2013 08:07 AM|
Always one guy out there... (:-
To clear up a couple issues:
Unlike the Chevy and earlier Pontiac heads, the stud "boss" is not "there". That is, the entre area has been machined flat to accomidate the guideplates. "Pinning" isn't really an option, except at an extreme angle (no "straight shot"). Not all is lost, though. You can remove the studs and tap the existing holes for 7/16-14 HeliCoils, and use conventional screw-in studs. It needs to be done on a precision machine, though (no "hand" tapping). HeliCoils are stronger than iron threads. The end result allows for the use of the bottle-neck studs if stem height and cam are "correct". BBC studs make the valve train adjustable, like the Chevy.
Stock springs are plenty good to .470" lift. I wouldn't take them any further. We use SBI "replacement" springs until loads required exceed them. Our most popular cam for a "stocker" is the Comp XE262H, and these springs are fine with it.
One can make 1 HP per CID with the 354 Pontiac using nothing but factory parts (including exhaust manifolds). You just gotta know WHICH parts... (:-
|05-14-2013 06:43 PM|
I think that cam is a very good choice. Probably perfect for the 350 CI.
Keep us posted.
|05-14-2013 01:36 PM|
|Nuck Chorris||I've read around, researched a little, considered what mousefink said in this and other posts. I've decided on that this cam would be a good fit for my performance goal of over 300 HP and reliability. Howard's Cam 410021-12 Duration@050 213/223 Lift .450/.450 LSA112 Centerline 108. Agreement?|
|05-04-2013 05:13 PM|
|05-04-2013 04:18 PM|
|AutoGear||told you so|
|05-03-2013 05:51 PM|
325 from a 350 Poncho aint hard.
More torque than a chevy 350 all day too.
75 CC Iron heads with mild port work
XE 262 comp cams , crower 86404 springs
dual exhaust with H or X cross
P4B intake or equiv
Recurve the dizzy a tad
325 horses on 89 octane all day long
The 350 2 barrel version in 71 starts at 250 horse with less than 8 to one.
|05-03-2013 03:15 PM|
If the 3 pontiac guru's here can't get 300hp out of a poncho 350 without blinking twice; I'll be surprised.
Start a separate thread for your 350 injun.
|05-02-2013 08:12 PM|
|streetpirate||so is getting 300-320hp from a pontiac 350 really this much of a PITA? at this point I would think the best bet would be to stick the numbers matching 350/350 in the corner of the garage and stick a chevy mill in it.|
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