[pmd400]

Iv read this whole thread, it's very interesting.
In a 9.5:1 iron headed 455, a cam with a 274 adv duration and 230 at .050 is considered to small. It doesn't make as much power as it should and is octane sensitive.

A crower 60919 has adv duration of 304 and .050 duration of 231. It makes great power but works best with 10:1 compression and rhoads lifters.

Is it possible that a cam with 230 at .050 and an adv duration of about 290 using standard lifter would be a good compromise? I understand that some companies also use a different lift point for advertised duration, so some cams seem to have a longer duration but in fact they are just measured at a lower lifter point.

Crower, comp, howards, lunati, melling all measure the advertised duration at 0.006 of tappet lift

[Will]

Originally Posted by pmd400

Iv read this whole thread, it's very interesting.
In a 9.5:1 iron headed 455, a cam with a 274 adv duration and 230 at .050 is considered to small. It doesn't make as much power as it should and is octane sensitive.,,,

I think this might be oversimplifying things a bit. Lobe centerlines play a very large role also as they determine valve opening and closing points in conjunction with the overall lobe profile. A fast-ramp cam like that might work just fine and have a broader powerband if modified to a 112 LSA and 108-110 ICL. Of course, the faster ramp cam will still have later opening and earlier closing points than a cam with similar .050" duration but longer seat duration ("slower" ramps) and the same lobe centers.

Isn't the point of a roller cam to minimize the seat-to-seat duration in relation to duration and lift off the seat? In that respect, a fast ramp flat tappet cam is an attempt to mimic the valve motion of a roller as much as possible. Of course it seems that running bigger rollers (as measured at .050" duration) than flat tappet cams is the way to go.

Which all comes back to valve opening and closing events and their relationship to other engine parameters being the key to whether an engine is a dog or a monster.

[nytrainer]

I happen to own a practically new (thumbs down in a friend's 455) Comp cam XE 262 cam (specs below).
To the gurus who can decipher the specs. would this cam work nicely in a 9:1 cr 350 with dual ex, iron manifold and q jet or is there no place for it in any Pontiac engine? I read all the posts in this thread but still can't answer that question myself.
Also, plans are/were for my 455 to get the 041 cam (9.8:1 cr 6x-4 with push rod holes enlarged) or should I be looking at the Crower offerings (619...). Car is a 4 speed with 3.23's. I'd rather do regular lifters and would be OK with a rumpity idle (but I do have power brakes). Are Rhoads a must? I think the ticking would send me over the edge. It's a once in a while cruiser car during nice weather.

[ponyakr]

"... is there no place for it in any Pontiac engine?..."


I've read that those cams were made to increase cylinder pressure in low compression engines. There were plenty of low comp(7.6-8.5:1) 350 and 400 Pontiac engines in the 70's. So, for those just wanting to increase performance a bit, without switching to high comp heads, these steep ramps are supposed to fill the bill.

But, since you don't want the noise of Rhoads lifters, you may wanna go with a Lunati Voodoo 262, instead of that XE 262. I've read that the XE cams make noise, because of slapping the valves shut. I've even read of several guys who pulled their XE for this very reason.

And for the 455 cam question, if you can't stand the Rhoads, but want lots of idle vac, you'll just have to settle for less cam, or go with a high dollar roller set-up. But, since I said that, I'm sure somebody will come up with some cam that is bigger than the 041 and has more vac, without Rhoads. That seems to be the way this thread has gone. What don't work for some, seems to work great for others. So, I reckin it all depends on who you believe. Or you'll just have to try 'em in your engine and see how they do.

But, then I'm no expert. Some of them will be along shortly.

[nytrainer]

Thanks Ponyacker. I have the XE262 and regular lifters. Both like new and lifters matched to the lobes when removed. Just looking for a place to use it. Thinking it might be a better performer than the orig. cam (pn 254?). '68 350 rated at 9.2:1 cr but reality probably 8.5:1 I'm guessing.
I had the springs setup for the 041 (ported, 10 degree locks, new guides, clean up mill, cut for Viton? seals, pushrod holes enlarged, new valves, etc) to use on the 455 block but after reading the thread it's as clear as mud as to what hyd. cam I should use. I think roller setup would need different springs too so I'd like to keep the heads as prepped. Just need to have the gurus direct me to which cam.

[Steve C.]

Running a big cam and getting less than adequate vacuum for your power brakes?

Solve those problems with a electric vacuum pump kit. Easy to hide if desired.

One of many companies: http://www.mpbrakes.com/accessories/vacuum-pump-kits


.

[neill]

Originally Posted by nytrainer

Thanks Ponyacker. I have the XE262 and regular lifters. Both like new and lifters matched to the lobes when removed. Just looking for a place to use it. Thinking it might be a better performer than the orig. cam (pn 254?). '68 350 rated at 9.2:1 cr but reality probably 8.5:1 I'm guessing.
I had the springs setup for the 041 (ported, 10 degree locks, new guides, clean up mill, cut for Viton? seals, pushrod holes enlarged, new valves, etc) to use on the 455 block but after reading the thread it's as clear as mud as to what hyd. cam I should use. I think roller setup would need different springs too so I'd like to keep the heads as prepped. Just need to have the gurus direct me to which cam.

I believe the stock cam for that motor had either 269 degrees or 273 degrees duration. my 455 with 275 duration often pings with 91 octane and 8.96 to 1 compression. I would be very hesitant to try it in the 350. But I am no expert

[Nicks67GTO]

I just saw a dyno video on facebook from a very well known Pontiac builder. 4.25" stroke 400 with aluminum D ports, RPM and FAST 2.0 EFI. I asked for details but he didnt disclose. It made 488hp@5000 RPM and 580 lb/ft @ 3900. Not bad but not overly impressive imo. I was curious about the cam selection and port work as it seems compared to others with similar combos like the KRE290/RPM/OF combo, that this one its leaving a lot of HP and probably 5-700 RPM on the table for minimal costs. Ive also seen people mention that these guys like to run the modern lobe, tighter lsa profiles, I guess thats why its maybe worth mentioning here.

[Squidward]

Originally Posted by nytrainer

I happen to own a practically new (thumbs down in a friend's 455) Comp cam XE 262 cam (specs below).
To the gurus who can decipher the specs. would this cam work nicely in a 9:1 cr 350 with dual ex, iron manifold and q jet or is there no place for it in any Pontiac engine? I read all the posts in this thread but still can't answer that question myself.
Also, plans are/were for my 455 to get the 041 cam (9.8:1 cr 6x-4 with push rod holes enlarged) or should I be looking at the Crower offerings (619...). Car is a 4 speed with 3.23's. I'd rather do regular lifters and would be OK with a rumpity idle (but I do have power brakes). Are Rhoads a must? I think the ticking would send me over the edge. It's a once in a while cruiser car during nice weather.

Satan cam. I gave one away to a friend after my low compression 400 failed with it installed. His first run out to the dragstrip with that cam wasted his rod bearings in a 70 350. I think the devil was inside...

I went with the Lunati 10510702. Couldn't be happier, on a 112 LSA. But I digress. Back to 455's...