Roller Rockers, 1.5 or 1.6

[powerdoctor]

You should be fine if your springs are good.... it's just close, thats all.

[sir loin]

I'm using 1.5 roller tip with this cam:

Duration @ .050": Intake204 Exhaust214

Adv. Duration: Intake270 Exhaust280

Lift: Intake.420 Exhaust.443

Lobe Center: Intake107 Exhaust117

I'm not as well schooled as some of y'all and don't have exact measurements, but with the stock ratio v. spring I have plenty of room before bottom out, I can't imagine with a 1.6 there'd be any trouble (with my cam anyway).

[ForcedFirebird]

To answer Ray's question, you will be fine with that combo - especially since you have no ECM.

There are quite a few iron head motors in stock form running around with a 270 Comp cam (again .440/.440, 212*/212*) and 1.6 rockers. In fact that's the biggest we can go on a stock tune in the fbodies

[powerdoctor]

What I was saying, just for an example.... was that a cam with a .400 lift and a 300 grind, can fill the cylinder as well as a .650 lift with a 200 grind, thats all.

Its not the "lift" that I felt was the issue, its the duration and the lobe timing as well as the grind lift ect....

The original point to all of this was to watch your open spring pressure and coil bind as well as know what you want the engine to do and how much stress you will need to compensate for with the increased lift....

Somehow we got onto all this other stuff, I think I did that with the "flow" question..... my bad.


And....
You aren't scared of " big cams " are you????

lmao... I was messin with ya ... calm down.

[ForcedFirebird]

Yes...

But still, if you have a .490 lift at the valve... and you do put in a .650 lift, we are looking at a difference of only .16 valve lift

Thats only a litttle over 1.5 tenths of an inch or 4 mm, which to me is still a small amount of added lift.

Duration is what the issue to me would be... messing with vacuum and port velocity, not the "big" lift.

You could go small duration and big lift, and accomplish for the most part what a smaller lift big duration cam will do, so long as the cam grind/ timing is set for it...

.490 to .650 is a big difference. My cam is "only" .486/.496" lift, but is 288/300* advertised duration (232/238* at .050") and will support more than 300hp at 7000rpm. The Comp 270 grind is only .440/.440" and 212/212* at .050" (270* advertised duration). Are you trying to say that there is little difference between the two cams?

[torq455]

You talk as if I am not a "part of the automotive world" here man....

I'm used to seeing lifts as high as .750 all day long on small blocks and big blocks.
And some big blocks with as high as .890 N/A

The difference betwwen .490 and .750 is huge, almost double... not .490 and .650, especially if you take into account duration as I stated...

The only way a .650 lift will ruin anything is if the springs, studs/ rockers/ guide plates/ pushrods/ lifters/ cam "base stock" / pistons ( notching )/ timing chain is not matched to the lift.....

You can run a lift like this all day long if you prep for it right....

Well, I don't know if you are a beginner or an expert. As you say, you are used to seeing huge lifts so you must be dealing with race engines to which you see those "little" increases all the time. Maybe for racing a .16 inch difference in lift isn't that much, but for a street application it's a big jump. Sorry if I offended you. Sometimes I don't word things in the best way. However this comment:

You aren't scared of " big cams " are you????

is unnecessary. Anyway back to what this thread is about....

[ezrollin]

Boys,boys ! If you compare Cranes 260-2 [427/454] and 272 [454/480] you will relize that the diff. is .027/.026 and will indeed show a power increase. The real ? is at what lift does the head flow become an issue. Are these roller tip rockers,not real roller rockers,if so I'd opt for a new cam/kit with more lift rather than change rockers.

[powerdoctor]

You talk as if I am not a "part of the automotive world" here man....

I'm used to seeing lifts as high as .750 all day long on small blocks and big blocks.
And some big blocks with as high as .890 N/A

The difference betwwen .490 and .750 is huge, almost double... not .490 and .650, especially if you take into account duration as I stated...

The only way a .650 lift will ruin anything is if the springs, studs/ rockers/ guide plates/ pushrods/ lifters/ cam "base stock" / pistons ( notching )/ timing chain is not matched to the lift.....

You can run a lift like this all day long if you prep for it right....

You aren't scared of " big cams " are you????

[torq455]

in the automotive world we deal with very small clearances and tolerances and the cam is no different. going from .490 to .650 is HUGE. think about adding .16 more bearing clearance or that much more stroke. in most cases that "little" amount will ruin an engine in no time!

[powerdoctor]

Yes...

But still, if you have a .490 lift at the valve... and you do put in a .650 lift, we are looking at a difference of only .16 valve lift

Thats only a litttle over 1.5 tenths of an inch or 4 mm, which to me is still a small amount of added lift.

Duration is what the issue to me would be... messing with vacuum and port velocity, not the "big" lift.

You could go small duration and big lift, and accomplish for the most part what a smaller lift big duration cam will do, so long as the cam grind/ timing is set for it...

[geoffinbc]

I think he means the flow wont stall until .650 lift. But even that seems like a lot to me.

[torq455]

i'm pretty sure even the 3500 heads with casting smoothed won't flow at .650! i mean they will still flow air, but that lift is well past a mild casting blend aif flow max let alone the old iron style.

[powerdoctor]

Does anyone know of any other 60 v6 books?????

[powerdoctor]

I have heard the stock iron heads, with only the casting flash removed will flow a .650 lift.

it was in this book I believe...

[powerdoctor]

Hey guys...

Im suprised only one of you meantioned coil bind and stress.

Your "lift" at the valve is a combination of lobe lift x rocker ratio.

you have stated that your cam is .420 (heh heh) and .443 lift at the valve.

if you take that valve lift and and run thruogh the math you will find that a .443 valve lift = a .295 lobe lift.

so a .295 lobe lift x 1.6 rocker ratio = .472 valve lift.

The stock springs on that head will have problems @ .490 lift., even though you say yours are different.

We are talking about a .063 margin here for stock springs, 63 thou does not make me feel warm and fuzzy about that at all.

Get some different valve springs....if yours cannot handle this.

watch your open rating of the springs (psi) or you will tear up your retainers and lifters, ect...