Question for the math majors
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,319
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Question for the math majors
Ok so I am wondering what the effect or changing the rocker ratio from the stock 1.5 to 1.6 would be in terms of net lift, and relate that to the effective increased lift at .050?
Anyone want to give this a stab/
tim
Anyone want to give this a stab/
tim
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Usually about .030.in on mild lift small block cams or you do the math
1.6 times current lift divided by 1.5 = new lift
The increase in lift will be the same on any part of the cam
1.6 times current lift divided by 1.5 = new lift
The increase in lift will be the same on any part of the cam
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,319
Likes: 7
From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Originally Posted by MotorHead
Usually about .030.in on mild lift small block cams or you do the math
1.6 times current lift divided by 1.5 = new lift
The increase in lift will be the same on any part of the cam
1.6 times current lift divided by 1.5 = new lift
The increase in lift will be the same on any part of the cam
Law of ratios , got it, now all i need to do is find the stock specck for a 300 hp 68 327 let me see....
thnaks
tim
Drifting
Joined: Jul 2002
Posts: 1,943
Likes: 1
From: Rosemount MN
Originally Posted by sweethence
Ok so I am wondering what the effect or changing the rocker ratio from the stock 1.5 to 1.6 would be in terms of net lift, and relate that to the effective increased lift at .050?
Anyone want to give this a stab/
tim
Anyone want to give this a stab/
tim
The 1.5 vs.1.6 rockers is just the ratio difference that the valves move compared to the cam face.
You did know that almost all cams are rated for lift with a 1.5 ratio rocker...right.
As far as changing ratios, make sure you have the valve clearance before you start, make sure you have enough spring to close the valves from their increased lift and not coil bind. Make sure that you have enough valve cover room for the rockers to move.
The increased ratio will affect valve lift at all points along the cam lobe face, so the valve will move faster at all points. This will put increased stress on all valve train parts. If you're running a full roller set up, it may be just about free HP, if flat tappet, either hydraulic or mechanical, it'll cost you HP to run it. Along with increased wear (shorter life)
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,319
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
so a stock cam with .390 & .410 after the rocker ratio change would give me an effective cam lift of .416 & .437 wich is less than the .447 lift of the 350 Hp version of the same motor. So im guessing no clearance issues, but is it really worth it? for the incremental numbers, comments about valve train incremental wear aside for now?
opinions?
I am looking to get a little better breathing the easy way and am just curious before i go ahead with a cam swap.
thanks
desk top dyno anyone?
tim
opinions?
I am looking to get a little better breathing the easy way and am just curious before i go ahead with a cam swap.
thanks
desk top dyno anyone?
tim
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Thread Starter
Le Mans Master
Joined: Jan 2006
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Originally Posted by zwede
This sounds like the old "300 hp" cam. It is beyond mild. Save your money and get a better cam. I believe the 300 hp cam only has 194 dgr duration @050. It's rediculously small.
yeah i was thinking i could get off cheap for the summer, and io got a set of headers on the way id like to take advantage of.
Im partial to the 70 z28 grind, used it before like it just fine
.447I/E lift 222 I/E duration 112 lobe separation. not to mention is only like 60 or 70 bucks as a GM Part from my local parts store.
But you right about thre duration, I forgot to check that good catch
looks like there is no getting off easy for me
thanks all
tim
Le Mans Master
Joined: Sep 2001
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From: Unreconstructed, South Carolina
Originally Posted by sweethence
Im partial to the 70 z28 grind, used it before like it just fine .447I/E lift 222 I/E duration 112 lobe separation. not to mention is only like 60 or 70 bucks as a GM Part from my local parts store.tim
Inexpensive parts store cams? ... also look at Speed-Pro/Sealed Power:
P/N CS1013R .443"/.465" 214*/224* icl 112*
P/N CS1062R .468"/.480" 220*/231* icl 112* (my pick)
P/N CS179R .447"/447" 222*/222* icl 114* ... apparently the cam you referenced ... CS179R equivalent to GM P/N 3863151.
BTW ... if you want cam with set of new hyd lifters ... simply replace "CS" with "KC".
Long Slot SP stamped rockers:
P/N R865R 1.5:1
P/N R952R 1.6:1
Thread Starter
Le Mans Master
Joined: Jan 2006
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Inexpensive parts store cams? ...
inexpensive insofar as you are buying a GM replacement part as opposed to an edelbrock custom/ HP grind, which can run you into the 140-180 range, so yeah its cheeper that way.
I figure the general put years of R&D in so why not take advantage of it
Keep in mind also that i am basically turning my low horse 327 inth the high horse one plus some extras for a highway cruiser + I like to take mine on road trips, and DD to have fun with as opposed to the all out ***** to the wall machine. ( which i have done before
)
thats for the tip on RAR and duration, i missed that one too.
Ill have to check the pricing on speed pro though, thanks for the tip
TGIF
tim
inexpensive insofar as you are buying a GM replacement part as opposed to an edelbrock custom/ HP grind, which can run you into the 140-180 range, so yeah its cheeper that way.
I figure the general put years of R&D in so why not take advantage of it
Keep in mind also that i am basically turning my low horse 327 inth the high horse one plus some extras for a highway cruiser + I like to take mine on road trips, and DD to have fun with as opposed to the all out ***** to the wall machine. ( which i have done before
) thats for the tip on RAR and duration, i missed that one too.
Ill have to check the pricing on speed pro though, thanks for the tip
TGIF
tim
Last edited by sweethence; Mar 3, 2006 at 11:59 AM.
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
Check out this cam:
http://store.summitracing.com/defaul...4&autoview=sku
It's a summit brand made by Crane. I used it in a Camaro w/ 350 and it is a great budget cam. I installed it in 1990 and it is still fine to this day (Dad drives the car now). 214/224 duration, 442/465 lift on a 112 LSA.
The cam alone is only $49.95. With lifters about $100.
http://store.summitracing.com/defaul...4&autoview=sku
It's a summit brand made by Crane. I used it in a Camaro w/ 350 and it is a great budget cam. I installed it in 1990 and it is still fine to this day (Dad drives the car now). 214/224 duration, 442/465 lift on a 112 LSA.
The cam alone is only $49.95. With lifters about $100.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,319
Likes: 7
From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Originally Posted by zwede
Check out this cam:
http://store.summitracing.com/defaul...4&autoview=sku
It's a summit brand made by Crane. I used it in a Camaro w/ 350 and it is a great budget cam. I installed it in 1990 and it is still fine to this day (Dad drives the car now). 214/224 duration, 442/465 lift on a 112 LSA.
The cam alone is only $49.95. With lifters about $100.
http://store.summitracing.com/defaul...4&autoview=sku
It's a summit brand made by Crane. I used it in a Camaro w/ 350 and it is a great budget cam. I installed it in 1990 and it is still fine to this day (Dad drives the car now). 214/224 duration, 442/465 lift on a 112 LSA.
The cam alone is only $49.95. With lifters about $100.
interesting, what are the advatages of a shorter duration intake than exhaust combined with higher exhaust lift?
thoughts
tim
Race Director
Joined: Sep 1999
Posts: 11,361
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From: Plano TX
The split duration cams are designed to compensate for street exhaust. If you run anything besides open headers I can almost guarantee you will make more power with a split duration cam. The longer exhaust duration also helps with the somewhat restrictive exhuast ports in most street-type heads. Factory heads especially have poor exhaust ports.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 8,319
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Originally Posted by zwede
The split duration cams are designed to compensate for street exhaust. If you run anything besides open headers I can almost guarantee you will make more power with a split duration cam. The longer exhaust duration also helps with the somewhat restrictive exhuast ports in most street-type heads. Factory heads especially have poor exhaust ports.
how does that play into you comments
though as i think about what you just said, it makes perfect sense
thnaks
tim
Last edited by sweethence; Mar 3, 2006 at 03:16 PM.
Drifting
Joined: Apr 2002
Posts: 1,743
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From: Stockton Ca
When I changed to 1.6RRs 2 things happened. I didn't notice more power, but engine ran 10*-15* cooler w/ac on and the engines sweet spot was 200-300 rpm higher. I would do it for those reasons alone.
Rick
Rick
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From: Millington Illinois
St. Jude Donor '08-'09
Originally Posted by zwede
The split duration cams are designed to compensate for street exhaust. If you run anything besides open headers I can almost guarantee you will make more power with a split duration cam. The longer exhaust duration also helps with the somewhat restrictive exhuast ports in most street-type heads. Factory heads especially have poor exhaust ports.
