Wishmaster's87IROC

iTrader: (4)

Ok....Ive figured out all my other problems...I think...thanks for the help.

But now Im thinking of changing to 1.6 promags in place of my 1.52 pros.
How much will that affect the performance? WHat kind of HP pickup would I be looking at and would it be worth it.. Will I have piston to vavle hit?

Right now im zero decked and using a 1003 head gasket which is .041 I think and my heads are 65cc afr's Im right at 10:66 to 1 CR

How can I tell if my vavles will hit? the cam I have now with the 1.52's is 226/232 531/537 @50 what will the 1.6's do to that?

thanks!

T-rick'srod

Hey Wishmaster , dividing your lift figures of .531/.537 by the 1.52 ratio gives
you .349/.353. now multiplying those figures by your new rocker ratio of 1.6 -
you get .558/.565 max lift. Your valves will be .027"/.028" closer to your
piston tops at max lift. With your zero deck,I would make sure they don't
touch.


"The secret of life is honesty and fair dealing...
If you can fake that you've got it made.
Groucho Marx

Wishmaster's87IROC

iTrader: (4)

How would I find out if they would hit?
would the only way to tell be to take the heads off?
what would that extra bit of lift do? give me more power? how much?

thanks

Supervisor42

Use the "light spring" method. After the engine has run and the lifters are pumped up, pretend you're changing valve stem seals.
Take the rockers off of #1 cylinder and air it up.
Remove each spring and substitute a light spring (like from a wheel cylinder or mastercylinder). Adjust valve lash to zero.
With the distributor aimed at firing #6 cylinder (#1 exhaust valve closing and intake opening) check the clearance every 2 degrees from either side of TDC for 32 degrees.
Like this:
16° BTDC check both valve's distance to piston by pressing down against the light spring and measure the travel with dial indicator.
14° BTDC " "
12 "
10 "
8 "
6 "
4 "
2 "
TDC "
2° ATDC "
4 "
6 "
8
10
12
14
16° ATDC "

You probably won't have to do the ones greater than 10° but this procedure is for really radical cams also, (like less than 108° LSA).
EDIT: oh yeah. don't forget to put the original springs back on and relash the valves on #1.

Wishmaster's87IROC

iTrader: (4)

LOL...ah? you do remember who your talking to right?...LOL

would it be worth me even changing to a different size?

Supervisor42

I didn't answer your other question. What will you get?
6-8% more horsepower and your valves will float 10% sooner.
It depends on the valve springs and how fast you're going to spin the motor.
I personally don't like 1.6's. Other people see them as "more lift, same duration"
If the cam maker could put more lift on a cam for a given duration without getting into trouble, they would.
This is why you don't see any 268 degree duration cams with .550 lift.

327???

I don't think it would be worth it to go to 1.6 RR's over 1.52 RR's, I think the money is better spent elsewhere.


They do make 268 degree cams with more than .550 lift. linky

Supervisor42

I stand corrected.
Read the fine print: Lift is with 1.6 rockers and bee-hive springs.

327???

Damn fine print....

Sorry

Wishmaster's87IROC

iTrader: (4)

well the only reason the cam maker didnt put more lift on the cam was because I gathered after talkin to him was that he didnt like AFR heads for some reason and didnt think the springs would handle alot of lift.
Do you think I can call AFR and then would be able to tell me if I am going to have PTV issues? I have no clue what your talking about with checking for it....and I really dont want to remove the heads to check.

My CR is 10:661 to 1 and my dynamic is 8.883 if that helps any.

how come you dont like 1.6rr's?
Lift means more power, correct?

Supervisor42

The procedure I quoted only involves pulling one valve cover. If the balancer has a scale, no degree wheel is needed.
A call to AFR will probably help.
The difference between the different ratio rockers won't make much difference because when the piston is close to the valves, the valves are just barely lifted off of the seat.
The 1.6's make the most difference in the acceleration and deceleration rates of the valves between half and full open. This affects valve float the most.
As I said before, it depends on how fast you are going to spin the motor.
And if you do not have a Rev Limiter, it may make the difference on whether the engine "drops a valve" when you miss a shift or have a driveline failure. (what actually happens is the piston finally catches the exhaust valve that it has been chasing to the seat. When it hits it, it breaks the head off of the valve and we know what happens next)
But on the other hand, the 1.6's make 6-8% more power in the mid rpm range...
My idea is: if you want a 226/232°@.050 cam with .558/.565 lift, buy one that has that lift with 1.5 rockers.

Wishmaster's87IROC

iTrader: (4)

Its funny how most will say do it when it comes to upping the ratio on a set of rockers to get more lift except for you... especially when the heads will handle it and the springs. I remember when I first got these heads and spoke with AFR...they told me that the springs have no problem handling .600 lift and sometimes more. I also have the revkit installed on the lifters too so that is suppose to help with valve float. I just dont see how going from 1.52 to 1.6's is going to create any kind of problem...if thats the case then I must be set right now BORDERLINE to PTV clearance which I dont think so.

Im hoping some one else will chime in and maybe give there opinion on the matter. I mean if I got to I'll pull the head off and check...but I dont think I will have a problem...I still need to call AFR on monday and ask them. They should be able to tell me, they recommended the head gakset Im using and when I told them about my motor being zero decked and with the gasket and their 65cc heads they told me I would have a problem. I think they run way bigger cams than what I got and have no problems. but I'll call them to make sure.

something else just came to mind...does it also have to do with the type of pistons Im using and the 7cc valve relief or whatever that is.....thats the little dimples in the piston that the valves sit in?

Supervisor42

I didn't know you had a rev kit on the engine. That changes everything with valve float.
The biggest factors with PTV clearance is the LSA and duration of the cam.
Other factors are: how big the valves are, how big the valve relief knotches are in the top of the piston, and how close the piston comes to the head (deck height + gasket thickness). With that many variables sometimes you just have to measure it. Remember, you don't have to pull the heads off and it doesn't take an hour to do. You could do it without a dial indicator first to see if it's even going to be close. Below is a scan from Isky's book of the procedure I paraphrased. The Isky part number for the light springs are 100-LSK. I don't think the 1.6's are going to make any significant difference with PTV clearance. I did say they would make a difference with valve float. The rev kit will take care of this.

Wishmaster's87IROC

iTrader: (4)

ok heres the cam specs...Im sure most of you have seen it before from way back...Ive done alot of searches and just want your input on the idea. I know it adds more lift and such but Ive read some stuff about it changing the overlap and the way the car with run..I just want to make sure Im not going to run into any problems once I do this.
Ok I had the cam installed just like it says on the card so I wont be pulling it out to do anything..I just want to R/R the 1.52 with the 1.6's
where will I gain the power? up top or middle or just all over the power band and how much is the usual?

thanks!


Cubic Inch and Engine Type 383 CID Small Block Chevrolet
Camshaft Type Hydraulic Roller
Firing Order STD SBC
Cam Bearing STD SBC
Lobe Separation 113.5
Overlap at .050” 2.2 Degrees

Camshaft Measurement Intake Exhaust
Duration at .006” 281.5 286.5
Duration at .020” 255.5 260.9
Duration at .050” 226.0 232.1
Duration at .200” 145.4 151.7
Lobe Lift .34961” .35323”
Rocker Ratio 1.52 1.52
Gross Lift .531” .537”
Lash HOT HYD HYD
Designed Lobe Centerline 110.9 ATDC 116.0 BTDC
Open at .050” 2.1 BTDC 52.1 BBDC
Close at .050” 43.9 ABDC 0.1 ATDC
Lift at Top Dead Center .0587” @ 110.9 In. Cente .0591” @ 116.0 Ex. Center

Cranking Compression 189 PSI
Vacuum At Idle 15.7 Inches
Idle RPM 850 RPM
Peak Torque RPM 4400 RPM
Peak Horsepower RPM 5500 RPM
Torque Convertor Stall 4000 RPM to 4500 RPM (Flash In High Gear At 5-10 mph)
Starting Shift Point RPM 6300 RPM
Starting RPM To Cross 6600 RPM

Wishmaster's87IROC

iTrader: (4)

Oh and Im in the process of pulling the DAMN motor again!...YEAH AGAIN!..LOL THis makes the 5th time this motor has been in/out of the car.
THe rear of the pan is leaking oil at either the pan to gasket of the rear main...but Im going to fix it or take it back to BUCK's and have them do it since they were the ones that assembled the short block anways.

THat is one thing I CANT stand is a leaking motor that makes a mess all under the car....and for my troubles Im going to tell them to check my PTV clearance and set the lash on the new rockers for me.

Supervisor42

In the mean time...
Here's a thread that may interest you:
ENGINE STAND.

Wishmaster's87IROC

iTrader: (4)

my engine guy says that by adding the 1.6's ...it will change the whole way the cam will act...when it was ground for 1.52 rockers to begin with.

whats the truth behind that? and if and how will it change the way the cam acts?

I was there when he was degreeing a pro mod motor and Im thinking that when I add the 1.6's it will change the centerline and stuff. So the cam should be re-degree'd with the 1.6's...which Im not doing.....

Im just going to add the rockers and be done with it. screw it if it changes something. should and hope it will be for the good.

Orr89RocZ

iTrader: (20)

1.6 rockers are suppose to give abit more duration while making abit more lift. slightly more lift is keeping the valve open abit longer while the lifter travels on the lobe of the cam. so technically it acts like its giving abit more duration.

i dont think on your motor with that cam and those heads you'll be making that much more power. those heads are suppose to flow great in the .550-600 range. A cam with lift in that range will help but its gonne be marginal. over the lift you have now. you'll just gain just a few more CFM at peak lift. not sure how it effects low lift flow numbers but i dont think you'll notice it. on the dyno you may see some ponies but you may not "feel" it or see it on the track. Its proby gonna be a small gain if any

Wishmaster's87IROC

iTrader: (4)

blah!..whatever!!...ANY is better than none!....its a done deal!.....

Orr89RocZ

iTrader: (20)

then again, ppl have said stock L98's wont notice anything with rockers and i think i did pick up since the heads flow so bad any additional lift will bring in more cfm which the motor needs badly. l98 heads suppose to peak at near .500 lift so bringin stock cam from .415/.430 up to .443/.459 did help put the cam in the heads best peak range.

So maybe your motor will also like that as long as your intake can outflow the heads which i think its near match as the HSR is rated at 275cfm and the heads are 280 i thought