Rocker Ratio 1.7 vs. 1.8
 

I am doing a stock rebuild of a 502MPI.
My plan is to use the stock cam, but maybe upgrade to 1.8 ratio roller rockers.
Is this a good idea?
I am thinking a little extra lift can't hurt and the roller vs. stamped steel is also a plus...

Re: Rocker Ratio 1.7 vs. 1.8
 

No comments?
Seems like an easy way to gain more lift.
Am I missing something?

Re: Rocker Ratio 1.7 vs. 1.8
 

i have seen 1.7 used , 1.7 and 1.8 between exhaust intake and just 1.8 used but the posts didnt give the cam info

I would go with 500 EFI cam and same valve size as the 500EFI's "1.7's"

Re: Rocker Ratio 1.7 vs. 1.8
 

I do agree that changing the whole valve train to like the HP500 is how to make lots more power.
It's just not in my budget to buy a new cam, new lifters, new valves, new springs, and have the machine work done to the heads... And have the ECU reprogrammed too. :rolleyes:

Just thinking that an extra $350 for 1.8 roller rockers and new studs may gain me a little... :cool:

I know it is quite common to go from 1.5 to 1.6 on small blocks; I thought maybe someone has tried upping the ratio on a marine big block too.

The engine builder that is doing the valve job said that he did used 1.8 ratio rockers on a truck pull engine last year, but that is the only big block with 1.8 he has done.
Glen did say that if I was to spend money on roller rockers, he would suggest 1.8 because the 1.7 rollers would not gain me much in the way of performance...

Re: Rocker Ratio 1.7 vs. 1.8
 

One thing you can try is to use 1.8's on the intakes and retard the cam 4 degrees. The extra duration at .050" lift will help stuff the cylinder a little more and retarding the cam will give you a little more RPM potential on the top end. I have never done this, but it would be a cool experiment to try! The best bet is to just get a better cam grind even if you stay with a flat tappet. (assuming the 502 MPI is a flat tappet??) Go with something in the 228/235 duration range on a 112+4 with .540 lift and you will be better off than just 1.8's.

Re: Rocker Ratio 1.7 vs. 1.8
 

:cool: :cool: going foom stamped steel rockers to rollers should gain 25hp may moor ,, going to 1.8s may be another 10--15hp, :p :p cheeep hp for 250 buckerurrrs,, picth the water pump for 15hp ,,ive have heard of stagering 1.7-- 1.8 ran mine 1.8s all the way,, using a hyd cam 637 lift --264 dur.hyd. 34 adv.1o.2 comp. 91 to 93 oct. 540 cu. 1050 domator. dart 2in. spacer, msd. 6000rpm chip++ alum heads = 750 hp

Re: Rocker Ratio 1.7 vs. 1.8
 

Guys, The engine is a Gen VI roller cam.
With stock rocker lift is about .480.
With 1.8s it would be about .508.
If going from 1.7 stamped steel to 1.8 aluminum roller is worth 20-25HP, I'll do it! :D

Re: Rocker Ratio 1.7 vs. 1.8
 

I went to the 1.8 ratio on a stock 365 mag , It had the staock valve guides and It gave me problems , wore the guids out , the 1.8 put more side load on the guild . Just my experance .

they are using up to a 2.1 rocker on the small block chevy race stuff .its kinda 50/50 one it helps on not having such a big lift cam and beating things up or the 2.1 rocker with it gemomerty and side loads?

there still running the higher ratios anyway.Trade off

Re: Rocker Ratio 1.7 vs. 1.8
 

Pat, I am no expert but while researching my engine build, I came across a section on upping the rocker arm ratios. As you know it is like having the same exact cam spes but higher lift. The author did mention that the tradeoff comes as additional stress to the valvetrain. ie. valve guides and springs as mentioned above.

If you do it, valve to piston, rocker to stud and rocker to valve cover clearances must be checked.

Re: Rocker Ratio 1.7 vs. 1.8
 

pat, ever thought of the zz502 set up that Dennis moore suggests? is this a new motor or rebuild?

Re: Rocker Ratio 1.7 vs. 1.8
 

Hi Guys,
I ran the add 0.028" of lift through desk-top-dyno and it would seem like the +8 horsepower is not worth the switch.
How much of a gain is there from going for stamped to roller? 5-10HP?

Yes, I have thought of the ZZ502 cam. But Mark at Precision told me that cam is not a vary good cam for an MPI engines with only 8.7:1 compression...
Also, I have the short captain call risers.

Re: Rocker Ratio 1.7 vs. 1.8
 

I would go with rollers either way, there stronger an much more precise

Re: Rocker Ratio 1.7 vs. 1.8
 

You'll never regret buying a good set of roller rockers (ie. Comp Cams stainless magnum version) if only for the piece of mind. I've broken/cracked most other aluminum body roller or stamped steel versions.

I now rev freely with no worries :drink:

Re: Rocker Ratio 1.7 vs. 1.8
 

The correct way to figure is take lobe lift times rocker ratio.

Example:
DUR:
248 IN----254 EX @ .050

287 IN----292 EX Ad.

Lift:
.663 IN---.680 EX

-----------------------------------------------------------------------
Lobe lift :
.390 IN---.400 EX

1.7 ratio .663 IN---.680 EX
1.8 ratio .702 IN---.720 EX
1.9 ratio .741 IN---.760 EX
2.0 ratio .780 IN---.800 EX
-----------------------------------------------------------------------
All cams are advertised with the lift amount for the rocker ratio the motor had stock. A small block chevy will sometimes have a cam with more lobe lift than a big block cam, but be advertised with less lift because of the factory ratio of 1.5.

Advantages to more rocker ratio is quicker valve movements in the same time frame so valve velocity is increased. The motor thinks it has a more agg. camshaft. The obvious reason is more total valve lift.

If you ever change anything in the valve-train you must figure valve geom. (pushrod length) at the very last. Nothing wrong with running more rocker ratio, but must check V to P clearance and pushrod length.

All cams are figured this way, it's just easier for them to give you the total valve lift for the stock rocker ratio when advertising.

Re: Rocker Ratio 1.7 vs. 1.8
 

Good Point!
I had not thought about that one... :cool:

Re: Rocker Ratio 1.7 vs. 1.8
 

Make sure you have enough clearance between the valve and the piston still.........