Pat McPherson

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...

Pat McPherson

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

IndianaHeat

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"

Pat McPherson

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.

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

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...

WETTE VETTE

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.

50boat

going foom stamped steel rockers to rollers should gain 25hp may moor ,, going to 1.8s may be another 10--15hp, 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

Pat McPherson

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!

Strip Poker 388

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

Hostile Takeover

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.

boatn70

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