1.6 in Rocker swap for 400 Pontiac

[Bandit400]

I have a Pontiac 400 (6.6L). 11 years ago a guy told me that swapping from the 1.5 to 1.6 inch rocker arms would give a little more low end. He said you could get away with just doing it on the intake if strapped for cash. He said used stamped steel and they were $4 each (11 years ago).
Well, I am finally thinking about doing this but wanted to see if anyone else had input on this. I need to change the pushrods anyway so I figured that it would be the right time to do both.
Thanks.

[Firebirdjones]

If you still run the stock rocker studs then you would have to use a factory stamped steel rocker. Since the studs are bell shaped (non adjustable) and small diameter.

If you are thinking of going to a full roller rocker or even comps roller tip rockers you will find that most of these require a larger stud diameter (a good thing) and also use poly locks.

These can easily be retrofitted to stock pontiac heads (with screw in studs) by simply installing stock screw in studs for a big block chevy.

With this done your rocker arm choices become more plentifull. Only difference is that with big block chevy rockers you will actually have to adjust the valve lash like a typical chevrolet motor etc....again this becomes necessary anyway when aftermarket camshafts come into play,,,since the base circle is generally smaller, which makes an adjustable valvetrain necessary.

With that said,,,as you mentioned you can get into different ratios from 1.5 up to 1.65. Pontiac even installed 1.65 rockers from the factory on the 69-70 ram air IV motors.
As far as whether your motor would benefit from it depends on alot of things. Some motors respond to them only on the intake side and others on the exhaust, while some motors respond well to a complete set. Usually what this means is the camshaft isn't optimized for the combination.

It's a great way (cheap and easy) to increase the lift of a camshaft of an otherwise stock motor though.

Best advice I can give would be to buy a set,,,,and experiment with it either on the track or on a dyno to find out what the motor wants.

What you may find though simply going from a stock stamped steel to a well made machined aluminum or chrome molly rocker is that the ratios will be more accurate and more consistent,,,so even staying with the same ratio but a better quality made piece has been shown to improve power. It doesn't have to be a roller to see a power increase,,,,todays stamped steel rockers are made with more precision and better quality control...
The stock stamped steel 1.5 ratio pieces from 30-40 years ago have been shown to have ratios as low as 1.4 and many variances in between. They were never very consistent. Hope that helps.

[Bandit400]

Thank you for the help. I wonder if I should use something "better" than stamped steel rockers arms. The engine is not stock:
The 400 is bored 30 over has and has forged domed pistons (9.5:1), molly rings, cam is .476in lift (CompCam270) advanced 4 degrees, the heads are ported and polished Pontiac 6X, Hedman headers, Edelbrock 625 carb and alum intake, ACCEL ignition with MSD6A, and it's balanced and blueprinted.
Unfortunately only stock push rods were in stock at the time of the build some years ago so I always planned on getting Lunatis or something better later plus figured it would be a good time to do the rocker swap.

[Firebirdjones]

Thank you for the help. I wonder if I should use something "better" than stamped steel rockers arms. The engine is not stock:
The 400 is bored 30 over has and has forged domed pistons (9.5:1), molly rings, cam is .476in lift (CompCam270) advanced 4 degrees, the heads are ported and polished Pontiac 6X, Hedman headers, Edelbrock 625 carb and alum intake, ACCEL ignition with MSD6A, and it's balanced and blueprinted.
Unfortunately only stock push rods were in stock at the time of the build some years ago so I always planned on getting Lunatis or something better later plus figured it would be a good time to do the rocker swap.

If you do a rocker swap then good pushrods are a must. You will find the new aftermarket rocker arms have a hardened area for the pushrod,,,and this will chew up a stock (soft) pushrod.

You will need a good hardened molly pushrod.
I would go with something other than the stamped steel if you have the money. A full roller rocker not only has more accurate ratio's than the stock stamped steel,,,,but the reduced friction reduces oil temps and valve guide wear. They generally give a few HP as a result.

My only concern at this point would be piston to valve clearance. Since you say the motor has been rebuilt and things changed,,,knowing your piston/valve clearance may be a concern.

[Bandit400]

It's been 11 years since I was into cars and I have forgotten a lot of the little I did know.
Could you possibly direct me to some push rod and rocker suggestions so I can look in the right direction? I am thinking it's worth getting something better than stamped steel and spending the extra $$

I'll have to double check but after a quick check on the internet I think my cam specs are actually 270 int 270 exh / Dur at .050: 224 int 224 exh / Lift: .476 int .476 exh / Lobe separation angle: 110

[Firebirdjones]

It's been 11 years since I was into cars and I have forgotten a lot of the little I did know.
Could you possibly direct me to some push rod and rocker suggestions so I can look in the right direction? I am thinking it's worth getting something better than stamped steel and spending the extra $$

I'll have to double check but after a quick check on the internet I think my cam specs are actually 270 int 270 exh / Dur at .050: 224 int 224 exh / Lift: .470 int .470 exh / Lobe separation angle: 110

Thats a great street camshaft for a 400, just a little bigger than the original 068 cam that I run.

As far as pushrods,,,,I prefer the 1-piece design,,,,a few different companies make them,,,comp cams is one if you want to keep everything from the same manufacture as the cam.....they also make quality chrome molly full roller rockers, these are pricey. Another chrome molly rocker would be Crower,,,,but I'm not sure they make a pontiac version.

For less expensive full roller rockers you could go with an aluminum design. These are not as strong but with that mild camshaft your spring pressures shouldn't be that high anyway. This will also help with the lifespane of an aluminum roller rocker as well.

Choices are endless here with aluminum,,,but one of the brands I like when it comes to aluminum would be Harland Sharp.

[Bandit400]

Thank you again. You seem to be quite versed in Pontiacs.
I talked to a couple guys and now am thinking about using roller tip only steel rocker arms and Comp Cam pushrods since full rollers might be overkill for a street engine. Sacrifice some performance that could be gained from full rollers but still better than what it had, i guess..

[Firebirdjones]

Thank you again. You seem to be quite versed in Pontiacs.
I talked to a couple guys and now am thinking about using roller tip only steel rocker arms and Comp Cam pushrods since full rollers might be overkill for a street engine. Sacrifice some performance that could be gained from full rollers but still better than what it had, i guess..

It will be better than a 30 year old stock stamped steel,,,as I mentioned those ratio's were all over the place.

The comp cam roller tip rockers have accurate ratio's. They even make a 1.52 ratio in this style rocker for pontiacs. They are pretty cheap too.

Just remember,,,hardened pushrods are needed for these rockers,,,they will chew the heck out of a set of stockers,,,,lol. Glad I could help. Cheers.

[STL2SLO]

You have to grind the heads to install 1.65"s. Ask me how I know, lots of bent pushrods. I used to have the tool to do it. Spotts Performance used to sell this tool but I don't know if they still do.

[67CamaroRSSS]

Back in the day (I'm talking 30 years ago) the quick and easy way to get more lift and duration out of a Chevy engine was to use Pontiac rocker arms. Chevy = 1.5; Pontiac = 1.6 with long slots.

[LS2Tuner]

No need to spend the money on a Comp. rocker if your strapped. Also with that baby cam it would make it a little over .520 lift you should have ample piston to valve clearance. Specially since it's advanced 4* because Comp already grinds 4* of advance into their cams.
Also remember that most aluminum bodied roller rockers won't fit under stock valve covers.


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[Firebirdjones]

Also remember that most aluminum bodied roller rockers won't fit under stock valve covers.

I use the sneaky way,,,,I double up the valve cover gasket to fit them under stock valve covers,,,,keeps it stealthy

[LS2Tuner]

I use the sneaky way,,,,I double up the valve cover gasket to fit them under stock valve covers,,,,keeps it stealthy

I've done that before also. The way I buzz the shit out of everything though most get stud girdles these days so it would take a triple set...........

[Firebirdjones]

I've done that before also. The way I buzz the shit out of everything though most get stud girdles these days so it would take a triple set...........

Ouch,,,,that would take alot of gaskets

[Bandit400]

Also remember that most aluminum bodied roller rockers won't fit under stock valve covers.

Will 6.5 Stamped steel fit under stock valve colvers? ...I like to keep mine looking mostly stock.
A Speed shop looked them up and said that Pontiac rocker arms are either stock 1.52 (called ~1.5) or 1.65.
Originally I thought there were also 1.6s available.

[LS2Tuner]

Will 6.5 Stamped steel fit under stock valve colvers? ...I like to keep mine looking mostly stock.
A Speed shop looked them up and said that Pontiac rocker arms are either stock 1.52 (called ~1.5) or 1.65.
Originally I thought there were also 1.6s available.

Yes even the stamped steel roller tip rockers will fit fine. All you need to do is install them on both In. and Ex. on 1 cylinder. Roll the motor over by hand to full lift on both rockers and take a pry bar or big screw driver and push the valve further open to check for clearance. I'm sure all you have is a single valve springs that you'll be able to compress by hand.

[Bandit400]

thanks. LS2Tuner, BTW I like that avatar.

[Firebirdjones]

On the stock valve covers what I find,,,even if the camshaft is a mild one,,,,that the poly locks are what may hit the covers because they are somewhat tall. An extra gasket will fix that.

On my fathers motor we just built, with a 1.5 rocker,,,,he actually had the pushrod side of the rocker hit the valve covers in a few places and dinged them. That was with the covers already doubled with gaskets........ With the old .600 lift solid flat tappet it never did that but this new .65x hydraulic roller camshaft they did. We ended up with machined aluminum spacers about 1/4 inch tall,,,,hardly noticable under the fat valve cover lips.

[67CamaroRSSS]

On the stock valve covers what I find,,,even if the camshaft is a mild one,,,,that the poly locks are what may hit the covers because they are somewhat tall. An extra gasket will fix that.

On my fathers motor we just built, with a 1.5 rocker,,,,he actually had the pushrod side of the rocker hit the valve covers in a few places and dinged them. That was with the covers already doubled with gaskets........ With the old .600 lift solid flat tappet it never did that but this new .65x hydraulic roller camshaft they did. We ended up with machined aluminum spacers about 1/4 inch tall,,,,hardly noticable under the fat valve cover lips.

Al spacers painted Chevy orange is what I used to do back in the street racing days to clear roller rockers and poly locks. Only the real astute observers noticed. You can also ding metal valve covers with a ball peen hammer where things touch. Most folks don't notice that they are evenly spaced about the rocker tips. Tell them that they are old and messed up. I used to be real good at stealth....