[jimmy daniel]

I rebuilt my black 69 GTO stock with the 068 in the 400. Will 1.65 give it a better sounding (more lope) idle? I enjoy driving the car and it runs good but I wish it had a better sound at idle. I already have a set of Crane 1.65 roller rockers is why I ask. Thought I might add Ram Air 2.5 manifolds too and a Q-Jet from cliff. Car has 3.23s and automatic. I've decided to keep this car as its my favorite to drive and I was wanting to make it a little more fun to drive.

[aldbeir]

did you modify the pushrod holes when you rebuilt the engine to give clearance for the 1.65 rockers?

[jimmy daniel]

No I didn't.

[Donovan]

I doubt it will change the idle character. I did this on a stock 350HO with a 2800 cam. Hopefully you have good springs? I was able to get away with not modifying the holes but I mocked it up and checked first. I did this by installing the rockers and rotating the engine over by hand, then checking. My engine was previously rebuilt and I probably lucked out.

For me the idle sounded more forceful, a little more 'tuned' sounding.

There are no downsides as long as you have room for the pushrods.

[70pontiaction]

I've used 1.65s on about a dozen stock-lift cams 067, 068 & 744.
I think they all have about .407 lift with 1.5s & .450 with 1.65s.

NEVER an issue with pushrod clearance.

I think the clearance issue is when lift is over .450 with the 1.5s.

And I agree that the idle sounded a little better with 1.65s and
the power was always better - not night and day but still better.

Go for it. Even if it still sounds "stock" it'll be more fun to drive!

[tryconcom]

The 1.65 rockers will add about 3 degrees duration, and add 10% lift or (.407 becomes .447 inch lift). Higher lift helps midrange torque while added duration boosts top end power. Your power peak will rise slightly. Thats what happened when Pontiac released the 041 cam in winter/spring 1968! with .470/.520 lift(1.65 rockers) and 230/240 degrees effective duration.

[jonmachota78]

I would check the retainer to seal clearance too

[Tim Corcoran]

I don't think going to 1.65's will change the sound of your engine enough to even notice. I ran both 1.5's and 1.65 rockers with an 068 in a 428/441 and didn't notice any difference in the idle. If you want a meaner sounding idle you will need to go with more duration. Then you will loose streetability and the car will go slower unless to get high stall converter and improve traction. X2 as stated above regarding pushrod clearance thru the heads.

[jimmy daniel]

Originally Posted by Tim Corcoran

I don't think going to 1.65's will change the sound of your engine enough to even notice. I ran both 1.5's and 1.65 rockers with an 068 in a 428/441 and didn't notice any difference in the idle. If you want a meaner sounding idle you will need to go with more duration. Then you will loose streetability and the car will go slower unless to get high stall converter and improve traction. X2 as stated above regarding pushrod clearance thru the heads.

I wish now I had put it a slightly better sounding cam when I had it rebuilt. I love to hear that choppy idle in a good looking street car that still drives good

[dmac]

The 1.65s will have a little more effect in a 400 than they would in a bigger engine. I say that if your springs are up to it and the pushrod holes can handle it, go for it. With the relatively low lift of the stock cam, adding 10% more lift may be possible with no changes to your set up.
Check your receipt from the rebuild or with the machinist to verify what springs you have now.

[MCronkGTO]

You can "tune" for a more choppy idle. A set of chambered mufflers (Flowmasters etc...) and playing with the timing and mixture you can "simulate" a little more chop in the idle. It won't be as much as doing it with the camshaft but the mufflers and tune will make it sound like a bigger than stock camshaft.

I have heard a 2 barrel 400 in a late 60's Catalina with flowmasters sound like a "built" motor! LOL!

Mark C

[trailwing]

Will they fit under your valve covers with poly-locks?