Half inch lift cam and stock rockers?

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Dave-R
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Half inch lift cam and stock rockers?

Post by Dave-R »

Seeing as I have decided to strip this 440 engine in my 69 Plymouth down and start from scratch I want to pick a decent MILD camshaft for it.

The existing ("sixpack" I was told) cam in the engine does not seem to have quite the lift a sixpack cam should have. So I want to replace it with a mild (Hot street) Hughes hydraulic.

I don't want a big cam like I put in my old Challenger and I want to keep the stock rockers.

But Hughes being Hughes their cams have massive lift for the duration. So my question is, will the stock rockers take a fast half inch lift OK?

The cam I am looking at is 224/228 duration @50 with 0.518"/0.530" valve lift with 1.5:1 rockers. Probably slightly less from what I hear about stock rockers.
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Pete
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Re: Half inch lift cam and stock rockers?

Post by Pete »

The biggest issue will be Valve to Piston Clearance if you have flat top pistons with no valve reliefs cut in them.

The biggest with stock 1.5:1 Ratio I could get in a flat top Piston was a .503 and maybe a .509...
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Re: Half inch lift cam and stock rockers?

Post by Pete »

I think from memory (no research!!) that a 6 pak cam was 0.484" lift, so I am not convinced it is worth all the effort - unless you just want to pull the engine apart for the hell of it - personally, I would rather drive it and save my money!!!

Say someone with 3 broken cars at the moment!!!
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

Six pack cam was 0.450 lift on the intake. The one in my engine measures at 0.441.

Yes pistons have valve reliefs.

The question was will stock rockers be OK at just over 0.50 lift combined with a high rate of lift. ;)

Engine is apart anyway because it's full of sloppy mistakes.
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Re: Half inch lift cam and stock rockers?

Post by Pete »

I cannot comment - I have always used aftermarket Roller Rockers when I have exceeded 0.500" Lift.
I think stock ones are the weak link - even proper 6 pak ones. It all depends on what you want to achieve.

Dave Billadeau will probably be able to advise.
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

Pete wrote: Mon May 18, 20 9:01 am It all depends on what you want to achieve.
Well what I want to achieve is to not have to spend big money on a complete new valvetrain if I don't need to.
I'm a pensioner now you know! :lol:

I'm not building a race car. This is a resto-mod street car that I would like to be just a little hotter than standard 440 sixpack instead of sounding like the motor home the block came out of.
Like you say if I were fitting something with 0.55" lift and above I wouldn't hesitate to fit roller rockers.

Sod it. I think I will chance it. 8-[
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Re: Half inch lift cam and stock rockers?

Post by Pete »

Do you know if you have actual 6 Pak Rockers (I am sure you know these are heavier duty than standard ones, as a Push rod penetrated one during the testing of the A12 cars).

I understand the cost of something like Comp cams rocker set up let alone Harland Sharp ones!!!

It may be worth checking Mancini to see if they do up-rated Stock style ones as that may be a more economic compromise...

I am sure you will be fine...
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

The rockers do seem to be quite heavy. I will look into that.
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

No difference in the 1970-71 rockers 6bbl or 4bbl
I don't have a thickness measurement for the steel used on the 1970-71 rockers or know if they have factory markings or not.
They have a slightly oval hole where the rocker shaft runs through.
MP parts did list stronger aftermarket rockers.

The steel used on '69 A12 rockers is 0.14 thick and they have factory markings on them.
They have a rounder hole where the rocker shaft slides through.

The ones I have do not have any factory markings. They do have the more oval hole for the shaft. They are 0.14 thick.
Possibly aftermarket?
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

After some digging around I found out another couple of things.

The factory stamped steel rockers are indeed 1.5 ratio. The "closer to 1.3 ratio" thing is a myth probably started by someone measuring lift on hydraulic lifters.

The later 440's (like this one) got the same HD rockers as stock that Mopar Performance sells now.

Guys have raced with cams around 0.55" lift with these rockers no problem. The key is to not go OTT with the spring pressure.

So I will stick with them I think. Saves £1000 for a set of adjustable rollers and new hollow pushrods that I have had bend in the past.
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Re: Half inch lift cam and stock rockers?

Post by Blue »

My late mate ran the old MP 509 on old stock rockers. He did stick a pushrod through a couple over time so we'd just pull another used one out of the bag of them we took to the track. If you are using the thicker ones you'll be fine I reckon. On one of my old six pack piston 440s, we did get the MP .590 cam in there with sufficient clearance, so you won't have an issue there. You might need to machine the heads for teflon seals to get spring and retainer clearance if you need a double spring, single with a damper is usually ok.
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Re: Half inch lift cam and stock rockers?

Post by Pete »

Sorted! :read2: :read2: :thumbright: :thumbright: :thumbright:
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Dave-R
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Re: Half inch lift cam and stock rockers?

Post by Dave-R »

Not getting any communication from Hughes Engines anyway so am going for the COMP Cams Xtreme Energy 21-224-4 which has just under 0.5 inch lift.

Playing safe. :thumbright:
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Re: Half inch lift cam and stock rockers?

Post by Pete »

:thumbright: :thumbright: :thumbright:

Hughes are incredibly hard work.... as can be ATI....
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Re: Half inch lift cam and stock rockers?

Post by Blue »

Dealt with Hughes a few times including talking to the man himself, can't say I found it difficult at all TBH.
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