question about cams and rockers

[440brian]

So, I had to build a new engine, I went with the 545 comp cam from 440 source, ported 906 heads, Arias(I think) pistons .060 over the machine shop guy ordered, I told him pump gas.
850 speed demon that ran great on my old 440. It bogs out right around 4000 if I stomp on it, but if I ease into it I can hit 6000 every time. I tried a different carb (holley 850) from another 440 that runs good on my brothers pontiac 400, it was the same. I put a different msd box on it, same. My question is the 440 source ad for the cam I bought says to go to adjustable rockers, but all the utube videos for guys that have used it used the stock rockers and had no problems. My old cam was the purple shaft .509, I didn't think this one was that much bigger. so I went with the stock rockers. I hit the track about twice a year but I still want to be able to blow the tires off when i want.

 

[beanhead]

Stock rockers with that cam is pushing it. With the spring pressure you should have, the pushrods have been known to bust through the rocker arm after awhile...as far as the carb issue, you've built a different engine so you'll have to start over with the tuning...timing, pump cams etc...the problem you describe sounds like secondary pump cam/arm needs some adjusting maybe? With some work you'll get it nailed. Sounds like a nice street engine.

 

[oldbee]

What is the current timing? Concur with the above tho.

 

[cryplydog]

Are the carbs vaccum or mechanical secondary?

 

[66Satellite47]

Just a guess, but accelerator pump tuning is required. Try different accelerator pump cams & shooter sizes. Sometimes it just takes trying a few things. I'm a adjustable rocker arm guy. Pick your price range. My old Isky 1.5 worked very well, so did my Crane Gold's. My current version is Hughes. My opinion.

 

[lewtot184]

probably multiple issues. those stock rockers will break at that level of performance. too much preload? going to a good adjustable will reduce retainer to guide clearance. you need to re-think the valvetrain while looking for other issues. valvetrain failure can be catastrophic.

 

[slepr1]

I just switched out my 509 cam for a cam and rocker set up from Hughes. BTW, that used 509 cam is worth some money if in good shape. I recommend anyone who can afford it to get their new rebuilt engine dyno'd. It will properly break in the cam and tune it up perfectly while doing a couple hits. My 440 did 485HP with a Holley 750 vac sec with all my mods.

 

[threewood]

What fuel pump are you running? Have you verified pressure at the carb under acceleration? Float levels correct? Maybe not an instantaneous bog but low fuel psi will cause it.