Author Topic: upgraded heads and cam on gmpp 350/290 hp do need rejetting/ rod change  (Read 2490 times)

Offline slowpoke

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I have a carb from a 1979 buick that I bought a rebushing and rebuild kit from cliff and it was re-jetted and new secondary rods installed to match the crate engine.
I have since put on a set of brodix IK-180 heads and changed cams to a comp cams 262 duration cam and 1.6 roller rockers and with the 1.6 ratio I am around .500 lift 
my truck runs alot better now but my spark plugs are white as snow but no rough running issues it seems a little cold natured now  . but i have been adjusting on the choke.

Would I need to upsize the jets and change the rods again to match the new setup.

Brodix said i should be in the 425 to 450 hp range and comp cams said near 425   that sounds a little high to me but i would like to make sure I am jetted correctly.
I will be in mount vernon next week for training at the ARIEL natural gas compressor factory. I could stop by and pick up the parts if they are needed.

Offline Cliff Ruggles

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Re: upgraded heads and cam on gmpp 350/290 hp do need rejetting/ rod change
« Reply #1 on: November 27, 2012, 04:48:09 AM »
Impossible to read plugs to determine the correct jetting.

Tune for best throttle response, smooth off idle, and best fuel economy. 

The plugs in my 455 are white to light tan when removed, you'd guess it was too lean, but the tune is dead on the money in all areas.....Cliff