Blumpkin55k

i origanlly planned on using some gt40ps i spent a ton of money on, but

now that ive been looking at other forums they say it will bottle neck the 347.
iam wondering if i could sell the gt40ps and spend probly the same amount of

money on some aluminum heads. this is my first engine build and not sure

what kind of heads to get. I also dont know what cc that would best fit my

combo... ive heard 170s or 185s. any feed back would be great thanks.

Duncan_GT

GT40p's are good budget upgrades for stock 5.0's. But yes, I would definitely look into getting a nice set of aluminum heads, the biggest reasons being weight savings and aluminum dissipates heat much better than cast iron. For a 347, I would look more into the 185cc range. That is what I would recommend for a 351w, and you are only 4 cubes short of that.

Blumpkin55k

ok will do the only thing that would stop me is i have 700 into the gt40ps and probly couldnt get half if i tried to sell them especially where i live haha

primetime5.0

High ports.

tinman

I will also recomend a head with at least 185cc on the intake port.
How much cam you are using is also going to enter into it.

Duncan_GT

Damn dude, thats lot of money for iron heads lol. What all have you done to them?

Blumpkin55k

i might just port the gt40ps for now, but they costed 250 from the junkyard then i bought a spring kit for 150 then took them to a machine shop to get a valve job and resurfaced which costed over 500 i think so actually 900 damn i shouldve just bought aluminum heads lol

Blumpkin55k

and my cam is a howards cam duration at 50 is 225in and 231ex and .533 lift on the intake and a .544 lift on exhaust thats is bout as much as my valve springs can handle. power band is 2200-6500.

Duncan_GT

That cam doesn't sound that bad. I would have liked to have a bit more duration but my custom cam from Comp in my 393 has 236/248 duration. Almost the same power band, but a little more umph on the valve lift .579/.579. But, my heads are Trickflow 205's and my springs can take .600 of lift.

But yeah, with the money you've spent so far on heads/springs you could have gotten a nice complete set of aluminum heads with springs and valves already installed for just a couple hundred more. I think Trickflow 170's are like $1200 complete. If you're not going to try and sell them to recuperate some funds, then I would probably port them if it were me.

Do you have your heart set on a 347?

tinman

Sounds like you screwed yourself good on those GT heads.
That cam really don't sound too bad but you could have run more duration.
185cc intakes are probably the smallest you should go with.
Whatever you do check the piston/valve clearance, you need about .100 and both inake and exhaust....