Pulling my hair out, hours to decide.....ported 289 or stock GT40 w/ roller rockers

Ok I need help to decide. Just have a few hours to make a decision here or this deal passes me buy.

Use the GT40 heads I have now and pay a machine shop 125 to outfit new springs and retainers and have a good set of heads or......

trade the GT40s to my friend for ported 289 small chamber heads.....3 angle valve job, more compression.....etc etc etc

Just have until around 4pm to decide so please chime in and cast your educated vote.

WHAT IS GOING TO MAKE THE MOST POWA!!!!!!!

 

My guess is the roller will outperform the flat tappet on such similar heads and setups.

 

Gt40 heads win it 6 to 1. They are at the ma hine shop now. Fortunately only the exhaust springs need to be replaced along with the retainers.
Should be fairly cheap.

Any head gasket recommendations? Will a regular old fel pro do the job?

 

Regular old felpro.

 

smallest bore thinnest gasket you can afford will bump the compression and help squish a bit over the old cookie cutter +.100 bore gaskets.

And like I already told you via PM.. those look to be larger diameter 1.45 - 1.5 inch beehives with at least 150 lbs seat pressure and way too much open pressures for any flat tappet short of full race mechanical that see's a quarter mile at a time. Like Scoop told you in the other GT40 thread.. you'll eat lobes in short order. Your machine shop is setting you up for disaster if they are telling you they're fine without hard numbers to back it up.

 

I read you guys loud and clear. Springs are not beehives and were removed and tested. They are only 120 closed and around 290 open pressure. The exhaust were similar but only safely would handle 470 max lift so he suggested we replace the exhaust springs and retainers to match the cam. Apparently intske sorings were right on for my flat tappet .484 lift with the 1.72 rocker arms.

 

Felpro p/n 9333. These are the O.E. expanded graphite gaskets that seal anything. They're listed as the HD 5.0 gaskets at the parts houses. I spray em with Kopper cote just as extra insurance, not that they need it to start with. Back when I first used my Canfield heads I used a set of Felpro POS gaskets (Print-O-Seal = also translates to something else) that were slightly thinner and they didn't do the job, failing after 304 months. I used the 9333's afterwards with the same heads on my 331, that was 9 years ago. They're still going strong. Even after many times having the coolant temps up in the 250* range.

 

heads

Go with the 289 heads. Port them and from what i've read do not polish, has some thing to do with atomizing I think with carbs. IMPO.

 

Hmmm...289 heads are catching up...

Still cannot beat a roller motor.

 

He can always add roller rockers to the 289 heads. But as I told him, with the block he's got, you're playing with fire adding more compression. But then again, with the larger valves added to those 289 heads, the chambers are probably "caught up" to the GT40's in chamber size. Its a dead cinch they're not the 54 ccs they had from the factory. Between the two choices, I'd say it's a dead heat as to which ones are better.

 

I voted 289 of course, got some on my 351 W.

 

Heads are on. Any tips for how to know my pushrods are correct? I colored the valve stem tips on two valves and installed rockers. Rotated engine several times working both valves. Intake shows a dead center mark and exhaust shows a slightly off center mark but not at the edge. Is that all the checking i need to do?

 

Were the lifters pumped up when you rotated the crank ?

 

Yes I think so.

 

Well "ideal" is centered on the valve stem, so that one that's slightly off is your call. The wear pattern on the tips of the stems on my 331 were slightly off and that was ten years ago. It's been fine since then. They are slightly noisy, much like a solid lifter cam, but no problems in ten years. It does not get driven regularly, 1-2 times per month, it's been to 7 grand a few times by my son, 6500 is usually my redline, that's when it stops pulling hard. Been on quite a few freeway runs at 3500-4000 for twenty miles or more.