gspfunk

You beat me to it....The thermactor bumps in the exhaust ports of the 3bar GT40's are the biggest hinderance of airflow. Get/borrow a Dremmel and you can grind them out pretty easily. I did my E7's w/ my Dremmel and the grinding/sanding kit.

SmokumsTheBear

Where exactly is the thermacator bump located on the cylinder heads?

gspfunk

Look into the exhaust ports. The bumps that stick up are the thermactor passages. Grind them down to match the rest of the runner and they will flow a lot better.

92hatchLX

Are the thermactor bumps just solid iron or is there anything inside the bump? Also, if you didn't see my post I found a site that's got rebuilt GT40 cast irons for $629 (for a pair). Sounds like an alright deal, it's right under half the price of AFR's.

I3atR!ce

the thermal bumps are solid, they were used as a way for ford to mark where holes needed to be drilled for there emissions channel.

AdderMk2

you are correct.. explorer heads will offer a lower compression ratio. but you can get them milled to have 64cc chambers, like the cobra gt-40's, which will bring your compression ratio to 9:1

nitrous_bob

don't believe the masses, the real 40's are the best choice hands down.
i wouldn't even consider p's unless i got them free, and they were already ported.

my buddies full weight '92 GT on 125 shot, 4.10's, slightly decked 40's w/ ported exhaust (barely, just cleaned up really) box stock 40 intake and t5 went 11.80's

i personally heve never seen real good numbers from p heads.

thats my opinion.

samseed101

You don't think they will be too restrictive? I know anything is better than stock E7, but I don't want the heads to be a big bottleneck. Only other decision I have to make...do I want cast iron or aluminum. Guess that depends on what deals I can find.

gspfunk

Why spend 650 on reman'd heads when you can buy some used for 300 and have a machine shop clean them up for cheap? That's just way too much IMO. The thermactor bumps have holes in the middle of them, or at least my E7's did when I ported them. The holes are where the smog pump puts in fresh air to help burn off excess hydrocarbons....or something along those lines.

nitrous_bob

no they are no where near restrictive. i am looking for iron gt40's right now.

if you put a total of $600 into a set of $300 40's they will outflow/outperform ANY box stock aluminum head on the market.
now if you happen to score some ported aluminum heads from someone hardluck , then thats a different story, but i sold some aluminum eddy heads, the 6037's , sold for $1200 on ebay they were done pretty nice , but you won't get them cheap. they sell too fast.