LT-1 Head porting. Help Please.
TECH Resident
Joined: Jul 2009
Posts: 772
Likes: 0
From: Bahrain
Be careful with the exhaust ports when trying to expand them. You don't know how thick the walls are (neither do I) and can carve into a water jacket.
Just blend the edges of the outlets, if you feel them, they seem to be cast inwards, like a slight necking. Nothing but shaving a tiny bit. Mirror polish the port if you can, smoother the better.
Just blend the edges of the outlets, if you feel them, they seem to be cast inwards, like a slight necking. Nothing but shaving a tiny bit. Mirror polish the port if you can, smoother the better.
I give kudos for guys that want to try DYI such as head porting, but as everyone has pointed out, its just not opening up an area, there are Flow Dynamics involved that you must understand.Again that is why there are professional porters out there, a lot of people say they ported their heads, put the motor together and say it ran great, but never did a before and after, there was a so called speed shop around here, they guy ported the crap out of LT1 heads, they looked good, but on his own car,the after, his car ran 3/10's slower and so did some of his other customers...so beware..
I give kudos for guys that want to try DYI such as head porting, but as everyone has pointed out, its just not opening up an area, there are Flow Dynamics involved that you must understand.Again that is why there are professional porters out there, a lot of people say they ported their heads, put the motor together and say it ran great, but never did a before and after, there was a so called speed shop around here, they guy ported the crap out of LT1 heads, they looked good, but on his own car,the after, his car ran 3/10's slower and so did some of his other customers...so beware..
What bout Gettin them shaved though? I was thinkin about that The Other Day. Get them cut to boost the Compression, but i didnt know if i would need to cut the intake too?? any advice on that??
Im Not Trying to Brag Cause i thought the School Sucked but I went to Wyotech and I mean they did Teach us alot in the Chassis Fab Class about P&P and I also took the Advanced Cylinder head Class at Powerhouse Performance down the road from the School and I mean i have done a few Mods to some heads. But Like i said i am not Hogging out these heads I am Just Pretty much going to Smooth them up.
What bout Gettin them shaved though? I was thinkin about that The Other Day. Get them cut to boost the Compression, but i didnt know if i would need to cut the intake too?? any advice on that??
What bout Gettin them shaved though? I was thinkin about that The Other Day. Get them cut to boost the Compression, but i didnt know if i would need to cut the intake too?? any advice on that??
Teching In
Joined: Feb 2008
Posts: 4
Likes: 0
From: Tomball, TX
lotsa feedback on this thread. HA. I do Have Experience porting and i Do already Have a compressor and a Die Grinder and bits. I have just never done a Set of LT-1 Heads mostly just Steel SBC heads and Some Old Buick 215 Heads. I, Personally, wouldnt use a dremel, but i have alot of resources backing me. i Can do this Work Was just wondering if there was any specific things that i would need to know. But Im not going to Flow These heads but Im Not Going To Go That Crazy on them, Its not like were cuttin out the Seats and putting bigger valves and im not Grinding on the Bowls or anything, but If you guys say that there wont be much Difference then i wont waste my time.
I attended the School of Automotive Machinists and took both, the block and head courses and the bowl is the most important part of the whole port, other than the valve job...its very hard for the beginner to actually do more good than bad without a flowbench...a dremel i guess could get you by since you do not own an air compressor and the trimmings...but the school issued us huge milwalkee electric grinders that have a 1/4in. collet and they use 1/4in. shank carbide burrs with various tip shapes and sizes...i would say send the heads to a shop...
I really want to go to S.A.M. but my GI Bill will not pay for the whole thing like it would a regular university. So I would have to come out of pocket on a pretty large portion of the school. I also have the option of getting student loans but I'm not a big fan of getting myself into debt. Where do you work now? Did SAM help you get a job?
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you can at least safely mill .03 without machining the intake surfaces. i use layout ink like dykem, and scribe the gasket port shape to the heads. i just use the outter most 2 bolts on the exhaust gaskets, and wrap masking tape around the 2 bolts until the diameter fits the holes in the gasket snugly. this will center the exhaust gasket perfectly for scribing. the intake gaskets should have little plastic dowels and center themselves. this gives very define lines to work to. there is a lot to take out to match the exhaust. not so much in the intakes. i took a ton out of my exhaust ports an didnt hit any water jackets or other problems, and thats blending into 1.600 exhaust seat. so, if you're careful, there should be no problems.
TECH Enthusiast
Joined: Jun 2002
Posts: 634
Likes: 0
From: In the garage fixing LT1
you can at least safely mill .03 without machining the intake surfaces. i use layout ink like dykem, and scribe the gasket port shape to the heads. i just use the outter most 2 bolts on the exhaust gaskets, and wrap masking tape around the 2 bolts until the diameter fits the holes in the gasket snugly. this will center the exhaust gasket perfectly for scribing. the intake gaskets should have little plastic dowels and center themselves. this gives very define lines to work to. there is a lot to take out to match the exhaust. not so much in the intakes. i took a ton out of my exhaust ports an didnt hit any water jackets or other problems, and thats blending into 1.600 exhaust seat. so, if you're careful, there should be no problems.
This has been my experience also. My machine shop told me the LT1 exhaust is where most of the gains are, so I went pretty far above the short side radius and did some nice smooth bowl work. I used telescopic gauges to measure. Overdoing the intake areas can get you into trouble though, so just smoothing the intakes and doing a bit of bowl work is all you need since only a limited amount of the gains are there. I only use a Dremel on the combustion chambers to remove the roughness and do some polishing. The rest I do with carbide burs, sandpaper rolls and pneumatic die grinders. BTW, it's pretty hard to make them worse than stock unless you really get stupid. GM castings are really damn rough. Just smooth things off, remove the casting crap and round off the bowls.
Last edited by Speedy; Jan 3, 2010 at 06:03 PM.
