SLP IROC-Z

iTrader: (14)

give me some ideas to help make my 243s flow better on a budget. porting is out of the question as i dont have a place to do it but how about 2.02/1.57 valves with stock seats?, valve job, any other ideas or should i just put them on as is?

low2001gmc

iTrader: (148)

I don't see an advantage going to bigger slightly heavier valves with no porting especially in bowl area. As for leaving as is, in part depends on cam. Stock 243/799s are generally good up to 595 lift. After that, not really taking advantage of higher lift. I have ported my own at home and even have sold many sets to budget racers. I'm no pro but detail oriented, patient, and have had good results.

Bspeck82

These engines are severely under valved and a bigger valve/good valve job will give you a small boost in upper rpm power. Could also mill them a tad for compression and ensure straightness.

I made 389 wheel with a baby cam and bone stock 799 heads with headers in 110 degree heat on an outdoor dyno. Still would gap brand new NA camaros, mustang's and challengers so I think they didnt do too bad

KCS

iTrader: (20)

IMO, a good valve job with bigger valves is the minimum you should do. Depending on the valves, you may want to see about a different back cut on the valve while you’re at it.

Summitracing

TEA has an amazing deal on bowl work; competition valve job and milling. Best deal for the money.

cino

iTrader: (28)

I’d just do a valve job and back cut on existing valves. LS1/LS6 have small bore and bigger valves may not be worth the money without some bowl work.
Stock valves, back cut with port/bowl work will bring best results for the money.
On 4inch bore, I’d definitely upgrade to bigger valves.

dreadpirateroberts

iTrader: (1)

looking at a few place's flow charts, bigger valves on a 243/799 only end up being worth 5-10 cfm. it's not like they are using a different shape port. PRC charts list like a 3 cfm gain intake, maybe 6 cfm on the exhaust side with 2.02/1.575 valves. TEA, like 10/4 i/e, i think with 2.040"/1.57". this is on top of their machine work and port shapes, which all work together to add power.

not saying bigger valves aren't worth it, but i don't think they will give you dramatic gains by themselves.

i would worry about a good valve job, blending the seats into the bowls, and milling for some added compression if you are looking for easy power. not sure how well that combined with larger valves will gain you, but i am sure combined it's worth a bit. AI claims like 20hp just doing that alone with no port job. They call it their "performance rebuild cylinder head package," but they do it with stock valves. you might gain slightly more with larger valves on top of everything.

if you're doing stuff on a budget, why not a DYI port? shave down the guide bosses, remove the rocker bolt boss hump, etc. won't be as good as a professionally researched port shape, but you should gain a little more on top of everything else.

wannafbody

iTrader: (2)

Stock valves work for a 3.9 inch bore. A larger bore would probably benefit from a larger valve.

SoCalDave

I say port them. Find a friend with an air compressor and buy a cheap die grinder and a cheap LS valve spring tool. Then you can remove the rocker stud boss lump, reduce the swirl ramp, back cut the valves and you will be ahead of the game.

Lsbmer

One word, pipemax. Here are some 243s
21.29 is 305fps , fastest centerline speed. (Double checked with water manometer) holds 218.5 cc and flows 308cfm. But the shape is what counts.

99 Black Bird T/A

iTrader: (4)

Honestly, I'd delay until the 243's cold be ported. I'm a big TEA fan. Have had TEA heads (S2 706's & S2.5 LS6) on two cars and had a total of like 20 years of use between them and like 145,000 miles of use. Quality and performance - outstanding value. Likewise, LandSpeed can do an equally excellent set.

Lsbmer

I agree if you don't have the equipment. Honestly you probably won't get over 270ish. Same on ex. With either a 243 or a 706.
but you could at least look up your combination in pipemax. Anyone and everyone that does heads has known this forever.

wannafbody

iTrader: (2)

Unless you have tons of time to waste, it's easier to get someone to cnc port them and know what you are going to end up with vs guessing how to home port a set.