pwrtrip75

iTrader: (8)

Ok... im rebuilding my 5.7 in my 99 vette.... just honing it, re-ring and bearing. (had 160k on it).
I have an extra cam im using... comp... 224/224 .580/.580 112.

Option 1. Use the 5.7 heads that came on it, i'll port them a little.

Option 2. Use a set of 706 5.3L heads..... also porting them a little.


----Both will have stock valves.... different springs of course.


My question.....It would be nice to have increased compression to take advantage of running it on E-85..... but the 5.3 heads have smaller valves..

So which ones would be better? 5.7 heads at stock compression and flow a little more... Or the 5.3 heads that flow a little less but have more compression?

On E-85 which one wins?

Car is just a daily driver.....probably never have sticky tires on it, and its an M6.

garygnu

I would use the the heads that came with the engine,better flowing.also do a good valve job on them.you can get a set of low mileage 241s for less than $100.

massls1guy

iTrader: (9)

If you're going to swap heads I would say get Stage 1 CNCd 243's or 5.3 Stg 2.5's from TSP. Both options are a bit over $1k but I think you will be happier with the results. You will get all new valves, good springs for that cam, new seals & guides, all good to go. I would get a 62cc chamber either way.

pwrtrip75

iTrader: (8)

Sorry...you obviously didnt read what I wrote. Im using one of the 2 sets of heads i have with stock valves (options 1 & 2). Im not putting a lot of money into this project. Its just a daily driver. I already have a new set of 918 springs, and seals. Stock valves work just fine. All im going to have into these heads is roughly $200. total, Springs and seals.

wytry

iTrader: (6)

Keep the stockers.

massls1guy

iTrader: (9)

Sorry, I guess my response was off topic. I did read what you wrote. I went a similar route as you putting the heads together myself and I have a similar cam. In retrospect I think I would have been happier with a budget CNC'd head. I see where you're coming from though, my suggestion doesn't fit into your plan.

synisterC5

take the 2.00" intake valves out of your LS1 heads and bring them to a machine shop with your 706 heads. i just did this on my 99frc and the machine work was very inexpensive(pm me if you want the name and # of the shop).
If you have the money then buy some cnc'd heads off one of the sponsors here, but if your like me you have more time than $$$. My heads were hand ported, flowed very well, and were Cheap!

garygnu

make sure your valves don't leak.pure some water down the runners and look for leaks around the valves.

1FastBrick

iTrader: (16)

Like synisterC5 said Since you have both heads If your looking to bump the compression use the 706 heads give it a nice clean up and have the Valves installed from the 5.7 heads. They use the same seat you just have to get them cut and a valve job for the larger size. I would assume since your basically rebuilding this your already gonna spend the money on a valve job any way... Food for Thought

http://www.performancetrucks.net/for...d.php?t=434396

pwrtrip75

iTrader: (8)

I usually do the valve jobs myself. I'll look and see what it takes to get the 2.00 valves in the 706 heads. (machine shops around here are either unreliable or take forever). How does the larger valve in a smaller combustion chamber work? How does the shrouding hinder the flow vs. the smaller valve during lower lift?

TRANS-DAD

iTrader: (1)

Just use the stock head w/a valve job & have them milled to obtaine the same compression as the 5.3!!........you'll never have p to v clearence prob. w/that cam!!

1FastBrick

iTrader: (16)

Well If you used a larger valve on a smaller bore you get a little bit of shrouding. I Asked Richard @ WCCH about this before geting the heads done on my little 5.3. He Tested them with the 2.00 valve on a stock 5.3 bore and in that case he was seeing valve shrouding and reduced flow on the bench. On an LS1 Bore you would not have that issue.
I know on certin LS1 castings you have to be carefull when opening up around the Valve stem are. I have not heard any thing negative about porting the 5.3 castings.

pwrtrip75

iTrader: (8)

Im not a fan of milling heads. Pushrods then wont work. I'd rather not have anything done by anyone else.


What about the actual combustion chamber? The 5.3 is smaller and closer to the valve. .220 on the shallow side and .630 on the deep side. So a lot of the low lift flow numbers I think would be more effected by the combustion chamber shrouding than the cylinder.... by putting the 2.00 valves in the 5.3 heads. Right?