V-10 Killer

iTrader: (22)

I have a set of heads that I think are pretty nice, and am planning on installing them on my new LS2 402. But should I have the combustion chambers re-worked to optimize them for the new 4.00" bore? About how many horsepower would it be worth to do/not do it? If I'm doing it, would it be worth going from 2.055" intake valves to 2.080" valves?

383ss

iTrader: (14)

going from a 2.055 to a 2.08 isn't going to get you very much at all. I would stay with the smaller LIGHTER valve. I went from a 2.02 to a 2.08 and ONLY gained at .550+ and that was minimal. with a cam in the low .6XX range or less you aren't going to get any gain.
as far as the chambers, if you don't go to a bigger valve, it won't do any good to get them opened up to the bore. again from my experience, I made 550rwhp on a 408 with 2.02 valves and stock sized chambers. opening the chambers is just going to get you less compression.

V-10 Killer

iTrader: (22)

Everything I needed to know, thanks a lot

baezi z06

iTrader: (2)

old threat....

is there not better to open up chambers to 4."bore, though iīm not changen Valves, ?
must be better airflow around the valves....

got 402cid -8cc dish Wiesco and gona use for now .06" GM 6-6.2l gasketīs

iīm running TFs 215 cc, 3.9bore milled to 57.5-58cc and iīm wondering if i open them a little bit up for bigger bore 4.05", am i losing a lot of compression, ?
think i will be in 11.7x like itīs now,
I wante to use pump-gas.

What am i gaining i cc, ?
and what am i loosing in comp.?

Baezi

Camaro99SS

iTrader: (4)

I don't have any documented gains, but even for his 347, Patrick G had Tony Mamo at AFR massage the 205 heads out to a 4" bore to eek out alittle more flow without going to bigger ports.
http://guerragroup.com/2000TA.htm

If you're set on getting some work done to the heads, you ought to consider re-doing the valve job to optimize low lift flow. That was key for Patrick's build because the stock style intake doesn't flow much past 300cfm even if it's a ported FAST 90.

Jason

baezi z06

iTrader: (2)

hi Jason

iīm working on my car now

I juste finished milling those heads, the plan in 1st was do go from 65cc 10.95:1 to 59cc 11.6:1 in compression and use the .06" GM gaskets, but the heads now have 57.5-58cc so iīm a little bit over the compression i was set for, donīt wante to be on the edge on bad gas, because iīm running pump gas premium.

but iīm wondering if i open the chambers up for bigger bore will i loose more then i wante in compression.?

And offcourse will i gain something on the opening?

this opening is something iīll do my self, here where i live there is no pro shop that can do the valve job and no flow bench, so iīll use the TFS 215ccīs stock valves.

so should i run the car whith 11.7x:1 and see how it goes on the pump gas or open the chambers up.?

thanks

Baezi

DSRE

iTrader: (7)

You can always cc the chambers, then take out some material, remeasure, then remove some more till you get to your desired comp ratio but you need to be carefull obviously, You need to find out what your Dynamic compression ratio is, 8.5:1 for most is about max on 91 octane unless you have a really good tuner, here is an address so you can find out what that is, for your DCR always use your cams Intake valve closing number on the seat not at .050

Paint_It_Black

iTrader: (1)

DCR is over rated.

baezi z06

iTrader: (2)

iīm running Shell V-power at all time , on usa standard itīs 93-95 oct.i think.

if i can get away whith 11.7x:1 - 11.8:1 on V-power then i will, but iīm not ready to throw the heads on, just to take them off again if that is too much compression for the car.
but iīm using it as a street car and a lot on the track, so i wante to take as much out off it as i can.

i was told whith 11.6 CP is a good spot for me, but 11.75 iīm on the edge, but then i would be weak for bad gas. So.....

but that chambers opening is that not ideal, are there no gains there, whith stock valves...?


btw iīm running a big cam TSP texas giant

Baezi

ls2 bait

iTrader: (11)

id be more concerned with ptv clearance at this point then anything else.

baezi z06

iTrader: (2)

the PTV clearance is not close., was 6mm, 0.234" before milling, and we tooke 0.035" off the heads., so that should leave me whith, 0.199" clerance.
iīve got -8cc dish pistons.

my concern now is: am i ok whith this compression on premium pump gas, or am i pushing it

but if i open up the chambers 4" how much should i loose in compression, or how much increasing ccīs.?

thanks

Baering

ls2 bait

iTrader: (11)

damn i dont know how that is. i thought the tsp giant cam was in the 24x/25x durations. mine with 10cc dish pistons, 60cc heads, and a 247/254 on a 114+4 was less then half of that.

baezi z06

iTrader: (2)

yes the specs are right, but before i milled the heads down i talked to Tsp and they said i should not be worry about the clearance but i decided to measure it , to be save. but i havenīt measured it again after milling, but it was so far off so i wasnīt stressed, but i will before i close it up.

my camīs specs are 248/254, .615"/.622 -114

and like i said iīm using .06" gm headgasket 4"bore
-8cc dish

my heads where 65cc when i measure the clearance 0.234"
and then i tooke .035" off


Baering

Camaro99SS

iTrader: (4)

Yes you would technically lower the compression ratio by making the combustion chamber bigger, but going from a ~3.905" to 4" bore will be a very small change, like maybe a tenth or 2 of a point. Someone with experience could help you more.

In theory yes, but that varies from basic head design and combination. For yours you could gain maybe 20hp+ with your stroker and big cam setup. Again someone who has the experience to back this up could help you better here.


Yes. You'll be fine on 93 octane, assuming Iceland uses the same ratings as the U.S. for measuring octane: (R+M/2). Also, with a cam that size and wide overlap to bleed off some cylinder pressure, that will put you farther into the safe zone on pump gas. You'll need a good dyno tune to be safe and to maximize what you have though. If you don't have the means to tune it in Iceland, TSP could get very close with a mail order tune since you're running one of their cams.

Jason

baezi z06

iTrader: (2)

hi
and tanks for replying....

I bought the LS2 402 short block last spring from TSP and have bought some of my mods parts from them too.
And Jason@tsp has been helping my whith the Tune threw the internet, using my friends HP-tuner to take logs for him, and hopefully he will help me go furter whith it.
I have been making few changes now;
Fast 92mm/ls2 90mm TB and ported them both me self , i was running ls6 combo.
ported/polished my z06 85mm MAf
SLP air bridge
bought set off Kooks 1"7/8 headers, was running kooks 1"3/4
3" electric cutouts
And off course now milling the heads from 65cc 10.95:1 compression to what they are now 57.5-58cc should leave my whith 11.7x:1 in compression if i donīt open them up.

so i will need to update the tune...

so now i have to decide, should i keep the heads whith that 3.9" opening or open them up.

iīve been serching the forum and i canīt seeme to find any compare before and after chambers opening, but it must be better to open the chamber up rather then not, but i is much less of an change for me going from 3.9" to 4" then for maby bigger cubes like 427 or bigger.

Baezi