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View Full Version : Bigger Turbo syndrome....Winter swapout of 67's to 76's?



chasgiv3
10-17-2011, 05:04 PM
I've been contemplating swapping out my 67's with perhaps 76's. They should bolt right in without any major tweaking of the piping and should provide me a little more sauce on the big end. I just don't know what I'll have to change out to help it breathe a little better to support the power.

Plus just for yucks I'd like to get my RWHP numbers over 1000.

xpndbl3
10-17-2011, 08:26 PM
ever get it to leave on bigger boost yet? Twin 76s, why not lol!

Wrencher
10-17-2011, 10:14 PM
How about fueling? Are you still on the edge there?
Then a whole new tune session with Jim :)

xpndbl3
10-17-2011, 10:17 PM
nothing a magnafuel pro tuner pump can't fix LOL....get ready to hear the noise!!!! these pumps rock but definitely aren't quiet

chasgiv3
10-19-2011, 11:47 AM
How about fueling? Are you still on the edge there?
Then a whole new tune session with Jim :)
My fuel system uses dual external pumps which one of them runs on a hobbs switch. They can be replaced pretty easily if need be. Injectors again will have to be replaced with something a lot bigger. Checking on converter box solutions as well as experimental injectors that are huge. My concern is driveability after it's all said and done. Some folks I've already talked to swear by either approach but I'm sure there'll be some pain points here.

New tune from Jim is correct. Whole new map for everything with the volume changing dramatically with the new Turbos.

chasgiv3
10-19-2011, 11:51 AM
ever get it to leave on bigger boost yet? Twin 76s, why not lol!

I did leave on 10PSI on one run and it spun pretty badly. I'm not sure if it was a track issue or if my slicks are just getting too old. They did sit in my garage over 1 winter. New slicks being ordered.

xpndbl3
10-19-2011, 11:53 AM
Don't order slicks until spring you want the freshest set possible, in fact...I prefer to order them from my local speed shop who gets them direct from M/T as a matched rollout set. Slicks are a one season then sell them as used type deal to slower cars.

chasgiv3
10-19-2011, 11:58 AM
At the end of the day I could just run it like it is for next season and be pretty happy. On the other hand I could crank up the HP a bit and play a bit more next year. I'd like to see if I could make 8.69 on 17" DR's and beat MightyMouse. He still has the record. Might put me in a mag or something.

xpndbl3
10-19-2011, 12:14 PM
will it still be shooting rust out next season at the starting line too? :laughing:

Thirdgen89gta
10-19-2011, 12:35 PM
Thats the only time I've ever seen a car blow red dust ever. I can't believe how much rust that thing would blow out.

Vink70
10-19-2011, 02:33 PM
id say stick with what you have and get used to that first. Its fast, we all know its fast. If I recall you arent too shy of the 1000 as it sits now... im sure with some tweaking and little adjustments it can get to 1000.

chasgiv3
10-19-2011, 03:19 PM
All piping will be removed and coated if salvagable. Others will be replaced. I really think the motor is being choked a bit by the existing turbos. Looking at other builds they get more rwhp with less PSI due to less restriction.

xpndbl3
10-19-2011, 04:21 PM
choked by exhaust or choked by existing turbo setup?

chasgiv3
10-19-2011, 06:22 PM
Well for what I saw in other cars with exact piping as I have they seem to be putting a lot more power down with different style turbos at lower psi. Now the intake or cold side may also be an issue. Eh one step at a time.

Wrencher
10-19-2011, 11:07 PM
Intercooler?
Would the current one be a concern if you up'd to 76's?
Any tuning issues with stock PCM & low impedance injector driver converter?

chasgiv3
10-20-2011, 06:56 AM
Intercooler?
Would the current one be a concern if you up'd to 76's?
Any tuning issues with stock PCM & low impedance injector driver converter?
More likely throttlebody and LS6 intake than the intercooler.

Pro Stock John
10-20-2011, 03:31 PM
Andy E. has run 7.52@191mph with twin 76's, T4's, ~28-29 psi, at 3450 race weight.

What is your raceweight?

chasgiv3
10-20-2011, 03:57 PM
Car weighs around 3600lbs but that's a guess. Add my 285 in there and it's closer to 3900lbs. I'll have to hit up Andy for some details on his build. Sounds like he's got it figured out. I won't be running more than 25PSI on mine. 4 bolts per cylinder scares me.

2QuikTA
10-20-2011, 07:31 PM
More likely throttlebody and LS6 intake than the intercooler.

I'm by no means an expert on any of this.....that said, I would think at your power level an LS6 would be a big bottleneck? I would think most at that level are running a FAST/ect.

chasgiv3
10-20-2011, 07:56 PM
I'm by no means an expert on any of this.....that said, I would think at your power level an LS6 would be a big bottleneck? I would think most at that level are running a FAST/ect.
You may be dead on. I can't find anyone that's made big power through it. Always seems to be capped at the 1000 rwhp level. I'm asking Jim from speed to look over my setup and give me his two cents. I've almost got a guy to let me borrow his lax intake and throtlebody to test it. I don't know him that we'll but he's curious and said he'd let me borrow it for a dyno session. Anything that's a restriction to flow could be a problem. Could be a combination of hot and cold being the culprit.

Pro Stock John
10-21-2011, 07:49 PM
Jim is knowledgeable about your combo, Andy's combo, Onfire's combo and some others so I think he'd have some thoughts on what you'd need to run quicker than MightyMouse.

Andy went 8.26@167 a few years ago with twin 66's at 3600 raceweight, so you might want to ask him about that combo since it's closer to what you have right now. His current combo is solid roller, sheetmetal intake, and is shifted above 8K. His old combo was with an OEM LS7 intake fyi. I know a fair bit about his combos since I've helped him at the track a few times.

His old combo was something like:
408 cid
twin 66's
a/a
th400
coan converter
28 slick
3600 raceweight
hydraulic cam shaft
ls7 style heads
ls7 intake

hawaiian helper

xpndbl3
10-21-2011, 10:08 PM
can't really compare ls7 heads to cathedrals though, big price difference

Pro Stock John
10-22-2011, 01:44 PM
Plenty of cathedral point combos that have run as good.

If I was Charlie I'd check to see what exhaust housings he has, and I'd upgrade there if necessary but I'd also try to pull weight out of the car. Trying to go 8.6's @ 3900 is tough on parts.