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So I built a 408 stroker with trick flow 225 heads and an Ed Curtis custom grind cam 627/625 248/255. It also has a fast 92/92. The pistons are dished 10cc to put the compression at 11.1. I have 1 3/4 long tubes with a high flow catted y pipe. The car made through a m6 483whp and 450wtq. I'm not sure why the numbers are so low?
From: Coast of San Mateo County Between Pacifica & HMB
Combo,Combo,Combo.
Not bad results but in order, Heads a little small AFR 230s, TFS235 or
MMS235s would all supply more air for 400+ CI, Headers
Definitely small, need 1 7/8" , need true duals, or the best y merge
Don't know what that is but seen many lose 20-30 with the wrong one,
FAST 102 worth at least 10 over 92 on 400"+ CI, ported well
Another 10, as mentioned another 1.0 compression would help
That cam.
Again not bad results but those are places to look for missing HP.
Just my .02
An easy thing to do is have a cutout put on it where the y meets the I pipe. This will probably help the numbers. I have a similar exhaust setup with 1 7/8 headers though. Not sure what muffler you have but opening the cutout on mine was worth 10-15hp.
An easy thing to do is have a cutout put on it where the y meets the I pipe. This will probably help the numbers. I have a similar exhaust setup with 1 7/8 headers though. Not sure what muffler you have but opening the cutout on mine was worth 10-15hp.
cutout is a great idea. I do think with the amount of air that motor can move, there should be two cutouts, prior to the merge.
intake and exhaust changes can definitely make a big change on big cube n/a motors. i was hunting for lost power as well for a while and i found a 30hp and 23tq gain going from a 3.5 inch maf intake to a 4 inch intake and speed density tune. I still have 1 3/4 headers and i'm only 6 hp from 500 with a cam smaller than a stock c6 zo6 everywhere cept intake duration
Hmmmmmm might actually make more power with smaller cam....
My 402 makes 502-490 at the wheel 6spd and I have the opposite of everything navy blue said lollollol
Afr205s
1-3/4 headers cheap y magnaflow cat back
90-90 ported intake stock maf SLP lid
I might actually slap a smaller cam in it soon 244-248 right now
Plus side 11.7:1 CR helps
Run it at the track and see what it does mph wise.
I had an 11.25:1 ls7 with basically stock ls7 heads (minor exhaust porting), 243/256 .650" cam, mildly ported ls7 intake, 90mm tb, 1 7/8" crappy headers into dual 3" random technology cats and then single 3.5". Made 520rwhp/472rtq in a 2900lb car(with driver) and m6 which I was a bit disappointed with. Went to the track and did 110mph 1/8 and 138mph 1/4. I was fine after that
Those aren't terrible numbers considering the parts used. Get a cutout on there and watch it pick up 20HP.
TFS 235s... 11.8:1 CR... FAST 102/102... 1-7/8" headers... cutout or True Duals. It's all 5-10HP here or there but it adds up. You have at least 50HP in different heads, more compression, more exhaust, and more intake. And then 530HP isn't too bad. But with that cam, I would think 550 would be the goal.
But given the size of the cam, it looks like you don't care about perfect streetability. However, you're running cats--so streetability is a concern? If so, you could do similar power with much less cam. And you'd make more torque. So... it all comes back to combo. And less cam would make it more fun and you wouldn't be down on power. It would drive better and have more midrange oomph. The way you've spec'd the rest of the combo, this seems like the goal. But, I don't know.
Since this was bumped I will just say that with most y pipes people don't realize that the outlet drops down to 2.5 in. inside diameter. If you are going to run a y pipe ditch that junk and put a 4in. flow master merger in there followed by a 4in. Cutout.
Shitty y pipe outlet
From: Halfway back on the Highway to Hell...again!
Getting into the specs of the engine...Who, exactly figured up your CR?
A 10cc dish will not yield a 11.1 CR unless you have very,very small chambers. Based on a general thought of builds I've been associated with (used to be the bottom end machinist)
that combo would be around 10:1, give or take a few tenths.
Have a good engine build pro take a better look at your exact components and see what it really has.
from crank to piston, gaskets, true chamber size, etc.
You may have a setup ready for some boost.
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408 low dyno numbers 
