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408 low dyno numbers

Old 04-30-2016, 02:28 PM
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Default 408 low dyno numbers

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?
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Old 04-30-2016, 05:10 PM
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I suggest ditching the Y for an X.
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Old 04-30-2016, 05:18 PM
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Mustang Dyno?
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Old 04-30-2016, 07:36 PM
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that much cam needs more compression.
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Old 04-30-2016, 09:10 PM
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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
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Old 04-30-2016, 09:51 PM
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Bad exhaust is bad
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Old 04-30-2016, 09:57 PM
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Doesn't seem too bad considering. Navyblue pretty much covered it.

You have some room to grow with the intake/exhaust.
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Old 05-01-2016, 01:54 AM
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Originally Posted by LSEod View Post
So I built a 408 stroker with trick flow 225 627/625 248/255......I'm not sure why the numbers are so low?
Originally Posted by NHRAFORMULA00 View Post
that much cam needs more compression.
Originally Posted by NAVYBLUE210 View Post
Combo,Combo,Combo......Heads a little small.......FAST 102.......another 1.0 compression would help That cam......
Yeah. About 12:1 CR would be much better, keep quench in the .030" to .035" range!

102mm TB along with a 102mm Intake.....back to the dyno and rev it to 6700 RPMs

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Old 05-04-2016, 11:46 AM
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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.
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Old 05-04-2016, 01:34 PM
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You are making excellent torque and decent HP. I agree the exhaust is likely your biggest hold back.
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Old 05-04-2016, 01:50 PM
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maybe i missed it but what about your fuel injectors? you could be maxxed out?
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Old 05-04-2016, 05:03 PM
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Originally Posted by jlrz28 View Post
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.
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Old 05-06-2016, 07:52 PM
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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
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Old 05-26-2016, 05:36 PM
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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
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
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Old 05-26-2016, 05:49 PM
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Ditch those "high flow" cats
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Old 05-26-2016, 07:03 PM
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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
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Old 09-04-2018, 02:01 PM
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I win the low dyno, my atk 403 makes 150 less rwhp than the stock bottom end ls1 made. At least it will make a great boat anchor.
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Old 09-04-2018, 04:55 PM
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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.
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Old 09-04-2018, 05:05 PM
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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

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Old 09-05-2018, 05:39 PM
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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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