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Stock 4.8 802RWHP but valve float now

 
Old 03-17-2014, 08:41 PM
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Default Stock 4.8 802RWHP but valve float now

Stock 4.8 engine
26 PSI on C16 made 802 RWHP but now I cant rev this thing past 6000 RPM. I guess thats right around 1000 hp at the crank through my TH400 and PTC converter.

My goal was to run faster than my old Turbo V6 with a stock Ls1 4.8. I almost did. The 4.8 finally went 6.5 @ 23 psi but the old v6 went 6.455. Although the 4.8 went 107 mph in the 1/8 and the V6 only went 105 so it looks like Im making more power anyways.

I ordered valve springs, trunion kit and push rods so I can rev it past 6k at 26 psi.

My question is has anyone DONE a turbo 4.8 if so what cam did you use.
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Old 03-17-2014, 08:49 PM
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Originally Posted by TurboTerry87gn View Post
Stock 4.8 engine
26 PSI on C16 made 802 RWHP but now I cant rev this thing past 6000 RPM. I guess thats right around 1000 hp at the crank through my TH400 and PTC converter.

My goal was to run faster than my old Turbo V6 with a stock Ls1 4.8. I almost did. The 4.8 finally went 6.5 @ 23 psi but the old v6 went 6.455. Although the 4.8 went 107 mph in the 1/8 and the V6 only went 105 so it looks like Im making more power anyways.

I ordered valve springs, trunion kit and push rods so I can rev it past 6k at 26 psi.

My question is has anyone DONE a turbo 4.8 if so what cam did you use.
a member here "stock48" used a isky triple 12 cam with great success.
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Old 03-17-2014, 08:59 PM
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6.50 @ 107mph with 802whp?

Doesn't sound right?
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Old 03-17-2014, 09:05 PM
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Yeah your right. my pass at 26 PSI, 802 rwhp would only rev to 6000 and my converter is too loose so the converter was trying to catch up to the motor but slipping. My data log showed 6000 rpm steady like a rev limiter. Too much intake manifold pressure causing valve float. It went slower at 26 psi 6.8 @ 104 mph. At 23 psi it would rev to 6800 and the converter was not slipping at much. I leave off the brake @ 5000 but can stall upto 5500.
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Old 03-17-2014, 09:13 PM
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I did a junkyard 5.3 with some 243's on my friends Silverado and went with our boostaholic 2 cam and pulled 823 RWHP. His truck ran 10.50's at 134 MPH full weigh plus added weight of roll cage
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Old 03-17-2014, 09:17 PM
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My car @ 8:35
Murder Nova @ 4:15 from Oklahoma

Last edited by TurboTerry87gn; 03-17-2014 at 11:03 PM.
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Old 03-17-2014, 09:47 PM
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Old 03-17-2014, 09:53 PM
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Originally Posted by BottleFedZ346 View Post
6.50 @ 107mph with 802whp?

Doesn't sound right?
Was thinking same thing when I read this. Should be 114-116 somewhere in that mph. But I see you explained Rev limited to 6000 and auto trans woos.

What turbo is that?
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Old 03-17-2014, 09:59 PM
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Turbo is an s475. i machined the big flange off and welded a stainless v-band to it
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Old 03-17-2014, 10:04 PM
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Originally Posted by TurboTerry87gn View Post
Turbo is an s475. i machined the big flange off and welded a stainless v-band to it
I also have this turbo. I'm making 21psi on my ls1 with it. Good turbo for the money.
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Old 03-17-2014, 10:13 PM
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Great turbo for the money. This is my first LS motor and I am very happy with my swap from the Buick turbo v6. I get alot of Buick haters but you cant go wrong with a craigs list 300 dollar 4.8. And I had it delivered to my shop too!!!
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Old 03-17-2014, 10:24 PM
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Old 03-17-2014, 10:26 PM
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Old 03-17-2014, 10:42 PM
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10 psi 525
18 psi 680
26 psi touched 802
The RPM scale was calculated from the rollers. 5250 dosent cross at the right point on some runs
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Old 03-17-2014, 11:13 PM
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mine just did 561 at 15psi so yours makes more power than mine..
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Old 03-17-2014, 11:14 PM
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100% stock motor ? springs cam etc, head bolts ....etc ?
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Old 03-17-2014, 11:53 PM
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yep everything in the long block is completely stock. Head bolts, gaskets, cam springs, ect. Everthing... Only edelbrock intake manifold and stainless headers I built. with a s475 turbo. And my tune.
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Old 03-17-2014, 11:58 PM
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I do have a comp behive spring kit ON THE WAY and the trunion kit with comp push rods. I will install them this week and hopefully next Sunday make some passes @ 26 psi PLUS now that I know what kinda timing this thing likes on C16
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Old 03-18-2014, 01:12 AM
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And to think I sold my '05 long block 4.8 with 34k miles for $650 recently..... F*ck. would've rather seen how bright it would burn now instead....
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Old 03-18-2014, 06:28 AM
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Originally Posted by TurboTerry87gn View Post
I do have a comp behive spring kit ON THE WAY and the trunion kit with comp push rods. I will install them this week and hopefully next Sunday make some passes @ 26 psi PLUS now that I know what kinda timing this thing likes on C16
i would use the Brian Tooley dual valvesprings, or PAC springs before i would use the comp cams behives (they tend to break faster than stock springs)
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