454 Throttle body or 46-47mm modified 350 TB?

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tayto

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I'm surprised L31MaxExpress didn't recommend anything here but sub-400fwhp, the stock throttle body is fine with the ridge ground down. I used a BB TBI throttle body on ~375fwhp 355cid, it worked but probably not necessary for my power level.
 

L31MaxExpress

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I'm surprised L31MaxExpress didn't recommend anything here but sub-400fwhp, the stock throttle body is fine with the ridge ground down. I used a BB TBI throttle body on ~375fwhp 355cid, it worked but probably not necessary for my power level.

I have commented a couple of times in here when I felt the need. I feel like 15.7s in decent weather near sea level can be done with a stock long block and the right bolt-ons, no need to re-invent the wheel. I had a stock 180 HP low compression 350 TBI with thorley tri-ys, 2" bored 3704 manifold, 1" open center spacer and 454 TBI unit with a custom tune I created make 200 RWHP and 300 RWTQ in my old 83 G20. That should be plenty enough to get into the mid to low 15s.

Stock bore small block throttle body starts to become restrictive around 330 flywheel HP and MAP will start to drop off above that, especially at high RPM.

PlayingwithTBI's truck has a substantial WOT MAP drop on his 383 and he can correct me if I am wrong, but it has a 46mm on it.
 
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1990Z71Swede

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Alright, I like how this is turning out :) So the stock TBI is back in from the Cold, just going to give it a little bit of love with the grinder. Is there a better alternative to the LT4 cam? like the COMP 08-300-8? which is similar in duration but I´m guessing gets more aggressive(to aggressive for Daily driver reliability?) than the LT4 after the 050 lift point. A wise man once told me, Pick the cam you think you want... Then buy one size smaller. So that´s what i did, (well sort off, haven´t bought any cam yet), and ended up with the LT4 :)

 
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PlayingWithTBI

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PlayingwithTBI's truck has a substantial WOT MAP drop on his 383 and he can correct me if I am wrong, but it has a 46mm on it.
Yeah I have a 46mm TB and a bored to 48mm 3704 intake and with the IAC opening to 255 counts at WOT, when I get up to ~5700 RPM my MAP is ~90 (IIRC without looking at my logs). I kinda look at it like when NASCAR races with restrictor plates, it still pulls strong throughout. I'm not racing it, and don't really plan to but, if I did I'd probably go to a 50mm 7.4L one.
 

L31MaxExpress

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Yeah I have a 46mm TB and a bored to 48mm 3704 intake and with the IAC opening to 255 counts at WOT, when I get up to ~5700 RPM my MAP is ~90 (IIRC without looking at my logs). I kinda look at it like when NASCAR races with restrictor plates, it still pulls strong throughout. I'm not racing it, and don't really plan to but, if I did I'd probably go to a 50mm 7.4L one.
You actually dropped into the mid-high 80s from memory above 5,000 rpm. Then again I did not see your key on Barometric pressure, so 86-88 kpa might not be that much loss.
 

PlayingWithTBI

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You actually dropped into the mid-high 80s from memory above 5,000 rpm. Then again I did not see your key on Barometric pressure, so 86-88 kpa might not be that much loss.
I just went out and did some more VE Learns and made a couple hits. Here's one when I merged onto I-10 at 82 MPH in 3rd with ~90° ambient temp. AFR dropped from ~12.5 to 11.9 quickly when it got over 5000. It is definitely wanting more air :33:

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Later I did a couple 0-60s, the 1st one I fed it too much pedal and spun out until I let off and hit it again in 2nd gear, made an 8.3 second run (accoding to my Dakota Digital dash). The next one I slowly fed her the pedal and turned a 7.2 (coincidentally). I really need a locker :rolleyes:
 
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PlayingWithTBI

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Is there a better alternative to the LT4 cam? like the COMP 08-300-8? which is similar in duration but I´m guessing gets more aggressive(to aggressive for Daily driver reliability?) than the LT4 after the 050 lift point.
I started with that cam in my 350 (before I threw a rod bearing). It idles fairly smooth and has good response. We're back to getting enough flow through the TB.

Here's a link to where I was tuning it and, with the IAC max set to 145. Notice even with this cam and 1.5 rockers, same 46mm TB, same aluminum heads, it's still wanting more air.

Another thought, you'll have to do something with your heads to allow .525" lift. Whether it's umbrella seals, machining and choice of springs. IDK what you can get out of 193 heads.
 

L31MaxExpress

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I just went out and did some more VE Learns and made a couple hits. Here's one when I merged onto I-10 at 82 MPH in 3rd with ~90° ambient temp. AFR dropped from ~12.5 to 11.9 quickly when it got over 5000. It is definitely wanting more air :33:

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Later I did a couple 0-60s, the 1st one I fed it too much pedal and spun out until I let off and hit it again in 2nd gear, made an 8.3 second run (accoding to my Dakota Digital dash). The next one I slowly fed her the pedal and turned a 7.2 (coincidentally). I really need a locker :rolleyes:

I don't know that a locker will even put down a 383s torque potential for you. As tall geared as my van is, in 50F weather a few days ago I was slipping both tires at 60 mph when I hammed it WOT. I thought my 4L85E was slipping until I noticed the speedo was pointing at 80 mph.

Pull a little more fuel there, maybe 2-3% and it will be closer to target. I had your upper RPM VE table flat lined to make sure it was not leaning out at rpms higher than you ran in your prior datalogs.

Given the low knock counts, looks like the last spark advance table has the engine much happier as well.
 
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L31MaxExpress

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I started with that cam in my 350 (before I threw a rod bearing). It idles fairly smooth and has good response. We're back to getting enough flow through the TB.

Here's a link to where I was tuning it and, with the IAC max set to 145. Notice even with this cam and 1.5 rockers, same 46mm TB, same aluminum heads, it's still wanting more air.

Another thought, you'll have to do something with your heads to allow .525" lift. Whether it's umbrella seals, machining and choice of springs. IDK what you can get out of 193 heads.
I think I like the look of that cams specs better than the Summit 8800 I am planning for my 383. I like the narrower duration split, makes for more low-speed torque than a wider split by reducing overlap and early exhaust blowdown. Guess I should model that cam next to the 8800 in DD2003 and Engine Analyzer for the overall torque curve difference.
 
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1990Z71Swede

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Later I did a couple 0-60s, the 1st one I fed it too much pedal and spun out until I let off and hit it again in 2nd gear, made an 8.3 second run (accoding to my Dakota Digital dash). The next one I slowly fed her the pedal and turned a 7.2 (coincidentally). I really need a locker :rolleyes:
So thats with a 383, hotter cam than I'd like to run, pretty darn good Summit/TF 170cc heads, Eddy TBI intake, 46mm TB and 4.11 Gearing right? I probably have to lower my expectations a bit, looks like. Because, 350, TBI heads, less cam and 3,73 gears... But on the bright side both the TH700 and the G80 is probably less likely to immediatly selfdestruct that way :)

By the way, the 08-300-8 cam is .450/.480 lift. But yeah, heads might still need some love for it to clear, good point.
According to a "Summit Racing Expert" the 08-500-8 cam is supposedly a better fit for the TBI, the 300 cam is claimed to be designed for TPI... IDK?

 
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