Bigger cam

[Thatguy0909]

I can't find the info on how big a cam you can run with the stock tbi injection. I have a cam that I have laying around and I'm wanting to know if I can run it with some fuel upgrades or will I have to go carb swap? I have done the carb swap before so I know what I'm getting into with that. If I can run the tbi can someone point me in the right direction? I'll post screenshots of the cam specs. Thanks in advance.

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[PlayingWithTBI]

I can't find the info on how big a cam you can run with the stock tbi injection.

I'm running a similar Lunati cam (10120700LK) with a little less duration (207/213 @ .050) but higher lift (466/484 w/1.6 rockers). I have a Throttle Body bored out to 46mm and an 18LB spring set to 20PSI with an EP381 Vortec fuel pump. With a 2500 stall converter it's great off the line and shifting @5000RPM I'm pretty much staying in its power curve.

If I were to do it over, I'd probably go with a roller cam since I discovered my block has the bosses for the spider and holes for the cam retainer plate. HTH

 

[Thatguy0909]

I'm running a similar Lunati cam (10120700LK) with a little less duration (207/213 @ .050) but higher lift (466/484 w/1.6 rockers). I have a Throttle Body bored out to 46mm and an 18LB spring set to 20PSI with an EP381 Vortec fuel pump. With a 2500 stall converter it's great off the line and shifting @5000RPM I'm pretty much staying in its power curve.

If I were to do it over, I'd probably go with a roller cam since I discovered my block has the bosses for the spider and holes for the cam retainer plate. HTH

Awesome. I've had several of these trucks but I've never messed with upgrading the tbi setup. I feel like a noob but how do you bore out the tbi and set the 18 lb spring ton20 psi lol. Also are you having to run a chip?

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[Thatguy0909]

Luckily my yukon is a stick shift so I don't have to worry about a stall or the trans acting stupid lol

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[Supercharged111]

With tuning I don't see an issue.

 

[Thatguy0909]

I haven't looked too much into tuning with the obd1. I've always been told that the chips were pointless and that you couldn't really tune them. Do you have any good info on tuning it or a link to an existing thread?

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[Supercharged111]

PlayingwithTBI can speak more to it, but I'd look into EBLFlash. It's a modified TBI PCM that's reflashable, eliminates chips. That truck won't be happy without a tune.

 

[df2x4]

Paging @PlayingWithTBI...

Apparently EBL Flash is the way to go, with support available on http://gearhead-efi.com/

 

[Thatguy0909]

Alright ill look into it. Thanks yall for the info

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[PlayingWithTBI]

I feel like a noob but how do you bore out the tbi and set the 18 lb spring ton20 psi lol. Also are you having to run a chip?

As far as boring your throttle body here's where I went. It's fairly expensive but they say it'll flow 650 CFM which is good enough for a 350 @ 6000 RPM. You tell him you want an 18LB spring.
https://www.ebay.com/itm/46mm-PORTE...837306?hash=item3d963196ba:g:mpwAAOSw2xRYWVJj

Then you get a fuel pressure adapter, an AFPR (Adjustable Fuel Pressure Regulator) and a gauge from these guys (around $116)
http://www.rvmorsemachine.com/product.htm

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Here's where I tried out a 28LB spring from a 94-95 7.4L but it wouldn't idle well.

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Now, the fun part - tuning. My 1st try was a "custom" chip, I wasn't impressed! 2nd shot was soldering in a ZIF (Zero Insertion Force) socket in my 1227747 ECM (88-91) and tuning with Dave w on Gearhead EFI. I'd drive around data logging with an ALDL/USB cable using TunerPro RT, email the log to him, he'd tweak the .bin, email it back to me, and I'd flash an SST 27SF512 flash EEPROM with the Moates Burn2 adapter. Rinse and Repeat until we got the VE tables dialed in.
http://aldlcable.com/aldl.asp
http://www.tunerpro.net/downloadApp.htm

The biggest issue with the 7747 ECM is it's slower than molasses on a winter day, 160 baud rate. Plus the tables only go up to 4800 or less RPM. The EBL Flash-II runs at a 8192 baud rate, its SA and VE tables go up to 6375 and 6000 RPM respectively. It has 8 "banks" you can flash to (each takes about 4 seconds) so, you can tune for different conditions without effecting the others. It comes with a USB cable that plugs into a mini audio socket (I mounted it under the dash for easy access). Plus it has the "VE Learn" function where you drive around and it automatically tunes your VE tables to the AFR you want like 14.7 or a little lower for ethanol level (10% likes 14.1 better). Get yourself a WBO2 and you can even tune WOT levels with this setup.
https://www.dynamicefi.com/EBL_Flash.php

Fun stuff!