I did some checking today. My truck turns about 2000 rpm at 70 mph. I counted the driveshaft vs. tire rotations just to confirm the 3.08's are accurate and they are. The glove box shows the GU5 code as well. 3.73's would really increase the rpm on mine at cruise, right? My calculations show about 2500 rpm?
With 275.60.15's and a 3.73 ratio, you will be right at 2400 RPM at 70 mph.
Square body stepsides forever!!!
Yeah thats getting a little high it seems like. Will the 454 tb support the blower? Maybe a better question is how much hp can they support?
The biggest overbored BBC TBI flows 850 CFM (I got mine on ebay) and YES you can run a lopey idle cam with a TBI, I'm running the Lunati Cam’s full Roller Conversion cam & roller lifters, Cam #20120712 (60112):
Advertised Duration (Int/Exh): 282/290
Duration @ .050 (Int/Exh): 231/239
Gross Valve Lift (Int/Exh): .535/.550
LSA/ICL: 110/106
They sell roller conversion lifters sets that have dog bones so any FT block can run rollers. Get ready to fork out $1000+ on cam and lifter set, if you want to go retro roller, however, no drilling is required, just drop those bad boys in. Also to note: I would steer clear of Comp Cams' roller retrofit kit, I just had to tear down my top end as I had one of the lifters fail at less than 6000 miles on a completely new parts/rebuilt motor. Now, all that said, I have done a ton to my motor to have it "happy-ish" with that HUGE cam. See below for my full build specs. Now, a good question is how much "bad" is OK for you... I run the below setup in my daily driver, but my commute is 4.9 miles each way. At lights I sit with my left foot on the brake as every once in a while, she'll try to idle at 400 rpm, however, a tap of the gas pedal fixes that instantly. Also, she's completely ball-less until 2000 rpm and hits like a turbo from 3500-6300. 0-60 times are just under 6 seconds, 0-100 is just under 11 seconds, on a 18 foot long 4500 LBS (without my chubby butt in the seat) car. SO... Do you want to sit there and spin tires at off idle speed? Or do you want to get crushed into your seat over 3K? The Lunati cam is down right nasty at idle, I have watched young children start crying in fear and hide behind thier mom when I rumble by. I think the Lunati one I have sounds better (nastier) then the comp cams thumper I just pulled out. Also remember big cams really like compression, so heads are going to be a important factor, or at least cc of your chambers. I'm running the AFR Vortec 190's, and they are killer, however, watch those exhuast flow # on any forced induction motor, that will be more important then it would be on a NA motor. Also I'm at 5420 ft, so I'm running even more compression then most on here will, as we don't have any air up here in the rockies.
1951 Cadillac series 62 4 door
WT: 4500 LBS
Trans: TH400 – shift kit’d (crisp shifting) and governor mod to WOT shift at 6300 rpm, 2300 RPM stall torque convertor
GM 12 bolt rear-end with 3.73 Yukon gears, 245-45-R20 (29” tall) Nitto INVO Tires
Engine: GM 355 ci – decked block, Eagle Crank, GM Rods, Speed Pro Pistons, Total Seal Rings, 0.030" over, calculated CR 10.91 to 1 (I live at 5420 FT above sea level)
AFR Street Vortec Heads (65 cc chambers) 2.02/1.60 valves, 1.5 ratio roller rockers, Edelbrock Performer RPM Vortec Intake Manifold
1989 1228747 GM computer(modified with a pull-able chip for re-burning), Big Block Throttle Body, bored out as big as it can get (850CFM), square bore to TBI adaptor/spacer ported to match over-bored throttle body, Big Block #5235231 fuel injectors at 28 psi (w/ AFPR), 255 LPH Walbro fuel pump, no EGR, thermostat 195*, 3630 CFM electric fan and summit racing universal all aluminum radiator, true dual exhaust with 1969 GM afterburner headers (no x-pipe or cross over), race mufflers (twist tube), (both narrow and wide band O2 sensors on drivers side exhaust: narrow to GM CPU, wide to AEM gauge) side exhaust. No power brakes or steering.
Lunati Cam’s full Roller Conversion cam & roller lifters, Cam #20120712 (60112)
Advertised Duration (Int/Exh): 282/290
Duration @ .050 (Int/Exh): 231/239
Gross Valve Lift (Int/Exh): .535/.550
LSA/ICL: 110/106
Runs on Shell V-Power (super grade) E10 fuel
Oh yea, one more comment, i'm on my 157th bin file at this point, and I'm still do not have PE turned on and am still working on VE & SA tables, and prob have 100+ more bins to go. So if you want a lopey TBI, be ready to spend a TON of time playing with it to make it work like you want it to. HOWEVER I make almost 500 HP and get 16-18 MPG (9 MPG if I'm doing WOT tuning runs), I'd love to see a carb get 16-18 MPG sitting over my motor.
agree with 1project2many on your gear ratio being most important factor atm with the setup your asking for, imo with the manual trans and the right gears i'm not seeing why some of the listed choices have been deamed too big.. the lobe seperation is more the problem on alot you listed that i see more then the actual size being too big...
atm i have a
adv dur 288-289
durr @ .050 214-224
lift .444 .466
112* lobe sep
1600-5200 rpm
its listed as a fair idle, but seems pretty smooth with just a note of lope in the exhaust.http://www.youtube.com/watch?v=V70PpbkwJJo i see no reason this wouldnt be a nice choice for a manual trans truck with gear ratio preferably in the 3's or lower . ex:3.40ish to 3.73ish or around there. even into the lower ratios like 4.10:1 ranges would be fine .. i guess some will disagree with me and thats ok i would just like to hear why.. . oh and you should be sure to have the compression ratio to support whatever cam you choose as well, if your getting heads as described or similer i'm assuming you will be looking at 10:1cr so you should be fine.
wow i'm really slow getting my post up... so many replies since started typing. or maybe i just didnt read them all such as the ratio thats already listed lol
but my opinion still stands
Last edited by xtreamvette69; 08-14-2013 at 02:52 AM.
If the transmission is a NV3500 or NV4500, in no way would I go under 3.42:1. In fact a 3.08 or even 2.73 posi would be ideal to me. 1st gear is much lower in a 5spd than it is in a 700r4 or 4L60E. If you happen to pull a load at highway speeds with 2.73s or 3.08s you can downgear to 4th or even 3rd as needed for hills and headwind.Originally Posted by xtreamvette69
The wider the LSA the smoother the idle and the higher the vacuum signal. Wider LSA cams will also tend to broaden the torque curve while reducing the peak. With a manual transmission, having a wide LSA is less important as you can keep the engine in its powerband more easily.
With my new 4L80E I am going to run 4.30s in my Express with 29" tall tires and a factory 4.3/4.8 high stall 4L80E converter. I'll be 2,500 rpm @ 70 mph give or take a little and I am perfectly ok with that. The old 4L60E was always shifting between 3rd-4th-3rd-4th with 3.42s as well as always slipping the PWM converter.
Last edited by Fast355; 08-14-2013 at 02:17 AM.
Sounds like it may need some tweaks with the AE. That cam with that compression ratio, heads, and intake should be responsive below 2,000 rpm and be pulling hard by 2,800.
Thanks!!! I'm pretty new to EFI tuning and AE/PE are not quite as straight forward (in my mind at least) as VE/SA; but I'm learning more every day. I'm just so thrilled I could get this motor working in the first place, 99.9% of the people I spoke to said it would never work... But I had a close friend who KNEW GM TBI could handle this setup, so I took the leap of faith... So the long crazy trip that is learning about EFI tuning is just starting for me, but I am so impressed that with my basic skills in this new field, how much I've been able to achieve already. Any tips for me on AE, just let me know... Thanks!
Last edited by 51caddyman; 08-14-2013 at 02:58 AM.
51Caddyman ,
That is a very cool build you have going there , and to run it with a GM TBI adds the "cool" to your project IMHO.
Keep at that tune , it'll get there , lots of good info right here on this site
FWIW , 28 psi is just getting started with those injectors , they will tolerate much more . Only thing to remember is flow is inversley proportional to pressure , there is a point of no return when you get too crazy ....
Just one point so others do not get misled , the Xtreme-FI TBI unit you reference on Ebay as being the "biggest you can get" is an incorrect statement , I as well as others use a BBC TBI that measures 56mm and is bored and sleeved to achive this (57mm is possible) . Flow is right around 900 CFM . Xtreme-FI does not sleeve theirs which is why the largest acheivable dimension is 54mm . While 2mm does not seem like much , it becomes alot on a healthy BBC .
TOM
1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
1992 S-10 434 SBC/Tremec - '7427
1986 Monte Carlo SS
1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
1980 Z-28 496/700R4
1979 Corvette 496/700R4
1977 Olds 98 Regency 403/700R4
I remember when you showed up here, awesome results for such a short time. Super cool car too!
AE usually has 2 settings. AE TPS and AE MAP. The TPS is a short blast to help compensate for instant increase in air. MAP is longer and helps finish the process.
HTH!
1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
-= =-
Awesome!!! Thanks again Mark... I'll play with those tonight. I have to say... You ROCK, you helped me so much getting started here, I can't thank you enough. Nasty-z, I stand corrected... and that is SICK where did you find that TBI? Also if anyone here goes very big cam wise... you'll want to play with (reduce):
O2 - Prop Gain Mult as Funct of Flow
O2 - Prop Dur Offset as Function of Flow
O2 - Prop Term Dur as Funct of Slow Filtered O2 error
O2 - Prop Error vs Slow Filt. O2 error
helped me a ton with surging under low throttle.
A gentleman in California that is on the 454SS site I frequent used to make them , they were one off hand made pieces , only a handful were made and it is rare to find one for sale .
I have attempted (and succeded) in making a few on my own , but be warned , the process is very time consuming and not for the faint of heart, I was thoroughly intimidated the first one I did.
By boring the TBI to 58.5mm (to fit the sleeves) you break through the walls in quite a few places (note the epoxy in the pictures) , and when inserting the sleeves you must allign and drill 3 vaccum bleed holes in the sleeves (one is square) . Fitting by hand new throttle blades , machining the throttle shaft , O ringing the shaft (for boost) , all of the time adds up. It is a very long process but the rewards are worth it IMHO.
I have attached a few pictures of the TBI's , these are not mine but ones of our board member that I have aquired over the years.
Enjoy
TOM
WP_20130813_001.jpgWP_20130813_002.jpgWP_20130813_003.jpgWP_20130813_004.jpgWP_20130813_005.jpgWP_20130813_006.jpgWP_20130813_007.jpgWP_20130813_009.jpg
1994 3500 Dually , 502 (509) , 264HR , Edelbrock MPFI , PFI '7427
1992 S-10 434 SBC/Tremec - '7427
1986 Monte Carlo SS
1984 S-10 , SAS, 496/700R4/205 , D44/14BFF -'7427
1980 Z-28 496/700R4
1979 Corvette 496/700R4
1977 Olds 98 Regency 403/700R4
2500 @ 70 isnt too bad at all considering most factory v8 type vehicles turn close to 1800 or so in od with lockup locked right out of the factory, so imo thats pretty ideal at 70... getting outta hand and crazy was the camaro i built with 4.11's and a th 350, no lockup no od and turned an engine wearing 3500rpm all day long @65mph lol
Idling and cruising with less vacuum his system will use MAP AE very sparingly and TPS AE will have to be added to compensate.
Before it came out of my TBI swapped G20 van I had a fairly lumpy cammed 305 running under a 350 marine tbi.
Its now in a caveman era car with the same single plane intake, a 500 cfm edelbrock and a HEI triggering a MSD 6A box directly with no hei module. We have had a few friends comment about the high speed misfire when driving it....MSD 6,000 rpm limiter saved the motor again.
May someday swap TBI or TPI back on it. Actually even considered the CSFI intake from my Express.
http://www.youtube.com/watch?v=8kYWYA7cYYw
Despite only having dual 8" long resonators its really not as raspy as the video would leave you to believe. It is obnoxiously loud under load though.
Last edited by Fast355; 08-14-2013 at 08:10 AM.
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