Going MPI with the Suburban!

[1BadAction]

I finally gave up waiting for Michelins for my Camaro (Fronts backordered for 5 months, so far) and bought a set of stock tires so I could start driving the damn thing this spring and do some engine work and PAINT on the Suburban. As it sits I really couldn't ask for more from the factory TBI, it's idling smooth and low, cold start is perfect, throttle response is incredible, torque is great, MPG is even pretty decent... The bad thing is it's pulling 3+ inches of vacuum at WFO, which tells me the TB is a sizable restriction.

Figured there is two options. Go the easy way and port my TB and a 3764 out as far as they will go, then hope that is enough. OR go with some kind of Marine style MPI setup, a little more exotic, cooler, but a slightly more involved swap. Of course me being me, I never do things the easy way, so I already have one of these on the UPS truck headed to my door.



Will be having the TB converted to one of these works of art by TPIS.



As it is right now, I don't need to port this throttle body (they are already 58mm) but I'm not sure how long TPIS will keep doing them, and sometime in the future I'll drop a larger cube long block in this truck so I want to be sure to have some room to grow...

Any thoughts? Suggestions? I also have an electric cruise unit to swap in place of the vacuum unit, which will simplify linkages. MAP, IAC, and TPS all use the same part number as stock, which will eliminate being stuck in BFE over a simple sensor problem.

[1project2many]

That isn't a bad setup. I have it from a good authority that the stock manifold is good for about 600hp, seem to remember something about lean cylinder RH side, not too sure anymore. Cruise isn't difficult to install with the electronic unit and everything worked with a 7730. Well, maybe the TPS needed to be replaced, can't remember if the stock unit was bad or signal was reversed. Overall it's a good way to go if the price of the manifold is right. And it's cool. Tell TPIS you want a discount for advertising their work or they should skip the brand engraving on the top. ;)

[Fast355]

As it is right now, I don't need to port this throttle body (they are already 58mm) but I'm not sure how long TPIS will keep doing them, and sometime in the future I'll drop a larger cube long block in this truck so I want to be sure to have some room to grow...

Any thoughts? Suggestions? I also have an electric cruise unit to swap in place of the vacuum unit, which will simplify linkages. MAP, IAC, and TPS all use the same part number as stock, which will eliminate being stuck in BFE over a simple sensor problem.

Looks like it should be a worthwhile project. I think you will love the way the MPFI setup runs with a cold engine and how much smoother it will run overall.

Good choice on the throttle body. Aftermarket stuff for non LS Chevy engines are dwindling quickly.

I think you will like the electronic cruise compared to the vacuum one too. My 97 Express has the electric cruise and my 1983 G20 had the vacuum setup. While the vacuum setup worked well I found some road conditions that it would run out of vacuum and not be able to open the throttle far enough to maintain speed, when it would slow down and downshift, it would get vacuum and with vacuum it would suddenly pin it to the floor and jump up over the set speed and was overall pretty jerky at times. I found with the electronic cruise it is smooth and consistant from 40 mph to 99 mph.

[1BadAction]

Yea, I'm going to tell them to hold the TPIS engraving if possible, I spent enough with them when I had my IROC they should give me the shit for free. LOL. I also need to have a bolt on piece made to adapt to an oval rubber boot so I can run a stockish looking intake/filter assembly. I'll worry about that more when I get most of the stuff here in my hands. Right now I'm into everything for less than $600 bucks. Thats including the rail and injectors, which are both proven and pretty durable in the marine world. The TB mod will be an additional 300 but I think its worth it to have a fresh throttle body. Nothing quite as annoying as fighting vacuum leaks.

I've never had much of an issue with the vacuum CC, other than it doesn't hold the speed quite as close in the hilly areas. It'll be nice to get that ugly looking servo off the back of the intake, though. I'm not going to tear the top of the engine apart until I have everything in front of me, tested and working correctly. The throttle linkage may be slightly tricky, but nothing thats a deal breaker. I have the whole cast iron front serpentine setup to throw on it in place of the stamped steel also, the whole engine bay will look a good bit cleaner with everything fresh black powder coated and the harness redone.

I hear ya on the LS vs SBC parts. Luckily the good ole big block stuff is alive and well, even though my Gen V is a bit of a bastard.

[1BadAction]

Then again, if I get a real bug up my ass between now and then, my air cleaner assembly for this intake might include a pair of these.

[1project2many]

Thats including the rail and injectors, which are both proven and pretty durable in the marine world.

If those injectors are Keihins, I might have flow data for them.

[1BadAction]

If those injectors are Keihins, I might have flow data for them.

I do believe they are, like most Merc injectors... I'd appreciate the post if you have em.

[1project2many]

I think I posted it here once...
Got it!
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post9977

Also, I might be able to work some data out of a MEFI calibration if your injectors aren't on the list.

[Nasty-Z]

The bad thing is it's pulling 3+ inches of vacuum at WFO, which tells me the TB is a sizable restriction.

The 3764 is more the restriction than the TBI unit , A good single plane setup and possibly a bored TBI unit would have been the hot ticket here IMHO.

Of course me being me, I never do things the easy way, so I already have one of these on the UPS truck headed to my door.

Nice setup , I have the same setup on a shelf in the shop I was going to use on my '92 SS , but I believe I will use the GenVI MFI setup instead when the time comes . What are you going to control it with ? Might be a lot of work for a little gain though ....... I have a friend who runs the same basic setup on a 509 with a lot of boost , RBob's EBL to control it , works very well , but I don't think the gains will be all that great N/A . I could be wrong .

Cool project though

TOM

[1BadAction]

The only one similar to this I've ever seen used was in the mid 90s on a 609ci 4wd Lingenfelter Suburban. 4.6 seconds 0-60, so there was some power there for sure. They were using an earlier version of this manifold though, so its unclear how this one will act. I've seen more than a few of the GenVI MPI manifolds, and while they work decent, I just can't resist being different. This intake is also a Rect port, whereas (I think) the one you are talking about is a vortec/large oval style port. The other cool thing, is as much as I have going on with the boat scene lately, it'll be a neat conversation piece having a "Merc" under the hood.

As it stands now, I'll use the 7427 for control. If I ever decide to do a real turbo build I'll go full sequential MS3Pro underhood and piggyback a 7060 to control the transmission. Hell by that time there may even be a viable all in one MS3 based PCM. As it is now, coming back from EFILive in the newer GMs and Microsquirt on the 2 stroke, I feel like I'm in the stonage. LOL.

[HAMMERHEAD46]

Hello,
Could you post any problems you run into doing this conversion?
I have a 78 C20 Suburban with a factory 454 T400 Edelbrock carb AFB Style (Spread Bore?) and headers that was given to me.
The guy that gave it to me said "I couldn't keep it running", so he used it for a rabbit hutch!
I have it stored at a friends house in AZ, and it is an AZ original so no rust. (I live in MI now) I will be working on it when I am in AZ winters.

I spent last winter after it was given to me removing interior and rabbit items, and lightly checking it over.

Three (3) electric fuel pumps in series from tank plus mechanical pump also.

Fuel tank was laying in front seat?? when we towed it to my friends house it handled great no pull or wonder stopped well even without power, it had the oversize drum brakes on the one ton axle that is under it.
I managed to get the smell out of it, but am keeping it closed up this summer and my friend is going to check and see if any smell comes back.

I do want to go EFI on this beast, although I did have a Sportscoach on a 1 ton chassis for 4 years that had a 454 in it that would get 15 when not towing my full sized E150 and 10 towing it from job site to job site.

I am looking for information to use EFI on this old beast and will greatly appreciate and help with it.

Adrian Flynn