anyone turbocharged their TBI? what are you using for a TBI hat?

[stackz]

with the tbi unit having two hold downs for the aircleaner coming up out of it, what are you using for a TBI hat if you boosted your setup?

did you just make it custom? I was thinking of welding the factory air cleaner together and just using it maybe.

I see this one as part of what looks like an old procharger kit.

M198643753.jpg

I did have the instructions from the old vortech truck kit on how to modify the TBI for blow through but cant seem to find them right this second. I remember it being that we had to drill two holes and put a TBI spacer in between with a port for a 2 or 3 bar map sensor IIRC.

I've got a 4.3, 5.0, 5.7, and 7.4 TBI unit and have both sets of 7.4 regular injectors as well (not the goofy ones that needed the higher fuel pressure to run higher).

I have also been dabbling with the idea of doing draw through as well. I have two 79 buick 3.8 turbos with the carbon seals and the 4bbl intake that bolts to it which I can get a tbi adapter plate for.

Just not sure which route I want to go at this point.

[In-Tech]

Hiya,
If the injectors are seeing boost, you will need to boost compensate the fuel pressure regulator.

[stackz]

didnt think about that. so something like a boost-a-pump would probably work.

[In-Tech]

Hello,
A "boost-a-pump" increases the flow, the pressure has to rise at least 1:1 vs. Meaning if base pressure is 12, at 10 lbs boost the fuel pressure needs to be 22 to maintain the flow. Any boost will push push back on the injector, reducing flow...hence the need for boost compensating regulator. If hooked to a vacuum/boost port, the pressure will reduce when in vacuum and VE table will have to be adjusted. Otherwise you can use a one way check valve just for boost, it will need a small "leak" so it doesn't work in vacuum.

[stackz]

so a fmu so a rising rate fmu then

[In-Tech]

If iirc a fmu is about 1.25:1
Your real struggle will be to find large enough injectors for the TBI. There was a time I had to use BBC 75's @ 12lb injectors and then use a 3:1 regulator. Figure out your hp requirement and then adjust accordingly.

[stackz]

it shouldnt be much honestly. I think the 454 injectors will be able to handle it.

everything is going on a 59 chevy 235 inline six. will probably only run 5 or so pounds so I dont shatter the bottom end hah.

[In-Tech]

Ok, cool
Sounds like you have a grasp on the struggles ahead :)

[stackz]

yeah, step one has been parts collection and research.

step two will be getting it on the truck and get it tuned n/a

step three will then be to toss the turbo on it and try not to scatter the bottom end hah.

[Fast355]

it shouldnt be much honestly. I think the 454 injectors will be able to handle it.

everything is going on a 59 chevy 235 inline six. will probably only run 5 or so pounds so I dont shatter the bottom end hah.

Sounds like a fun build. I want to put a late 90s to early 2000s 4100 MPFI into an older 30s GM truck myself and turbo it. That was a factory port injected 250 I6 using a TPI like manifold with a MAF based ECM, with an OEM split exhaust manifold and factory serpentine belt system. I drove one in a 1999 Tahoe with the factory 5spd and it was a strong runner in the heavy 4 door Tahoe.

[stackz]

Sounds like a fun build. I want to put a late 90s to early 2000s 4100 MPFI into an older 30s GM truck myself and turbo it. That was a factory port injected 250 I6 using a TPI like manifold with a MAF based ECM, with an OEM split exhaust manifold and factory serpentine belt system. I drove one in a 1999 Tahoe with the factory 5spd and it was a strong runner in the heavy 4 door Tahoe.

yeah I wish the 250 stuff was compatible with this engine honestly but alas, nothing interchanges. I am going to see about the toyota 1F and 2F head though. I already have the HEI distributor for this engine and its actually an HEI for a 1F engine lol. lots of stovebolters use it. my friend has a 2F head sitting in his garage that I'm going to borrow along with the head gasket and match it all up to my spare 235 head just for giggles. I know I would have to modify the oil feed to the rocker assemblies but that doesnt bother me. I just want to see how well it matches up to the block and all. it would be nice to have a better flowing head on this old girl.

but first priority is getting the HEI on, and then getting the TBI on so the ignition and fueling is all modern and working. then I'll play around with stupid stuff.

[1project2many]

Hi,

I love projects like this.

Ok, in deference to In-Tech and his far greater experience than mine, I believe pressurizing the throttle body will expose the FPR to boost. The factory regulator has a port on the air cleaner side which exposes it to atmospheric pressure. If you pressurize this side of the regulator and TB, the atmospheric pressure port will see boost just like the injectors. The TBI pump usually does not create high fuel pressure so a TPI pump is probably in order. Regardless of injector choice, you may find the injectors need a RRFPR to help make tuning easier. I'd do some research though as low pressure TBI injectors are not always happy to operate at high pressure.

One issue folks have found by pressurizing the TB is that fuel and air will be forced out the TB around the throttle shaft. One answer is to supply boost to the throttle shaft on both sides of the TB. This can be done by drilling holes that are connected to air from above the injectors in the TB opening. Another is to drill ports from outside the TB then use fittings and vacuum hose to route boost to the shafts. This solution uses both methods for the one barrel TBs used on crossfire injection.


You said you have a '59 engine which should have pressurized oiling. This is good. I would not be comfortable adding boost to a splash oiling engine. I would strongly recommend considering thermal barrier coatings on the pistons and cylinder heads. Techline Coatings sells this as a DIY product and I have had great results using it. 235 rods are strong. And they're heavy. For a boosted engine at 5 psi I would only be concerned with bottom end failure if the engine were seeing detonation.

Speaking of detonation, have you selected a knock sensor yet? Knock sensors are tuned to the engine bore size. The 60 degree V6 family also uses 3.5" bore engines so I'd start there. The trick is matching the knock sensor resistance to the ecm family. 89 S10 Blazer was available with TBI and uses a knock sensor. 90 Lumina APV (All Plastic Van) was available with 3.1 TBI. If you're using an early TBI ECM that uses an external knock module, it wouldn't hurt to get ESC from one of those vehicles.

Is it too late to consider alternate TB choices? A Clifford dual carb intake and a pair of model 700 TB's might give more injector choices as it uses the same injector as Saturn TBI and GM 366/427 engines from Kodiak trucks. And it could allow you to use an aluminum TB "hat" from a late '80s 2.0 TBI engine.



There are plenty of threads to read through although few people stay with the thread until a project is finished. I hope you find success with your project.