Does anyone have any experience with the Holley Throttle Body Injection systems. I just came across them while I was looking up some fuel injection systems. The 2bbl system looked like a possibility for a well built /6. Just wanted to see what you guys might know about them.

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Kenny P
28 Rat Rod Slant 6

I ran the 1st gen Holley Pro-Jection 2bbl 670 CFM TBI on my '64 and '68 Darts, fighting with the crappy Holley analog computer the whole way. I got it to run OK after building some auxiliary circuits of my own.

In the end, I used all the Holley hardware, but am running it with Megasquirt v2.2 (MS I so far). It runs quite nicely on my built 225 in my '64 Dart. It is more tunable than a carb and better mileage. Latest performance is 14.50s in the 1/4 and 25-27 MPG hwy.

If you really want to do EFI right, multi-point (port) EFI is the best way. My '68 Dart is Megasquirt port-EFI. I will likely switch my '64 to MP-EFI and put the TBI on my Slantkota over the next year.

Lou

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Home of Slant6-powered fun machines since 1988

Thanks Lou, Stuck over here in the desert for a few more weeks and will be jumping on the Slant Rat when I get home. I am looking to build a 225 around 250 hp and still be a little streetable. I have a couple of tubo's laying around. One may find its way stuck to the side of the block. I am really leaning toward a fuel injected turbo build.

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Kenny P
28 Rat Rod Slant 6

Ken,

Sounds like a great project. I hope you are doing OK over there - take care.

For a turbo, I would highly recommend port EFI, so you have a "dry" manifold system and fuel puddling/condensation will never be an issue. However, even TBI will be better tunable than a carb, with the right computer (like Megasquirt).

For a NA build, focus on the cylinder head flow. For a turbo, boost overcomes lots of engine flaws.

Lou

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Home of Slant6-powered fun machines since 1988

IDK anything about "pro jection", other than I remember a former co worker buying a used take-off setup, and it sat there in that box collecting dust til he moved onto another job (and he had long since sold the car that he bought it for, by the time he quit that job) I think this was the 4 bbl version;

but their OE setup, as used on 88-91 Dodge trucks is total, absolute GARBAGE....... I am going to be looking for a 4 bbl SB intake to retrofit my son's 89 Ramcharger to carburetion because I am sick of dealing w/ the TBI headaches....... and as large as day right on the throttle body it is stamped, "HOLLEY". this is the 2nd TBI equipped Dodge truck we have had; I'd almost rather deal with keeping a Lean Burn system operational.

IDK if the Pro jection aftermarket system is anything the same as the OE setup, or not. but if it is,then it isn't worth anything but a toss into "file 13".

A GM TBI can be put on a slant; with good tuning it's likely to have better drivability than a carb but it's likely to have minor fuel distribution issues. Probably no more than with a carb though.

As near as I can tell from having examined a Pro-Jection 2 barrel TBI and pictures of the TBI V8 setup, Holley seems to have taken the TBI design they supplied to Chrysler and paired it with different electronics. The first Pro-Jections used an analog computer that was apparently built by MSD. Not sure where their later electronics came from, but I suspect they too were outsourced.

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"Mad Scientist" Matt Cramer
'66 Dart - turbocharged 225
My blog - Mad Scientist Matt's Lair

The Holley 670 is based off GM's big block TBI unit, and flows way too much air for even a built 225. Driveability would likely be crap, and calibrating the ECM might be a pain as well. If you use one of GM's 2 smaller TBI units, it would make for a lot better response and mileage, and you can use the same ECM as the Holley uses...same IAC, TPS etc. We use the smallest TBI for anything up to 4.3 liters, the medium bore TBI for between 4.3-5.7 liters, and reworked Holley 670's for most engines above 5.7 liters. I get 30-50 Holley 670's at a time at the shop, and every single one of them has to be totally reworked just to make them usable...casting flash everywhere (even between the throttle bores, right where the flakes can be eaten by the engine it's trying to run) and all sorts of quality control issues. I'd stick with the GM unit and an adapter to your 2V inlet manifold if you're going to do any TBI setup. Good luck!

I just re-read, and saw that you had a built motor. Still the 670 might be a bit much for decent low rpm stuff. If you're still considering a TBI setup, you can message me for the shop number and call for the technicals, we send out conversion kits for all kinds of engines. I don't want to make this an ad or anything, but just glad to help out if I can. - Dan

Yes, using the 400 or so CFM 2bbl TBI from a V6 would be better for a milder or stock Slant. Should have mentioned that, yes. GM 4.3L V6 used these.

Lou

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Home of Slant6-powered fun machines since 1988