gearheadmb said:In reply to bobzilla :
I always thought two TBI units with progressive throttle linkage would be cool if you good enough at tuning to make it all work.
I agree. Maybe machine the intake to take a pair of the 670cfm Holley TBI's and a decent pair of heads and a cam that has more lift than the bearing height.
bobzilla said:gearheadmb said:In reply to bobzilla :
I always thought two TBI units with progressive throttle linkage would be cool if you good enough at tuning to make it all work.
I agree. Maybe machine the intake to take a pair of the 670cfm Holley TBI's and a decent pair of heads and a cam that has more lift than the bearing height.
Saw that setup on a tunnel ram sbf years ago. Power tour 99 actually. ..
It's been in the back of my mind to do dual TBIs on a tunnel ram for a year or two. I have a tunnel ram mani in waiting in a relative's garage, and i think i have one each of the 4.3, small block and big block TBIs. I figure a second 4.3 tbi is probably the way to go for that idea. I've heard one of the downsides of using the big block tbi on small blocks is it leaks too much air even when closed to idle down to a low rpm (haven't verified this). So, that being the case, having TWO too-large tbi's probably wouldn't be so great for idling even if it worked fine everywhere else.
curtis73 said:I'm going a different way. I detest the TBI, partly because I worked for Rochester Delphi when it was being developed. Yes it is pretty reliable. The nozzles (they're NOT injectors) will start leaking, but they are cheap to replace. The valve seals will leak and you'll get a big puff of smoke when you start it. Fix it, live with it, your choice. 700r4 is not happy with all that weight. Be very nice to it. Almost all TBIs have flat tappet cams which comes with its own set of troubles with modern oil.
The TBI flows horribly. Everyone claims 500-600 cfm, but wet flow with nozzles installed is 390 tops. Very well suited to the 180 hp the engine makes, but if you plan on bumping hp more than 10-15, throw it in the trash and put a Qjet on it. If you want to improve your MPG, throw it in the trash and put a Qjet on it. The whole top end; heads, intake, TBI, cam, compression is perfectly suited to the 180hp it makes. Getting over 225hp will require lots of work.
If you want to keep it bone stock, not tow, and never break 13mpg, it will serve you well. It just rubs me the wrong way that such terrible technology is passed off as good stuff just because it sucks equally at everything. It squirts liquid fuel at low pressure, it gets terrible fuel economy, barely squeaked by EPA standards (a Qjet was actually better on all but HC), and doesn't make enough power to get out of its own way. It is a big conglomeration of completely inadequate parts that live perfectly happy lives because it only makes sub-200 hp.
Having said that, it is a reliable setup, but be prepared for 1/2 the power and 2/3 the mpg of something 96-up. If you're going to keep it 100000% stock, then you'll have a reliable, boring, unsatisfying lump.
The early 90s - 95 TBI 454s came with mild hydraulic lifter cams. No solid lifter tappets.
In reply to udidwht :
I never said anything about solid lifters.
...Almost all TBIs have flat tappet cams which comes with its own set of troubles with modern oil."
In the VW air cooled world a flat tappet cam uses solid lifters. Hydro camshafts differ from solid lifter cams and hydraulic lifters. Back in early -mid 2000s we were experiencing lifter failures during break in with respect to Type-4 engines. Initially it was equated to possibly lack of ZDDP. In reality it was cam manufactures changing manufacturing process (metallurgy issue) that ended up being the issue.
Cams going flat were exclusively related to flat tappet cam & flat tappets (aka...solid lifter/s).
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