V6

[Darwinskeeper]

Actually with the 267/200 engines, it wasn't so much the large stroke as the small bore and (presumably) small ports. The curious thing is that, in some ways, the 267 is not that different than the 262 V6. They both have the same 3.48in stroke, the difference is that the 267 has 8 3.50 bore cylinders and the 262 has six 4.00 bore cylinders. I have heard that Guitar Goalie's Monte Carlo did well with the 267 V8 even though he had an exhaust system sized for a larger, more powerful engine. There may be something about the relative breathing ability of 16 small ports vs 12 big ones that led to the advantage, or it may be the fact that he used a Quadrajet where I'm forced to use a Holley 4160.

Good luck with your continued work. I'm looking forward to see how it goes.

 

[mhamilton]

You're running a Holley carb? There's your economy problem right there. There's no intake for a Qjet on the 4.3?

I'm sure the 267 was capable of more power, but the small bore and valves did hurt it. It really wasn't bad considering the other engines of the era. Only 20 hp less than the 305, but more torque (and smoothness) than the V6s. I'm sure that engine did not like to be reved either, so would have worked well with the high axles.

 

[Darwinskeeper]

mhamilton,

There are two intake manifolds that can be used to mount a Q-Jet to a 4.3 V6 but each has its problems. :-k There is a GM factory cast iron manifold that was used with the 4.3 on Astros and full sized trucks in 1985 & 1986. I'm told it is a reasonably good manifold but that it is a bit of a high riser and I'm not sure that the intake manifold could be made to clear a flat hood. GM also offered an aftermarket manifold (14097284) for Marine use looks like a cast iron version of the Edelbrock Performer (it seems to be a single plane manifold with a divider down the middle) but I'm concerned that the ports may be too large for efficient operation in the 1400-2600rpm range.

I suppose that a well tuned Quadrajet might be the best carb for an mpg motor, but I'm just not ready to sacrifice the front end weight and face the technical concerns for that cause, at least not yet.

 

[mhamilton]

Hmmm... that's a bit surprising, considering how much (more) popular the 4.3L is. I'm not a fan of the aftermarket carbs, have seen the mess Holley makes when those accelerator pump diagphrams go bad. The Qjet has all the adjustments you'd ever need, so it can make economy and power.

Sounds like you might be better off stealing the entire EFI off a late model 4.3.

 

[Darwinskeeper]

"...how much more popular the 4.3L is."??? Than what?

If I were a skillful mechanic, and were a little more comfortable with reprogramming microprocessors, then adapting a TBI or multiport fuel injection system wouldn't have been a bad idea. Unfortunately, I'm not and thought it would be best to keep things simple. Hence the Edelbrock Performer and the Holley 4160. Maybe some day someone will build a good aluminum manifold to match the Qjet to the 4.3L, or I may finally take the plunge with the GM Marine manifold. Until then, I'll seek a little more efficiency elseware.

Just purchased a Performance Distributors' DUI (custom curved HEI). I'll keep you posted.

 

[80ECLT]

Im pretty sure GMPP makes an aluminum 4.3 spreadbore manifold.... They also make aluminum blocks and heads for the 4.3. They even make a 4.125" bore V6 block!

 

[mhamilton]

"...how much more popular the 4.3L is."??? Than what?

Than any of the other Chevy V6s, and except for turbo Buicks, the 3800.

Probably not what you want to spend money on now, but could swap in a Vortec 4.3L with a roller cam. Those were good for about 200 hp stock. Not sure what reprogramming would be needed. I guess if it had a computer trans then you'll have to adjust that. You can send the PCM out to be reprogrammed for about $100, I know there are places to do that for the LT1 B bodies.

 

[Darwinskeeper]

80ECLT,

If GMPP, or anybody else is making an aluminum spread bore manifold for the 4.3 or any of the Chevy 90deg V6s I haven't found it and I've been hopping around the internet in search of such an animal. ](*,) The problem is that while the 4.3 does have some limited racing use, it doesn't have much of a profile on the street. Thus, while one can get bored out blocks, 18deg aluminum heads and the mother of all single plane manifolds, something as simple as a mild roller cam or a dual plane spread bore aluminum manifold just doesn't exist. Or at least they are so rare that I haven't found them.

 

[Darwinskeeper]

mhamilton,

Between getting Pandora roadworthy and the things I would like to take care of on Darwin, I'm really not in the mood to go into another engine swap. Besides, I'm kind of computerphobic when it comes to engines. I have found getting Darwin's "old school" carbureted V6 sorted difficult enough, I'm not sure I'd want to tempt fate with efi. I know, that stuff is brilliant when its working properly, but first one has to get it to work.

 

[80ECLT]

80ECLT,

If GMPP, or anybody else is making an aluminum spread bore manifold for the 4.3 or any of the Chevy 90deg V6s I haven't found it and I've been hopping around the internet in search of such an animal. ](*,) The problem is that while the 4.3 does have some limited racing use, it doesn't have much of a profile on the street. Thus, while one can get bored out blocks, 18deg aluminum heads and the mother of all single plane manifolds, something as simple as a mild roller cam or a dual plane spread bore aluminum manifold just doesn't exist. Or at least they are so rare that I haven't found them.

GMPP makes 23deg 4.3 stuff too. Also Brodix makes, or used to make, heads amd manifolds for them too.