[darkmaster]

I would like to get 300 hp out of my astro. is it going to be more cost effective to stroke and turbo charge my 4.3 or swap to a 305/350. I want to maximize fuel economy while doing this and need daily driver reliability. whataya say fellas whats makes more sense. :think:

 

[bkn_1971]

That is a mixed question hp/cost/fuel mileage.Well here it goes 1.If going with the 4.3 w/turbo then I would not stroke it as that brings up the comp ratio .I would want to lower the ratio comp a little so I can run regular unleaded fuel.I would also change to forged dished pistons to bring the ratio down a bit.In my opinion the turbo 4.3 would be the better way to go for fuel mileage.As long as the turbo is sized right it is like having your cake and eating it too. option 2 a v8 is a easy swap and 300 hp would be super easy .
Both could be made reliable.
I would say the turbo if the mileage is the key.
If easy 300 hp and simple is the goal a 350 will do that but at the cost of a little mpg.
Just my .02

 

[Mr_Bowtie]

I think in the long run going with a 350 would be cheaper up front and less head aches for a daily driver especially when it comes to tuning. Running a turbo you may have to mess with the tune a couple times a month depending how conservitive you are with the tune. If you run the boost low enough or keep it just on the rich side enough you may never have to touch it again(depending on what season of the year you tune it for too). I think the 350 would be easily less hassle upfront and down the road!

I'm not even sure what boost levels the 4.3L can handle, but you would probably need to run at least 14lbs. of boost to even get close to 300hp at the flywheel with supporting mods like. Anybody got any idea on this?

I personally think a 305 wouldn't even be worth the upgrade from the 4.3L. :shrug:

 

[stocked]

If built right i can personally attest for a 4.3 handling 300+hp without adding the PSI factor (i.e. Turbo/super charger). From what i KNOW he had in it was as follows, 98+ heads (ground for bigger valves and cleared for .500 lift), forged pistons/rods, balanced/hardened crank, comp cams custom grind (you would have to talk more with comp about what you want and such), Walbro 255lph fuel pump with helper pump on fuel rail too, eldelbrock intake mani with tbi adapter and a 454 tbi with 350 injectors, custom pcm ofcoarse, shorty headers with 2.5 true duals with x-pipe going into thrush glasspacks, high volume oil pump, clevite 77 bearings (main, rods, and cam). And i'm sure i'm forgetting some. o and he runs Royal Purple 5w-30 lol. But he is running high 13s in the quarter in a stock bodied 4wd 4door 1g Blazer, which with him in it is roughly 4100lbs, so iirc that comes out to about 350hp or so at the wheels. Now you wouldn't have to go all out like that to get just 300hp. But i am pretty sure with just heads, cam, intake, exhaust, and a tune you can get close to 300 without a turbo. And with all he has done he still gets about 17mpg city and 25 hwy.

Also if you wanted to stray from the forum i know someone on another forum that built a N/A 300+hp 4.3 that you could get advice from.

 

[darkmaster]

Thank alot guys I think I'll go for the na 4.3 upgrades. because this is my family ride I just cant stand how gutless it is. If I can beef up the power plant a little I could justify other upgrades like custom black vinal seats dvd player ect.... :ty:

 

[astro355]

The first step in whichever powertrain you use is regular maintenance. Modifications only multiple what you already have. If you have a "unhealthy" running engine, modding it will only make it run worse. So if you need to do things like an oil change, trans flush, tune-up, fuel filter, PCV valve, belts and hoses, etc, your money would be better spent on those items first.

 

[Mr_Bowtie]

If built right i can personally attest for a 4.3 handling 300+hp without adding the PSI factor (i.e. Turbo/super charger). From what i KNOW he had in it was as follows, 98+ heads (ground for bigger valves and cleared for .500 lift), forged pistons/rods, balanced/hardened crank, comp cams custom grind (you would have to talk more with comp about what you want and such), Walbro 255lph fuel pump with helper pump on fuel rail too, eldelbrock intake mani with tbi adapter and a 454 tbi with 350 injectors, custom pcm ofcoarse, shorty headers with 2.5 true duals with x-pipe going into thrush glasspacks, high volume oil pump, clevite 77 bearings (main, rods, and cam). And i'm sure i'm forgetting some. o and he runs Royal Purple 5w-30 lol. But he is running high 13s in the quarter in a stock bodied 4wd 4door 1g Blazer, which with him in it is roughly 4100lbs, so iirc that comes out to about 350hp or so at the wheels. Now you wouldn't have to go all out like that to get just 300hp. But i am pretty sure with just heads, cam, intake, exhaust, and a tune you can get close to 300 without a turbo. And with all he has done he still gets about 17mpg city and 25 hwy.

Also if you wanted to stray from the forum i know someone on another forum that built a N/A 300+hp 4.3 that you could get advice from.

Did he get it dyno'd to confirm your claim of 350HP at the rear wheels? A lot more then motor comes into play when drag racing. Maybe I'm just a non-believer(cause the TBI 4.3L is like 160HP stock), but I find it hard to believe a NA 4.3L motor with most everything that any SBC guy would do it pushing just as much HP as a SBC. But, then again it just depends on how deep your pockets are. :lol:

 

[evil_motors]

well mr bowtie there are quite a few articles if you look on the net for them about 4.3L engines with upwards of 500hp. in fact they built one up in one of the car magazines not a super long time ago. i will have to see if i can find it. I think i was on the 4.3L forums.

 

[$uperJoe]

well mr bowtie there are quite a few articles if you look on the net for them about 4.3L engines with upwards of 500hp. in fact they built one up in one of the car magazines not a super long time ago. i will have to see if i can find it. I think i was on the 4.3L forums.

i would have to agree with this as well. all racing sanctions have their own rules of course but i am most familiar with score. they have rules that state vehicles must have a form of stock power plant in them unless they are in outlaw class. most people dont try to go to that class due to money involved. this is why there are many upgrades for the 4.3 that can get them to 300 easy and 500 with some machine work. the local prerunner truck that the machine shop built for the team was pushing 650 whp and dynoed at about 730 on the bench. keep in mind they can do whatever they want since they were the machine shop and it was free. they stayed in stone stock class to keep from outlaws competitors like team duralast and teak rivera. the most well known score race is baja 1000

also the 4.3 turbo factory was rated at 280 hp due to an inadequite trans that followed them. the actual numbers were closer to 330 and with a minor adjustment of the vacuum line to the regulator can pull 400 in a factory tune.

 

[Taffy25]

I know this post is a bit old but i found this while looking for the max i could get out of the 4.3,

 

[Mr_Bowtie]

well mr bowtie there are quite a few articles if you look on the net for them about 4.3L engines with upwards of 500hp. in fact they built one up in one of the car magazines not a super long time ago. i will have to see if i can find it. I think i was on the 4.3L forums.

i would have to agree with this as well. all racing sanctions have their own rules of course but i am most familiar with score. they have rules that state vehicles must have a form of stock power plant in them unless they are in outlaw class. most people dont try to go to that class due to money involved. this is why there are many upgrades for the 4.3 that can get them to 300 easy and 500 with some machine work. the local prerunner truck that the machine shop built for the team was pushing 650 whp and dynoed at about 730 on the bench. keep in mind they can do whatever they want since they were the machine shop and it was free. they stayed in stone stock class to keep from outlaws competitors like team duralast and teak rivera. the most well known score race is baja 1000

also the 4.3 turbo factory was rated at 280 hp due to an inadequite trans that followed them. the actual numbers were closer to 330 and with a minor adjustment of the vacuum line to the regulator can pull 400 in a factory tune.

Stocked was talking of a 4.3L motor with worked over stock heads, .500 lift cam, intake, carb, headers, and exhaust pumping out 350HP.........I was simply saying BS to that as I don't believe that and would hate to see someone on here do those exact mods and come up with like 250HP. I want a little more proof then just hear say! :shrug:

 

[unrreal]

here guys i found the article, here's the link:
http://www.hotrod.com/techarticles/engi ... index.html
or the 500hp supercharged version:
http://www.hotrod.com/techarticles/engi ... index.html

 

[Mr_Bowtie]

Thank you thats exactly what this non-believer wanted to see. That article is stating 300HP at the flywheel not bad. The would be more a build a normal joe would do coming in at about $3K. Still a V8 swap would be more worth while as they stated in the article a 350 built the same way would be at 400HP. Still cool to see the potential of the 4.3L is there though. :clap: