ILikeFtLbs

Swapping the 350 crate 12499529 290 hp into a 1984 in place of a broken 305 HO. I'm keeping all of the exhaust from manifold on. Keeping intake and quadrajet carb. Keeping most everything possible because I have to pass emissions. Now, what kind of numbers do you all think I'm ACTUALLY going to get hp and tq-wise?

five7kid

iTrader: (14)

The L69 was rated at 190 net flywheel horsepower. The 290 crate is gross flywheel horsepower. Typical knock-down is 15-25%. So, you should get at least 210 net FWHP compared to the 190 apples-to-apples.

VenomX-87

wow that is a huge power loss, If a L69 is 190 net HP what is its gross HP?

DJP87Z28

The L69 Hp was 190 at the the flywheel so if you take the drive train loss it is about 152 RWHP. so your new engine is about 58 hp better.

five7kid

iTrader: (14)

Remember "net" means flywheel horsepower as installed in the car - full exhaust as in the car; the engine running the water pump, fuel pump and alternator; air cleaner as installed in the car; emissions equipment installed as in the car, etc. They don't require A/C or P/S running, though.

"Gross", as in crate engines, is on a dyno with a facilities-powered electric water pump, fuel pumped to the engine, open headers, the best carb/intake set-up they can match to the engine (and sometimes different for the HP # vs. the torque #), a velocity stack on top of the carb rather than an air cleaner, etc.

So, the L69 could very well be in excess of 250 gross FWHP.

You're looking at somewhere between a 20 to 40 HP gain with that crate 350. Obviously, the L69 is the more efficient powermaker of the two. Put the L69 heads on the 350 with 1.94" intake valves and basic bowl clean-up, and upgrade the cam to something like a Comp XE262 or XE268, and you'll be making well over 275 net ponies with headers and good exhaust.

wgripp

iTrader: (1)

I say keep the blower

five7kid

iTrader: (14)

I believe "blown" referred to what happened to the engine, not what was attached to it. . .

ILikeFtLbs

When I say blown, I mean as in a rod is blown and the engine needs to be completely overhauled.

My biggest worry is dropping in a 350 for $800 more than a replacement 305 HO, but I guess I can always mod it later.

Anybody done exactly what I'm thinking of doing? How did it turn out?

atc3434

iTrader: (4)

Somebody needs to say it, exhaust manifold are are going to be killing you. They make smog legal headers... SLP's are really nice, there are others as well. The the other emissions stuff doesn't hurt, but those stock manifolds are terrible.

five7kid

iTrader: (14)

Nah, the L69 exhaust manifolds are basically the same thing as L98. Just about the best the factory ever offered on 3rd gens (dual cats were better, that's it).

But, headers will be better, without a doubt. The only outfit that makes strictly-legal L69 headers is Edelbrock with their TES. But, Hooker 2055HKR's will bolt to the engine and fit in the chassis, and are arguably the best available for stock routing and ground clearance.

As to what to do to replace the 305 with the new window in the block: Take your 305 heads and have them rebuilt: Have 1.94" intake valves installed (do 1.60" exhaust if you're up for the extra expense), do basic port clean-up, concentrating in the bowl and short-side radius, have the press-in rocker studs pinned or replaced with screw-in, put Comp 981 valve springs and appropriate retainers installed. Bolt these improved heads to an L31 shortblock from GM http://www.sdparts.com/product/12556...eAssembly.aspx . Put in a nice cam like a Comp XE268. Performer or Action + intake manifold, above-mentioned exhaust, and you'll have yourself a very nice running engine and car.