305 writeup

1BadElky · Posted: Sun Sep 30, 2007 6:32 pm Post subject: 305 writeup

I finished the article from the site topics forum. Should it go in the performance forum, engine forum, magazine, or performance link from the categories list on the homepage? I have marked areas I'm not sure of or would like input on in red font. If something needs corrected, please let me know. The writeup follows:

Due to the frequently asked questions about how to upgrade the 305, I've decided to do a writeup on the topic.

The 305 was produced from 1976-1994 as an alternative to the 350. This engine was designed to be emissions-friendly, as well as reliable. The 305 cubic inches come from a 3.735" bore and 3.484" stroke (which was shared with the 350). By using a small bore, less heat is produced, resulting in increased reliabily, while keeping emissions to a minimum. As a result however, the engine is notorious for detonation.

The 305 uses the same block as the 350, 400, etc. So the parts are interchangeable for the most part. What kills the 305 for performance purposes however, is the small bore as compared to the 4.00" bore of the 350. because of this, most performance heads are out of the question because the larger valves will either have severe shrouding, or will contact the cylinder wall, depending on the cam. Also, even with 58cc combustion chambers, the compression ratio will still always be lower than the 350 with the same heads, because of the smaller bore. Needless to say, It is not a very high-revving engine.

Here are some upgrades which can be done to free up HP.
-Emission removal
-Non computer carb and distributor
-Aluminum intake
-Dual exhaust

*This is as far as It's practical to go, but there are other upgrades possible*

-Vortec heads
-Camshaft
-Roller rockers
-Higher compession pistons

The problem is, if you go to all the trouble to do the latter upgrades, you will probably want to have a total overhaul or machine work performed. And it costs just as much to rebuild a 305 as a 350, which will still produce more power for about the same fuel economy.

Here is a link to a 305 build if you wish to build your own.
Link
_________________

Formerly 86Conquista

Currently undergoing resto.
Planned:
-350/?/3.42
-ZQ8 wheels
-Disc Brakes
-More

1BadElky · Posted: Wed May 14, 2008 9:39 pm Post subject:

TTT

does anyone have input as to whether this should be stickied? it still needs minor revision, but I think it would be beneficial to these never ending 305 threads.

Edit: For those who may not have known the original idea http://elcaminocentral.com/ftopict-22632-.html
_________________

Formerly 86Conquista

Currently undergoing resto.
Planned:
-350/?/3.42
-ZQ8 wheels
-Disc Brakes
-More

toms84ss · Posted: Wed May 14, 2008 10:10 pm Post subject:

You can also add TPI and/or TBI to the 305. Makes for a little better driveability. TPI looks cool when you pop the hood.

dougs85 · Posted: Thu May 15, 2008 9:12 am Post subject:

Question, Nate. Just how does emissions removal, non-computer carb, distributor and aluminum intake manifold increase HP? If you are writing about these components and stating performance increases, you must explain how you came to this conclusion based on fact and not opinion.

Example. How does a non-computer carb and distributor increase HP. Also what are the ramifications, gas milage, driveability etc.

'the engine is notorious for detonation" where does that information come from? I have owned 305 engines for 20 years, never experienced detonation. I would think the engine is not properly tuned if that happens. Also the engine has a knock sensor to control detonation, at least on the 305s I own. I believe most modern engines are fitted with knock sensors.

If a 305 owner is experiencing detonation it's probably BECAUSE of emissions removal, computer-controlled distributer advance, disabled knock sensor, EGR removal etc.

Doug
_________________
85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO

66trar · Posted: Thu May 15, 2008 4:21 pm Post subject:

Hey, I figured if you're wanting to post a sticky covering "How do I get more power out of my 305" questions, you might want to include this article:

http://popularhotrodding.automotive.com/44779/0667-phrs-305-chevy-engine-blocks/engine-testing.html
Here's the text in case the link goes down. It made 372 HP and 350 lb ft. of torque. Not bad for a 305.

EDIT: Whoops, it was a lot longer than I thought

I'm not sure what's tougher, being a 305 Chevy, or being a 305 owner. It's all abuse and insults, and never any respect. Talk about building or hopping up a 305 and guys will generally shun you, or even boldly accuse you of being a fool. You'll hear, "Why mess with that junk motor? You're wasting your time." Wouldn't it be nice to lay waste on their stuff instead, with a few discrete bolt-ons? How about a bolt-on package that will add 150 crank hp, and still pull a good 13 in-hg of manifold vacuum at 850 rpm? And what if all the stuff comes in cheaper than what it would take to build the average high performance 350 short-block, and all the parts will transfer over to a larger engine and work great if you ever decide go bigger? We know there were tons of 305s built in the 1970s right through to the mid '90s, many of them in cars with definite performance undertones, most notably GM F- and G-bodies. We'll go out on a limb and presume that there are quite a few of these guys on a working man's budget who'd love to spring for a fresh up-sized engine, but have to make do with the 305 that's in it now.

No engine modification effort will be successful without giving it plenty of thought and planning. First, we really had to think about why the 305 has such a reputation as a pooch. We deduced right away that all of these engines were built during an era when horsepower took a back seat to other considerations, and were generally choked with all sorts of add-on emissions do-dads. Factory 305s came with anywhere from a low of about 130 hp, to a high water mark of 230 hp for the hot Camaro LB9 injected engines in 1990. Most 305s made right around 140-150 hp as the factory net rating, and that isn't the kind of output legends are built on. We also identified that the engine is small, and has a particularly small bore at 3.736-inches, while the stroke is the same as a 350 at 3.48-inches. The small bore is an immediate red flag to most guys; but is it really when things are looked at in proportion to the engine's size? In fact, the factory 305 bore/stoke ratio is actually slightly better than a stock 454 Chevy, and way better than any of the 4.030x4.000-inch strokers. Conjuring the Power Pack Actually, with the right heads, there is nothing inherent in the bore to stroke ratio of an engine of this displacement that will cripple cylinder filling, especially in the street rpm range of under 6,500 rpm. We had just the heads in mind for this project, the 180cc intake runner EngineQuest (EQ) replacement Vortec castings. These heads are machined for 1.94/1.50-inch valves, which are proportionally large for a 305-cube engine, and their low cost makes them a natural for a budget conscious 305 build. The flow of these castings is a major step up from restrictive stock 305 heads, and we have seen firsthand that they can support excellent output, even on a larger 350-cube engine. On a 305 engine, their 233-cfm of intake flow, if taken in proportion, would be the equivalent of running a 290-plus-cfm head on a 383 small-block combination. Our 305 should be more than happy with the flow these heads provide.

Shaver's Specialty Service supplied the EngineQuest cylinder heads, which retail for about $225 each as bare castings. We had Shaver's mill the heads a modest 0.030-inch, to reduced the chamber volume to 60cc, so that we wouldn't lose compression ratio compared to the typical production small-chamber heads used on these engines. Shaver's assembled the heads with a budget 1.94/1.50-inch valve combination, along with convention single performance springs with dampers. Later in testing, we wished we'd stepped-up to Shaver's extra-cost COMP No. 26918 beehive spring package, which would have allowed even more rpm, and possibly allowed the engine to make more peak power.

The cylinder heads from Shaver's were the cornerstone of our 305 modification plan. Besides the heads, we only intended a few other complimentary mods, intending to use a factory 305 short-block for the testing. Our 305 test engine had been stashed unused and unloved on a pallet rack at Westech Performance Group for years. It wasn't until the casting numbers at the back of the block were verified that they were even certain of what the engine was. It took considerable persuasion to build enough enthusiasm in the Westech crew for them to even consider forklifting it down. It turned out to be a low-end 305 with dished pistons and a regular flat-tappet cam. Some of the high-end 305s came with flat-top pistons for more compression ratio, as well as factory hydraulic roller cam setups. Our engine isn't ideal to show off the 305's potential, but if nothing else it does represent the typical 305 that people love to hate.

Obviously, cam and valvetrain would be part of the strategy. With the engine's small-displacement and undoubtedly compromised compression ratio, too much cam would be counterproductive. Since this is a flat-tappet engine, we decided to stay with that type of camshaft, as opposed to a retro-fit hydraulic roller, which would have been considerably more costly. Had this been a higher compression roller block, we definitely would have gone with a more aggressive hydraulic roller camshaft. While erring too big would ruin the build, erring too small is also a mistake-one that would curb peak power. After much consideration, a COMP XE268H flat-tappet hydraulic was chosen. This cam allows a smaller engine to make power up into the 6,000-plus rpm range, yet its relatively short duration, at 224/230-degrees, preserves cylinder pressure and maintains acceptable street idle quality. For a general purpose real street cam, this stick is hard to beat. The final components of our 305 power package related to the induction system. This engine was a carbureted unit, and we intended to keep it that way. Later 305s had some form of fuel injection, but for all-out power and a broad rpm range, a properly chosen carb/manifold will out-gun the factory EFI stuff, and is far more cost effective than a trick aftermarket injection setup. The manifold decision was easy, since the Edelbrock Performer RPM AirGap consistently shows the capability to make good peak power, while having much better torque than a single plane. With the 180cc EQ heads, the AirGap would be a perfect match when considering the port sizes. To top the manifold, we decided upon a 650-cfm Speed Demon carb, a good general high-performance carburetor, in a flow capacity that seemed about right for an engine of this displacement.

The Test
We had essentially mapped out our entire modification plan before hitting the dyno, a basic heads/cam/induction package that we figured would breathe life into one of these underachieving mills. For a baseline combination, the engine was all stock, including the short-block, heads, cam, a cast iron GM two-plane intake manifold, and a Quadra-Jet carb. As the engine was docked to Westech's SuperFlow 901 dyno in this form, the engine's virtue was disparaged as is usual for 305s. The scuttlebutt indicated the engine would be well short of the 200 hp mark, except for one optimistic passerby who put the number at 275. Well, the engine was being tested bare of all of its factory smog equipment, through excellent long-tube dyno headers, and with an electric water pump in place of the factory belt driven accessories. My 225 hp guess proved to be pretty close, with the 305 delivering 221 hp at 4,800 rpm, and 291 lb-ft of torque at 3,200 rpm. Normally, we like to make changes one step at a time, but in this case, we planned to make the changes all at once. There seemed to be no use in trying to run the good heads with the tiny stock cam, and the big cam with the junk heads also seemed like a dog of a combination. Finally, we weren't going to add a good set of heads and a hot street cam, and then cap it with a stock iron intake. This program was more of a full power package, so with the baseline numbers in, we stripped the 305 to the bare short-block and got to work. The heads were bolted on using Mr. Gasket's thin 0.018-inch head gaskets, actually the same set that had been under the stock 305 heads. The COMP cam got a new set of COMP's standard hydraulic lifters, along with COMP's pushrods and their Pro Magnum steel rockers. Shaver's supplied the rocker studs and guide plates that work with these heads, and before long we were bolting on the Edelbrock Vortec AirGap intake and hooking the linkage to the 650 Speed Demon carb.

What would the 305 make? We had plenty of time for conjecture while the engine was being run for the cam break-in cycle. Even though the stock 305 had show better output than most of the detractors had anticipated, there was little confidence in the 305's potential. Jawboning in the cell predicted numbers in the low 300hp range. There were a few surprised expressions when the 305 cranked 367 hp at 6,000 rpm on the first pull. With some fine-tuning of the air/fuel ratio via a jet change to the Speed Demon carb, power inched up to 372 hp at 6,100 rpm. That's credible power for any street small-block; enough to make a Third Gen Camaro really scoot. Had we started with a higher compression hydraulic roller 305, as is typical of the later F-bodies, there likely would have been even a little more. The lesson here is that any engine can be made to perform with the right combination of parts, even those that the vast majority of people are reluctant to love.

The EQ Lightning cylinder heads were a key component in making our engine modification package a success. Without a doubt, one of the worst features of the production 305 is the factory "smog" cylinder heads, which are choking even at a measly 305 ci of displacement. With decent heads, a small engine can breathe, and that allows it to take advantage of its rpm potential to make power. Without good heads, it isn't going to happen. These Vortec-style castings are just the ticket, with the right size valves, at 1.94/1.50, to fit and function in the smallish bores. Besides good flow, price is a key consideration when dealing with a 305. Enthusiasts do not typically regard these as their "ultimate" engine, so very few would spring for pricey race parts. However, if a substantial improvement can be had at a modest cost, why not go for it?

Shaver Specialty Service, a legendary name in the sprint-car engine world, is our local dealer for these EQ heads. Shaver receives the heads as bare machined castings, and prepped our set in record time to make this dyno test a reality. The heads were milled 0.030-inch for a little more compression with the small, dished-piston test engine. Shaver's completed the assembly by fitting their assembly package, including the valves, springs, retainers, seals and locks. The heads were also flow tested, showing very respectable numbers, particularly considering the valve sizes.

Hope that's helpful.
_________________
It's not the prettiest, but it's all mine....
"This is my El Camino, that's Spanish for........the Camino!"
1966 El-Camino 327, M22 4-speed.
1968 Mustang Coupe, 289, C4.
1968 Cougar XR-7, 390, C6.
1975 Corvette L48, TH400

1BadElky · Posted: Thu May 15, 2008 7:40 pm Post subject:

That is a very good point about the emissions removal. I guess I could put that in more of a setion of its own as far as how to rather than a perfomance upgrade.

the detonation statement was one of the things I was unsure of, so I highlited it. I will go ahead and remove it in the revision.

aside from detonation, are the other red statements accurate?
_________________

Formerly 86Conquista

Currently undergoing resto.
Planned:
-350/?/3.42
-ZQ8 wheels
-Disc Brakes
-More

dougs85 · Posted: Thu May 15, 2008 10:21 pm Post subject:

I don't have any objections to the other red highlighted statements. It's a foregone conclusion that dual exhausts will enhance output on even a stock engine. Don't believe aluminum intakes will increase performance much on a stock engine without other mods. Heat and weight reduction would be of some benefit.

Personally I don't like the tradeoffs associated with most headers such as heating up starters, sparkplug access, oil pressure sensor relocation and their tendency to not stay tight to the heads and also to rust out. I must admit however they will contribute a lot on a modified engine, not so much on a stock one.

Good luck with the write-up, doug
_________________
85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO

MarkZ28 · Posted: Mon May 26, 2008 7:32 am Post subject:

Removing the smog crap does not make the engine detonate worse. It makes the engine run cooler and much better, at least the older cars like the Caminos it did. The factory computer controlled crap is the worst, just replacing the carb and distributor with a pre computer HEI and Quadrajet makes a big difference. Set the timing and mixture right and it will respond much baetter, make more power, and maye even get better fuel mileage. Has worked on all the cars I have had. Also helped make the engine run cooler as a side effect and had less detonation. I also always removed the EGR and Cat converter. The newer cat converters are not as bad though, the old pellet type really choked the exhaust off.

dougs85 · Posted: Mon May 26, 2008 11:06 am Post subject:

Okay Mark, You made a lot of statements how removing the computer controlled carb, HEI distributor and EGR with pre-computer carb and dist. made the engine run better and cooler. What are the reasons for this? Most everything I know does not back up your findings. When you post statements like that clue us in on the facts and whys behind your conclusions.

I don't believe vacuum, weights and springs can control distributor advance better than a computer and a computer can control fuel mixture better than a non-controlled computer carburetor. And how does removing the EGR help an engine? The only thing I agree with you is about the older catalytic converters.

When I see the words "smog crap" and "factory computer crap" written, It tells me more about the author than what's in their post.

Doug
_________________
85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO

464elky · Posted: Mon May 26, 2008 4:43 pm Post subject:

this one is going to turn into some interesting reading. Poke Tounge

_________________
84 Elky with 455 Buick, Tremec TKO600 5 speed, 8.5 3:42 posi -
My Members Page Album
Another 3 to 9 years should finish it.

toms84ss · Posted: Tue May 27, 2008 3:44 pm Post subject:

If you install a non CCC carb and distributor I believe you could dial in the timing curve to pull a few more MPG out at cruise. And if the smog equipment is gone you could run a cooler thermostat and help the engine run cooler and possible get rid of some detonation.
Lets face it. Back when all this stuff was new, it was for emissions mostly. Driveability took a back seat to the smog police. Now on newer stuff with fuel injection I cant argue with that. But the older stuff leaves room for improvement.

dougs85 · Posted: Tue May 27, 2008 9:56 pm Post subject:

Tom has made some good points, although I don't agree with all of them. First of all I don't see how a non-feedback carb could match a CCC-carb on fuel management. Since the carb is controlled by the computer that is getting info from engine sensors such as The O2 sensor, TPS, temperature, etc. Same thing goes for the CCC distributor timing. My El Caminos run very good with this equipment thank you. And have seen 24 MPG out of them, which is probably the max one could expect with a V8 in these vehicles.

The thing is, some owners prefer to keep the emissions and engine management systems intact their cars came with even when they don't have to pass emissions tests. I just get a little erked when someone calls this equipment "crap", and the majority don't even understand it or know how to maintain it. To me that is disrespectful of these owners. It is not
everyone's goal is to see how much HP they can get under the hood.

Doug
_________________
85 El Camino 305, TH350, K&N, dual exhausts
87 El Camino 305, 2004R, K&N, dual exhausts
1964-1/2 Mustang conv, 260 V8, dual exhausts
2002 Jaguar XJ8, 2000 Harley Road King
Lakewood, CO

toms84ss · Posted: Tue May 27, 2008 10:24 pm Post subject:

Who the hell is Tim??? Use a wideband O2 sensor and you can do a great deal of tuning on a carb. And their easy to wok on.

bigjames4xl · Posted: Tue May 27, 2008 10:35 pm Post subject:

dougs85 · Posted: Tue May 27, 2008 10:44 pm Post subject: