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Discussion Starter · #1 ·
Hello,

I have a 74 with a turbo 350 automatic. 30 over cylinders, isky cam with 485 lift, 280 duration. Double hump 186 heads. edelbrock performer and 650 holley. long headers and 2" dual exhaust. I was told it had 400 – 425 HP. That sounds high to me.

My question is what are my best options to get 100 more HP?

I have looked at:
1. stroking it
2. nitrous
3. new pistons, heads, cam, and intake

What have you guys done to get the HP to about where I want it? I know HP costs money, but I don't want to go crazy.

Also when I had my oil pan off I noticed it is a 4 bolt main block. Is there any way that was the stock motor or has it been changed?

thanks
 

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Hello,

I have a 74 with a turbo 350 automatic. 30 over cylinders, isky cam with 485 lift, 280 duration. Double hump 186 heads. edelbrock performer and 650 holley. long headers and 2" dual exhaust. I was told it had 400 – 425 HP. That sounds high to me.
My question is what are my best options to get 100 more HP?
What have you guys done to get the HP to about where I want it? I know HP costs money, but I don't want to go crazy.
Also when I had my oil pan off I noticed it is a 4 bolt main block. Is there any way that was the stock motor or has it been changed?thanks
If those are stock 186's, then a new set of AFR 180's will net another 50HP, a RPM will go an additional 20HP plus re-plumb for 2 1/2" pipe and you will be close. Add a simple shot of 50 to 75 Nitrous and it will put you well over the top and then some. If money is an issue just go with a 100 shot of Nitrous. Easy, simple and cost effective plus no major work involved. Nitrous is going to want some extra exhaust duration on those 186's. I would try 1.6 rockers on the exhaust side if you go that route....Jack
 

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Hello,

I have a 74 with a turbo 350 automatic. 30 over cylinders, isky cam with 485 lift, 280 duration. Double hump 186 heads. edelbrock performer and 650 holley. long headers and 2" dual exhaust. I was told it had 400 – 425 HP. That sounds high to me.

My question is what are my best options to get 100 more HP?

I have looked at:
1. stroking it
2. nitrous
3. new pistons, heads, cam, and intake

What have you guys done to get the HP to about where I want it? I know HP costs money, but I don't want to go crazy.

Also when I had my oil pan off I noticed it is a 4 bolt main block. Is there any way that was the stock motor or has it been changed?

thanks
First thing I see is a 280 duration cam with a stock Chevy head casting. If this is a street driven car (doesn't live on a trailer) I wouldn't consider any cam above 225 degrees of duration (measured at 0.050" of valve lift). A 280 may sound "bad" but you will discover you have no bottom end power what so ever.

Second thing that is wrong is expecting "400 – 425 HP" out of a stock headed Chevy motor. Chevy put their engines on an engine dyno to test the engine's horsepower. They were conservative and knocked off twenty to forty horsepower from what it states on the valve cover or air cleaner just to keep a customer from calling them out for an under powered car. As an example the 290 rated horsepower Z/28 302 motor made 448 horsepower when the dual carbs were mounted on top of the optional cross-ram manifold and it was used without an air cleaner installed, but with the optional Hooker competition headers also bolted to the motor. It was dyno tested with the air cleaner and it cost seven horsepower, but the point is it was tested on a dyno with the two optional engine upgrades that could have been ordered with any Z/28. The single carb stock manifold didn't make near that level of power as the dual plane intake with only 800 cfm of carburation was a restriction in getting air into the motor at high RPM (tested a 7,800 RPM).

448 horsepower is a far cry from the rated 290 horsepower, but the cam was so radical that there was very little to any bottom end torque. By being conservative and installing a rear gear no smaller than a 3.31 while also pushing the 4.11 rear gear coupled with the close ratio transmission they made a race car for the public that with the single four ran well at the track. The fact that you couldn't parallel park the car without burning up the clutch while in front of all of the cops walking in and out of the courthouse as you went down town to pay your latest speeding or reckless driving ticket, it had enough top end power to get you into trouble.

If driving on the street you want bottom end and midrange torque. You gain that by installing a long stroke, large displacement, engine that has a modest cam (you are looking for something similar to a gasoline powered motor out of a late sixties dump truck). Believe it or not they were a well made motor (all HD parts) that with a slight cam change would scream on the street.

You can not add 150 to 250 horsepower worth of nitrous oxide to a 200 horsepower 350 as you should never exceed half of the normally aspirated engine's horsepower; or a 100 shot of horsepower. If you do you will be buying a replacement junk yard stock motor every week as you can get about four hours of racing out of it. I know this from direct observation as an acquaintance I know did exactly this with his wife's car regularly; until she divorced him.

As to your car's four bolt main motor it was unusual for a car motor in 1974, but common for a medium duty truck engine (C30 through a C50). You need only look at the APLICATION CODE stamped onto the front of the motor to find out were it was installed originally (it also tells number of carb venturies and transmission type).

Big Dave
 

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I'm betting that "280" duration has to be "Advertized" not at .050, if it's at .050 can't believe anyone would put that big of a cam in a stocker, but then again some people do weird things,lol..
 

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Discussion Starter · #5 ·
engine part compatability

first, thanks for all of your input!

I have been doing a lot of reading on the web about cam/carb/intake/head/exhaust compatibility. Most of what I read tells me to go by what somebody else discovered through trial and error, ( ie. flow rates, compression, chamber size, stall, gearing).

Is that the only way to get good info? Are there any reliable reference materials out there to study?

Is there any formula for comparing flow rates of intake to head to exhaust ports and runners? Or does it just come down to experience of someone else's trial and error?

thanks
 

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I don't believe you are pushing 400 horse with that setup. That cam shaft basically sounds like an RV camshaft setup. I had a Michigan Cam Shaft (447 lift and 290 duration) in my 355 a decade ago. My heads were similar to yours as well. The car sounded good but no bottom end torque.

I also ran a 350 turbo tranny and a 650 electric choke carb, eddy performer RPM intake, flattop pistons but stock bottom end. This was basically an econo build street driver. Seemed like all my buddies built/drove these due to finances. It was an advertised 325-350 horse at the block. I blew up five of them. They were so popular in the early 90s that the engine shop had a short block ready to go for about 1200 dollars. Same with the 350 turbo tranny. I went through so many of these that I just went down to the tranny shop and gave them my old core and $250 for another one.

I have moved on to 400-800 horse power applications since than. I currently have 11 motors on engine stands. I collect and build them. I have three 327 small journals, one 302, 2 283, 2 350, 1 364, 1 406, 1 457. I have noticed that the driveability of the car goes down once you start adding horsepower to the car.

For example, a 327 hat injected on alcohol with a 671 blower (Teflon blades) makes 700+ horse power but is not very streetable (I have one of these). Now if I did away with the hat injector and the alcohol and replaced them with carbs and gasoline it would be more streetable, but less fun.

If your goal is 500 horse, you need to upgrade the bottom end of the motor. A good rotating assembly will cost you $1600 (crank, rods and pistons). You will need machine work. Balance, hone, block deck, heads milled, etc. This is another $1000. New hydraulic or solid roller Camshaft, lifters, pushrods, rockers will cost another $1000. Need to pay someone to degree the cam for another $125. ARP main studs, head studs, capscrews, good rings, HD wristpins (these don't come with the rolling assembly if you are doing nitrous, blower, turbo, etc). This is another $300-500. Buy after market heads with big valves, springs, etc. Ready to go they will cost you $3000. Blanks plus machine work will cost you about the same. I have bought several sets of the Dart Patriot Head Blanks. Seems like the valves, springs, and head work end up costing about $1000. The blanks are about a $1000. These make a good head for street use. A good intake is about $300. Upgrade your carb to an 850 double pumper. This is $350-500. You will need a fuel regulator and a fuel pump if you do nitrous.

Now you see why Dave's acquaintance just blew motors up and replaced them with junkyard ones. I basically did the same thing until I could afford to build real horsepower.

Once you put the horsepower into the motor than you will be buying a new tranny; guaranteed. I have busted a bunch of 350 turbos. They are not as cheap as they were 20 years ago to replace. I just busted a 4l60E with 400 horse. Upgrading to a 4l80e. This is costing me $3500 for one built for street/strip and with a warranty.

Once you upgrade the motor and tranny you will need to upgrade the rear end and suspension.

Good luck
Dave
 

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Hello,

I have a 74 with a turbo 350 automatic. 30 over cylinders, isky cam with 485 lift, 280 duration. Double hump 186 heads. edelbrock performer and 650 holley. long headers and 2" dual exhaust. I was told it had 400 – 425 HP. That sounds high to me.

My question is what are my best options to get 100 more HP?

I have looked at:
1. stroking it
2. nitrous
3. new pistons, heads, cam, and intake

What have you guys done to get the HP to about where I want it? I know HP costs money, but I don't want to go crazy.

Also when I had my oil pan off I noticed it is a 4 bolt main block. Is there any way that was the stock motor or has it been changed?

thanks
Cheapest and quickest power added would be a SMALL shot of nitrous. Heavy on the small... It will be enough to be able to feel the difference and have some fun. That being said, the power is not there all the time. This can be a good thing or a bad thing. Good in the respect that you can have a very streetable car that is very mild mannered but then performs like a more stout engine for short bursts. The bad thing is that it is not always there, you can run out of nitrous, you have to play with tunes (run cooler plugs, pull timing out...), you can melt cast or hypereutectic pistons if you use too big of a shot...

The best way to add HP to a N/A motor is heads and cam. Again there are trade offs here too. Big flow number heads and large cams look good on paper and sound nasty at an idle but for street driving they don't have power down low. For a steet car, I would sacrifice 20-40 PEAK HP to have a broader HP and torque curve that came in sooner at a lower RPM band. Seat of the pants feel will be better on the street.

This is a spot where displacement can help too. Larger displacement will take better advantage of good flowing heads and give you better power down low (no replacement for displacement).

All this being said, if it were me and I was looking for 400-425 HP, the 350 you have has the potential to get there. I would buy a head/cam/intake/carb combination (maybe pistons too) and have some fun. 1.14 HP per CID is not out of the question at all (400HP/350CID) and will not require "trick" stuff to get there.
 

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Re: engine part compatability

first, thanks for all of your input!

I have been doing a lot of reading on the web about cam/carb/intake/head/exhaust compatibility. Most of what I read tells me to go by what somebody else discovered through trial and error, ( ie. flow rates, compression, chamber size, stall, gearing).

Is that the only way to get good info? Are there any reliable reference materials out there to study?

Is there any formula for comparing flow rates of intake to head to exhaust ports and runners? Or does it just come down to experience of someone else's trial and error?

thanks
Experience helps. Being in my seventies now allows me to look back at years of drag racing experience. I built more than my fair share of engines because I read books that helped me to understand what is going on under the hood. As a result of knowing more than my peers they came to me for motors that met their needs which allowed me to buy more tools to do a better job of building the next motor.

Two years after I had dropped twenty five thousand (1966 dollars here were worth more than today's dollar: as proof I could buy three pieces of Double Bubble or Bazooka bubble gum for a penny back then) dollars into my motor to power my 1967 Chevy II I read Bill Fishers and Bob Waar's How to Hotrod Big Block Chevys.

[ame="http://www.amazon.com/How-Hotrod-Big-Block-Chevys-HP42/dp/0912656042"]How to Hotrod Big-Block Chevys HP42: John Thawley: 0075478001156: Amazon.com: Books[/ame] .

I was amazed to discover that they knew as much about the engine as I did. I had taught myself about the big blocks through trial and error (mostly error). I also figured out that it is a lot cheaper to buy a brand new $12.50 cent book than it was to drop $25K and two years of my life learning the same thing.

That was an epiphany for me. So I started to read more technical books (I also got an Engineering degree but not so much to race but to get a better job than being a street cop as I had been shot once and stabbed twice by the time I retired from the department).

I can recommend a bunch of books to read to get you started. They are all written by another Mechanical Engineer who worked for Mopar and Ford and British Leyland (as he lived in England for a while).

The authors name is David Vizard and he wrote these books because in addition to being an engineer he experimented scientifically on motorcycles, British car engines (almost the same thing) and American V-8's. His published articles for car mags led to publishing books on the subject .

[ame="http://www.amazon.com/David-Vizard/e/B001JOWD4M/ref=sr_tc_2_0?qid=1390874419&sr=1-2-ent"]Amazon.com: David Vizard: Books, Biography, Blog, Audiobooks, Kindle[/ame] .

By the way we don't race flow benches, but generally you take a head's flow rate and double it to see it's MAXIMUM horsepower capability. Heads are also tested with intakes attached to them, and the results are published in car mags (Hot Rod, Car Craft, Popular HotRodding, Super Chevy, Chevy High Performance, etc.).

Big Dave
 

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Doug, my build was based on David Vizard's book "Chevy Small Blocks on a Budget". (Newest Addition) I built my engine using his exact spec's and recommended parts. It made 389HP @ 5800 RPM at the rear wheels on a Mustang Dyno and 430 TQ. The TQ and HP curves are almost dead flat. Killer street motor. This is with a Q-Jet carb'ed 383 and a little 270 duration cam with a @.050 of 219. It idles with a nice lope at 700 RPM and lugs down in 4th gear almost to a crawl. I have changed to a Holly Ultra DP 850 (Better with my 4-speed car) and probably (Seat of the Pants Feel) picked up another 20 HP or so. I highly recommend this book for getting the knowledge to build a super street friendly high HP engine on a budget.
 
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