318 upgrades

Bewy said

Is this the AI?

Click to expand...

I asked AI how to make a 300 hp 318 and pretty much gave the standard answers.



"how to make 300 hp with a mopar la 318 ?"








Making 300 horsepower with a Mopar LA 318 is a very achievable goal for a street engine. While the 318 is often seen as the "little brother" to the 340 and 360, it has a lot of potential, especially with the right combination of parts.
Here's a breakdown of the key areas to focus on:
1. Cylinder Heads:

• The biggest bottleneck. The stock 318 heads are quite restrictive. This is where you'll see the most significant gains.
• 340/360 Head Swap: A common and effective upgrade is to use factory 340 or 360 heads. These have larger ports and valves, which dramatically improve airflow. You'll likely need to perform some milling to increase the compression ratio to a desirable level, as the larger chambers can drop compression. You may also need to "gasket match" the intake ports if using a manifold designed for 340/360 heads.
• Porting Stock Heads: If you're on a very tight budget or want to keep original components, you can port and polish your existing 318 heads. This requires a good understanding of cylinder head flow and proper tooling to avoid damaging them.
• Aftermarket Heads:For the most significant power, aftermarket aluminum heads are the way to go. Brands like Edelbrock offer excellent options specifically designed for Mopar small blocks. While more expensive, they offer superior flow and often come with better valve train components.

2. Camshaft:

• Crucial for horsepower. A performance camshaft is essential to take advantage of improved cylinder head flow.
• Hydraulic Flat Tappet vs. Hydraulic Roller: For a street build aiming for 300hp, a hydraulic flat tappet cam is usually sufficient and more budget-friendly. However, hydraulic roller cams offer better performance and durability, especially at higher RPMs, but are more expensive.
• Cam Specs:Look for a cam with more lift and duration than stock, but be careful not to go too wild for a street engine, as it can hurt low-end torque and drivability. Brands like COMP Cams offer a wide range of options specifically for Mopar small blocks.

3. Intake Manifold and Carburetor:

• Dual Plane Intake: A good dual-plane aluminum intake manifold (like an Edelbrock Performer RPM Air-Gap) is ideal for a street 318, as it provides a good balance of low-end torque and high-RPM power.
• Four-Barrel Carburetor: A 600-650 CFM (Cubic Feet per Minute) four-barrel carburetor from brands like Holley or Edelbrock will be a significant upgrade over a stock 2-barrel. Ensure it's properly jetted and tuned for your specific engine combination.

4. Exhaust System:

• Headers: Long-tube headers are highly recommended for maximizing exhaust flow and scavenging, which directly translates to more horsepower.
• Free-Flowing Exhaust: A dual exhaust system with performance mufflers will allow the engine to breathe freely.

5. Ignition System:

• Electronic Ignition: Upgrade to an electronic ignition system (if not already equipped) for a stronger, more consistent spark. This can be a simple aftermarket kit or a full MSD setup.
• Distributor Recurve: Ensure your distributor is properly recurved to match your engine's new characteristics.

6. Compression Ratio:

• Optimize for Pump Gas: Aim for a compression ratio in the 9.0:1 to 9.5:1 range for reliable operation on pump gas. This can be achieved through head milling, thinner head gaskets, or higher compression pistons.

7. Bottom End (Optional, but beneficial):

• Freshen Up: While 300hp can often be made on a stock or lightly rebuilt bottom end, if you're doing a full engine rebuild, consider new pistons, rings, and bearings for reliability.
• Stroker Kit: If you want to push beyond 300hp or build a really stout 318, a stroker kit (e.g., to 340 or 349 cubic inches) will significantly increase displacement and power potential. This is a more involved and costly modification.

General Tips for Success:

• Balance and Blueprint: For any performance build, having the rotating assembly (crankshaft, connecting rods, pistons) balanced will improve smoothness and durability. Blueprinting ensures all engine clearances are optimized.
• Proper Tuning: Once assembled, the engine will need proper tuning (carburetor, ignition timing) on a dyno or by a skilled tuner to extract maximum power and ensure reliability.
• Consider a 360: While building a 300hp 318 is satisfying, it's often more cost-effective to achieve higher power numbers (especially 350hp+) with a 360 LA engine, as they start with more displacement and generally better heads. However, if you're committed to the 318, the above steps will get you there.
• Research and Consult: Join Mopar forums, read reputable engine building books, and consult with experienced engine builders to get specific recommendations and advice for your budget and goals.

By focusing on these areas, you can definitely make a strong and fun 300 horsepower Mopar LA 318!


"what camshaft would you recommend for a 300 hp la 318?"







You're aiming for a solid 300 horsepower from your Mopar LA 318, and the camshaft is undeniably one of the most critical components for achieving that. Given the modifications you'll likely be doing (especially heads, intake, and exhaust), you want a cam that complements those upgrades and broadens the powerband.
Here are a few strong recommendations for hydraulic flat tappet camshafts that would be excellent choices for a 300 hp LA 318 street build, along with explanations of why:
Key Camshaft Parameters to Understand:

• Duration (at 0.050" lift): This is the most common and useful way to compare cams. It tells you how long the valve is held open. Longer duration generally means more top-end power but can reduce low-end torque if too aggressive.
• Lift: How far the valve opens. More lift allows more air/fuel mixture in, but is limited by your cylinder head's flow and valve spring capacity.
• Lobe Separation Angle (LSA): Affects powerband width and idle quality. Tighter LSAs (e.g., 106-108 degrees) tend to have a choppier idle and more peaky power. Wider LSAs (e.g., 110-112 degrees) provide a smoother idle and a broader powerband.
• RPM Range: The manufacturer's recommended operating range for the cam.

Recommended Camshafts for a 300hp LA 318:

1. COMP Cams Xtreme Energy XE262H (Part Number 20-222-3)
   • Duration @ 0.050": 218° Intake / 224° Exhaust
   • Lift with 1.5 Rockers: ~0.462" Intake / ~0.470" Exhaust
   • Lobe Separation Angle (LSA): 110°
   • RPM Range: 1300 - 5600 RPM
   • Why it's a great choice: This is a very popular and well-regarded cam for street small block Mopars. The Xtreme Energy series is known for its aggressive lobe profiles, which provide excellent throttle response and a strong mid-range punch without sacrificing too much streetability. The 110 LSA offers a good balance of power and a slightly noticeable, but not overly radical, idle. It's a fantastic match for upgraded heads (like ported 340/360 heads or aftermarket aluminum heads) and a dual-plane intake.
2. Edelbrock Performer RPM Camshaft (Part Number 7177)
   • Duration @ 0.050": 234° Intake / 244° Exhaust
   • Lift with 1.5 Rockers: ~0.488" Intake / ~0.510" Exhaust (check specific details, some sources list slightly different lifts, especially with different rocker ratios)
   • LSA: Typically around 112°
   • RPM Range: 1500 - 6500 RPM
   • Why it's a great choice: This cam is designed to be paired with Edelbrock's Performer RPM intake manifold and cylinder heads, forming a well-matched system. It's a step up in aggressiveness from the XE262H, offering more top-end power. While it has higher duration, the wider LSA helps maintain street manners. If you're going with Edelbrock Performer RPM heads and intake, this cam is engineered to work seamlessly with them. It will likely give you a noticeable performance idle.
3. Mopar Performance Purple Shaft (e.g., P4120235, "284/.484")
   • Duration @ 0.050": Often in the 228-232° range for street versions (gross duration is higher)
   • Lift with 1.5 Rockers: Often around 0.474" - 0.484"
   • LSA: Typically 108°
   • Why it's a classic choice: These cams are "old school" Mopar performance. They tend to have tighter LSAs, which gives them a choppier, more aggressive idle. They can make great power, but might be a bit more finicky to tune for optimal street manners than the Xtreme Energy series. If you want that traditional Mopar muscle car sound, a Purple Shaft is a contender, but confirm the specific grind details as there are several "Purple Shaft" options.

Considerations when choosing:

• Cylinder Heads: This is paramount. If you're still running very restrictive stock 318 heads (even with porting), a cam that's too big will not perform well. The recommended cams above assume you've upgraded to 340/360 heads or aftermarket aluminum heads, which are crucial for getting the airflow needed to support 300 hp.
• Converter Stall Speed (if automatic): More aggressive cams require a higher stall speed torque converter to allow the engine to get into its powerband more effectively when launching. For these cams, something in the 2000-2500 RPM range would be a good starting point.
• Gear Ratio: Taller (numerically higher) rear end gears will help the engine get into its powerband more quickly with a performance cam.
• Valve Springs: Any of these performance cams will require upgraded valve springs that can handle the increased lift and spring pressure. Do NOT reuse stock valve springs.
• Rocker Arms: While 1.5:1 ratio rockers are common, some builders might opt for 1.6:1 rockers to increase valve lift further, but this must be done with careful consideration of piston-to-valve clearance and spring capacity.

My top recommendation for a balanced 300hp street 318:
I would lean towards the COMP Cams XE262H (Part Number 20-222-3). It offers an excellent blend of strong mid-range power, good throttle response, and still maintains decent street manners. It's a proven performer in Mopar small blocks and will work very well with the other upgrades you plan to make (heads, intake, exhaust, carburetor).
Always consult the cam manufacturer's full specifications and recommended component list (valve springs, retainers, pushrods, lifters) to ensure compatibility and optimal performance.


"What about stall speed and gearing for a good mix of street strip driving ?"







You're hitting on two of the most critical elements for balancing streetability with strip performance: stall speed and gearing. These need to work in harmony with your camshaft and the engine's powerband.
Let's break them down for your 300 hp Mopar LA 318 with a camshaft like the COMP Cams XE262H.

Stall Speed (Torque Converter)​

The torque converter's job is to allow the engine to rev up into its powerband before fully engaging the transmission, which provides a stronger launch.

• Understanding your Cam's Needs: The COMP Cams XE262H has an RPM range of 1300-5600 RPM. While it makes good low-end torque for a performance cam, its real power starts building higher up. A stock torque converter will likely only stall around 1600-1800 RPM, which is too low for this cam.
  
  
  
• Street/Strip Sweet Spot: For a good mix of street and strip, you generally want a stall speed that is slightly above the engine's idle RPM with your chosen cam, but not so high that it makes daily driving feel "loose" or inefficient.
  • Recommendation: 2200-2800 RPM stall.
    • 2200-2400 RPM: This would be on the tighter side, offering excellent street manners, minimal heat, and still a noticeable improvement over stock. It will allow the engine to get just into the lower end of its powerband before the car starts moving. This is a great choice if you prioritize street cruising comfort.
    • 2500-2800 RPM: This range will give you a stronger hit off the line at the drag strip and better exploit the cam's mid-range power. It will still be very streetable, though you'll notice the engine revving a bit more before the car moves from a stop. This is likely the ideal range for a "good mix." You'll feel it more on the street, but it won't be obnoxious for daily driving.
• Things to Consider:
  • Transmission Type: We're assuming an automatic transmission (likely a 904 or 727 for a Mopar).
  • Converter Quality: Don't cheap out here. A good quality performance torque converter from a reputable brand (e.g., Hughes Performance, TCI, B&M, Coan) will be more efficient, generate less heat, and be more durable than a generic "high-stall" converter.
  • Heat:Higher stall speeds generate more heat. If you're going above 2500 RPM, strongly consider adding an auxiliary transmission cooler. This is cheap insurance.
    

Gearing (Rear End Ratio)​

Rear end gears multiply the torque sent from the transmission to the wheels. Higher (numerically larger) gear ratios provide better acceleration but reduce highway cruising RPM and fuel economy.

• Understanding your Goal: "Street/strip" means you want quick acceleration at the track but still comfortable cruising on the highway without the engine screaming.
• Factors to Consider:
  • Tire Diameter:Taller tires effectively "lower" your gear ratio, while shorter tires "raise" it. You'll need to factor in your tire height (e.g., 26-28 inches for a typical street/strip Mopar).
    
    
  • Transmission Gearing: Mopar 3-speed automatics (904/727) are 1:1 in high gear. If you were considering an overdrive transmission, that would significantly change gear recommendations.
  • Engine RPM at Highway Speed: This is crucial for streetability. Use an online RPM calculator (many available) to predict your highway RPM based on tire size, gear ratio, and transmission ratio.
• Recommendations for a "Good Mix":
  • 3.23:1 to 3.55:1:This is the sweet spot for a well-rounded street/strip setup with a 3-speed automatic and a 300 hp 318.
    • 3.23:1: Excellent for highway cruising. Still offers a noticeable improvement in acceleration over stock gears. Good if your street driving involves a lot of highway miles.
    • 3.55:1: This is often considered the ideal "performance street" gear. It provides strong acceleration from a stop and through the gears, making the car feel much more responsive. On the highway, it will run slightly higher RPMs than 3.23s, but generally still very tolerable for most. This ratio pairs extremely well with a 2500-2800 RPM stall converter.
  • 3.73:1: This would lean more towards the "strip" side of the equation. It will offer fantastic acceleration and really wake the car up at the track. However, highway RPMs will be significantly higher, making long cruises less comfortable and impacting fuel economy more noticeably. If you spend very little time on the highway, or if you're willing to sacrifice some highway comfort for more strip performance, this is an option.
• Axle Type: For Mopar small blocks, the 8 3/4" rear end is highly desirable. It's strong, has easily swappable gear sets ("drop-out" third member), and is widely available with aftermarket support. If your car still has a smaller 7.25" rear end, an 8 3/4" swap is a very worthwhile upgrade for durability and gear availability.

Synergy of Stall and Gearing:
The chosen stall speed and gear ratio work together. A higher stall allows the engine to jump into its powerband more quickly, and the numerically higher gears keep it there as you accelerate.
For your 300hp 318 with an XE262H cam, a 2500-2800 RPM stall converter combined with 3.55:1 rear end gears would give you a fantastic balance. This setup will launch hard at the track, feel lively on the street, and still be quite manageable for regular driving. If highway comfort is a top priority, dropping to 3.23:1 gears with a 2200-2400 stall would still be a good combo.