Holden HQ HJ HX HZ WB 283-400 Small Block Chev Pacemaker Headers PH5320

Pacemaker PH5320 headers (extractors) are designed for Holden HQ, HJ, HX, HZ and WB applications fitted with Small Block Chevrolet V8 engines.

Pacemaker lists PH5320 for 283, 302, 305, 307, 327, 350 and 400 Small Block Chevrolet V8 engines. The Tri-Y design uses larger 44mm (1¾") primary pipes, feeding into 51mm (2") secondary pipes and 57mm (2¼") outlets.

PH5320 provides a larger-primary Tri-Y option compared with PH5310, making it particularly suitable for higher-output Small Block Chev combinations where increased exhaust-flow capacity is required while retaining the characteristics of a Tri-Y header.

IMPORTANT – PH5320 will NOT fit slant-plug or raised-port cylinder heads.

Correct engine mounting spacers are required. RH spacer is 1¾" high and LH spacer is 1¼" high.

Please check availability and current lead time before ordering.

Key Features

• Tri-Y header design
• 44mm (1¾") primary pipes
• 51mm (2") secondary pipes
• 57mm (2¼") outlets
• Suits 283-400 Small Block Chevrolet V8 engines
• Manual and automatic transmission compatible
• Power steering compatible
• Air conditioning compatible
• Will fit Turbo 400 automatic
• Will fit Powerglide automatic

Construction

Pacemaker PH5320 uses a Tri-Y configuration with 44mm (1¾") primary pipes feeding into 51mm (2") secondary pipes and 57mm (2¼") outlets.

The standard Pacemaker finish uses the distinctive Pacemaker Blue heat-resistant coating, designed to withstand temperatures up to approximately 800°C.

Additional Options

Ceramic Coating: PHC10 ceramic coating may be available for improved heat management and corrosion resistance. Please contact Best Mufflers for current availability.

DSF9: Replacement cylinder-head exhaust gaskets are available separately.

PEMP350: Pacemaker engine mounting spacers are available where the original correct engine spacers are not fitted.

Vehicle Fitment

• Holden HQ: Small Block Chevrolet V8
• Holden HJ: Small Block Chevrolet V8
• Holden HX: Small Block Chevrolet V8
• Holden HZ: Small Block Chevrolet V8
• Holden WB: Small Block Chevrolet V8 application
• Engine: 283 / 302 / 305 / 307 / 327 / 350 / 400 Small Block Chevrolet V8
• Transmission: Manual / Automatic
• Power Steering: Yes
• Air Conditioning: Yes

Pacemaker lists PH5320 as an HQ-WB 1971-1985 application. Engine availability varied between models and years, so the engine list represents PH5320 header compatibility rather than factory engine availability in every HQ-WB model.

Header Specifications

• Part Number: PH5320 L/R
• Brand: Pacemaker
• Design: Tri-Y
• Primary Pipe: 44mm (1¾")
• Secondary Pipe: 51mm (2")
• Outlet: 57mm (2¼")
• Power Steering: Yes
• Air Conditioning: Yes
• Oxygen Sensor: N/A
• EGR: N/A
• Replacement Gasket: DSF9
• Approximate Fitting Time: 2 hours

Fitment Notes

Slant-Plug Heads: PH5320 will not fit slant-plug cylinder heads. For a larger-primary 4-into-1 header that accommodates slant-plug heads, see Pacemaker PH5325.

Raised-Port Heads: PH5320 will not fit raised-port cylinder heads.

Air Conditioning: PH5320 is compatible with factory air conditioning.

Power Steering: PH5320 is compatible with power steering.

Turbo 400: Pacemaker confirms PH5320 will fit Turbo 400 automatic.

Powerglide: Pacemaker confirms PH5320 will fit Powerglide automatic.

Engine Mounting Spacers: PH5320 will only fit with the original engine mounting spacers or Pacemaker PEMP350 spacers. The spacers must be installed on the correct side:

• RH spacer: 1¾" high
• LH spacer: 1¼" high

Turbo 350 / Column Automatic: Older application information lists Turbo 350 compatibility and modification of column-auto linkages. Pacemaker's current PH5320 application does not specifically state these details, so please confirm the individual vehicle and transmission configuration before ordering.

Protect painted surfaces during trial fitting and check steering, starter motor, transmission, engine mounts, linkages and exhaust clearances before final tightening.

What's Included

• Pacemaker PH5320 left-side header assembly
• Pacemaker PH5320 right-side header assembly

Header bolts, gaskets and other installation hardware should not be assumed to be included unless specifically confirmed with the current kit before ordering.

Recommended With

• DSF9 exhaust manifold/header gaskets
• Pacemaker PEMP350 engine mounting spacers where required
• Suitable intermediate pipes, joiners or exhaust adaptors

PH5320 vs PH5310

PH5320: Tri-Y design with larger 44mm (1¾") primary pipes, 51mm (2") secondaries and 57mm (2¼") outlets.

PH5310: Tri-Y design with smaller 41mm (1⅝") primary pipes, 51mm (2") secondaries and 57mm (2¼") outlets.

The main difference is primary pipe diameter. PH5320 increases the primary size from 41mm to 44mm while retaining the same secondary and outlet dimensions.

PH5320 vs PH5325

PH5320: Tri-Y design with 44mm (1¾") primaries, 51mm (2") secondaries and 57mm (2¼") outlets. Suits air conditioning and Powerglide, but does not suit slant-plug heads.

PH5325: 4-into-1 Competition design with 44mm (1¾") primaries and 76mm (3") outlets. Suits slant-plug heads, but does not suit air conditioning, Powerglide or column automatic.

Why Good Headers & Exhaust Systems Matter

At 4,000 rpm, a 350ci (5.7L) Small Block Chevrolet V8 theoretically draws approximately 11,400 litres of intake air per minute at 100% volumetric efficiency and expels around 34,200 litres of hot exhaust gas per minute at approximately 600°C.

Actual airflow varies with engine capacity, RPM, volumetric efficiency, camshaft, cylinder heads, induction system and engine specification.

A well-designed header and exhaust system helps manage this high gas flow efficiently, reducing restriction and improving exhaust scavenging, torque, throttle response and engine performance.

Installation Tips

Before ordering, identify the cylinder-head configuration and confirm the engine uses standard-port, non-slant-plug heads.

Check that the correct engine mounting spacers are fitted. Pacemaker specifies a 1¾" RH spacer and 1¼" LH spacer, or the corresponding Pacemaker PEMP350 spacer kit.

Where the vehicle has a Turbo 350 or column-shift automatic transmission, confirm the individual transmission and linkage configuration before installation.

Professional installation is recommended.

Warranty & Compliance

Pacemaker headers are covered against manufacturing defects subject to Pacemaker's current warranty terms and conditions.

Installation must comply with applicable Australian state or territory requirements relating to exhaust noise, emissions and vehicle modifications.

FAQ

What vehicles do PH5320 headers suit?
Pacemaker lists PH5320 for Holden HQ-WB Small Block Chevrolet V8 applications, covering the 1971-1985 platform.

What engines do PH5320 headers suit?
Pacemaker lists 283, 302, 305, 307, 327, 350 and 400 Small Block Chevrolet V8 engines.

Are PH5320 headers Tri-Y?
Yes. Pacemaker's current specification identifies PH5320 as a Tri-Y header.

What size are PH5320 headers?
They use 44mm (1¾") primary pipes, 51mm (2") secondary pipes and 57mm (2¼") outlets.

What is the difference between PH5310 and PH5320?
Both are Tri-Y headers with 51mm secondaries and 57mm outlets. PH5310 uses 41mm (1⅝") primaries, while PH5320 uses larger 44mm (1¾") primaries.

Will PH5320 fit slant-plug heads?
No. For the larger-primary Pacemaker option that accommodates slant-plug heads, see PH5325.

Will PH5320 fit raised-port heads?
No. Pacemaker states PH5320 will not fit raised-port cylinder heads.

Will PH5320 fit with air conditioning?
Yes. Pacemaker lists PH5320 as air-conditioning compatible.

Will PH5320 fit with power steering?
Yes. Pacemaker lists PH5320 as power-steering compatible.

Will PH5320 fit a Turbo 400 automatic?
Yes. Pacemaker specifically confirms Turbo 400 compatibility.

Will PH5320 fit a Powerglide automatic?
Yes. Pacemaker specifically confirms Powerglide compatibility.

What engine mounting spacers are required?
PH5320 requires the original correct engine mounting spacers or Pacemaker PEMP350 spacers. Pacemaker specifies RH 1¾" high and LH 1¼" high.

What gasket suits PH5320?
Pacemaker specifies DSF9.

Can I pick up from the store?
Yes. Pick up is available but must be pre-arranged before collection.

How much is freight?
Freight varies depending on your delivery location and where stock is available. Please contact us for freight charges before ordering. Where possible, we can arrange dispatch from the nearest available product location to help reduce freight costs and delivery times.

Do you ship to the USA?
Yes. Best Mufflers regularly ships exhaust systems and exhaust parts to customers throughout the United States.

Please note that import duties, tariffs, taxes, and customs clearance fees are not included in the product or shipping price. Once your order is processed and the applicable charges are calculated, we will send you a secure payment link to finalise the import duties and tariff charges before dispatch.

Customer Support

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