Our Chevy Pickup Gets a New Firewall, Engine & Transmission

By Ron Ceridono   –   Photography By the Author

We’ve been following along as Paul Wilson has been in the process of transforming a random pile of parts into a complete ’52 Chevy pickup. So in the pages of Classic Truck Performance we’ve shown how a mildly tweaked ’55 Chevy pickup frame has been straightened and stepped in the rear. It was then equipped with a C4 Corvette independent front and rear suspension by way of kits from Flat Out Engineering. With a rolling chassis (albeit on wooden mock-up wheels) the next step in this evolutionary process was installing the engine and transmission.

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02 Holley carburetor on the newly installed chevy firewall
To secure the small-block, a Speedway universal tubular engine mount will be cut to fit between the framerails.

Read More: How to Restore the Interior of Your ‘41-’46 Chevy Truck

While LS engines and overdrive transmissions are all the rage, Wilson decided to take the old-school approach and go with a Gen II 350 Chevy from BluePrint engines coupled to a Turbo 350 transmission. Speaking of the evolutionary process, the engine Wilson chose is virtually all aftermarket with BluePrint’s own cast-iron block, aluminum heads, and internal components. Equipped with a single four-barrel carburetor and roller hydraulic cam the engine dyno showed 341 hp and 371 lb-ft of torque, which will make for a good daily driver. The transmission has been rebuilt and equipped with a mild shift kit and a “tight” stock stall speed torque converter for efficiency.

03 it was necessary to modify the Chevy’s stock firewall chevy firewall
Due to the long water pump and serpentine front drive on the new SBC, it was necessary to modify the Chevy’s stock firewall.

One of the BluePrint engine options that Wilson chose was a serpentine belt drive system that included an A/C compressor, power steering pump, and alternator. As this system includes a “long” water pump  with all the accessories hung on the front of the engine, its overall length is considerably greater than an engine with a short water pump and “compact” V-belt driven accessories. This brings up the first rule of engine swaps that is absolutely critical: With the length of the engine determined always start at the radiator and fan with measurements then work to the rear of the vehicle—in our case to make room for those vital components the firewall would have to be modified.

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04 A cutoff wheel in a grinder was used chevy firewall
A cutoff wheel in a grinder was used to make a rough cut to allow a test-fit of the firewall.

Read More: Presto-Chango!

To solve our space issue we turned to Chevs of the 40’s in Vancouver, Washington. With over 800,000 parts in stock and a vast dealer network, if Chevs of 40’s doesn’t have what you need, they can get it. For our application we selected a 4-inch setback firewall (PN 3693009S54) for ’47-54 Chevy pickups that is suitable for small- and big-block installations.

05 This initial cut allowed the recess in the replacement firewall chevy firewall
This initial cut allowed the recess in the replacement firewall to fit without interference.

To make absolutely sure we had room for a radiator and fan we cut away the center of the stock firewall to temporarily positioned the replacement. A test-fit of the engine revealed an interference problem with the BluePrint HEI distributor, but that was easy to solve. With a smaller-diameter distributor in place the engine could slide back enough for cooling system clearance, it also allowed it to drop down slightly with the vibration damper and timing cover straddling the rack-and-pinion steering. Which brings us to the second rule of engine swaps. Always have the chassis at ride height and at the intended rake angle (usually around 2 degrees low in front). Then, when locating a carbureted engine, don’t level the valve covers, make sure the carburetor mounting pad is level side to side and front to back so the float(s) will operate correctly. Conventional carburetor intake manifolds have a built in angle for this purpose (with fuel-injected engines this isn’t an issue).

06 Self tapping sheetmetal screws were used to hold the Chevs chevy firewall
Self-tapping sheetmetal screws were used to hold the Chevs Of The 40’s firewall in place.

Read More: DIY Custom Upholstery For 1947-54 Advance Design Chevys

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Satisfied with the engine’s position, the original firewall was cut away, leaving only a flange around the edge to weld the replacement to. The recessed firewall was also welded where it joined the original toeboards. With the firewall installation finished the Speedway Motors tubular engine mount (PN 910182120) was trimmed to fit and welded in place. That brings us to the third rule of engine swaps: Make sure there’s room for steering linkage and exhaust—and we’re happy to report there is (which we’ll show you later).

07 Here the perimeter of the new firewall is screwed to the body chevy firewall
Here the perimeter of the new firewall is screwed to the body, at the bottom it’s clamped to the original toeboard on both sides.

From the outset Wilson’s goal has been to build an affordable truck that will be a comfortable, reliable driver that can go anywhere with no fuss. With Corvette suspension under both ends and a tried-and-true engine and transmission combination in place, we’d say he’s well on his way to meeting his goal.

08 the crankshaft flange and the bellhousing mounting surface were cleaned chevy firewall
To prepare for a test-fit of the BluePrint engine, the crankshaft flange and the bellhousing mounting surface were cleaned before the transmission was installed.
09 As this engine is externally balanced a weighted flexplate was required chevy firewall
As this engine is externally balanced, a weighted flexplate was required.
10 We used ARP flexplate bolts chevy firewall
We used ARP flexplate bolts. No lock washers are used, however thread locker is used and the supplied lubricant is applied under the heads for accurate torque wrench readings.
12 To gain more firewall clearance the HEI distributor was swapped chevy firewall
To gain more firewall clearance the HEI distributor was swapped for an MSD with a smaller-diameter cap.
11 large diameter HEI distributor would prevent the engine from going back chevy firewall
https://inthegaragemedia.com/wp-content/uploads/2024/02/11-large-diameter-HEI-distributor-would-prevent-the-engine-from-going-back-chevy-firewall.jpg
13 the carburetor pad was leveled side to side and front to back chevy firewall
With the engine in place (and the chassis at ride height), the carburetor pad was leveled side to side and front to back so the engine mounts could be positioned correctly.
14 the edge of the new firewall was marked on the body chevy firewall
Satisfied with its fit, the edge of the new firewall was marked on the body, masking tape was used to establish a cut line with a 1-inch lip.
15 With the old firewall cut away a 1 inch lip remained chevy firewall
With the old firewall cut away a 1-inch lip remained. The new firewall will overlap the outside edge and be welded in place.
16 a series of holes were punched in the body that will allow rosette welds to be done chevy firewall
To help tie the old and new sheetmetal together a series of holes were punched in the body that will allow rosette welds to be done from the inside of the cab.
17 The edge of the new firewall was welded to the body then carefully ground chevy firewall
The edge of the new firewall was welded to the body then carefully ground to blend them together.
18 the bottom of the firewall was notched for transmission clearance chevy firewall
With the engine and transmission positioned, the bottom of the firewall was notched for transmission clearance.
19 No sophisticated means of measurement were required chevy firewall
No sophisticated means of measurement were required; this old bowl was the right shape to mark the firewall for transmission clearance.
20 A cutoff wheel was used to trim the bottom of the firewall chevy firewall
A cutoff wheel was used to trim the bottom of the firewall. The trick is to keep the transmission hump as small as possible to maintain foot room and space for the throttle pedal.
21 The Speedway Motors engine mount was notched to sit on top of the framerails chevy firewall
The Speedway Motors engine mount was notched to sit on top of the framerails and wrapped around the inner edges. For strength, a gusset was added on top of the ’rails that also encloses the ends of the tubing.
22 engine mount comes with flanges that would allow it to be bolted in place chevy firewall
The Speedway engine mount comes with flanges that would allow it to be bolted in place; we elected to weld it in.
23 There are a variety of engine mounts available we used the factory Chevrolet style chevy firewall
There are a variety of engine mounts available, we used the factory Chevrolet style.
24 the Progressive Automotive transmission mount was put in place and tack welded for now chevy firewall
With the 350/350 combo located, the Progressive Automotive transmission mount was put in place and tack welded for now.
25 the engine could be positioned back far enough to tuck behind the Corvette rack chevy firewall
Thanks to the Chev’s Of The 40s recessed firewall the engine could be positioned back far enough to tuck behind the Corvette rack-and-pinion steering and allow plenty of room for a radiator and fan.

Sources:
ARP
(805) 339-2200
arp-bolts.com

BluePrint Engines:
(308) 236-1010
blueprintengines.com

Chevs Of The 40’s:
(800) 952-8156
chevsofthe40s.com

Flat Out Engineering:
(714) 639-2623
flatout-engineering.com

MSD:
(888) 258-3835
holley.com

Progressive Automotive:
(740) 862-4696
progressiveautomotive.com

Speedway Motors:
(855) 313-9173
speedwaymotors.com

Click on this issue’s cover to see the enhanced digital version of Our Chevy Pickup Gets a New Firewall, Engine & Transmission.

ctp january 2024

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