1988 K5 Blazer modifications.

I've had this Blazer since around 2002. The parts collection and prep work for this project took about ten years...

In Fall 2009 the body shell was replaced with one that has no rust/rot. This is why it was changed. When the rusted out section was cleared, there was a hole big enough to drop a basketball through. The rest of the body wasn't any better. It took about five months of fairly intense work to do. About 250 hours of work. Cost was pretty high. Overall, still cheaper than buying a new and similar SUV. This was not done as if it was a show truck. Not cleaned to bare metal, nor polished and chromed. Just a street truck. New aftermarket body mounts. Painted underneath with grey POR-15. Frame painted with black POR-15.

In August 2010 the original 350 Chevy gasoline engine was removed and a rebuilt 1996 Cummins 4BT diesel engine swapped in. Wasn't really a difficult job. The seller painted it black with POR-15 paint. I would have kept the factory beige color, but it wasn't worth stripping and repainting. The positioning of the 4BT was directly related to the 350 location. When the 350 was removed the transmission was kept in the same spot and the 4BT was set front to rear to match that. The Blazer motor mount brackets were moved forward on the frame 1 1/2 inch. A jig was made to drill the holes. Passenger side and Driver's side. Spacers added to the motor mount brackets to fit the Ford van mounts for height and angle. The factory crossmember was removed and replaced with a diesel version Offroad Design crossmember that went directly under the engine. Vertical position was quite close to the 350 and pretty much centered. The stock Ford van motor mounts and adapter plate/flywheel were used. Unlike the Chevy adapter plate, this has the engine straight up and not tilted to one side. Linkages were simple. The throttle cable needed a bracket to mount on the injection pump. The throttle arm on the pump was lengthened an inch to match the pedal travel. Engine clearance was OK except for two issues. First was the oil pan and front axle. The Blazer front was raised 3" and now clears quite well. The other problem was the exhaust clearance to the firewall.

The exhaust system was bought as an aftermarket Dodge truck type. The provided front pipe just didn't fit. A common galvanized 2" pipe elbow was bought at Home Depot. The outside ends were machined to match the raised ring that the clamps engage. The threads were ground out so the inside diameter matches the turbo output flange and the pipe clamp ring. The pipe was cut and modified to fit. Worked fine and gave good clearance on the firewall. The muffler and tailpipe fit well in the Blazer. The tailpipe did require to be shortened a bit at the muffler end. The front pipe from the turbo outlet was connected to a flexible junction, and then adapted from 3" to 4" before the muffler. A mount was made to hold the turbo outlet pipe to the bellhousing before the flex coupling. Another mount in front of the muffler and another toward the back of the tailpipe. Clearance is good and it doesn't rattle.

A panel was cut into the rear floor for easier fuel pickup access. It can now be reached without dropping the gas tank. For the 4BT swap the fuel tank was drained and flushed with kerosene. The fuel pickup was modified. Stock electric pump removed and replaced with a piece of 3/8" steel tubing and diesel approved rubber hose. A brass fitting was machined and soldered to the bottom to remove the stock input filter as shown. A separate feed line was added for the winter heater. It's positioned several inches off the bottom of the tank so the heater won't run it out of fuel. The stock Blazer fuel lines were modified or replaced to fit the Cummins input and the return connection. Then, fastened to the back of the block and down to the stock lines. A Racor 10 micron front fuel filter is now used. Much easier to change and works better than the stock one. Provides extra filtering for the diesel fuel. The Cummins mechanical lift pump was replaced by a Chevrolet diesel electric pump close to the tank. A 30 micron Racor fuel filter was used just before it as Racor recommended. The electrical pump makes it very easy to bleed air from the fuel system. The worst problem was fuel filters clogging and blocking fuel so it stalled. Took a fair bit of parts to make it reliable. Replaced the Racor R60S filter with the 10 micron R60T model. Made a big improvement. The fuel pressure gauge was very important for seeing the problem.

The normal air filter did not pass enough air. When going up hills on the interstate, it couldn't keep at 65mph. Even the new air filter wasn't better. This was changed to an air filter used for larger diesel engines, a NAPA Gold 6562. The Blazer now easily keeps speed on the hills, and seems to increase the mileage by 2 or 3 more MPG. Very helpful.

Original 10 bolt front axle was replaced with a 1979 Ford F-350 high pinion Dana 60 with 3.54 gears. All rebuilt, new PowerLock differential added. Brakes rebuilt. Shock mounts changed, new shocks. 1995 Dodge u-bolts used. New 3" lift springs installed. Chevy Dana 60 steering arm used. New steering damper. New brake dust shields. New kingpins. A special tool was made from a Mopar torsion bar to remove/install the upper kingpins. Since the front was raised 3" to clear the axle and oil pan, the drag link was at an angle. It wore out fairly fast. A spacer was added when the drag link was replaced. Offroad Design is the source.

The rear axle is a 1995 Dodge 2500 Dana 60HD. Naturally, with 3.54 gears. Detroit Locker 35 spline differential added. Aftermarket Moser 35 spline axle shafts used. Stock 13" drum brakes kept for the better parking brake. One benefit is simple repair of the brakes. Just remove the wheel and the brake drum comes off. No need to remove the axle and hub. New hub seals. Shock mount bolts extended, new Monroe 37098 Sensa-Trac shocks. Brackets changed to dual shocks which is an improvement and more rugged. A 3 degree wedge is used to correct pinion angle. New u-bolts. Heavy duty 7 leaf springs kept. Moved the spring hangers 1/2" out from the frame to match the Dodge axle spring perches. Parking brake connected to stock Blazer cable, pedal. Aftermarket aluminum back cover also.

Bellhousing, flywheel, clutch, transmission and transfer case replaced in 2009. The Ansen adapter bellhousing is an aftermarket steel type that accepts both Chevy and Ford transmissions, and it also bolts to either a SB Ford or Chevy engine. The Cummins aluminum adapter plate had to be machined to clear the various Ansen bolts. Done on a drill press with a 3/4" end mill. Not difficult. All bolted up very well and cleared the McLeod 12" clutch and pressure plate. A Ford T-19 four speed transmission was chosen over the stock SM-465. It was a more useful close ratio and has a synchronized first gear. The T-19 first gear ratio is 4.02:1 while the SM-465 is 6.55:1. The other gears are closer ratio as well. It works much better for daily driving. A Ford NP205 transfer case used. The transfer case has the front driveshaft on the driver's side to match the Ford Dana 60 front axle. A hole had to be bored in the tailhousing of the T-19 to clear the NP205 shift rod. The tailhousing was for a different transfer case. Fit fine once done. Two new driveshafts, all 1410 u-joints. Custom speedometer cable. Changed problematic hydraulic clutch linkage to the earlier mechanical linkage. All aircraft rod ends used. Z-bar reinforced. Pedal to z-bar link is 3/4" aluminum rod. New pilot bearing, throwout bearing and fork. Lakewood boot. Custom z-bar mount on bellhousing.

The flywheel that came with the 4BT was made for an 11" clutch. I wanted the 12" clutch, so I drilled the flywheel for it. I used an aftermarket flywheel as a jig. The two flywheels were bolted together using the 11" bolt holes. This centered it. Then, the 3/8-16 tap drill was run through the 12" holes in the aftermarket flywheel to precisely mark the new holes on the Cummins flywheel. It was run maybe 1/8" deep so there would be no variation. Then, the flywheels were separated and the holes drilled straight on a drill press. Depth was set to be identical to the 11" tap holes and all equal. The holes were then drilled by a 3/8" bit to a depth of a quarter inch. Then, the tap was put in the drill chuck and started exactly vertical. It was finished afterwards with a blind hole tap to the same depth as the 11" pressure plate holes. The taps were lubricated with moly grease which I have found the best for tapping any metal. The 12" pressure plate bolted up perfectly well and has no vibration. Since the engine tops out at around 2,500 RPM balance isn't critical. If it were a 7,000 RPM racing engine I'd do it differently.

Radiator replaced with an aluminum version. Dual electric fans. Upper hose is Gates 21729 from Dodge diesel truck. Lower hose is a generic FM68 from NAPA. New aluminum heater core. The first days the Blazer was back on the road with the 4BT the outdoor temperature was in the mid 90's. Water temperature never got over 180 even in stop and go traffic. Heater and radiator hose connections were simple. The lower hose connection on the Cummins was pointed straight down. This would have been a problem. I sawed off the original hose end, and also cut off an end from a used small block Chevy Edelbrock aluminum water pump. Then had a welding shop put them together. Worked fine.

Wiring was simple. The Chevy alternator was kept by a pulley swap. A single spacer was made to bolt it in and the back housing rotated 90 to make the wiring easier. The starter was jumpered so a Ford-type external relay could be used. Makes overall wiring simpler. Stock starter purple wire connected to the relay, large cables between the battery, relay and starter. A #10 red wire from the relay battery post to a new 30a breaker on the firewall, then to the firewall fuse block plug. The pink wire was connected to the Cummins fuel shutoff solenoid and cold start switch and solenoid. A bunch of wiring associated with the 350 TBI was removed along with the computer.

Changed to a rebuilt hydroboost 1 ton truck power brake unit. Stainless steel brake lines used throughout. New master cylinder. Brakes are essentially new and equivalent to a 1 ton truck.

The rebuilt power steering pump was removed and the reservoir modified for a second return line. A small 3/8" tubing elbow was welded in place. The pressure hose had too many bends at the pump end. It was shortened and welded back together.

Borgeson steering shaft with needle u-joints replaced the stock rag joint type. Seems better.

Gauges changed to aftermarket mechanical oil pressure and water temperature, and voltage. Later added a good quality fuel pressure gauge. That warned if there were fuel pressure problems. If pressure dropped, the engine stalled and wouldn't start. This really helped.

Upgraded to an aftermarket 43 gallon gas tank several years ago. Large ID diesel fuel filler used. I dislike the one with the flap and small hole. Hard to add fuel from a five gallon can.

BF Goodrich 37" tires used. Rubber overdrive, in effect. I had to do a bit more trim to the front fenders for clearance, but nothing else. Offroad it would need more lift so it wouldn't rub. Aluminum 17" rims from Zeke's in North Dighton, MA.

New paint job done in December 2009. Late model Dodge PB7 Patriot Blue color. Doors and tailgate replaced by the body shop. Body in essentially new condition.

Second battery added, Optima Yellow Top. Cole-Hersee battery isolator used so both are charged by the alternator, but neither battery will discharge the other. Primary battery is an Optima Red Top. The Optima Yellow Top is used to power a radio, the 110vac inverter and the Espar Airtronic D2 heater. The Airtronic heater keeps the Blazer interior around 60 24/7 in the winter. Very comfortable and no frost or snow stays on the windows.

Original parts left are the frame rails/crossmembers, glass, dashboard, rear roof, hood, radiator support and numerous smaller parts like wiring. Most of the Blazer has been replaced. Old parts were scrapped, sold or given away. Frame is OK. Otherwise I would have changed it. The one that I bought with the body shell was decent.

Eventually the interior may be upgraded. Later model seats, new rugs.

Over time, the fuel and air made a significant improvement. Reliable in cold weather, and better mileage. That is better than factory equipment.

It's been an interesting project, but a whole lot of work... Most of it was fun or "educational".