HT4100 Swap Guide

The Only Way To Cure Hot Knock!


Car: 1984 Cadillac Eldorado FWD HT4100 (4.1L) V8 FI, 92k Miles  - Symptom: Infamous HT4100 "Death Rattle"

Donor Car: 1980 Cadillac Eldorado FWD 368 CID (6.0L) V8 FI, 68k Miles - Engine virtually brand new. Body rotted away - Cost $600



Why Do This?

Well, my buddy of mine bought the car in 2004. Drove it for 3000 miles and then discovered the infamous hot knock that these aluminum engines (HT Series - 4100 4300 4500 4900) have. The run smooth, but lack power and once they warm up, they knock, AKA “Hot Knock” or they have a “death rattle”. The lower connecting rod bearings go which causes the knock. They also are known for leaking antifreeze into the oil because the cylinder walls are floating - meaning that the top of the block does not have a full flat deck where the cylinder wall would meet the block. This provides a very small surface area where the cylinder head meets the block. Causing notorious head gasket leaks and cross contamination of oil and antifreeze.

In short, these engines are junk. No matter what weight of oil (10w30, 10w40) you decide to use in them, they will all eventually knock. Most of them sooner than later. The best thing to do to cure the problem is to get rid of the engine! Don't spend your money buying a rebuild or fixing the one you have. Swap it out!

Complexity & Time Involvement: Keep in mind that this project took us many hours to complete. Several weekends and week nights. This is not something you will get done in an evening.

Things you'll need:

  • New Engine - Parts car's are great for this. Swapable engines would be the 368 CID 6.0L Cadillac engine (known as the little bro), Oldsmobile 403 or 350 CID - many others as well. We decided to keep the Eldo all Caddy and use the 368 cubic inch 6.0L Cadillac Engine. The little bro of the 500CID big block.
  • Engine Lift / Cherry picker
  • Long Breaker Bar
  • Common Sockets & tools.
  • Torch
  • Crank Hub Puller
  • Degresser's, Spray oils (wd40, seafoam) to break away rusted bolts
  • Floor Jack & saftey stands
  • Wheel Chalks
  • Patience!


1984 Eldo HT4100

1) Disconnected the battery & put wheel chalks against the rear wheels

2) Disconnected the hood shocks and unbolted the hood. You will need 2 people for this. Place the hood on its side so that you dont damange the paint on the corners

3) Even though there is this guide, service manuals, etc - it is always good to take pictures of your engine compartment so that you can easily identify the way everything was on the car incase you need to reference back. Now is the time to take as many pictures as you want.



-took old engine out

-got passenger side bracket for driveshaft from ht4100

-drilled out cross member for engine

-used distributor harness from HT4100. Used existing connectors, spliced wires to make it reach to the new location of distributor. Old distributor location was close to the firewall.

- spliced and extended alternator lead

-Throttle body from HT4100

-intake from 368ci dubbed as little bro

-O2 sensor from HT4100

-modified Y-Pipe for 6.0 litre

-TV cable from HT4100 (hard time finding gasket for Tranny)

-new injectors

-Rad from 80

-engine mount from 80

Engine – had 80K on 6.0 litre

-Bought new injectors – had to manually pulse injectors

-new gaskets for entire engine

-new oil pump ->  make this gasket good

-new water pump

-timing chaing gear set (old one was plastic)

-cleaned everything, wire brish,

-boiled intake manifold

-Valve stem thing

-Air pump from 80

-polution / emission control from HT4100

- primed oil pump to get car going

- engine lube oil with all engine components

-look at sensors and see which ones to take (maf, oil, and o2 are from HT4100)


-Primed oil pump with drill

-assemble timing to how it was before

-jumper two wires inside car to disable spark advance, then time manually with timing light

-adjust tps sensor so that the tps is slightly engaged against the throttle flap forward


Additional Resources: