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KDS Engine Mounts B,C or D Body - Which Headers Fit
For those of you using KDS engine mounts in your 77-96 RWD full size GM, which headers fit. KDS says that 97-02 F-Body LS headers fit, but in his own thread on impala SS Forum KDS tried a number of 97-02 f-Body headers that did not fit.
FYI From KDS
KDS brackets fit using the OEM installation locators. They locate the LS engine in the same place as the 5.7L LT1 or 4.3L L99 used to fit. You maintain your transmission location, and driveshaft. You can reuse your existing 4L60E transmission. Even if you have modified your car with any of the aftermarket B Body transmission crossmembers, you can retain the parts you already have.
While there are solutions that include headers (BRP Hot Rods) I don't want to take the chance of driveline vibrations. The Headman headers in the BRP package appear to be made after order. This might make returning them difficult if they did not fit.
The description they’ve provided is not comprehensive enough to allow you to evaluate how it will affect engine fitment in your application, which in turn affects header fitment. To simplify things for you, there is no way to leave the engine and the transmission in the stock location. If you locate the engine/transmission mating plane in the stock SBC location, the transmission will remain in the stock location as they described, but the front surface of the LS engine and the cylinder heads will sit 1-1/4” further rearward in the car. That is the result of the LS engine being 1-1/4” shorter than a SBC and having all that length missing off the back end of the block. In many cases that puts the right side cylinder head so close to the firewall that you can’t install an OE automatic trans dipstick tube, and also creates interference with the stock A/C evaporator housing or heater core inlet/outlet stub pipes. On the bottom side, it moves the motor mount holes in the block so far back that it requires a lot of forward cantilever in the geometry of the engine mounting brackets, which usually means you won’t be able to install a low-mount A/C compressor. Finally, the bulkier bellhousing of the 4L60E transmission you are using may require you to have to cut and modify trans tunnel to achieve desirable U-joint working angles at that same engine position that would clear an old-school GM automatic just fine. In many cases, it makes more sense to mount the front of the LS engine and its cylinder heads in the stock SBC location and move the transmission forward to mate up with the back of the engine. To do that means you need a specific oil pan in many cases. The best approach depends on what you are trying to achieve at the end of the project.
Toddoky thanks for you comments but here is some additional information
1) Body to frame swaps (77-92) Cadillac body into 94-96 Cadillac frames complete with LT1/4L60E are know to clear the 4L60E in these cases. These are bolt on swaps and several have been completed.
2) Its already known that the oil pan will need to be F-body (98-02) or Holley 302-2 Oil pan per KDS instructions. I also already have the 302-2 oil pan.
3) AC clearance is not an issue. I have KWIK Performance relocation mounts to move the compressor up. Low mount AC in pre 93 cars will not fit unless you notch the frame. This is also a long established fact. Anyway I'm old and don't want the AC mounted low, I want it up where I can get to it.
4) Using this swap procedure guarantees that the drive line angle does not change and that factory components (94-96 transmission crossmember, drive shafts, etc) are bolt in.
My only issue seems to be that most people using the KDS mounts used one of the following Manifolds.
It seems its hit or miss as to which 98-02 f-body headers fit. In the Impala SS forum, quite a few installs of the KDS engine mounts have been done, but they all budget installs and used a factory exhaust manifold.
From the KDS website
KDS customers have reported good fitment with various headers made for 98-02 LS1 F-bodies. Minor trimming to the engine crossmember braces may be required
, however in the guys own thread he listed a number of f-body headers that did not fit. Nowhere did anyone list a specific brand and part number for the header that was used. This does not give a good feeling about ordering some random f-body header and hoping for the best.
As to components I already have.
LS3 GM Crate engine 430 HP
4L70E transmission
Speartech engine harness
KDS engine Mounts
KWIK AC relocation brackets
A 94 Fleetwood to source transmission crossmember, driveshaft and rear end)
Car was already setup with 94 b-body gas tank with fuel pump upgrade. (to support the Fi-Tech EFI on the existing 512 CID engine)
94-96 Impala Dynomax 2-1/2 exhaust system
The only piece missing form this puzzle is the header selection. Exhaust system will be from a 94-96 Impala (Dynomax) with only a short piece of custom make pipe from the "X" to the header.
I believe the crate engine has G8 exhaust manifolds (not totally sure), these would probably fit, but at almost 64 years old, if I don't install headers now, I probably never will since changes in my life (not bad, moving a few states away, getting a new house, girlfriend moving in, setup, lawns, etc) will probably take several years. I can't even count on a place to be able to work on any cars once I move. I can see my self saying damn, I lost 40HP by not installing headers while I was swapping the engine.
The info I provided was only intended as general reference data. I’ve not spent any time with those particular GM platforms so you would have more vehicle specific insight than I do. Good luck to you in your search for a well-fitting set of headers.
You should join the group on f.b. called......LSX b-body only............Mike the owner of Kds is on there all the time.....He is a engineer at GM and a vary nice guy....
For those of you using KDS engine mounts in your 77-96 RWD full size GM, which headers fit. KDS says that 97-02 F-Body LS headers fit, but in his own thread on impala SS Forum KDS tried a number of 97-02 f-Body headers that did not fit.
FYI From KDS
While there are solutions that include headers (BRP Hot Rods) I don't want to take the chance of driveline vibrations. The Headman headers in the BRP package appear to be made after order. This might make returning them difficult if they did not fit.
My swap is a LS3/4L70E into a 77 Cadillac.
This is the car about 10 years ago.
did u ever find headers to fit? I’m currently in the middle of a 6.0 swap and I can’t find any information anywhere about headers.
03-19-2019, 10:19 PM
KDS Engine Mounts B,C or D Body - Which Headers Fit 
