How do you line up the engine mounts and trans crossmember on an LS swap when holes don't line up?
Make one end adjustable and set the other where it needs to be.
Last updated
Engine side:Adapter plates bolt to the LS block and take a classic small-block Chevy 3-bolt mount; different hole positions move the engine fore and aft. Flat adapters like ICT's give several mount positions and raise the crank centerline slightly (0.177 in in ICT's case — note it if hood clearance is tight). Adjustable mounts use carriage bolts in slotted plates, so you can slide the engine fore and aft, then lock it down. One builder used them to dial the engine position exactly after changing headers and dropping a supercharger that had needed the engine 1-1/4 in forward.
Transmission side: adjustable swap crossmembers have slotted holes and use the frame's multiple factory holes for fore/aft adjustment. Some also offer multiple heights to set the driveline angle.
Order of work: set the engine position first (firewall, header and hood clearance), then locate the crossmember under the transmission, then measure for the driveshaft.
LS mount bosses are roughly where SBC mounts were; common adapters convert the LS block to the classic three-bolt Chevy mount; adapter hole offsets move the engine fore/aft.
Related fixes we recommend
How do Dirty Dingo slider mounts work with the stock stands, and what are the fitment trade-offs?
What we recommend
Dirty Dingo sliders replace the engine-side brackets and bolt to the stock frame stands and stock-style SBC motor mounts, so you keep your existing stands. The main trade-off is that they raise the engine about 1/2 inch, which affects oil pan clearance and driveline angle; the angle can be corrected at the transmission crossmember. With a GM Hot Rod pan the pan sits just a hair below the crossmember, while a truck pan sat 1.75 inches below, and a CTS-V pan is about 2 inches shallower. We recommend poly mounts, because aftermarket replacement rubber mounts tear out quickly. During install, leave the exhaust manifolds off and keep the sliders loose so you can position the engine, then tighten them once it sits on the mounts. On a 67-72, running clamshell-style mounts with this setup requires changing to the 73-87 frame tower brackets.
Check this first:
Check oil pan clearance to the crossmember
Check driveline angles after setting engine height
Confirm your frame tower style if using clamshell mounts
Check this first
Check oil pan clearance to the crossmember with the engine at final height.
Check driveline angles after setting engine height.
Confirm frame tower style (67-72 vs 73-87) if using clamshell mounts.
Try this, then this
Bolt sliders to the block and set the engine on the stock stands with poly mounts.
Leave sliders loose and manifolds off; position the engine, then tighten.
Verify pan clearance and driveline angle; correct at the transmission crossmember.
How you know it's fixed
Engine sits level, pan clears the crossmember, driveline angles are within spec, and nothing contacts at full suspension travel.
Still not fixed?
If the pan hangs too low, switch to a shallower pan (Hot Rod or CTS-V); if angles are off, adjust at the transmission crossmember.
Key numbers
What
Value
What sliders replace
They take the place of the engine side brackets on the original small block and mate up to the stock stands and motor mounts on the frame.
Engine raise
The Dirty Dingo mounts raise the engine 1/2 in, which is the main fitment trade-off.
Poly vs rubber mounts
Swappers recommend poly mounts because aftermarket replacement rubber mounts are junk and tear out quickly.
Oil pan clearance examples
With the sliders, a truck oil pan sat 1.75 in below the crossmember, while a GM hot rod pan sat just a hair below it.
Driveline angle correction
Driveline angle changes from the raised engine can be corrected at the transmission crossmember.
67-72 clamshell note
On a 67-72, the frame engine tower brackets need to be changed to the 73-87 design to use clamshell engine mounts with the sliders.
Install tip
Leave the exhaust manifolds off and keep the sliders loose so the engine can be slid around for adjustment, then tighten once it sits on the mounts.
Every option we know of
Maker / product
Part #
Fits
Price
Where
Status / notes
Dirty Dingo Adjustable slider engine mounts
Bolt to stock frame stands and SBC-style mounts
about $150-$250 (approximate)
dirtydingo.com / sdparts.com
In production Raise engine ~1/2 in
Energy Suspension Poly motor mounts
Replacement for stock-style mounts
about $50-$80 (approximate)
summitracing.com
In production
Prices are approximate as of September 2026. We list every option we know of, including small shops and used parts we can't link to. Confirm fitment with the seller.
