diff --git a/fuzzers/007-timing/Makefile b/fuzzers/007-timing/Makefile
index c164609e..60a3fad5 100644
--- a/fuzzers/007-timing/Makefile
+++ b/fuzzers/007-timing/Makefile
@@ -1,5 +1,5 @@
-SLICEL_SDFS = bel/build/CLBLL_L.sdf bel/build/CLBLL_R.sdf bel/build/CLBLM_L.sdf bel/build/CLBLM_R.sdf routing-bels/build/slicel.sdf
-SLICEM_SDFS = bel/build/CLBLL_L.sdf bel/build/CLBLL_R.sdf bel/build/CLBLM_L.sdf bel/build/CLBLM_R.sdf routing-bels/build/slicem.sdf
+SLICEL_SDFS = bel/build/slicel.sdf bel/build/carry4_slicel.sdf routing-bels/build/slicel.sdf
+SLICEM_SDFS = bel/build/slicem.sdf bel/build/carry4_slicem.sdf routing-bels/build/slicem.sdf
 
 run: all
 all: pushdb
@@ -8,17 +8,17 @@ clean:
 	cd bel && $(MAKE) clean
 	cd routing-bels && $(MAKE) clean
 
-bel/build/sdf.ok:
+bel/build/all_sdf.ok:
 	cd bel && $(MAKE)
 
-routing-bels/build/sdf:
+routing-bels/build/sdf.ok:
 	cd routing-bels && $(MAKE)
 
-mergesdfs: bel/build/sdf.ok routing-bels/build/sdf
+mergesdfs: bel/build/all_sdf.ok routing-bels/build/sdf.ok
 	mkdir -p sdfs
-	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEM_SDFS) --site SLICEM --out sdfs/slicem.sdf
-	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEL_SDFS) --site SLICEL --out sdfs/slicel.sdf --json debu.json
 	cp bel/build/*.sdf sdfs
+	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEM_SDFS) --site SLICEM --out sdfs/slicem.sdf
+	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEL_SDFS) --site SLICEL --out sdfs/slicel.sdf
 
 pushdb: mergesdfs
 	mkdir -p ${XRAY_DATABASE_DIR}/${XRAY_DATABASE}/timings
diff --git a/fuzzers/007-timing/bel/Makefile b/fuzzers/007-timing/bel/Makefile
index 7267b8d6..da76f091 100644
--- a/fuzzers/007-timing/bel/Makefile
+++ b/fuzzers/007-timing/bel/Makefile
@@ -1,10 +1,16 @@
-all: build/sdf.ok
+SLICEL_SDFS = build/CLBLL_L.sdf build/CLBLL_R.sdf build/CLBLM_L.sdf build/CLBLM_R.sdf
+SLICEM_SDFS = build/CLBLL_L.sdf build/CLBLL_R.sdf build/CLBLM_L.sdf build/CLBLM_R.sdf
 
+all: build/all_sdf.ok
+
+build/all_sdf.ok: build/carry4_slicel.sdf build/carry4_slicem.sdf
+	touch build/all_sdf.ok
 clean:
 	rm -rf build
 
 build/run.ok:
 	bash runme.sh
+	touch build/run.ok
 
 build/fixup_timings: build/run.ok
 	python3 fixup_timings_txt.py --txtin build/bel_timings.txt --txtout build/bel_timings.txt --site RAMBFIFO36E1 --slice BRAM_L --type timings
@@ -21,3 +27,14 @@ build/sdf.ok: build/bel_timings.json
 	python3 ${XRAY_UTILS_DIR}/makesdf.py --json=${PWD}/build/bel_timings.json --sdf=${PWD}/build
 	touch build/sdf.ok
 
+build/slicem.sdf: build/sdf.ok
+	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEL_SDFS) --site SLICEM --out build/slicem.sdf
+
+build/slicel.sdf: build/sdf.ok
+	python3 ${XRAY_UTILS_DIR}/sdfmerge.py --sdfs $(SLICEL_SDFS) --site SLICEL --out build/slicel.sdf
+
+build/carry4_slicem.sdf: build/slicem.sdf
+	python3 carry4delays.py --input build/slicem.sdf --output build/carry4_slicem.sdf
+
+build/carry4_slicel.sdf: build/slicel.sdf
+	python3 carry4delays.py --input build/slicel.sdf --output build/carry4_slicel.sdf
diff --git a/fuzzers/007-timing/bel/carry4delays.py b/fuzzers/007-timing/bel/carry4delays.py
new file mode 100755
index 00000000..a8b78ef4
--- /dev/null
+++ b/fuzzers/007-timing/bel/carry4delays.py
@@ -0,0 +1,126 @@
+#!/usr/bin/env python3
+
+import sys, os, argparse
+from sdf_timing import sdfparse
+
+model_carry4 = {
+    'type': 'CARRY4',
+    'srcs': {'O5', '?X', '?X_LFF', '?X_LBOTH'},
+    'out': {'CO0', 'CO1', 'CO2', 'CO3', 'O0', 'O1', 'O2', 'O3'},
+    'mux': '?CY0',
+    'pins': {
+        'DI0': {
+            'type': 'A'
+        },
+        'DI1': {
+            'type': 'B'
+        },
+        'DI2': {
+            'type': 'C'
+        },
+        'DI3': {
+            'type': 'D'
+        },
+    },
+}
+
+
+def compute_delays(model, fin_name, fout_name):
+    data = ''
+    with open(fin_name, 'r') as f:
+        data = f.read()
+    sdf = sdfparse.parse(data)
+
+    keys = sdf['cells'][model['type']].keys()
+    if 'slicel'.upper() in keys:
+        sl = 'L'
+    elif 'slicem'.upper() in keys:
+        sl = 'M'
+    else:
+        print("Unknown slice type!")
+        return
+
+    nsdf = dict()
+    nsdf['header'] = sdf['header']
+    nsdf['cells'] = dict()
+    nsdf['cells']['ROUTING_BEL'] = dict()
+
+    for p in model['pins']:
+        pin = model['pins'][p]
+
+        outs = dict()
+        for o in model['out']:
+            outs[o] = []
+
+        res = []
+        cells = sdf['cells']
+
+        for src in model['srcs']:
+            source = src.replace('?', pin['type'])
+
+            _type = model['type'] + '_' + source
+
+            if _type in cells.keys():
+                cell = cells[_type]["SLICE" + sl.upper()]
+
+                for o in model['out']:
+                    iopath = 'iopath_' + p + '_' + o
+
+                    if iopath in cell.keys():
+                        delay = cell[iopath]['delay_paths']['slow']['max']
+                        outs[o].append(delay)
+
+        for src in outs:
+            s = sorted(outs[src])
+            for val in s:
+                res.append(val - s[0])
+
+        delay = round(max(res), 3)
+
+        muxname = str(model['mux'].replace('?', pin['type']))
+        rbel = nsdf['cells']['ROUTING_BEL']['SLICE' + sl.upper() + '/' +
+                                            muxname] = dict()
+
+        iname = 'interconnect_' + pin['type'].lower() + 'x_' + str(p).lower()
+
+        rbel[iname] = dict()
+        rbel[iname]['is_absolute'] = True
+        rbel[iname]['to_pin_edge'] = None
+        rbel[iname]['from_pin_edge'] = None
+        rbel[iname]['from_pin'] = pin['type'].lower() + 'x'
+        rbel[iname]['to_pin'] = str(p).lower()
+        rbel[iname]['type'] = 'interconnect'
+        rbel[iname]['is_timing_check'] = False
+        rbel[iname]['is_timing_env'] = False
+
+        paths = rbel[iname]['delay_paths'] = dict()
+
+        paths['slow'] = dict()
+        paths['slow']['min'] = delay
+        paths['slow']['avg'] = None
+        paths['slow']['max'] = delay
+
+        paths['fast'] = dict()
+        paths['fast']['min'] = delay
+        paths['fast']['avg'] = None
+        paths['fast']['max'] = delay
+
+        # emit new sdfs
+        with open(fout_name, 'w') as f:
+            f.write(sdfparse.emit(nsdf))
+
+
+def main(argv):
+    parser = argparse.ArgumentParser(
+        description='Tool for computing CARRY4 muxes delays')
+    parser.add_argument(
+        '--input', dest='inputfile', action='store', help='Input file')
+    parser.add_argument(
+        '--output', dest='outputfile', action='store', help='Output file')
+    args = parser.parse_args(argv[1:])
+
+    compute_delays(model_carry4, args.inputfile, args.outputfile)
+
+
+if __name__ == "__main__":
+    main(sys.argv)
diff --git a/fuzzers/007-timing/routing-bels/Makefile b/fuzzers/007-timing/routing-bels/Makefile
index ed041a1a..8cf875de 100644
--- a/fuzzers/007-timing/routing-bels/Makefile
+++ b/fuzzers/007-timing/routing-bels/Makefile
@@ -1,4 +1,5 @@
 all: build/slicel.sdf build/slicem.sdf
+	touch build/sdf.ok
 
 clean:
 	rm -rf build