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CHEMICO
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Chemico: understand the range before choosing
Chemico makes grinding and lapping compounds. Both AutoMotoPart entries on this page repeat the same 110 g double-ended valve-grinding-paste product rather than two different grades or pack sizes. One end contains coarse 80-grit silicon-carbide paste for initial cutting; the other contains fine 220-grit paste for finishing, both in Chemico's lithium-grease base.
AutoMotoPart currently lists 2 Chemico items. The largest Chemico groups are 2 duplicate entries for the same 110g double-ended tin. Chemico totals can change, so a category count is orientation rather than proof that a particular reference suits a vehicle, workplace or job. The exact Chemico listing, its current technical information and the item in front of you must agree.
What the Chemico page actually covers
| Product group in this range | Current entries | Selection focus |
|---|---|---|
| 110g coarse/fine valve-grinding paste | 2 duplicate entries | Both entries are the same 110g double-ended tin: verify coarse 80/fine 220 ends, engine permission, valve/seat condition and complete abrasive removal. |
There are two identical titles but one product specification. The tin supplies both stages, not a choice between two packs. Keep the lids/end labels readable and use separate clean applicators so 80-grit coarse material cannot contaminate the 220-grit finishing end.
Build a reliable shortlist
Begin with the engine repair manual and measured failure. Confirm head/valve design, whether lapping is permitted, seat/face material and the accepted inspection method. Strip, label and clean components in a controlled area before opening the abrasive tin.
| Check | Why it matters | Useful evidence |
|---|---|---|
| Repair permission | Some coated/hardened valves or seats must not be hand-lapped | Exact engine manual and component material |
| Damage | Paste cannot repair cracks, burning, bending, recession or guide wear | Visual inspection, measurements and leak/compression diagnosis |
| Grade | 80 grit cuts faster; 220 grit refines and can still remove metal | Chemico end label and minimum necessary process |
| Geometry | Seat contact width/location and valve margin control sealing and heat flow | Maker's angle, width and recession specifications |
| Contamination | Silicon carbide left in an engine can rapidly wear moving parts | Isolated work area, solvent cleaning and clean-wipe check |
| Assembly | Springs, collets, timing, clearances and torques remain safety-critical | Service procedure, renewed seals/fasteners and final tests |
If the manual prohibits lapping, dimensions are outside limit or a continuous band cannot be achieved without substantial cutting, stop. Have the seat/valve machined or replaced by a competent engine specialist; do not keep grinding until the visible defect disappears.
One 110 g tin, two controlled abrasive stages
Chemico's official page identifies the double-ended tin as 110 g net, with coarse 80 grit and fine 220 grit. Silicon carbide is sharp and brittle, continually exposing cutting edges as particles fracture. The lithium-grease base holds abrasive at the contact area; that persistence is useful during lapping but makes cleanup especially important.
Coarse is for initial cutting only where light pitting and the service procedure justify it. It creates deeper scoring and removes geometry faster. Fine is the finishing compound and may be the only grade needed for a lightly marked serviceable seat. Never mix the two, dip a coarse-coated stick into fine or turn the tin over with an unclean lid/workbench.
Teardown and inspection before any lapping
Make the engine safe, drain fluids where required and remove the cylinder head by the maker's sequence. Keep debris out of cylinders, ports and oil/coolant passages. Use the correct valve-spring compressor, eye protection and a controlled tray for springs, retainers, collets and shims. Mark each valve and mating position unless the manual requires replacement.
Clean carbon by an approved non-damaging process, then inspect under good light. Measure stem diameter/guide clearance, valve face and margin, seat contact, runout/recession and head flatness as specified. A shiny line alone does not prove serviceability. Cracks, burning, impact, a knife-edge margin, loose guide or deep corrosion are reasons for specialist repair, not more paste.
Apply paste without contaminating stem or guide
Chemico instructs users to apply a small amount to the valve seat and avoid stem/guide contact. A few spaced dabs are easier to control than coating the entire valve. Insert the clean valve into its identified guide without dragging paste along the stem. Use a suitable suction lapping tool where the manual permits.
Rotate back and forth with the specified light hand pressure rather than spinning continuously. Lift the valve periodically so paste redistributes instead of cutting the same track. Do not use a power drill unless the engine maker explicitly authorises a controlled method; speed can embed grit, overheat or produce a misleading polished band while altering seat geometry.
Judge the contact band, not a fixed lapping time
Clean the face and seat before checking. The desired band must be continuous, concentric and at the width/location specified for that engine; there is no universal acceptable width. Use engineers' marking compound, vacuum testing, solvent leakage or another manual-specified method. Do not confuse an even grey finish with correct valve recession or guide alignment.
If coarse was used, remove it completely from valve, seat, tool, hands and bench before fine paste is opened. Repeat only enough fine lapping to produce the specified contact. Re-measure after every material-removal stage. Seat cutting changes valve position and can affect clearance, spring installed height and hydraulic operation.
Zero-abrasive cleanup and controlled reassembly
Chemico says the satisfactory seat must be cleaned and degreased before assembly. Use a compatible solvent under its safety sheet, brushes and lint-free wipes; clean ports, chambers, guides and adjacent passages. Keep wiping with fresh material until no grey/black residue appears. Do not blow abrasive around with compressed air or rinse it into an assembled engine.
Dry and lubricate only as the engine manual directs. Renew valve-stem seals, gaskets, single-use fasteners and any out-of-limit parts. Refit springs/collets securely, set clearances, time the engine and torque the head/cam train in sequence. Turn the engine by hand where specified, prime lubrication and complete compression/leak, fluid-leak and running checks.
From identification to a checked result
| Stage | Good practice for this range | Mistake to avoid |
|---|---|---|
| Diagnose | Measure valve, seat, guide and head; confirm lapping is permitted | Using paste to cure an unknown compression fault |
| Prepare | Strip/label parts, control springs and isolate every engine opening | Lapping in situ where grit can enter the cylinder |
| Cut/finish | Use minimal approved grade and hand action, checking frequently | Power-spinning or grinding until deep damage vanishes |
| Clean/inspect | Separate grades, degrease fully and verify contact/measurements | Leaving silicon carbide in guides, ports or oilways |
| Assemble/test | Renew specified parts, set timing/clearance/torque and test sealing | Assuming a grey band proves the engine is ready |
Record cylinder/valve position, pre/post measurements, which grit was used, contact-band result, cleaning method, renewed parts, valve clearance and final compression/leak test. That traceability matters more than how long the hand lapping took.
Reading real Chemico references
The Chemico names below are examples from the current range and show why the complete description matters. They are not universal Chemico recommendations and should not be treated as a fitment list. Within Chemico, a shared family word can conceal a different dimension, connector, material, pack format, operating condition or installation side.
| Example listing | What to verify beyond the name |
|---|---|
| Valve Grinding Paste - 110g | Same 110g double-ended Chemico tin: coarse 80 grit for authorised initial cutting and fine 220 grit for finishing |
| Valve Grinding Paste - 110g | Duplicate listing of the same product: confirm end labels, clean applicators, engine permission and zero-abrasive cleanup |
The duplicate titles do not represent separate formulas. Product reference, double-ended tin and net weight should agree; quarantine a damaged, unlabelled or cross-contaminated tin rather than guessing which end is fine.
Common errors around Chemico products
- Ordering both duplicate entries expecting separate coarse and fine 110 g tins.
- Lapping a coated/hardened component when the engine manual prohibits it.
- Using paste to conceal a burnt valve, cracked seat, loose guide or wrong geometry.
- Allowing coarse or fine silicon carbide onto the stem, guide, cylinder or oilway.
- Using a drill or excessive pressure and removing too much seat/valve material.
- Judging only by colour instead of contact width/location and measurements.
- Cross-contaminating the fine end with 80-grit paste or dirty tools.
- Reassembling before every trace of abrasive and solvent has been removed.
Chemico questions and answers
Q: Why are two Chemico listings shown?
A: The live evidence duplicates one 110 g valve-grinding-paste product; they are not separate grades.
Q: What is inside the double-ended tin?
A: Coarse 80-grit and fine 220-grit silicon-carbide pastes in a lithium-grease base.
Q: Which end is used first?
A: Only use coarse first when authorised and needed for light pitting; otherwise the fine side may be sufficient.
Q: Can paste repair a burnt or bent valve?
A: No. Replace or machine damaged/out-of-limit parts according to the engine procedure.
Q: Can valves be lapped with the head fitted?
A: Do not risk abrasive entering the engine; follow the manufacturer teardown and contamination-control method.
Q: Can a drill speed up lapping?
A: Avoid power lapping unless the exact engine procedure authorises it; it can overcut and embed abrasive.
Q: How much paste is required?
A: Chemico says a small amount on the seat, kept completely away from the stem and guide.
Q: How long should lapping continue?
A: There is no fixed time; stop at the engine maker's correct continuous contact band and dimensions.
Q: How is the seat checked?
A: Use the specified marking, vacuum/leak test and dimensional checks, not appearance alone.
Q: Can coarse and fine use the same tool?
A: Only after complete cleaning; separate labelled tools are safer against grit transfer.
Q: How clean must parts be?
A: No visible or wipe-detectable paste may remain in the seat, face, guide, ports or passages.
Q: What completes the repair?
A: Correct seals/fasteners, spring and collet assembly, timing, valve clearance, torque and sealing/running tests.
