Engine Valves Chambers Springs
2.5 33.2 x 28.0 28.5cc’s Single Conical
2.7 33.2 x 28.0 29.5cc’s Single Conical
3.2 37.0 x 32.4 35.0cc’s Single Conical
3.4 996 37.0 x 32.4 35.5cc’s Single Conical
3.4 987 40.2 x 34.4 41.0cc’s Dual Straight Intakes Single Conical Exhaust
3.6 40.2 x 34.4 41.0cc’s Dual Straight Intakes Single Conical Exhaust
3.8 40.2 x 34.4 42.0cc’s Dual Straight Intakes Single Conical Exhaust
X51 40.2 x 34.4 39.5cc’s Dual Straight Intakes Single Conical Exhaust
Cracks?
2.5 Occasionally occur in the spark plug wells
2.7 Occasionally occur in the spark plug wells on 5 chain models
3.2 Occasionally occur in the spark plug wells on 5 chain models. Can occur in secondary air ports on 2003-2006 model 3 chain heads
3.4 996 Very common in spark plug wells. The most common location radiate out toward an exhaust valve guide bore.
3.4 987 None observed to date. Will update if we see one.
3.6 None observed to date. Will update if we see one.
3.8 None observed to date. Will update if we see one.
X51 None observed to date. Will update if we see one.
Failures?
2.5 Occasionally valve spring, probably related to hydraulic follower malfunction.
2.7 Occasionally valve spring, probably related to hydraulic follower malfunction.
3.2 Occasionally valve spring, probably related to hydraulic follower malfunction.
3.4 996 Occasionally valve spring, probably related to hydraulic follower malfunction.
3.4 987 Occasional dropped intake valve seat, and fretted intake keeper grooves. Most notably on track cars.
3.6 Occasional dropped intake valve seat, and fretted intake keeper grooves. Most notably on track cars.
3.8 None observed to date
X51 Dropped intake valve seats, and severely fretted keeper grooves. These heads use very heavy intake valves with a wide margin and flat face. Despite the increase in valve weight they use the same valve spring pack as the standard 3.8.
Guide Wear?
2.5 None to moderate, depending on maintenance regimen and use (mild street or aggressive street/track).
2.7 None to moderate, depending on maintenance regimen and use (mild street or aggressive street/track).
3.2 None to moderate, depending on maintenance regimen and use (mild street or aggressive street/track).
3.4 996 None to moderate, depending on maintenance regimen and use (mild street or aggressive street/track).
3.4 987 Severe intake. Significant exhaust
3.6 Severe intake. Significant exhaust
3.8 Severe intake. Significant exhaust
X51 Severe intake. Significant exhaust
All valve stems: 6mm with 3 keeper grooves
All keepers are floating type, meaning the tips butt for rotation.
All valve angles: 45*
Dual springs are non-interference type
All springs use round wire
All retainers are steel and impressive in design and quality.
All seats exhibit zero wear characteristics.
All heads have very rigid decks. We have never seen a head of any model warp in excess of .005”
All models use Euro style valve stem seals
Hoffman Automotive Machine
1461 Greensboro Hwy.
Watkinsville, GA 30677 706 769 3783
Hoffman Automotive Machine (706)769-3783 