diff --git a/core/headerchain.go b/core/headerchain.go
index 1dbf95878..d9f3b575a 100644
--- a/core/headerchain.go
+++ b/core/headerchain.go
@@ -165,6 +165,7 @@ func (hc *HeaderChain) writeHeaders(headers []*types.Header) (result *headerWrit
 	)
 
 	batch := hc.chainDb.NewBatch()
+	parentKnown := true // Set to true to force hc.HasHeader check the first iteration
 	for i, header := range headers {
 		var hash common.Hash
 		// The headers have already been validated at this point, so we already
@@ -178,8 +179,10 @@ func (hc *HeaderChain) writeHeaders(headers []*types.Header) (result *headerWrit
 		number := header.Number.Uint64()
 		newTD.Add(newTD, header.Difficulty)
 
+		// If the parent was not present, store it
 		// If the header is already known, skip it, otherwise store
-		if !hc.HasHeader(hash, number) {
+		alreadyKnown := parentKnown && hc.HasHeader(hash, number)
+		if !alreadyKnown {
 			// Irrelevant of the canonical status, write the TD and header to the database.
 			rawdb.WriteTd(batch, hash, number, newTD)
 			hc.tdCache.Add(hash, new(big.Int).Set(newTD))
@@ -192,6 +195,7 @@ func (hc *HeaderChain) writeHeaders(headers []*types.Header) (result *headerWrit
 				firstInserted = i
 			}
 		}
+		parentKnown = alreadyKnown
 		lastHeader, lastHash, lastNumber = header, hash, number
 	}
 
diff --git a/eth/downloader/queue.go b/eth/downloader/queue.go
index ac7edc2c6..04ec12cfa 100644
--- a/eth/downloader/queue.go
+++ b/eth/downloader/queue.go
@@ -40,10 +40,10 @@ const (
 )
 
 var (
-	blockCacheMaxItems     = 8192             // Maximum number of blocks to cache before throttling the download
-	blockCacheInitialItems = 2048             // Initial number of blocks to start fetching, before we know the sizes of the blocks
-	blockCacheMemory       = 64 * 1024 * 1024 // Maximum amount of memory to use for block caching
-	blockCacheSizeWeight   = 0.1              // Multiplier to approximate the average block size based on past ones
+	blockCacheMaxItems     = 8192              // Maximum number of blocks to cache before throttling the download
+	blockCacheInitialItems = 2048              // Initial number of blocks to start fetching, before we know the sizes of the blocks
+	blockCacheMemory       = 256 * 1024 * 1024 // Maximum amount of memory to use for block caching
+	blockCacheSizeWeight   = 0.1               // Multiplier to approximate the average block size based on past ones
 )
 
 var (
@@ -783,8 +783,9 @@ func (q *queue) DeliverHeaders(id string, headers []*types.Header, headerProcCh
 func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) (int, error) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
+	trieHasher := trie.NewStackTrie(nil)
 	validate := func(index int, header *types.Header) error {
-		if types.DeriveSha(types.Transactions(txLists[index]), trie.NewStackTrie(nil)) != header.TxHash {
+		if types.DeriveSha(types.Transactions(txLists[index]), trieHasher) != header.TxHash {
 			return errInvalidBody
 		}
 		if types.CalcUncleHash(uncleLists[index]) != header.UncleHash {
@@ -808,8 +809,9 @@ func (q *queue) DeliverBodies(id string, txLists [][]*types.Transaction, uncleLi
 func (q *queue) DeliverReceipts(id string, receiptList [][]*types.Receipt) (int, error) {
 	q.lock.Lock()
 	defer q.lock.Unlock()
+	trieHasher := trie.NewStackTrie(nil)
 	validate := func(index int, header *types.Header) error {
-		if types.DeriveSha(types.Receipts(receiptList[index]), trie.NewStackTrie(nil)) != header.ReceiptHash {
+		if types.DeriveSha(types.Receipts(receiptList[index]), trieHasher) != header.ReceiptHash {
 			return errInvalidReceipt
 		}
 		return nil