Purchased 2 sets of merlin heads new from merlin,1st set 2 vavles hung an hit piston called bill mitchel racing and he said ill replace heads sent back old ones they sent new ones and same thing after 30 minutes of run time hung 3 vavles.hit pistons i took heads to machine shop they said they were machined wrong and honed the guides put them on my bb motor they are perfect now .so after all the labor and gaskets plus the $550.00 charge for machine shop sent bill to brad at merlin an they admit i was correct they wouldnt even pay the machine shop bill .. Nice huh ? Ill buy dart for now on;motor is a 572.cu everything standard ...........thanks for nothing brad at merlin factory bill mitchel ill always do business with you but never buy merlin products again

Sorry you had issues, there's been other threads about different companies with off the shelf heads with to tight tolerances, hind sight tear every thing down and check it.

How much time do you have on the heads now? I had the same issue years ago. What were the measurements from stock setup? How much were they opened? Did you buy the heads from Bill to begin with?

I though everybody knew to double check off the shelf heads before running them

Apparently not. That`s a costly mistake.
Has nothing to do with Merlin, put a set of AFR heads on you`ll get the same thing

My engine builder said the same thing, check all heads, they are set up for street use. I buy my heads bare and check everything first then add my preferred parts. I have AFR heads and the guides had to be honed. Wouldn't put to much faith in Dart either, my engine builder had a set with bad guides. They were too soft and wore our in a very short time. He checked the hardness and there was a wide variance in the bronze guides on the same head. Worst part is they wouldn't stand behind them. He had to put new guides in and eat the cost and labor to R&R both motors.

I always buy bare , my guides , my seats , my valves , my clearances. It saves money in the long run.
Never trust a ready to run head , they are production run to huge tolerance ranges for speed of production.

Anyone whos been in the game a while or reputable builder will tell you, always pull heads apart to check guides and valve seat/face mating

thks guys i guess your never too old to learn.just dont go buy what the manufactor says. i spoke directly to merlin an they said they were good to go no need to check nothing SHAME ON THEM,,,dumbass me

The administrator has restricted use of the private message system to members with less than 10 posts.