[Peteyk]

I am installing a ZZ454 crate next mth and want to get my new hedman mid length heddars jet hot coated before i install everything but jet hot tells me it might be a waste to do it before breaking in engine becuase over 1250 degrees will mess up the coating. I do not want to break in engine and then have to install headers after engine is in place if at all possible. Any advice or experience with this? My 67 chevelle new ZZ 454 is naturally aspirated, no power boosters or anything like that. Its street only and i drive it all the time. I cant imagine heddars will get above 1250 degrees during break in unless i got the timing way off or carb too lean? Need some experienced advice please.

 

[123pugsy]

Hydro roller. Does it need hi winding break in RPM's?

 

[shovelrick]

We broke my engine in on a dyno with the coated headers that are in the car now, didn't hurt the finish and IIRC we did 5-6 pulls to 6200-6300 after about 15-20 min break in time, builder did break it in with his dyno carb so jetting was good so be sure you're using a known good carb

 

[427L88]

Unlke Rick, my headers went a bit gray and hazy due to running in my cam; they got cherry red even with a fan pushing air. I actually preferred the look, but.....

Even had the center carb of the tripower set on the richer side, but there ya go.

If you are breaking in a flat tappet, JetHot is correct. If its a roller and doesnt need the 20+minute run in at rpm, then its not an issue.

 

[mr 4 speed]

it has a roller cam, turn the key and go-no cam break-in required...and no worries with the coating.

 

[Peteyk]

Yup they are rollers and thank you all for the insight and advice. Im shipping them off to get jet hot.

 

[mrpaticular]

Ceramic coating greatly reduces under hood temp.
I was surprised how soon you can remove spark plugs.
Been running mine for 4 summers and they look like new.