Edelbrock heads - acceptable tolerances
I am hoping a couple of the experts can share their opinions, findings, and experiences with Edelbrock heads. I am in disagreement with one of the volume sellers of the LA Performer RPM heads over what are acceptable "out of the box tolerances" for these and his immediate response was if you have a problem, call Edelbrock. No problem, except in this case it was stated that "we buy them bare from Edelbrock and machine the pushrod holes". The P/N I was shipped was not the "bare" head P/N, it was a "flat tappet complete" P/N 60779. (They seem unaware that if they take a product and add value by machining it, they create a
warranty of merchantability of their own in the eyes of the UCC.) The tolerance issues I had were in 3 areas - what is acceptable "out of the box"
- seat concentricity
- MnBr valve guide clearance intake & exhaust
- deck flatness
I went to change out the Edelbrock springs and retainers to ones that were matched to my cam for seat and over the top pressure and I was pretty surprised with what I found. Manganese bronze valve guides are designed to run tight, I'm familiar from use on H-D V-twins and aircraft. When I took the out of the box springs and retainers off and did a hand clearance check on the valve stems, I couldn't get comfortable with how tight they were. I mean tight. I also checked the deck with my 12" machinists straightedge and wasnt impressed with the daylight I could see but lacked a longer one to get a better measurement. So I took them to the LMS to get gauged and checked on modern race shop measuring equipment. What they found I couldn't run with in any engine; street or race. Out of the box - well you be the judge. If these are selling in quantity and folks aren't screaming, must be good 'nuff. I have to emphasize I was not looking for blueprinting. This is a somewhat philosophic argument once you start measuring and correcting clearances, but "out of the box" has to be held to a standard. Valve seats/seal. First seat that they measured was .008 out of concentric. Avg across 16 > .006. To have any chance at valve seal and smooth running engine needs a real valve job. They told me most all the Edelbrock heads they see are bad in this regard. Valve guides. Precision ball measuring. Intake I flagged was .0008". Average intake .0010". My machinist wants intakes .0012" +/- .0001. Exhausts were all over the place but all tighter than the .0015" +/- .0001 target. I would appreciate an AERA or other best practices reference, but too tight is too hot, and too hot is too short lived.. Deck. This is pretty basic machining and for all the Made in USA and precision manufacturing, ISO 9000, etc Edelbrock touts, the .006" out of flat (dished) on one and .004 on the other (humped) is pretty poor. Not my first experience with Edelbrock tolerances. Plenty over the years. Even the RPM AG intake on this motor was also badly out of tolerance on the parallel planes of the intake surfaces. Over .100" out of parallel in fact. So before I go to Edelbrock or the reseller I am looking for other experiences with these. The seller says of course we sell these blueprinted, that's not what you bought. I said I bought a ready to run product, short of going a fully blueprinted or CNC ported route it still needs to meet some clearances and specs based on best practices and standards. My only expectation was getting the advertised quality, performance, and reliability from the heads.