abrush

I decided last minute to buy a set of Edelbrock e street aluminum heads for my 65 Mustang with a 289. I see on Edelbrocks instructions that you must drill steam holes in the block before installing the heads. This sounds pretty straight forward but the instructions are vague and left me with a couple of questions. How far down do you drill? Edelbrock shows to drill 2 holes, one each located by the front cylinder however I have heard conflicting thoughts on doing 4 on each side for a total of 8 holes. I also read that some drilled at an angle or else you will hit a valley and break the bit???? Who has done this and has any advice?

Another question I had was regarding the push rods. The car currently is set up with a Comp cam xe268h with cast iron heads that were modified with screw in studs, guide plates and valve springs to support the cam. I also am running roller rockers of course. I am thinking I won't have to change the pushrods since I am just swapping to an aluminum head vs. a cast iron head with the same parts but want to verify??? I decided to swap the heads out as my cast iron ones weren't ported and by the time I pay for the port work I figured I am much more ahead just buying the aluminum heads.

jojobanks

I haven't drilled steam holes so I can't help you there.

as far as your current push rods working, I doubt it. You can check them though. It's best to use a solid lifter and seat it all the way closed(best to use a dial indicator). mark the top of the valve with a dry erase marker and install the pushrod and rocker and seat until the pushrod has just a little bit of resistance to rotate. Turn the engine over 2 times and remove the rocker and look at the mark on your valve. There will be a worn off portion where the rocker meets the valve. If it's not dead center you'll have to get an adjustable push rod and re-do the process to determine what length push rods to use.

kalli

i have drilled them for a mate of mine. the edelbrock instructions clearly show where they go and you can use the head gasket as a template for marking, but edelbrock miserably fail to pass the info if you need 2 holes or 8. I drilled two as that was what was pictured in the instructions. thinking about it and seeing what others have done you can drill all 8 and next time I will drill all 8.
edelbrock should have been a lot more clear on this. and ya, i broke a bit as well, but after that I knew what pressure to look for with the drill (length) so I made sure to have the drillbit not too far extended from the chuck.

as for the cam/pushrod question: when changing heads _always_ measure pushrod length.
don't really need a dialgauge, work with the wear pattern. You have to use a solid lifter though, or convert a hydraulic lifter to a solid one. but that requires that you know the measurements.
what other people do is to use a very very light spring as valve springs that needs very little pressure to compress. so that it compresses that spring (open valve) instead of preloading the lifter ...

I was lazy and used my used filled lifter. I am not sure if I should have or if it can be done that way.

there's a recent post (this week) where someone attached videos of how it's done (wearmark)

Starfury

Trick Flow's instructions are a little better, explaining that you should drill 8 holes. Use a good carbide bit, otherwise you'll break a couple in the process. You only have to go down 1/2" so, iirc. You'll know when you break through into the water jacket.

Like the others said, always measure for correct pushrod length when changing valvetrain parts. Proper valvetrain geometry is critical for a well-running and reliable engine.

MonsterBilly

So i assume this forum is for me too. i will be installing a set of used trick flow heads on my car in a week. i assume that i will need to drill the holes as well?

can someone please explain their function and porpose

scott4.6

I have never drilled holes in my heads. I dont think it has to be done. ON my 400 sm block chevy the block has steam holes, also on stock 400 heads. i had dart pro one heads and they did not have steam holes, or did the gaskets. The car did just fine, did not over heat, no problems what so ever. I would not drill into the heads, i would just put them on and enjoy your ride.

JMD

Not much I can add to this except that whenever I have drilled cast iron, it cuts like butter....

and,,,, at least some of the later blocks already have steam holes.....

abrush

I am not drilling holes in my heads but rather my block. The heads already have the holes in them. The instructions say you must put these holes in the block to match the heads. I plan on drilling them as I have read online about others having overheating problems with 289/early 302 engines when they are not drilled.

Starfury

I've never actually read a story about overheating issues resulting from not drilling holes in the block, but seeing as most of the aftermarket heads out there recommend it, and Ford did it themselves in later block revisions, I don't see any reason not to do it. As long as you've got a good bit, it's super easy.

scott4.6

Their is no way i would drill holes in my block. It can cause stress cracks around the holes and weaken the block ( IMO ). Their is no need for it what so ever.