Why plane your intakes w/ milled heads???

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swinger340

swinger340

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Why is normal practice to plane the intake when the heads have been milled? A buddy of mine w a machine shop up here in Maine planes the intake side of the head so ootb intakes will bolt rite on. Only dif. is you cant use the cork on the front and rear of the intake. Once the intake has been planed its pretty much ruined for another engine. Just wondering why. Figured id throw that out there for people to ponder.
 
swinger340 said:
Why is normal practice to plane the intake when the heads have been milled? A buddy of mine w a machine shop up here in Maine planes the intake side of the head so ootb intakes will bolt rite on. Only dif. is you cant use the cork on the front and rear of the intake. Once the intake has been planed its pretty much ruined for another engine. Just wondering why. Figured id throw that out there for people to ponder.
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your buddy does what ive been doing and what your saying.ive wondered too.i was told one time that the intake face can get a little to thin but ive never ever seen that soooo good question
 
swinger340 said:
Why is normal practice to plane the intake when the heads have been milled? A buddy of mine w a machine shop up here in Maine planes the intake side of the head so ootb intakes will bolt rite on. Only dif. is you cant use the cork on the front and rear of the intake. Once the intake has been planed its pretty much ruined for another engine. Just wondering why. Figured id throw that out there for people to ponder.
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normal practice.....i rather mill the intake face of the heads the corresponding amount so that the intake fits without cutting it...
 
Standard formula is .0048 milled from head=1cc, and for every .0048 off the head,you need to remove .0095 from the intake side

Thanks 70aarcuda,I did not think of cutting the intake face of the head...My AirGap Manifold will remain stock now on my 318 build with J heads.
Martin
 
70aarcuda said:
normal practice.....i rather mill the intake face of the heads the corresponding amount so that the intake fits without cutting it...
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Ive seen some do it the same way as my buddy, but it seems like Ive been seeing alot of milled intakes for sale. Which are now useless unless you have the heads to match. Just curious why people are planing the intakes instead of the intake face on the head. Good to see others are doing the same, and not ruining there intakes.
 
Some plane the intake manifold because they don't find out the intakes don't fit until the heads are already bolted on. But yeah milling the intake side of the heads down is the way to go so that any intake will fit. Best bet would be after heads milled but before heads assembled mock up the engine and verify fitment and mill intake side of heads accordingly. Remember not all blocks the same height.
 
never cut an intake except for clean-up purposes. and than just enough to clean up any imperfections. if you cut the cylinder head surface you than cut the intake surface of the head. that way the heads and the intake minafold can be swapped around to different engines without causing problems. cutting the intake surface of the head creates the same geometry as cutting the intake manifold, so why mess up a good set of heads or intake. Al
 
I've had to when the heads are cut a ton (open chamber trying to get the chamber size down) but you're right.. The best way is to cut the intake side, but evetually you run out of material for the valve cover to seal on, and hit the bolt holes.
 
Always cut the intake . Never the heads and there is several reasons. But to each his own. I would never cut the intake side of the head unless i was skimming it for straightness. never cut the heads for intake fitment. Thats just me And I ran into problems doing this that trashed the heads. Just think about what you are making thinner. You can't add threads once they are not there. You are also not cutting at a different angle . They have to be cut at a specific angle so it seals on the valley side. so The head would need to have more off at the top then the bottom. Usually double.
 
At .0095 on the intake side of the head, it is not alot. It will take A LOT of deck milling to rid yourself of the rail for the valve cover gasket. It really is a simple math question.
Milling the intake makes it aone off intake for that combonation and a ***** to resell.
 
rather than mill a head that far, that you would have not enough threads left on the intake side is foolish. you would do better to get a better piston for the job. do it right or don't do it! Al
 
swinger340 said:
Thanks captain obvious. Why not plain the intake face of the heads so you dont have to plane the intake is the question, in case you didnt read the whole thread.
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Actually, "captain obvious" was dead nuts on the money. Why be so condescending? He answered your question. ...and correctly I might add.
 
They don't know that the heads have been cut on the chamber side, cuz they picked them up at a flea market, the shop that cut them didn't mark them for how much the cut them, nor did they do a compensation cut on the intake face. Some shops won't do it unless you ask. There's alot of reasons why people cut manifolds.

In the end, it's to make the manifold fit.
 
StrokerScamp said:
Actually, "captain obvious" was dead nuts on the money. Why be so condescending? He answered your question. ...and correctly I might add.
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So it will fit seemed as though it may be a smart *** answer to me. If it was not intended that way, I apologize. That is how i took it. The question is wondering why one method seems to be used, or preferred to the other. End result= the intake fits both ways. That is why it seemed like a very obvious answer.
 
StrokerScamp said:
Actually, "captain obvious" was dead nuts on the money. Why be so condescending? He answered your question. ...and correctly I might add.
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he didn't answer the question AT ALL
also to make the intake face so thin that the bolt wont hold any more you would probably have cut tooo much off the head to make it work any more... the price of the head is no issue if your building the piece you need pistons would be the way to go but i have run in local roundy round were a stock piston must be used therefore the head must be cut a ton.it does get into the valve cover sealing area but i have yet to have a problem with this issue either.
 
Things that cause poor intake matching:
heads milled a lot,more than .025
thin heads gaskets
Deck milled to square it and has a lot removed,more than .010
More than 1 line honing
intake that has been used a on a machined motor that has more than .020 off of each side.if a intake that has been milled a lot,can still be used with perfect results,you must use .030-.060 paper intake gaskets and with he original sheet metal intake gasket for big blocks.Will seal and match up perfect
If a owner wishes to replace or try different intakes or does a lot of internal work,(racer) its best to mill the heads,as you can then interchange intakes in minutes,same goes for the street performance owner.if the owner does not intend to ever change the intake,then by all means cut the intake the minimum amount.You only have the two options,and the the reason listed will determine the way to go.milling the heads will not cause bolts to fly out or snap out threads,unless you mill the intake surface .200,only small amounts of the head intake surface is needed,.020-.030 on a angle cut at that,and its .030 cut at one end to zero on the other,so get that worry out of your head.Small block need to have the ends milled to allow the intake to have a gap so silicone or gasket can fit,pre- fitting the intake will determine this.So if you have a milled intake and think its no more good,call me and I will buy them and have them running on good cars and with no problems,and i will make a ton of money off of you.mrmopartech
 
Ive had the opposite problem W2 heads that had the intake side milled so much that you need a spacer to run them. My bad on the purchace, didnt see the surface cut. Even though I asked if there was any machine work done. Got screwed on Ebay. Never again.
 
mopar373 said:
rather than mill a head that far, that you would have not enough threads left on the intake side is foolish. you would do better to get a better piston for the job. do it right or don't do it! Al
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Bingo. Once asked the question to shave a big chamber J head enough to make compression on a 318 i decided to go with really tall 318 pistons and shave just enough to clean up the deck face on the head. Wild.
 
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