Surfer69

I've had my heads milled maybe 0.005 for clean up. I dont know if the block has been decked so I'm trying to figure out if the intake will have fit problems.

How can I determine if my block was decked ever? What is the max you can deck or mill heads and block before intake fit problems? THX

Scott Marzahl

If your block was decked, it would have circular marks rather than straight lines across the surface and your numbers would be milled off too.

You really won't know how your intake fits until you set the heads on the block and set the intake on and inspect the fit.

cardo0

0.005" is hardly anything to worry 'bout. Sorry can't remember how much the intake needs to be milled for an increment change in deck height or head height. But a check u can use for the intake is to set it on the heads after heads installed on block and use a feeler gauge to measure gap between head and intake (don't worry 'bout the bock end walls as u can seal those with generous silicone sealer application). If the gap anywhere between the head and intake is greater than the thickness of intake gaskets, guess what, it ain't gonn'a seal. And since the intake gasket gets compressed, u really don't want any gaps larger than 1/2 the intake gasket thickness.

The stock blocks have a specific surface finnish/pattern that helps the head gasket seal and is hard to describe. Yes usualy if block has been decked then the stamped ID at front of block is most likey gone but the machine shop/rebuilder could have replaced the number with his own.
But the important item to know from deck height is the distance down the hole the piston is at TDC.
U need a micrometer with a flat base-bar that stradles the bore for this and u can more than likely rent one locally if u can't borrow 1. Measure at the piston's middle above where the piston pin is located (to minimize piston side rock errors) and find the highest part of the piston as it reachs TDC. U would need to do this before final install of heads. Add this distance down the hole to your compressed head gasket height. U want .035" - .055" total for good quench. And i expect u can easily do this Surfer if u have degreed your camshaft (as i assume u did).

BTW intakes are fairly cheap so having a spare $20 swapmeet aluminum intake milled down in steps could be a way to dial in the correct milling.

Hope this helped. cardo0

Surfer69

cardo0, I have checked the piston depth at TDC and it's only around .010 on all cylinders. I guess that right there should tell me since you think it should be stock around .035. Fitting the intake and checking with feeler gage sounds like the best deal, no fuzz. I just bought a RPM intake but expect to maybe shave the AFR heads more since my best CR now is only 9.7 and I've bought everything already but would like 10.5. With gasket I still have quench of .030-.040 though.

So if I exceed the gasket half thickness at the heads after checking, then it's time to have the intake machined? I still havent degreed new cam yet.

Scott Marzahl

Don't shave the heads, just use a thinner head gasket to achieve your comp ratio. With the pistons at deck height .010, are you sure you are calculating CR correctly. Head gaskets start at 015" and go up.

cardo0

Difference in hp between 9.7 and 10.5 c.r. is small Dude. Something like 10hp, 15hp maybe, 20hp i doubt it! That stroker still gonn'a rock! Look at C2632 (on the c3 forum) making well over 400 RWHP through iron exhaust manifolds on his 383" using <9.5c.r.. Will u even notice 10hp? Maybe on a 1/4mile timeslip.
And really a lower c.r. motor sees much less stress, can take a thrashing and live on to become your kids toy.
If you haven't installed the cam yet then u can replace it with a short duration cam - but really >9.5c.r. will support most any streetble cam duration. If u really can't live with 9.7c.r. then spend the money and swap for tight heads/chambers. But don't shave new heads or u really will need to mill the intake also. And u maybe able to save 60cents a gallon burning regular 87 octane too.

Hey heads aren't that bad to replace as u don't have to remove the radiator and drop the oil pan like u would to replace the cam. Yea u can replace the heads while the hood is still on. So y not try those heads as is and if not enough power then later u can remove heads and mill for tighter chambers along with milling the intake to match.

Most stock blocks are only +.025" deck (9.025" total from crank CL) so i don't know what u mean by .035" stock height. Maybe u should recheck piston height at TDC as i described before.
Now with alum hds u want an good composite hd gasket and most are .039" or .041 when compressed. So with .010" piston clearance that adds up to .049" - .051" for quench height and should be fine. Not bad and should work fine but to improve it would require decking the block as i don't know of any thinner composite hd gaskets.

Well if u verified .010" down the hole then i think u have it covered. If u need any help to dial in the cam feel free to PM me and i'll see what i can do neihbor. U can expect a lot of small issues to get it running depending how much u altered the ign and carb systems.
cardo0

bob

I think it is possible the wording terms ( quench, deck height) are being used by different folks in different ways. Surfer69 says he would still have a quench of .030-.040. 40 is great but 30 is getting pretty tight.

Surfer69

Sorry I havent been back for a while here. I confused what Cardo0 was saying about quench .035 - .055, I thought you were talking about piston depth. I have found thinner gasket at .030 compressed that's where I got the .040 quench. And my 0.010 is dead on.

I thought 9.7 to 10.5 would make a big difference, but if you dont think so then I need to re-think this. If the difference really is only 20 HP at best then I'm good to go with feeler gage check. Thanks.