Im in the market for a set of heads and found some AFR 185's with 61cc chambers for a killer deal. My problem is I have always heard that the pistons have to be clearenced with the 2.02 valve except with the Trickflows . Today I had two seperate people tell me they would work with a lower lift cam and 1.6 ratio rockers since they are the 61cc instead of the 58cc. I have the tfs stage 1 cam, will it work, would I have to change the cam, any help appreciated.
AFR 185's on stock short block.
- Thread starter trendkilllx
- Start date
88stangmangt
Active Member
stangbear427
Active Member
Michael Yount
Mustang Master
....and, the issue has nothing to do with lift. Here's a site that simply explains the p to v clearance issue. Read up if you want to learn about it before you buy a set of heads.
http://www.geocities.com/jjonibones/PVC.html
http://www.geocities.com/jjonibones/PVC.html
stangbear427
Active Member
Right. The Trick Flow heads will work with stock pistons because of the "twisted" 2.02 valve that doesn't hang down onto the piston as far as everyone else's do; like the AFR's with the 2.02 valve that won't work. That's one of the nice things about the TW's, they made a way to cram a bigger intake valve into a head that will still bolt right on to a stock 5.0 without modification. Regardless, fly cutting the piston isn't that big a deal, you don't exactly have to be a machinist to do it- then AFR's will fit. Or, you could always order them with the 1.90 intake valve.
Michael Yount
Mustang Master
Brad - when you say you had no issues - did you measure clearance? From a procedural perspective, if you didn't, then you really don't know whether you have a clearance problem or not; you just know nothing has caused a problem yet. There are many people out there that assemble a package without checking clearance, start it up, smile because nothing seems to hit anything. Then they find the first time they over-rev it with a missed shift and float the valves, that all the exhaust valves hit the pistons. Oops - guess we did have a clearance problem. Furthermore, it's not safe to conclude because one engine had sufficient clearance that another with the same parts is gonna be ok. There are a huge number of dimensions that impact p to v clearance -- check out the link above, it lists just a few of them. When you start measuring in hundredths and thousandths every engine is different - even two equipped with the same parts. And when all those tolerances add up in a way that hurts or helps you - it's called tolerance stacking. One engine can be fine with clearance, and another with the same parts can have even more/even less clearance. So it's unwise and unsafe to conclude 'it worked in mine, it'll work in yours.
As a practical matter - a lot of folks have used the TW parts. Stangbear's right (as usual) - the TW angled combustion chamber 'twists' the intake valve in a way where it's a bit further from the piston than other 2.02 heads. However, that same twisting also usually positions the exhaust valve a bit closer to the piston -- the good news is that these engines usually have an excess of exhaust valve clearance because of the smaller valve. Combine the AFR185 head with big intake valve, with a cam that opens the intake valve earlier and closes it later (stage 1) -- not only do you need to measure clearance, you probably have to cut the piston. And procedurally, unless you're willing to chance major internal engine damage on a guess, if you're changing to heads with larger valves, or changing the cam to one with more duration or a tighter LSA, you need to measure p to v clearance to be sure you have enough. .080" intake and .100" exhaust should be sufficient for most street engines that stay under 6500 rpm.
As a practical matter - a lot of folks have used the TW parts. Stangbear's right (as usual) - the TW angled combustion chamber 'twists' the intake valve in a way where it's a bit further from the piston than other 2.02 heads. However, that same twisting also usually positions the exhaust valve a bit closer to the piston -- the good news is that these engines usually have an excess of exhaust valve clearance because of the smaller valve. Combine the AFR185 head with big intake valve, with a cam that opens the intake valve earlier and closes it later (stage 1) -- not only do you need to measure clearance, you probably have to cut the piston. And procedurally, unless you're willing to chance major internal engine damage on a guess, if you're changing to heads with larger valves, or changing the cam to one with more duration or a tighter LSA, you need to measure p to v clearance to be sure you have enough. .080" intake and .100" exhaust should be sufficient for most street engines that stay under 6500 rpm.
Michael Yount
Mustang Master
Depends on how it's done - machine shops can do it for you, probably the easiest if you can afford it. Many do it themselves with a tool that can be bought or rented. Heads off the the car and all the valve springs and valves have to be removed. The piston is positioned down the cylinder a bit, and the cutting tool gets inserted into the head in place of the valve, put a few bolts in the head to stabilize it - you attach a drill to the tool stem which sticks up through the head just as the valve would and as you turn the tool with the drill it cuts the piston. You have to go slowly, measuring carefully to only cut as deeply as you need to. And you need to take some careful measurements before you start so you have an idea how deeply you'll need to cut for clearance. Each time you get ready to cut a new one (16 times) the head comes off and the tool gets inserted in the appropriate valve location. And then there's cleaning up the mess which is made much more difficult if the engine's in the car. Personally, I wouldn't dream of trying it myself unless I had the engine on a stand. But I'm sure having said that now 27 people will post saying they did the whole thing in 10 minutes including cleanup and that the car has run fine for the last 400,000 miles. 
Search around Isky's cam site - I believe they are the most well known supplier of the cutting tools.
Search around Isky's cam site - I believe they are the most well known supplier of the cutting tools.
stangbear427
Active Member
Heh heh. Thanks Mike. Guess I don't need to answer that question... Mr. Yount is technically precise and systematically thorough (as usual) 
I tried the whole piston notching thing, and all I have to say about the Isky piston notching tool is, "**** ISKY!" That tool sucked, was a waste of my damn money and didn't work anyway. I ran the 185's with a B-cam and 1.7's, and apon engine dissamebly (sp?), found I did have some slight clearnence issues. So I rebuilt everything with new pistons and more cam.
IndyBlk5.0
New Member
NeQX
Founding Member
Ok Ok Here is my advice
AFR 185's on a stock block wont be GREAT like you would think..just cause they have big valves, first thing is like you guys are discussing pistons will need to be notched, also you will need alot of n/a power to fully benefit from them (turbo, s/c, etc etc) so in the end is it really worth it on the 302? i have 165's and they make good n/a power, my advice is if you can get them real cheap...resell them, go with tfs tw's or afr 165's and trick flow, afm, or fti cam...and you will be very pleased.
AFR 185's on a stock block wont be GREAT like you would think..just cause they have big valves, first thing is like you guys are discussing pistons will need to be notched, also you will need alot of n/a power to fully benefit from them (turbo, s/c, etc etc) so in the end is it really worth it on the 302? i have 165's and they make good n/a power, my advice is if you can get them real cheap...resell them, go with tfs tw's or afr 165's and trick flow, afm, or fti cam...and you will be very pleased.
stangbear427
Active Member
I've been meaning to say something like this too, only I was thinking more along the lines of putting the good deal 185's in a box until you get some real power parts in there- but I don't know what your plans are or if they will ever be justified. Regardless, they are way too big for a stock 302. Same deal with stock heads- there's only enough room for so long of a valve in there regardless of what head it is (except the TW's) a 2.02 valve is 2.02" long, and that's too long to fit with stock pistons. It's the valve that's the problem, not the head it's in.
Michael Yount
Mustang Master
"a 2.02 valve is 2.02" long," ???? Not sure what you meant Stangbear. A 2.02" valve has a head that is 2.02" in diameter. Same for 1.90", 1.84" valves, etc. The length of all those valves is very close to the same, if not identical. And even if valves were significantly different lengths, it's the cam's lift and rocker ratio that deterine how far down into the cylinder it goes - not the length of the valve. And as mentioned before, since the pistons are way down the cylinder at peak lift - even big lifts don't cause clearance issues.
It's the larger diameter of the head that causes the problem. Because the valve opens at an angle to the piston head, the bigger the diameter of the valve head, the closer it gets to the piston top during overlap. So, IndyBlk - yes, any head for these motors (stock or otherwise) with larger valves is gonna have less p to v clearance than a smaller valve with all else equal.
REmember - this isn't necessarily an issue. The only way to know if you enough clearance or not is to measure. If you've milled the heads, decked the block, installed heads with valves bigger than stock and/or bigger than the reliefs in your pistons or with the valves canted differently than stock (like TW), installed different pistons, or installed a cam that has earlier opening intake timing or later closing exhaust timing - then you've changed p to v clearance. Unless you know for certain that your changes INCREASED your clearance (and you had enough before), then you should measure p to v.
It's the larger diameter of the head that causes the problem. Because the valve opens at an angle to the piston head, the bigger the diameter of the valve head, the closer it gets to the piston top during overlap. So, IndyBlk - yes, any head for these motors (stock or otherwise) with larger valves is gonna have less p to v clearance than a smaller valve with all else equal.
REmember - this isn't necessarily an issue. The only way to know if you enough clearance or not is to measure. If you've milled the heads, decked the block, installed heads with valves bigger than stock and/or bigger than the reliefs in your pistons or with the valves canted differently than stock (like TW), installed different pistons, or installed a cam that has earlier opening intake timing or later closing exhaust timing - then you've changed p to v clearance. Unless you know for certain that your changes INCREASED your clearance (and you had enough before), then you should measure p to v.
stangbear427
Active Member
That's what I meant- but now that you put it that way I see I definately didn't word it right at all. Looking at it now I don't know how anyonoe could have interpreted it right (sorry all) I shoulda just let you say it since it was so far past my bedtime... thanksMichael Yount said:
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