Help: How much Lift can you run?????

[stooges701]

I need to know how much clearence I have for a cam.

I have a 302 thats bored .30 and the piston comes up out of the bore .004
I am using afr 165s with 1.7 rr. The cam I am looking at the lift is .544 with 1.7 rr. Will this cam clear or is thier a mathmatic way to figure this out without buying the cam then finding out it wont work?

 

[tylerrocks]

I have the same setup with an F303 cam. I have not put it togather yet but i asked the same question and got a unanimus aswer that there would be no problem.

Tyler

 

[84blkstang]

The peak lift is insignificant when it comes to p/v clearance. When the valve is at peak lift, the piston is at the bottom of the cylinder. The only way to know is to clay it up and measure. You really need to pay attention to the duration and LSA when it comes to peak lift. I know someone else will chime in on how much clearance is ok i am not for sure but you should always measure. And no one will be able to tell over the board

 

[stooges701]

Well then can anyone tell me what types of cams and they are running with 165 heads, so i can get ta general Idea what lift I can look at. I have talked with alot of companys that will custom grind me a cam but thier lift sounds way to high so I would like some suggestions on what otther are running before I spend lots of money on a cam.

 

[Modular2v]

only way to tell is to do the clay test for sure (you should always do it anyway just to be safe unless you KNOW it is going to clear)

 

[2000xp8]

What kind of pistons are in the engine? Valve reliefs?

You can likely use the cam, if there is a clearance issue you just may have to switch to 1.6 rockers, not the end of the world.
I belive the clearance you are looking for is 80 thousandths.

 

[Michael Yount]

stooge - read 84black's post again. PEAK LIFT HAS NO BEARING on p to v clearance. The variable is going to be valve timing. Cams that open the intake earlier and/or close the exhaust later are going to reduce p to v if all else is equal. Increased duration, more overlap, tighter LSA's are what cause the reduction in clearance. You don't have to worry about lift w/regard to p to v; you do have to worry about lift with regard to valve spring coil bind.

 

[Topdowncruise]

When I installed my cam we measured and there was well over .100 of P/V clearance on both intake and exhaust..I also have 1.7rr's and .544 lift.As michaelyount indicated though, the reason mine worked probably had to do with the fact the duration of my cam is modest (264/270) and overlap (determined by duration and LSA) is very close to stock.Of course,everbody's setup and circumstances are different so measuring is mandatory.

 

[stooges701]

Well thanks for all the great info, but i would still like to know what cams poeple are running with these heads for power and clearence wise. So what cams are being run with Afr 165s? And are the afr 165s better for torqe or horsepower. I will be ordering the heads monday soi need so suggestions so i can get this project going.

 

[PonyBoy95GT]

If you are concerned on too much lift, you can order the heads with upgraded valve springs from most manufactures. This will prevent your problem on coil bind, then just adress the other issues.

 

[Michael Yount]

Stooges -- HP=Torque(in lb-ft) X rpm/5252 ----- with ANY head, you don't get one without the other. The rpm where each peaks is a function of many things besides the head -- camshaft, intake, exhaust, etc.

 

[stooges701]

ok then this is what I running,

Forged 306
tubuar gt-40 intake
75mm throttle body and 75mm EGR
30lb fuel injectors
afr 165s heads

what would you recommend for a cam?

 

[Michael Yount]

I recommend you get really clear on how you're gonna use the car and what you want out of the engine -- fuel mileage, emissions?, daily driver? year round use? Lots of traffic? A/C? Auto or 5 speed? rear gear? Long highway cruises? Race? STrip? Autocross? Road race? What kind of vehicle is the engine in? For all we know you've got it in a rock crawling jeep ( ) -- how much does it weigh? What kind of idle quality do you want? What rpm range do you want your peak torque in? Peak Power in what range?

Once you're clear on all that I'd contact one of the custom cam guys and have them help you with your cam choice. They have lots of experience and sophisticated models that will predict with pretty good accuracy what the output of your pieces is gonna be over operating rpm range of the motor. Any other approach is pretty much guessing -- which doesn't make a lot of sense to me given that the cam is arguably the most important piece of the motor.

Buddy Rawls did mine and I couldn't be happier; working with him was the best single choice I made on the motor ---- Jay Allen and Ed Curtis also have good reps on the boards.

 

[skip nay]

I know this wasn't the question but anyhow. I had a stock bottom end and I had a F cam with performer RPM heads with 1.90/1.60 valves and I didn't have no troubles at all.

 

[Michael Yount]

skip nay - how much p to v clearance did you have when you measured it?

 

[skip nay]

I had double of the minumium I think and when I checked mine I bolted it down to 65 ft lbs without a head gasket either.