problem with cam selection on a pi swap

ruler · May 14, 2009

I posted pics in the introduction section.

Hi guys I am new to this site but I have had my mustang for a couple of years. I have a 1997 autumn orange gt with minor mods. kicker subs autotec amps and kenwood deck, k&n fpik, mac longtubes, stage 8 bolts, mad dog clutch plate, steeda quadrant, lakewood 90/10's and 50 50's, roush lower control arms and double adjustale uppers, subframe connectors, edlebroc victor junior intake manifold and fuel rails with a 4150 wet plate kit, hurst short throw shifter, clock replacement with a wideband and electric nitrous gauge and a few mods Im not remembering right now.

Here is the problem and what brought me to the site. I have recently swaped to pi heads and the edlebroc intake manifold and I decided to do a cam install as well. I picked out the 102-300 (comp cams part number) cams from comp and the beehive springs. during the dyno tune the valves and pistons made contact and Im not sure what the problem is. I dont turn my own wrenches on internals or tuning and I dont know what is going on. My mechanic says we need a smaller duration cam but I dont know which one to go with. I know this is a lot of info for a first post but im stuck and i saw people recommend this site to new sn95 owners and I figured you guys could help me.

blown98gt · May 14, 2009

valve float would be the correct word here, and if i understand correctly i think you just chose the wrong springs for the cams. Valve Float is when your valves and pistons make contact, it can happen when you spin too high rpms for your springs or if you are making too much hp for your springs. Regardless the reason i'd put my money on the springs, could be installed incorrectly or just not be right for your application.

ruler · May 14, 2009

I went with comp's beehive springs for this application but I reused the stock retainers. I think I am just going to have to downgrade back to the pi cams as this budget and time line has been destroyed.

DropTopPony · May 14, 2009

You went with the XE274H and they are the most aggressive of the NPI Lineup and the problem most likely is who ever installed your cams did not degree them. Comp puts @ 5 degrees of advance in their cams and with the stock timing not being exactly on the mark from Ford you experienced PTV. Your Valves are probably bent so check them out and check the pistons and if no damage reinstall the cams correctly and it will run right.

They must be degreed

ruler · May 14, 2009

My mechanic knows his fords pretty well and has never done me wrong. He keeps telling me the duration of the cams is the problem and we need a different setup. I am hearing from everyone else that it was the install or the degree of the cams. On a street tune this thing ran fine and it did not make contact until about 5500 rps. I am going to talk with him tomorrow and I will post what route we are taking. This whole ordeal has me stressed and I can only imagine how many valves are bent.

glittle75 · May 14, 2009

not trying to undermine blown98, but i doubt you had valve float. valve float is when the valves don't stay in contact with the lobe during closure, or the 'backside' of the lobe. beehive springs on a npi cam running less than .500 lift, on a engine spinning to MAYBE 6500 rpm will eliminate the chance for valve float.

heres what happened, you paid for, and/or got, shitty work on your cam install. the 274 cams have to be degree'd in EXACTLY, especially on a PI swap, thats alot of duration for a piston with not as much dish, and the stock PI valves with that huge lip. im guessing if you pull those heads, you will have an indention for each valve, about 1/4-3/8 in. long. the 274 (npi) and 278 (pi) stage 3 comp cams MUST be degree'd in exactly. i would go so far as to say it would be worth it to buy ARP head studs and clay the pistons after degree'ing to ensure there is adequate clearance.

claying pistons is putting play-do type putty on the piston top, installing heads, degree'ing cams, turn the engine by hand a few times, then remove the heads and measure the thickness of the putty with a caliper or micrometer at the thinnest point. anything less than about .06" and you need to get SS valves, or valve notches, or a different cam.

hope this helps.

glittle75 · May 14, 2009

trust me, i was running the same cams (no shit) in my pi swap, and i degree'd each side 4 times, and clayed them as well. wasn't about to do the work twice.

and if 1 valves is bent, or has made contact, they all have.

bobtsgt · May 15, 2009

yep. a 274H cam has to be degreed in your situation. On my NPI heads I still degreed them. The left was off by 2 and the right off by 4*. Chances are your guy lined the marks up, slapped the chains on and called it a day. That only works with stock cams. Hell even with stock cams you should degree them as they can still be off quite a bit.

ruler · May 16, 2009

the cam was degreed. Comp is saying the cam wil not work on pi heads. I have to find retainers and the mechanic is replacing the valves. He is also going to cut notches in the pistons for clearance. Apparently the lifters puff up a little bit at higher rpms. This site has been helpful and please keep the advise flowing and I will post the results as I gather them.

NERD · May 16, 2009

bobtsgt said:
yep. a 274H cam has to be degreed in your situation. On my NPI heads I still degreed them. The left was off by 2 and the right off by 4*. Chances are your guy lined the marks up, slapped the chains on and called it a day. That only works with stock cams. Hell even with stock cams you should degree them as they can still be off quite a bit.

Degree'd and notched... That's a big little cam.

ruler · May 18, 2009

too many issues and Im not waiting any longer. Im just gonna go with pi cams and be done with it. I will post these up for sale cheap if anybody wants to try them. Il post dyno numbers and mods when I get her back in a week or two.