When i was backfiring a couple of months ago in the higher rpm after i switched heads, how come noone mentioned i could have weak valve springs? I bought a set for my flat tappet cam and the did fine but im guessing the big lift of the roller cam was a little too much first motor and heads - 456 lift 268 duration, comp cam springs to match, e7 heads, 80s motor second motor and heads - 499 intake 510 exhaust 280 duration, used the old comp cam springs and e7 heads that were on the first motor. Here is my theory If the springs were to weak for the cam Then they would have worked for the first pair of heads (same as the second pair, with the comp cam springs) because my valve train geometry was off. The valves in the heads were too big for the heads and were not cut for the heads. Someone just basically shoved valves in them. Because my valve train geometry was off by lets say 2 mm, then this would have caused the valve to "close" Now with the new set of e7s i had "checked" with the same springs i was using, it idled a little funny but did not backfire until a quick rev or over 3000 rpms. Very confusing but i think i have said it all So in return my bad valve train geometry somehow aloud my car to run great for about 2 months or so and now that its fixed, it wont run because i have a burnt valve due to my valve springs not being strong enough... correct? Now that i have reread the other thread, Bryant mentioned it in the beginning of the thread... If i would have seen that then i would probably have had the car on the road but Ill learn one of these days
Why wouldn't the machine shops say "hey lets check your valve spring pressure and see if it matches your cam specs" Because..... yeh. Just had this thread on my mind
Pushrod length too. Pushrods for roller lifters may be different length and depending on what head you are using and if they are adjustbale rocker arms or stud mount rockers. Might be something to check while you got it apart again.
so can i say i told you so? just kidding. it sounds like your on the right track. the machine shop probly didnt ask you about the springs because most cylinder heads that go through a general machine shop are not geting a cam change at the same time. expecialy going from a flat tappet to a roller. doing all this on your own with out an experienced person overseeing every thing means your learn these things the hard way.
After eating my first cam and a couple lifters, I asked the guy at the shop which springs, retainers, etc. I needed so I wouldn't have any issues. It seems he knew what he was talking about, since i have had no valvetrain issues since installation of the roller cam and matching springs, etc. So, did you ever ask about the correct springs when you swapped cams? After reading all my posts and destroying my cam, you should have learned from my mistakes! That is why I post them up here...so nobody else has to go through the same extra work and heartache.
Why cant you use flat tappet springs on a roller cam? i know the spring pressure is a little different but i dont recall seeing "roller or non roller" springs section on summit. Pushrod length is correct. I checked it twice! (actually more than that) Yeh bryant, thats why i keep you around Your always a big help. Live and learn. Nope, didn't ask about springs because i figured they would hold. They are the double spring springs haha. Told the machine shop to make the heads work because i had the wrong retainers too, ect.... They said they were good to go after a couple days. Spring pressure test probably next week and ill see if that was my problem.
a hydrolic roller lifter is alot heavier than a flat tappet liffer. its that weight that requires a heavyer spring rate. you would definitly encounter valve float at lower rpm than expected with that combo.
