help! valve spring - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

jmartion · 10-13-2004, 01:33

got a worked 351.. not exactly sure what valve springs its got in it, but one of em broke yesterday..

i'm pretty sure they're plain old 'heavy duty' or somethin like that.. what kind of spring can i buy to replace it? anything? must be harder? softer? or just suited to what i want(like the rest should be anyway)..

cam has 480thou lift on intake, and 490 on exhaust..

and its got rollers.. whether that applies to valve springs....

ta.

also.. some tips on how to change it??

xacoupe · 10-13-2004, 01:44

You could be lucky and have someone able to tell what it is from the broken spring but I suspect you would be better off taking a working one off and getting it tested.
If you don't want totake the heads off there aren't a lot of options about getting the springs out. You need to get the valve to stay in the closed position .. I know you can use compressed air but I am sure that I saw someone else post another method .. it had something to do with making sure the pistone was at TDV and using a spring compressor. Hopefully they will reply and explain it better.

xdclevo · 10-13-2004, 02:28

I took my springs off a few months ago to install the inners after the cam run in. I didn't use compressed air, but did just put at top dead centre to be safe. All 16 valves were held there by the seals, but the seals were new and still firm on the valve.
If you have broken a valve spring, replace ALL of them. Get some new springs that will suit that sized cam and make sure they are shimmed to the correct height. Oviously, just do one cylinder at a time and have on TDC when doing those springs/cylinder.
If it is a hydraulic cam, 100 pound seat pressure would probably do fine, but what do you called a worked engine. What revs will it do?

jmartion · 10-13-2004, 04:17

what i call worked? well no less than this engine i spose.. - this donk should pull abit over 450hp/450ftlb(max power at 6, max torque at 4500, 80% torque available at 2000rpm). been balanced, close+honed rods, pillow block bored 30thou and the heads have been worked to hell and shaved to pull a comp ratio about 12.5 to 1.

yeh gonna get the piston up to TDC so that valve doesnt drop in.. me mate who built the motor is gonna gimme a hand.. see how we go this weekend..

damnit... i only just put a big fat alloy radiator in with AU thermofans and an autometer sport-comp external temp guage.. and two days ago!!

xdclevo · 10-13-2004, 19:57

Quote:

Originally Posted by

cam has 480thou lift on [email="intake@27"

intake[/email], and 490 on exhaust..

Did i read correct on your cam lift. That seems like a stock ford cam. If you can ring 450 hp out of that cam, i want one. Also with that compression/cam, you're going to need some damn wicked fuel.
I am running a solid 570 and 590 lift cam and will be happy if i make 450 ish.
What are the rest of the specs. Is it hydraulic?
You would also have to have lumpy top pistons to have that compression.

jmartion · 10-13-2004, 20:27

its a roller cam but i dont know bout hydraulic... haf to ask my mate... according to dyno2000 it pulls those kind of ponies anyway(well with the right exhaust and LPG, it supposed to pull 485 at 6500, but it does have very high compression..)... have yet to dyno it properly tho..

the cam is actually out of the supercobrajet mustangs engines from 1971.. specs -

intake lift - .480 duration - 270
exhaust lift - .490 duration - 290
lobe centre - 112 valve overlap - 56
IVO (BTDC) - 27.0 IVC (ABDC) - 63.0
EVO (BBDC) - 81.0 EVC (ATDC) - 29.0

put that in dyno2000 with a dualplane manifold, 12:1 comp ratio, about 800cfm of carby and well-ported canted heads(roughly my combo). valve sizes are 2.045/1.650 for int/exh.