ke20 king Posted August 20, 2012 Report Share Posted August 20, 2012 hey guys i just finish building a 5k its got a stage 2 cam port polished head, converted to solids using custom push rods. twin webers and double valve springs. i have run the motor in and the thing wont rev past 5grand in 1st and 2nd and in 3rd it may go to 6grand. sounds like it is value bouncing. has anyone had this problem before? does the standard fuel pump pump enough fuel for twin 40s or does it pump too much and i need a regulator. I think it may be my valves that the valve springs are too soft and causing the valves to stay open. does anyone know of any strong valves springs for a 5k that has been used in someones car and running right. If anyone knows what this may be please help us out. thanks Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted August 20, 2012 Report Share Posted August 20, 2012 If it pumped too much fuel it would flood low down, and it won't starve because a 5K will haul better than that in stock form. I don't reckon its the fuel pump. Check the float levels, both up and down, and do a plug cut when it is playing up in 3rd so you can see what the plugs look like at those revs. Just turn the key off and push the clutch down until you stop. Can you get a dial gauge onto a rocker and a circular protractor onto the crank pulley. That way you can get exact degrees of when the valves are opening and closing. Its a pain to do, but it will show you if the cam is timed correctly. You only need to do one inlet valve and one exhaust, and if you don't ahve a dial gauge then you can feel with your hand when the rocker comes loose as the valve shuts, or suddenly tightens up as it opens. It will suddenly wiggle sideways, or stop wiggling. Was the cam cut for hydraulic 5K lifters or solid 4K lifters? I don't know how important that is, but I know there is a difference. Are you using an electronic dizzy?? Timing set OK and no points to bounce? Quote Link to comment Share on other sites More sharing options...
coln72 Posted August 21, 2012 Report Share Posted August 21, 2012 mmmmmmm. My old 5k used to rev better than that with stock springs and hydrolic lifters. Another reason not to stuff around with the standard set up....... Just a silly question, your tacho is accurate? Quote Link to comment Share on other sites More sharing options...
kickn5k Posted August 21, 2012 Report Share Posted August 21, 2012 hey guys i just finish building a 5k its got a stage 2 cam port polished head, converted to solids using custom push rods. twin webers and double valve springs. i have run the motor in and the thing wont rev past 5grand in 1st and 2nd and in 3rd it may go to 6grand. sounds like it is value bouncing. has anyone had this problem before? does the standard fuel pump pump enough fuel for twin 40s or does it pump too much and i need a regulator. I think it may be my valves that the valve springs are too soft and causing the valves to stay open. does anyone know of any strong valves springs for a 5k that has been used in someones car and running right. If anyone knows what this may be please help us out. thanks Have you had it on a dyno? What are the air/fuel readings? I doubt a STD fuel pump would keep up with twins. I don't know 100% because I've never been game to try. I'd buy an electronic pump and a regulator(you'll need 3-4psi for them). Quote Link to comment Share on other sites More sharing options...
Evan G Posted August 21, 2012 Report Share Posted August 21, 2012 I'm 99.9% its cam timing. my old 4k was the same! didnt like any revs past 5 grand. when i decided to put a bigger cam in it because i conviced myself that was the problem i found the cam was a tooth out. fml Quote Link to comment Share on other sites More sharing options...
GJM85 Posted August 21, 2012 Report Share Posted August 21, 2012 I spent a year trying to get my head around my 5k. Had the Tight 104 grind. Finally admitted to myself it must be the cam timing and decided to pull it out. 1 tooth out. I then attempted to adjust the cam timing with the engine in the car. ʞ©$ɟing nightmare. I snapped the gear locating key out of the cam. ʞ©$ɟed it. ʞ©$ɟ me. ʞ©$ɟ the world. But that was 6 months ago now and with help from the right people and plenty of meds (beer) i'm back on track and working towards a better me. Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted August 21, 2012 Report Share Posted August 21, 2012 lol!! Dontcha just love sidecam motors!! Get that protractor out KE20King... Quote Link to comment Share on other sites More sharing options...
ke20 king Posted August 22, 2012 Author Report Share Posted August 22, 2012 Thanks guys... I've had my engine builder come and check the cam timing he says it's fine but I will check it myself! Electronic dizzy I'm using it's been checked running fine. It's weird if I go half throttle it will rev to about 6000-6400 then flattern it and it will just bog down and sound like value are bouncing.... So weird... Haven't had it on Dyno yet tho don't know if I should while running like that. Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted August 22, 2012 Report Share Posted August 22, 2012 It's weird if I go half throttle it will rev to about 6000-6400 then flattern it and it will just bog down and sound like value are bouncing Well, lets ignore the noise part... So it will rev OK, but slowly I assume, if you use half throttle, but bogs down when you open the throttle wide?? That makes it sound more like a fuel problem, so over the carbs carefully, make sure it has pump jets working on both carbs, and see if you can learn anything from a plug cut as it bogs down. A dyno run or a drive with an A/F meter up the exhaust would show it straight away. If you feel the valve bounce noise is correct then go back to single valve springs, which will change the harmonic interference, and see if that makes a difference. Holden 202 springs are the usual alternative for hot cams.. In theory the nice new valve stem seal will hold the valve up when you take the springs off, but you can always put a cyl on TDC and have a compressor hose screwed into the spark plug hole. Quote Link to comment Share on other sites More sharing options...
ke20 king Posted August 23, 2012 Author Report Share Posted August 23, 2012 I've got it booked to go on a Dyno on Saturday I'll keep you guys posted. What main jets do people normally run with a worked 5k? My chokes are 32 I know that. Quote Link to comment Share on other sites More sharing options...
Evan G Posted August 23, 2012 Report Share Posted August 23, 2012 this is valve bouncing Quote Link to comment Share on other sites More sharing options...
coln72 Posted August 23, 2012 Report Share Posted August 23, 2012 I've got it booked to go on a Dyno on Saturday I'll keep you guys posted. What main jets do people normally run with a worked 5k? My chokes are 32 I know that. Not that it helps you much, but my 5k ran very nicely running a slightly modded 3KB (factory twins) set up. Quote Link to comment Share on other sites More sharing options...
Taz_Rx Posted August 23, 2012 Report Share Posted August 23, 2012 Well, lets ignore the noise part... So it will rev OK, but slowly I assume, if you use half throttle, but bogs down when you open the throttle wide?? That makes it sound more like a fuel problem, so over the carbs carefully, make sure it has pump jets working on both carbs, and see if you can learn anything from a plug cut as it bogs down. A dyno run or a drive with an A/F meter up the exhaust would show it straight away. If you feel the valve bounce noise is correct then go back to single valve springs, which will change the harmonic interference, and see if that makes a difference. Holden 202 springs are the usual alternative for hot cams.. In theory the nice new valve stem seal will hold the valve up when you take the springs off, but you can always put a cyl on TDC and have a compressor hose screwed into the spark plug hole. Another old trick for changing springs with the head on is filling the cylinder with rope. Quote Link to comment Share on other sites More sharing options...
ke20 king Posted August 24, 2012 Author Report Share Posted August 24, 2012 hi guys i have attached my cam specs to this post, would anyone be able to tell me if the cam is any good for what i am running? not real good in reading this kind of stuffcam specs.pdf Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted August 24, 2012 Report Share Posted August 24, 2012 289deg is pretty wild, but all that means is that it shouldn't run UNDER 5000! :D The way I see it you have only 0.325" of valve lift, so its not going to stress the valve springs. Stock springs are OK to 0.4" plus a bit. If you can check that an inlet opens 40deg BTDC then the cam timing is fine and the problem is somewhere in the carbs. Check the float levels, make sure the jets and drillings are clean and do a plug cut when its dying on you. See if the plugs look suspicious when it bogs down, because with that cam it should fly high up. While you're sitting at the roadside pulling out plugs, take the top off the carbs adn see if its drained them or flooded them right up. You can't let the motor idle down, its a case of ignition off and clutch down immediately from hard power. Quote Link to comment Share on other sites More sharing options...
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