cam timing on rv8

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2

2005lyndon

New Member
Posts
50
Location
stafford
im struggling to get my rebuilt sd1 engine to start, ive gone through the test manual for the flapper efi and that all checks out, ive replaced the coil,nice new magnecor leads, new plugs(3 times), timing to tdc etc etc, and have checked and triple checked the tdc timing, but it wont get close to starting, but will misfire quite alarmingly if at the wrong/other tdc(it blew the afm off), when timed "correctly" there is no sign of starting even with some "start you b*&~@trd" squirted in the intake, but there is an occaional pop/ fart or explosion in the exhaust port, could i have possibly miss timed the cam? therefore tdc is when the cam isnt fully closing the inlets/exhaust, the other change/upgrade was fitting a std 3.9 cam during the overhaul.
ive disconnected the cold start injector, and checked we have fuel, pulsing, good pressure, etc etc live to ecu
ii would appreciate any thoughts please:cool:
 
According to Haynes the valve timing for an early 3.5 is as follows:

Inlet opens 30 Deg BTDC
Inlet closes 68 Deg BBDC
Duration 285 Deg's
Peak opening 112 Deg 30min ATDC

Exhaust opens 68 Deg BBDC
Exhaust closes 37 Deg ATDC
Duration 285 Deg's
Peak opening 105 Deg 30 Min BTDC

Later 3.5's changed and then there were further revisions for the EFI engines. The valve timing for a standard 3.9 is as follows:

Inlet opens 32 Deg BTDC
Inlet closes 73 Deg ABDC
Duration 285 Deg's
Valve peak 104 Deg ATDC

Exhaust opens 70 Deg BBDC
Exhaust closes 35 Deg ATDC
Duration 285 Deg's
Valve peak 114 Deg BTDC

So there are some differences in there. I would guess you need to take the top off and carefully check/set valve timing. Ignition timing might also be in need of checking and setting, but as a generality, a V8 will run on anything between 3 and 6 degrees BTDC.

Have you tried advancing your ignition to get it to fire up? might be worth a shot.
 
start at basics and remove front cover and check cam timing on sprockets and that valves on no1 look to be were they should be i had a cam once with key way 180 out
 
thanks for the advice, ive tried "swinging the timing" is that legal?? any way all that happens is that the popping or back firing disappers or comes back,
front cover off is the next step, im convinced that could be an issue, as the engine at tdc, timed correctly shouldnt be "firing in the exhaust", plus i have done a quick compression check and no2 cylinder was only 3 bar, even "wet" which makes me think im timed wrong.
ive an issue with clearances on inner wing that might mean i take lump out to do this, not sure yet, but the clearances would be easier with potential coffe table removed.
im assuming the v8 is a "safe head"
 
cheers for the info, checked the cam sprockets after a gigantic struggle getting crank pulley off, and i seem to have made an error, the top cam pulley, didnt as the haynes manual have "front" marked on it, so id originally lined the face with a large lozenge shaped tab on with the crank pulley mark, when i pulled it off tonight and flipped it, on the other side was a pointer/arrow, thats 90degrees different, have lined it up, and retimed cam, and engine to tdc, refitted all (which in this case was the reversal of removing but easier) crossed fingers and still it wont start, triple checked tdc, and timining sequenbce, then just for measure moved the plug leads 180deg, and tried again, nothing allthough it has to be said it feels closer to firing, its too late now to pratt about anymore, back to basics tommorow,
fuel, spark, timing, firing order, then run through the efi checking sequence, losing the effing will to live...................:(
 
Eyup 2005Lyndon, how did you lock the crank to remove the crank pulley? Ive spent all day trying to get mine off to change the timing gear.
 
moving the plug leads by 180 deg is the hard way! just pull out the dizzy and turn the rotor arm 180 deg, much quicker.
 
bushwwacker said:
Eyup 2005Lyndon, how did you lock the crank to remove the crank pulley? Ive spent all day trying to get mine off to change the timing gear.
Click to expand...

I find using the notch in the bottom pulley wedged against the chassis using a suitable metal bar or similar works just fine. Another method I have heard but not used is a long breaker bar against chassis rail then flick the starter over but beware you'll need a strong bar or there'll be bits 'o metal all over the shop.
 
still not got it started, i seem to have lost my spark, any one got a spare 8 or so just to get it running!
not sure when i lost the sparks, coil has power, and if i connect a spark plug to coil and lay it on plenum, and short the coil across i have sparks but nothing form dizzy cap, or plugs whne attache to that, also now, i have fuel pressure but injectors have ceased, working (when tested with a test light) and no fuel at plugs


i think therefore the dizzy/ amp arent working, causing no negative pulse for the ecu, hence the injectors arent firing,
anyone suggest a good coil dizzy combo.
anyone know someone handy in staffordshire who could have a look, im getting a pile of grief about it not running, and im about to damge it if it doenst start soon.
 
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