Timing Belt Snapped

[dsp26]

You seem to know the answers to your own questions but you’re just not putting it together.
Get back to basics & think of it in simple terms.
You’ve got larger than std cams,
If the cam timing is out,
this affects the dynamic compression of the engine & therefore what it shows on a compression test…
So, check/set the cam timing.

Valve seat sinking,
You know this is an issue…
It may not be perfect but it works.
If you want to fix it, pull it down & use 0.5mm oversize valves.
This will allow you to reclaim the seat.
Worse than sunken valves is core shift…
Hopefully you don’t have that…

Going back to your original intake manifold you can see plain as day…
The cam timing is retarded.
Lack of low end, then coming to life in the last part of the rev range.
Again check/set cam timing.
Once cam timing is sorted together with a good tune, you’ll probably make some decent power.

Dizzy being full whack one way or the other is not right…
Cam manufacturers aren’t complete retards rarely ever machine the distributors drive in the end of the cam, in a position when the timing cannot be effectively set.
If the dizzy is near the middle chances are the cam timing is near right, if it have to go full whack one way or the other.
Mate, you know the answer…
Check/set the cam timing.
Hope that helps

Thanks for the details Adrian just wanna clarify some things though...

- I discounted the dynamic CR issue because the BC3+ low lobe wasn't that much bigger than stock.. 30psi difference between first build and now.... sooo.... so your suggesting i loosen LSA on the cams to reclaim some CR?
- Cam timing, you mentioned its retarded, currently setup at +6 +4, each marker on the gears = 2*@crank. i'm guessing the +4 +4 is to account for my head shave to reset to TDC.. the additional +2INT is as per Buddy Clubs recommendation. (those are rough observations btw, they were dialled on a degree wheel/tool)
- Is there any guideline I can use to somewhat gauge P2V clearance while i play with my cam gears with head still on? jack the car up and rotate wheels?
- does the graph indicate to you sunk valve seats? i just know it creates a powerloss due to the shrouding but i don't know the resulting curve characteristic and how much. Does this also mean cam gears have to be adjusted to account for the sunk amount? is this contributing to retard?

- i'm going to estimate that my head is shaved 0.040" / 1.016mm all up. rough guide from research says that every 0.040" removed = roughly +1 on cam gears or 2* crank.
- Written down on one of my papers was LATDC.... INT = 0.93mm/4.5*A + EXH = 1.04mm/1.5*
- so cam gear correction is roughly +2 +1 for head shave
- To loosen LSA is to advance int + retard exhaust? but this decreases V2V clearances right? but since i have sunk valves its less of a risk?
- wouldn't this mean +6 +4 is too far advanced already?
- Should i try +7 +5 to advance them more? or should i +8 +4 to loosen LSA some more? or since the top end is fine now +6 +2??

- relative to TDC (assuming 0 0) does the P2V clearance increase/decrease for the below scenarios:
Adv Int =
Ret Int =
Adv Exh =
Ret Exh =

- can you please explain "Core Shift". Is this something that should be obvious to a builder/head specialist?

- On a side note... how come i'm the only loser that lost power with an ITR (copy, aebs) manifold and 65mm TB?

- How did my AF change between Pic 2 and 3 from leaning FPR (i thought this would cause linear movement) + retarding dizzy all the way?

- Why are there so many drastic/extreme changes just to get me back to similar peak power + nowhere near the same midrange because i snapped a timing belt and had valves replaced?? when the engine was first put together cam gears were in the vicinity of +4 +2 and dizzy timing at 14* and fpr at 40psi??

- With some of the above info (especially cam timing so far advanced and dizzy so far retarded) does this still look like a case of cam timings retarded? or its powerloss from head failure?



But i'll be honest.. i can't afford to screw my own engine a 2nd time... my expense so far has already far exceeded a b18c7 motor :/ Are you able to have a look at it for me and do the fiddling? PM me?