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Adjustable cam gear help

VB242

I.M. Weasel
Joined
Sep 21, 2011
Location
Driving the No Malarkey Bus
I'm having issues with detonation after I retarded the cam timing on my 8V B23+T, enough to pop the GD head gasket once again. I keep adding fuel, the timing is 7 degrees in the range I'm getting the knock. Is there something I don't understand about dynamic compression ratio that I will not be able to tune this problem away? It's an IPD turbo cam, microsquirt, fuel system and injectors are fairly new. I'll be testing volume from the injectors to rule that out. It runs fine though the rest of RPM range and only knocks between 10-15psi around peak torque.
 
I had to retard the hell out of the ignition timing...the only way I could get the +T to not knock.... but especially around the torque peak (3500 or so rpm for an 8v)... after the torque peak it's ok to have a little knock, but it's most devastating at the torque peak.

I'll tell you what though.... the moment I switched to e85, I was able to add most of the timing back.
 
Retarding the cam timing will raise the DCR and usually make low end know worse. Try advancing the cam a few degrees to bleed off some of the DCR at lower revs, or a bigger cam.
 
Retarding the cam timing will raise the DCR and usually make low end know worse. Try advancing the cam a few degrees to bleed off some of the DCR at lower revs, or a bigger cam.

It has stock B23ET pistons and a 530 head, opened up a little around the intake valve, which i believe should be 8.5:1, I didn't have any problems with 25psi before I installed the cam pulley. I have a 3.35 first gear with a 4.10 rear, so it has plenty of jump off the line, I was trying to get a little more top end for autocross.
 
Have you measured the actual timing at the crank at a few rpms?
 
The only reason i say this is to verify that the timing you have programmed in the spark table is what's actually showing up in the cylinder. It's a pain to do with one person but have a bud rev the engine while checking it with a timing light on the crank to see if your 30 degrees at 2500rpm/50kpa isn't really 55 degrees.

It's a relatively quick check that could explain why you're getting severe knock on such a low compression setup.
 
The only reason i say this is to verify that the timing you have programmed in the spark table is what's actually showing up in the cylinder. It's a pain to do with one person but have a bud rev the engine while checking it with a timing light on the crank to see if your 30 degrees at 2500rpm/50kpa isn't really 55 degrees.

It's a relatively quick check that could explain why you're getting severe knock on such a low compression setup.

I totally agree with you, I'm bringing the timing light home tonight to check
 
Soooo yeah, it was totally the static timing, I forgot the timing light at work when I put the pulley on at home. And over estimating my mechanicing skills I just assumed i had the timing belt and pulleys back where they started from. It did have a lot of power of course with the static timing advanced 9 degrees, I need i get it to the dyno and work on the timing cause there's definitely more to be had. . And much to my great relief my coolant leak appears to be the coolant pipe that runs from the water pump to the heater hose behind the block and not blown HG, I also just figured that puddle was from the coolant bottle. I need the one that works with the 940 water/ oil cooler, thankfully there's a 940 turbo at the pick and pull. I even ordered new ARP studs from Yoshifab and an Elring HG kit from FCP. I reckon I'll be ready if/ when I do blow the HG again.
 
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