Cam Timing and Lowered Compression
02-03-2014, 06:52 PM
#1
Junior Member
Thread Starter
Join Date: Nov 2011
Location: Helsinki, Finland
Posts: 45
Total Cats: 7
Cam Timing and Lowered Compression
OK Usually i can use the seek and ye shall find option for all my amatuer woes but on this occasion it has failed me.
I have a 91 1.6 that originally had a Greddy turbo set up on it, i removed almost all off its nasty parts and fitted MSPNP, new EV14 injectors (670cc) and an intercooler kit.
When we replaced the timing belt we found the inlet cam was out by one tooth and the idler pulley had been machined to have an elongated hole instead of the usual round hole.
The timing belt was uber tight and impossible to fit with a std idler pulley so I fitted a second adjustable at max out setting on both the timing belt fitted but is snug. Further investigation has revealed a thick metal head gasket has been installed.
Am i correct in thinking this would be why the cam timing had been adjusted? on the dyno day it wouldn't pull more than 135bhp but was achieving 200nm TQ. then at 4500rpm it just lost all gains.
If the compression has been dropped by the thick head gasket, am i right in thinking the timing on the cams will need adjusted now?
as a side bar, the greddy kit has now been ditched in favour of an ARTech manifold and T25 Turbo.
I have a 91 1.6 that originally had a Greddy turbo set up on it, i removed almost all off its nasty parts and fitted MSPNP, new EV14 injectors (670cc) and an intercooler kit.
When we replaced the timing belt we found the inlet cam was out by one tooth and the idler pulley had been machined to have an elongated hole instead of the usual round hole.
The timing belt was uber tight and impossible to fit with a std idler pulley so I fitted a second adjustable at max out setting on both the timing belt fitted but is snug. Further investigation has revealed a thick metal head gasket has been installed.
Am i correct in thinking this would be why the cam timing had been adjusted? on the dyno day it wouldn't pull more than 135bhp but was achieving 200nm TQ. then at 4500rpm it just lost all gains.
If the compression has been dropped by the thick head gasket, am i right in thinking the timing on the cams will need adjusted now?
as a side bar, the greddy kit has now been ditched in favour of an ARTech manifold and T25 Turbo.
Reply
0
0
02-03-2014, 10:33 PM
#2
Former Vendor
iTrader: (31)
Join Date: Nov 2006
Location: Sunnyvale, CA
Posts: 15,442
Total Cats: 2,099
It sucks, but you need to pull the head gasket and replace it with a .030" OEM unit. Reducing the squish area on these motors makes them even more prone to detonation than they already are.
Advancing the intake cam will also make the car prone to detonation by increasing dynamic compression across the rev range.
Advancing the intake cam will also make the car prone to detonation by increasing dynamic compression across the rev range.
Reply
1
1
02-04-2014, 04:30 AM
#3
Junior Member
Thread Starter
Join Date: Nov 2011
Location: Helsinki, Finland
Posts: 45
Total Cats: 7
The answer i feared most, sigh
I really do wonder what this cars original Turbo installer was thinking, i have now and will no have removed every single component of his work
It was supposed to be so easy!
I really do wonder what this cars original Turbo installer was thinking, i have now and will no have removed every single component of his work
It was supposed to be so easy!
Reply
0
0
03-19-2014, 08:50 PM
#6
Junior Member
Thread Starter
Join Date: Nov 2011
Location: Helsinki, Finland
Posts: 45
Total Cats: 7
To SavingtonIt was worse than we thought, when we got the head off
a 4.5mm steel plate with a headgasket on either side, not to mention the RTV covering some of the oil ways
further issue were found when i got the head off that the rubber blank from the very back of the inlet manifold for a vacuum takeoff was absent compounding my tuning woes,
Now reassembled with genuine mazda gasket, and everything associated with the Greddy kit now in a box, she fired up and runs nicely.
10 internet points for you sir!
Reply
1
1
03-21-2014, 06:56 AM
#10
Junior Member
Thread Starter
Join Date: Nov 2011
Location: Helsinki, Finland
Posts: 45
Total Cats: 7
This whole car has been about trying to "do it once, do it right"
My stepfather was an engineer building race bikes and all i have in my head is his words about "if a jobs worth doing.."
Sorry i am not one for posting too often, i tend to prefer to spend my time tinkering. I will dig out the cars thread somewhere and update it.
short version is
91 J LTD, formerly Ghetto Greddy set up, with cams out by teeth to adjust timing, vortec FPR jack through the roof, Tan injectors. running std plastic pipe with gaffa tape to pass the boost from turbit to inlet mani.
Now fitted with
ARTech manifold and T25 Turbo, Custom stainless downpipe, Front mounted intercooler, MSPNP2 with EBC, Bosch EV14 670cc injectors, VTPS, MTXL WIdeband, SVT Big Brakes waiting in the shed to go on after running is sorted,
My stepfather was an engineer building race bikes and all i have in my head is his words about "if a jobs worth doing.."
Sorry i am not one for posting too often, i tend to prefer to spend my time tinkering. I will dig out the cars thread somewhere and update it.
short version is
91 J LTD, formerly Ghetto Greddy set up, with cams out by teeth to adjust timing, vortec FPR jack through the roof, Tan injectors. running std plastic pipe with gaffa tape to pass the boost from turbit to inlet mani.
Now fitted with
ARTech manifold and T25 Turbo, Custom stainless downpipe, Front mounted intercooler, MSPNP2 with EBC, Bosch EV14 670cc injectors, VTPS, MTXL WIdeband, SVT Big Brakes waiting in the shed to go on after running is sorted,
Reply
0
0
Thread
Thread Starter
Forum
Replies
Last Post
