How much compression do I need?

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Tait72

Tait72

Member
Hey guys,
I have a thrown together dohc 1.8L B-series that I have been running for two seasons, now its burning a butt load of oil. Gonna rebuild it over this winter. Its gonna be an NA DD engine, that see's the track about twice a month.
My question is about cams, I have a GSR head that "had" Buddy Club 3's but one cam sheared in half. Now it has stock B16s cams in it.
The head is ported and has an upgraded valve train "crower springs" blah blah, now I want big cams again, like Skunk 2 Pro1 or Pro2, how much comp do I need to get the most outta these?

Thx for any advice
 
go ask your tuner what he can tune safely. My tuner can go up to 13:1 on 91 pump.

Dont expect to make great power with a high as hell compression on the street on pump gas, the real point is when your at the track running your choice of race gas.
 
In other words your going to run a real conservative tune on pump gas with a high compression.

then you can have a aggressive tune with your choice of race gas when your at the track.
 
That is some good advice bro, with so many variables it only makes sense talk to the tuner. I will see what he thinks will suit my purposes and make good power for track. Don't know why I didn't think of that.
Thx.
 
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This is going back a month or so but I thought I would share what went down. I had a track day coming up on Sept 30 when I had started this thread. I thought my car was down on power and comp test showed 60psi in cyl 1.
We pulled the motor that night and tore it down the next day to some broken rings and lots of damage to valves head and especially the piston. this was shitty cause they were Wiseco on Manley Rods for a gsr crank. So I got a stock LS block had the head repaired. "had to take off 20thou"
Took it to the track and ran a 15 flat shifting at 7000rpm trapping in 5th gear.
B16 trans, 21" Hoosier Road race Tire.
Asked my buddy if he would dolley me home, rev'd to 8000 crossed the line at 8400 in 4th.
Needless to say home on a dolley but 14.4 @96mph 4door ek.
Now Im rocking a stock Ls while building a Ls crank rods B16 piston for my GSR block over the winter love that tourque.

Shannonville Drags Sept 30/12 - YouTube
 
Yup, did you add in fuel for the larger combustion?
 
Nope no tune just a stock LS Vtec copy off crome, fuel was about 48-50psi at idle that's where it worked best. It was just a stock $100 block to use that day. I didn't want to sit the afternoon out and watch, I spun the bearings out that bitch after about 12-13 passes. That's why I asked my buddy to dolley me home. Not a big deal I knew it wouldn't last. It was the last day the track was open this season. Was well worth it, approx 10 cars from my town went that day we were all just waiting for it to happen.
So I got third out of all of us H22 EL 14.03, B16 coupe 14.33, My sedan 14.42. We all had a blast and that's what it's all about. I will have a "pro" tune it this spring, I just got my LS crank back from the machine shop so the process is starting all over again.
 
Well, that's probably why it blew up then. Make sure you have some larger injectors (like 310s) so there's room to add fuel.
 
I wrote a big paragraph about tuning but then I realized I just dont care anymore.

Next time use stronger internals, no tune, and make more POWAAAAAAA! hell run it as lean as you can and maybe melt a piston at IDLE! or make the bearing clearance so tight it melts the lead off of em.
 
Ah geez man, you guys are taking it a bit too serious, I would have been crazy to spend $500 plus tax on a tune for a garbage block with over 250k on it. I would be halfway to new rods and pistons for that price.
Dont get me wrong I totally respect your experience, and opinions about these motors and what they need, but it was a throw away block and just something for one day.
I'm having a real bottom end assembled for me and it will be tuned by a pro, not me a timing light and a fuel press reg! Plus it didnt "blow up" it spun a bearing cause I rev'd it too high.
Peace.
 
Ok, as long as you were planning to trash the engine anyway.... but the tune is THE MOST IMPORTANT thing for ANY engine that has mods beyond intake/header/exhaust.
 
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