TheSamba.com :: View topic

Thu Aug 14, 2008 9:13 am

My generic 40x35.5s are crap. The engine hasn't run worth a damn since I got them (three years ago). I was using mildly ported 39x32s and they were wonderful, but I cracked them with detonation.

I'm trying to decide between the 40x35.5 CNC roundports or the 42x37 Mini Wedge ports. I'm liking the roundports better because I only get to the drags maybe twice a year, if that, and they will be easier to match-port.

I've got a 1915 turbo with a VZ-25 cam and a t3/t4 turbo that also isn't worth a damn. I'm going to get a GT2871RS eventually.

Thu Aug 14, 2008 3:01 pm

I have the CB 044 Round Ports in 40x35.5 size on a 1915, and thought they could use a fair amount of cleanup work out of the box.

Sharp edges around the valve seat pockets, unshroud the valves to the edge of the chamber, lose the step in the chamber, etc. Wasn't exactly impressed with the valve job either. Chambers were 60cc as delivered, so it was a bit big for a 1915, and required a good sized flycut. Probably a positive if you're turbo'd.

Basically, if I had to buy heads again it would be a hand ported head, or at least a CNC'd head with those important details worked out.

Thu Aug 14, 2008 4:23 pm

I had been folllowing your Mega Squirt post I thought it you had running great with the T-3, cb intakes and new control unit? All the work you have done so far is incredible. Maybe someone who ports a lot of turbo heads might be a good place to start. Here in Arizona Mike Fischer at Competition Enginering does lot of porting CB heads for turbo powered engines.

Thu Aug 14, 2008 5:49 pm

perrib wrote: I had been folllowing your Mega Squirt post I thought it you had running great with the T-3, cb intakes and new control unit? All the work you have done so far is incredible. Maybe someone who ports a lot of turbo heads might be a good place to start. Here in Arizona Mike Fischer at Competition Enginering does lot of porting CB heads for turbo powered engines.

I've got it running great on the low-end, but it has zero top end. It wouldn't even do 90 going flat out yesterday.

I always thought my lack of performance was something relating to the MegaSquirt making it not work, but everything is new now except the heads, so it looks like they're the culprit. Honestly, I never thought they were very good, but they were what I had.

Lately, it hasn't been wanting to pull over 4500, with or without the water injection. I think my valve springs have gone soft. The engine runs pretty well, just driving around, but it falls on its face when I get on it.

Thu Aug 14, 2008 6:05 pm

I must of misread it I thought at one time it was sorted out. You definitely do not give up. I was wondering about the cam. Its the same style cam (Weber 183 with Weber dual valve springs) I use in my off road 2180. Its more like a short track cam with its quick acceleration. Maybe the fast ramps and the turbo don't get along at higher rpm.Just curiosity as I never built a turbo engine let alone turbo it. I have seen weak valve springs on a stock engine it would hardly move with a load on it. Are you considering knock control like the 1.8T has.

Thu Aug 14, 2008 9:43 pm

perrib wrote: You definitely do not give up.

I'm about to. With all the money I've spent, I've only broken out of the 9s in the 1/8 twice, though my trap speeds are in the mid-high 80s.

Quote: Maybe the fast ramps and the turbo don't get along at higher rpm.

This same cam would make power and pull extremely hard past 7000 RPM with the 39x32s. It must be the heads.

Thu Aug 14, 2008 10:06 pm

Sounds like the heads unless maybe the fuel pressure or volume changed. I would say 9s are very repectable. The 28 miles per gallon you were getting at one time was also real good.

Fri Aug 15, 2008 9:46 pm

*ahem* :oops:

I got to thinking. Until a few days ago, I was running E85. The biggest water injection jet I have, 625cc, worked just fine with the E85 but never would with gasoline. I checked and, sure enough, the 625cc jet was the one I was using.

I replaced it with the smallest jet I have, 175cc, tuned on it for a while, and my engine will pull hard to 6900 RPM now.

Woops.

I still want better heads, though.

Fri Aug 15, 2008 9:59 pm

Too much fuel instead of to little. Simple enough fix. :D