• Hello Guest, welcome to the initial stages of our new platform!
    You can find some additional information about where we are in the process of migrating the board and setting up our new software here

    Thank you for being a part of our community!

What did I do wrong assembling the big bore b20?

I?ve never seen hot and cold lash come out the same.
Aluminum heads you subtract lash cold, iron heads you add lash cold. It can be small (like .002?) on a smaller engine, but it changes.
 
OK a little update.

I reset the ash to 0.020" cold (because I didn't feel like hot tonight) and then redid the compression test. I think I forgot to open the throttle last time I did the test because we got much more even numbers across the board.

I did the test three times per cylinder and here are the averages

CYL 1 - 143.3 psi
CYL 2 - 147.3 psi
CYL 3 - 145.0 psi
CYL 4 - 141.3 psi

I drove the car around the block and it still felt weak, even around the 5k range.
 
Well, those cam specs sure seem to indicate it's a very low RPM cam.

Those compression numbers are still pretty low, but being even is a good sign. It could still be something wonky with cam timing to drop the numbers down.
 
Interesting topic and I don't really have any more info to add. Sorry to be interested in your pain, but it definitely sounds like you have a small camshaft based on the measurements you gave and the powerband shown, but your cranking compression numbers disagree with it being a small camshaft unless your static compression is actually much lower than you think.

I just played with that calculator and it is also way off for our engine. That being said, trying to enter the actual intake valve close is not easy if you don't have a degree wheel on the car and actually measure it. Using data that I was given by the cam grinder and another number based off of what another forum member measured is showing we would have a cranking compression of 160-180psi depending on what valve close time I enter, but our actual cranking compression is 205-220psi(b230F with approximately 10.8-11:1 static compression and an Enem K13 camshaft).
 
There's an update!

Volvo George was gracious enough to help me understand my problems and figure out what the hell was going on.

Turns out I was way off on my carb settings. 36mm chokes and 4.5 aux venturi were way too big. Too much air was asking for too much fuel and the engine couldn't do anything with either.

He dropped the chokes down to the 32mm I had (but suggests I get 34s) and the Aux Venturi to 3.5s. Then rejetted it a bit to match those settings.. (but suggested I pick up a few things to match the 34s.)

The car really woke TF up. There's power down low and pulls all the way to redline. It feels like it could pull even further, I'm just afraid to find out.

George also suggested I figure out a way to use the vacuum retard with the 123+ distributor to compensate for the DCOE's wanting such a high idle. As well as figuring out a catch can system since the way I had the crank case vent hooked up wasn't optimal for the engine.

There's still more tuning to do, but we at least figured out the culprit!

So my next steps are:

Need 34 choke , 50 f8, f15 emulsions, lightened flywheel, catch can, tinus tuning runners (to have a second vacuum port), 123 distributor with vacuum retard hooked up​
.
 
I tried 36mm chokes back when my motor was closer to stock, and they didn't work very well either. Mostly, you really had to ease into full throttle, if you worked up to it slowly it would work OK, but if you just floored it, it would sputter and bog. It was much happier with the 32's. Until I had more mods on the engine (R-Sport head, better exhaust, cam, etc), then I tried the 36's again and they worked very nicely.
 
I too am suffering with a low power condition in my rebuilt 2130 B20. Same engine I ran for 10 years and 120k. R-Sport s3 head, Stahl header, Mikuni 44PHH with 41 chokes, Mallory Uni-Lite.
Only 2 differences in this build were:

1. A thicker Cometic head-gasket (.120") to lower compression to 10.25-1.
2. A new-in-box ipd "R" cam. It came with a 1990's ipd stroker kit.
This cam should give .480" of lift, but is more like .400".
Engine feels like it is strangled or fuel-starved, slow to rev up and never really makes power.
Very frustrating!

I'm cam shopping now, this "R" camshaft is not what it should be...once I get it out, I'll pop in a new/real Isky r cam or some other make.

"As per the cam, I took the cam to ISKY to confirm it is a VV-71 profile, but they told me it wasn't actually one of their cams. This was a NOS IPD big bore kit from the 90s back when they still made it for the 6-bolt crank. So I know for a fact it's the vv-71 profile but can't confirm the quality of the cam since the manufacturer is unknown. "
 
Rara-Avis said:
I too am suffering with a low power condition in my rebuilt 2130 B20. Same engine I ran for 10 years and 120k. R-Sport s3 head, Stahl header, Mikuni 44PHH with 41 chokes, Mallory Uni-Lite.
Only 2 differences in this build were:

1. A thicker Cometic head-gasket (.120") to lower compression to 10.25-1.
2. A new-in-box ipd "R" cam. It came with a 1990's ipd stroker kit.
This cam should give .480" of lift, but is more like .400".
Engine feels like it is strangled or fuel-starved, slow to rev up and never really makes power.
Very frustrating!

I'm cam shopping now, this "R" camshaft is not what it should be...once I get it out, I'll pop in a new/real Isky r cam or some other make.

"As per the cam, I took the cam to ISKY to confirm it is a VV-71 profile, but they told me it wasn't actually one of their cams. This was a NOS IPD big bore kit from the 90s back when they still made it for the 6-bolt crank. So I know for a fact it's the vv-71 profile but can't confirm the quality of the cam since the manufacturer is unknown. "
Click to expand...

Honestly, I'd start by reducing the size of the chokes. That was 100% my problem. It couldn't make any power down low, and then it throws off the AFR reading because you can't get enough fuel to match the increased air.

I went back down to 32mm from 36 and it's been fine ever since. (well, I still need to have my carbs rebuilt but still)
 
Low Cam Lift

I ran the big chokes for 100k over 12 years. My current problem is cam lift is all wrong for an "R" camshaft...should make .460" lift, I'm getting .395-.410.
I think I have the wrong and/or a defective camshaft.
 
Rara-Avis said:
I ran the big chokes for 100k over 12 years. My current problem is cam lift is all wrong for an "R" camshaft...should make .460" lift, I'm getting .395-.410.
I think I have the wrong and/or a defective camshaft.
Click to expand...

Sure. That could definitely be the case. But it?s probably cheaper to try smaller chokes and rejet than it is to change the cam.

My cam was supposed to be an r-cam and it turned out to be a VV71 when I had isky check.
 
You must log in or register to reply here.
Back
Top