TheSamba.com :: View topic - race 1600 engine not making power over 3800rpm

Thu Aug 02, 2018 2:26 pm

Brian_e wrote: Nope.

I built an engine that was on the edge of single or dual springs. I used what I thought were decent HD singles shimmed .100" to bind. After one summer of use it started cutting out about 4000rpm. It ran awesome and pulled hard till just over 4000rpm, then it was like someone pulled 2 plug wires.

The owner chased his tail swapping fuel pumps, complete ignition systems, adjusting valves, etc. Everything was tried. I had a hunch, and pulled a spring to find they had less pressure then new stock springs. Almost all of them were shot.

Being you have Empi springs I would be changing them regardless. A dropped valve makes a pretty big mess of nice new parts.

This would be a really good application for Dan's beehive spring kit.

Brian

Thanks for the vote of confidence but my beehives would be overkill for a stock cam with 1.25 rockers. I would not trust any Empi springs, most likely made in china and are a hit or miss. I would get some Berg HD singles which would be all you need for your app and you can trust the quality control. This might not be your problem but springs are too important to use crap.

I would never run more than .430" lift with HD singles, they just have harmonic problems and too much lift makes it worse resulting in a very short spring life. I have a beehive customer who runs a FK7 with 1.4 rockers and new HD singles broke in just 17k miles. He got tired of having to change his springs every 15k and went beehive. Stock cam with 1.25 rockers is only .380" lift.

Dan

Fri Aug 03, 2018 12:23 pm

delamarrr wrote: I dont think anyone that replied actually read my first post besides capt. calzone and glasser.

Cant be fuel, it has a perfect lambda reading right across the rev range.

Why would it be a dead valve spring? The heads are brand new.

Why would it be a dead cam, the cam is brand new.....

It didnt run as it should on the dyno, it stopped making more power at 3800...

capt calzone + glasser: maybe, im in the process of making a new carb up for it so ill try that soon. however my lambda reading is spot on all the way to 5500 on the dyno. I should add that i serviced the carby after the first dyno run and before the second. The problem was still there on the second run. I think its going to be something internal, so its going back to the builder after my race this weekend.
ok you have a good point there so....my question is ...WHY WONT IT RUN!!!since everything is spot on..... possiably the dyno is on the fritz...and fritz is on vacation...

Fri Aug 03, 2018 12:28 pm

"It's can't be *****, because they are new" has put more egg on face than anything in the Automotive Hobby.

Fri Aug 03, 2018 6:33 pm

I dont directly know about what you are doing.
But a couple years ago when my girlie was racing a spec class of dirt track (non vw), we had to run spec springs and cams (among other things). Cam timing and valve springs were short lived and super critical when running continuous 6 to 6.5k the whole time.
Valve springs would do very similar to what you are saying, but would also start taking peak rpm off the top. A cam change had to be dialed back in, none were ever the exact same lobe center.
Very small things made all the difference running that spec class.
Not even all spec race valve springs ran the same.

And again....all this was non vw....it may not fully apply.

Fri Aug 03, 2018 8:20 pm

You think everything is the same both engines but clearly it isn't.
All you need to do is find out what the difference is.

Sun Aug 05, 2018 6:36 am

The first thing I thought was springs too. Try another brand.

Btw, I have an engine with non HD stock single springs that is still alive lifting to .400" and occasional 6,000 rpm for over 85,000 miles.

If it's not your springs, look into either valvetrain (pushrod) flex or loss of ring seal at upper rpm.

Mon Aug 06, 2018 8:31 am

It was good on they dyno and not when installed? Hmmnn? You think something might be amiss?

If you build an engine for racing build it so. So what did you do to the motor? What kind of work went into the heads? Valves? springs?

Did you take a compression test before and after the dyno session?

Are the exhaust pipes HOT on all 4 cylinders?

Mon Aug 06, 2018 8:51 am

JUST BECAUSE SPRINGS ARE "hd" OR NEW DOSENT MEAN THERE ANY GOOD.THE SAME GO'S FOR EVERYTHING ELSE....INCLUDING THE FUEL HOSE.AND THE LAMB THINGY. AND DONT FERGET ABOUT THE ASSEMBLEY GOO~ROO. AND THE 3 TEETH OFF CAMSHAFT THINGY OR MULTI PEICE LIFTER'S.

Mon Aug 06, 2018 9:08 am

No need to yell Mark :lol: