race 1600 engine not making power over 3800rpm

[bugguy1967]

No need to yell Mark
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[mark tucker]

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.

[nsracing]

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?

[bugguy1967]

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.
_________________
"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine"

[modok]

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.

[DeathBySnuSnu]

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.
_________________

[[email protected]]

"It's can't be *****, because they are new" has put more egg on face than anything in the Automotive Hobby.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[mark tucker]

[Dan Ruddock]

[Brian_e]

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

[chrisflstf]

If it was a " dead" spring, would not it make noise or racket, or rough running at higher rpm? Seems you should be able to hear it, if that was the case

[vwracerdave]

The cam could have been advanced or retarded 1 or 2 degrees when ground and that could make a big difference when dyno'ing a race engine. Just because any part is new DOES NOT mean it is correct. EMPI has been know for shitty quality control, and you are trusting their accuracy.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[[email protected]]

because some heads are shipped with $#!^ valve springs. Check them.

The cam could have gone flat too, the most common time for it to happen is during break in, when it's "new".
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[Brian_e]

I am with John. Check the valve springs.

Stock springs are OK for 4000rpm on a stock cam. The second you add ratio rockers, ask it to rev higher, more lift, or add heavier valves, you need at least HD single springs.

Just cause they are new doesn't mean they are good or correct.

Brian

[Bugsy61]

Cam off one tooth?

[delamarrr]

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.

[67rustavenger]

[[email protected]]

First thing I'd check are dead valve springs.
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[mark tucker]

dead valve sppringy thingys can also affect things like this.

[vwracerdave]

It's the new EMPI cam or the new EMPI heads.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK