Drag and Drive Baja

[buguy]

You can advance it and get another 500 rpm if you wanted to.

[Bruce.m]

You mean move it forward? Ie retard it?
Closing the intake valve later moves the rpm range up.

[buguy]

You are correct. You would retard the cam to move power up in the rpm band.

[Bruce.m]

It’s interesting to compare to German made cams such as Schleicher. They typically have less lift for a similar duration. Puts less strain on the valve gear I guess?
I recall a tuning yardstick that says while the valve lift is less than approx 1/4 of the diameter of the valve, the flow constraint is usually the valve to seat gap. Above that amount of lift, the port neck under the seat can become the restriction. All a generalisation but interesting to mull over.

[Ol'fogasaurus]

I'm not a turbo guy but for what it is worth (if I remember correctly) cam design is a bit more complicated than most of us understand. I usually run "split duration" cams; e.g., higher lift but shorter duration lobes and the lobe's the shape/angles are also a bit different are different than stock. Their design mostly for lower end torque and not top end HP.

Lee

[Clonebug]

If you want to read about cams I suggest getting Smokey Unick's Books.
One of the things that stuck in my mind was his statement about cams......he spent a LOT of time grinding and regrinding cams in the early years of NASCAR.
He said...and I quote......."A cam is optimal for a 300 rpm range....where do you want that rpm range????"
In racing that was a big question depending on the track in those days.
They would make him pull an engine apart after winning a race so they could measure the cam......way back when.

[Schweg]

Well.

After 9000 or so boosted fuel injected miles the mystery engine in the Baja gave up the ghost.
Knocking very hard and not wanting to run I’m not sure what I damaged but it’s a show stopper.

On the bright side I’m a few parts away from being able to assemble a big valve 1679 that I have been collecting parts for.

The build is as follows.

Standard crank, rods and fly wheel.

Full flowed case

88 mm slip in bottoms machine in tops.

041 ported heads

SCAT c25 cam with 1:25 SCAT lifters.

I’ll build the long block and swap the parts off my current engine to top it off.

Also gonna try and wrap my headers while I’m rebuilding.

Also Happy Father’s Day gents.


Sent from my iPhone using Tapatalk

[Chip Birks]

Gonna highly recommend not wrapping your header. Unless of course it is stainless. You'll the murder a steel one. Especially in a humid climate.

[Ol'fogasaurus]

Also gonna try and wrap my headers while I’m rebuilding.

Why wrapping them other than for keeping the heat in the tubes so as to not heat up the rest of the area?

One option is to do the heat shield thing which allows any moisture that potentially could be caught in the wrap to escape. While not always the prettiest thing they do have advantages... both pro and con.

Lee

[Schweg]

Wrap to keep heat in. Not for looks.

Hoping to gain a bit more heat transfer.

[V8Nate]

I've seen steel headers rust thru really fast with wrap, I don't remember if yours is stainless or not though. It might be ghetto in some people's mind but how would coating the header in something like jb weld hold up do you think? I would imagine it would hold the heat in kinda like a cast manifold

[Schweg]

Not stainless.

I may just ceramic coat them.

Or ceramic coat and wrap I’m not sure it’s gonna be a timing thing.

[Ol'fogasaurus]

https://autoguysland.com/header-wrap-pros-and-cons/

One of several discussions on doing exhaust wrapping. It was popular years ago then went away so I am not sure if it has really made a comeback. The heat argument in the engine bay, as I remember, was the big reason for doing it but the length of life of the header was diminished (tube vs. casting). Not sure about the pros and cons of the life of wrapped CRES tubing though.

Lee

[buguy]

I didn't watch it, but that HP Tuners channel just had a video out a few days ago about wrapping the header.

[Schweg]

Been one super interesting weekend



I had some issues a few weeks ago, the car just shut off on me two burbles and then it stopped. Try to start it and got some real bad noises. I have had a 1679 that I have been putting together as I found some parts for some good deals.



It is a stock crank, C25 cam 1:25 rockers, Ported 041 40/35 heads.



That was my first VW engine so I have been getting it together slowly I was a few parts away from completion. With the sudden stoppage of my mystery engine I finished the engine build and got it installed last weekend. Though a work trip stopped me shy of adding oil and breaking it in.



Well yesterday I slammed some oil in it and lit it off for a 2000 rpm 20 min lifter break in. Talk about nerve wracking by my self I’m running back and forth trying to make sure everything is good. Got that done with only a few oil seeps to clean up, I addressed those and changed the oil and filter and let it cool for a valve adjustment.


Took it out for some local runs to get a feel for it and things where going well. Not running high boost and avoiding full throttle I was just running different RPMS trying to get the rings seated.


Saw some low vacuum numbers and was chasing that decided to run over to a friends house. On the way felt a marked drop in performance at cruise but thought it might just be this engine not liking my old ignition table.


Then it happened gave it a little boost and POP! Engine chokes out and dies. I push it off the road try to start it in a parking lot. Get a pop then nothing. Last attempt the engine stopped HARD.



I get a friend to help recover me and get it home.



Popped the valves covers off and I found 2 lash caps the spring retainer and one valve lock. In this time I was talking to guys trying to see how bad this was I got asked of the valve moved, the stem did!








So one bent pushrod a snapped valve spring and maybe a hole in a piston remains to be seen. The highest of highs and lowest of lows.



Need to decide if I am going with Beehives or VW650s and what pushrods any advice is appreciated.



Schweg