Need more top end (UPDATE)

artz1731

True Classic
So as spring slowly approaches us here in PA I have started to get the itch o plan out things I want to improve on my X. As most of you on this board I have a bad habit of constantly trying to improve all aspect of my X. Working on my cars on the weekends gives me great joy, I'm not sure everyone enjoys working on cars but I do.
Anyway one of the things I would like to improve is getting more top end out my X. I have plenty of bottom end but i can't seem to get it to pull compleatly to the redline. So I'll give you as much info on the motor as I can and look forward to any suggestions.
It's a 1980 1500 with a shaved 1300 head, 40/80 Faza cam, Single 42 DCNF carb,MSD ignition and Facet electric fuel pump with regulator. It also has 4 to one exhaust manifold which currently is attached to a fairly open (loud) muffler that exits straight out the rear.
So while it has good power it seems it should pull a little longer on the rpm band. I have been thinking an adjustable cam gear might help me achieve this but I am open to suggestions.
Thanks, PS I love this Forum!
 
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When you say 4 into 1 manifold, do you mean the stock cast iron item? if so get rid of it and fit the factory twin out manifold and matching front pipe and you'll be amazed how well it goes.

SteveC
 
No, I'll try to find some pictures. I used yo know what type it was but I fogot. This car used to be a hill clime racer many years ago and after driving many other exes I know it has plenty more power than stock. I just think there's some to gain. My 4 to 1 claim might be inaccurate.
 
The head has been shaved, but has any porting work been done on it or the intake manifold? A 1500 at high revs with a high-overlap cam wants to pull in an amazingly huge amount of air compared with a stock 1300.
 
Head has been ported, not sure about about the intake. But I belive it has. Does not have big valves.
 
I think you have a lot of the right stuff there Art...

... and its probably time to diddle a bit.

1. Carb jetting, venturis, tubes and rods.
2. Ignition timing, advance, centrifugal and vacuum or removal thereof.
3. Centrifugal advance weights, springs, and overall throw, as well as when it comes in.
4. Adjustable Cam Gear
5. Intake snorkel for cool air, carb spacers & filter types.
6. Exhaust tune, header and muffler.

Find a repeatable COURSE or DYNO... and then do ONE THING AT A TIME, noting, temperature, humidity and road condition... and use a WATCH to PROVE what your butt is telling you.

Much of this stuff is FREE or inexpensive and I would do those FIRST.

That oughtta keep ya busy for the next six months...
 
Thanks for the replies, there's nothing like a Saturday night performance chat. I did try different jetting and tubes last year. After many trials I ended up pretty much where I started. I wrote all that down somewhere I just need to find it. I am planning on changing to the Camaro Muffler with twin pipes going out the rear grill in the next few weeks. Keeping the current header. As much as I love the the loud ass sound of the current setup its a bit too much on longer drives.
I think my first experiment will be with an adjustable cam gear and go from there.
Maybe I'm looking for more than the motor can give me. I often read posts on here about being others being able to pull past the redline and I keep thinking why not me.
 
Carb Venturis

What Venturis are in the Carb?
Although I am running a 40-80 cam shaft with a shaved head as well, try for starters advancing the cam 1 tooth. I found that by changing it 1 tooth I had better top end at the expense of bottom end. In 1st gear with the set up you are running the engine should pull okay to about 5000 rpm and then just take off like a rocket to 8000 rpm. You either are choking the engine from breathing or the cam is off by a tooth or more.

TonyK,

Grimsby Ontario Canada.
 
That header is considered a 'shorty' and isn't designed for high end power. A long tube header with 2.5" pipe will help you move the power band up a bit.

The adjustable cam gear would be a good idea. You'll likely find you are currently several degrees off from true zero. Playing with cam timing will move your power band around by pretty noticeable amounts. Before you remove the current pulley, set up the degree wheel and dial indicator on the cam. Get a reference of where you are now so you can see just how far out you are.

You can also try adjusting your ignition timing. You've changed a lot of parts and you may find you can do with a bit more or less timing.
 
Thanks, all good advice. I'll check the ignition timing again I believe it's spot on but I could advance a little. Forgot to mention the distributer is mechanical, no vacume advance. Maybe you all figured that much.
I do believe an adjustable cam is my next addition. I always wondered if the header might be designed for low end tourqe.
 
OK Art... FIRST... Just how much is the...

centrifugal advance giving you? Check using a timing light and making two other TEN degree marks on your flywheel or crank pulley for a total of 30.

It should have been "re-curved" to give you a full 30 - 32 degrees as the original centrifugal gave you maybe 17 - 20... and the vacuum advanced it another 8 or 10.

Your top end problem might be right there. You need to INSURE you are getting all the advance you can (or need) from the ignition BEFORE you mess with anything else.

LASTLY... or maybe even MORE FIRSTLY... Our tachs are HIGHLY inaccurate and can be made even more so with different needles and wear and age. Find, borrow, buy or steal another aftermarket tach or tuning tach and "stare and compare".

Do keep us in the loop with what you do and find. PICTURES PLEASE, or else!
 
Hah Black Tooth I'll get some pics when it warms up a bit. When I had the head machined after a blown head gasket we checked the ignition timming advance and it was all good. My father also has a digital Tach reader, it it dead on. I had a Buber of a time getting the belt on correctly, didn't have all the slack taken out in the front. So I kinda thought I migh be off a tooth. But if one tooth is 8 degrees then I don't think she would run very well. I have smooth idle and very quick throttle response with no studder. I will recheck the timming advance as your advice is spot on. I believe an Adjustable Cam pulley might be the fine tuning tool I'm looking for. I am looking at the one Vicks offers. Maybe a different header pipe would help but that's an expensive experiment. I'll probably need to do more fine tuning when I get the Camaro muffler fitted. Thanks fo R all the suggestions.
 
Maybe I'll throw the velocity stack setup back on. I went for a cleaner look with air filter base in the second picture. Here are some photos from last summer.






 
Well changing the cam timing will move the torque curve up or down the scale, but can only do so much, usually limited to about 4 crank degrees of adjustment...if it takes more of a change than that to get it to run better, then it's time to look at different cam options.

SteveC
 
Tachometer correct?

I know it sounds silly but I had a 1500 X that was stock and could never get it to rev to redline. Turns out the tach was off by 1,000 rpm at the top and I was trying to rev that poor motor to 8,000rpm.

carl
 
Yep Tach was checked with a digital Tach reader. Even though it's cold here today I plan on taking the X on its first drive of the year. I'll start taking note of exactly what rpm she stops pulling and report back.
 
Sounds like an adjustable cam gear may do a lot for you. Too much slack in the belt to get the gear aligned would indicate you have natural cam retard. The combination of belt, gaskets, and machining of head/block will all effect this. If you start playing with the cam timing, do one thing to make life easier for belt changes years from now. Clean a spot on the cam and tower and mark them with paint while the cam is at zero degrees. Then use a pick or something else with a sharp end and scratch a single line through the pain on both. This will give you a fairly accurate mark for when you change belts. If you take the cam tower off from the head though, you'll need to check it.
 
Air cleaner may also be an issue

I went for a cleaner look with air filter base in the second picture.


Your air cleaner looks a bit small. In fact the surface area looks smaller than a stock cleaner. Obviously this will have an effect on how much air can be drawn into the engine at high revs. This is an area that is often overlooked with modified engines.

Mostly, I agree with others that your cam timing may be retarded.

Cheers,

Rob
 
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