5K Dies Under Load

[GJM85]

So i'm completely dumb founded on what is wrong with my ke20. I've gone to all extremes trying get this thing sorted but still no cigar.

 

This a 5k, 4k head, solid lift conversion.

 

The car runs and free revs very well. As soon as you drive it and put load on the motor it just coughs and farts. It has a lot of blow back through the carb.

We've checked the cam and it appears to be spot on. We've set the time from 6 - 30 degrees and it's always the same problem. I've had a stock 3k carb, twin sidedrafts, a weber and now a rejetted 4k and it's always the same probl.. no power under load.

 

I'm using a stock 3k points dizzy with a MSD Streetfire CD ignition and the cam is a Tighe 104. (270 adv duration, 25/65, "423 valve lift). Currently using a depolutionised 4k carb with 153pri/162sec mains, .80 idle. There is definately no vacuum leaks.

 

Do I just need to regraph the dizzy or could the cam still be out?

 

Any ideas? because i'm all out...

[Twinky]

If it free revvs with no load it sounds like fuel starvation, but the blowback through the carb sounds like timing. So I would say

maybe you need to check your cam timing. Did they machine a new timing mark on the cam?

[ke70dave]

does your setup retain the little condensor on the distributer?

 

that went on my old 4k, caused all sorts of dramas like you describe.

 

you could do a compression test and if you get a decent result, that should be enough to prove the cam is in good enough? (at least good enough to run remotely well)

Edited November 14, 2011 by ke70dave

[GJM85]

Yeah i've still got the condensor on the dizzy. I might swap it with a spare I have. See if it makes a difference. I don't believe there is mark on the camshaft. I just installed it as standard. The last compression test I did ranged from 140 to 170 psi.

 

My old man reckons I should take the cam out and put a stocker back in and see what happens, but i'm really not down with that.

[Evan G]

Ring Tighe and ask if there's any advance on that cam, are you using the same balancer and timing cover?

[GJM85]

Ring Tighe and ask if there's any advance on that cam, are you using the same balancer and timing cover?

 

Yeah just standard stuff there.

[Clapped out]

might be able to shed some light on your situation, as i have stated in a previous thread, i have had a dud grind before from tighe, although in saying that they were pretty good with the whole situation (accidental), i'm not dissing them. I'd be checking your timing of your camshaft, it would be advisable if you can get hold of a degree dial wheel to check if the cam is in time with the standard timing placements of the cam wheel, if its out you might be lucky enough to skip a tooth either way on the cam sprocket to get it into time, if not you may have to fabricate a new position for the cam sprocket. All the info you need is on the paper supplied with your cam,

 

cheers!

Edited November 14, 2011 by Clapped out

[GJM85]

fabricate a new position for the cam sprocket. All the info you need is on the paper supplied with your cam,

 

cheers!

 

That's interesting, though i didn't get any paper with my cam. Too bad I din't get a rollmaster timing kit.

[Clapped out]

you can request a info sheet on the specs of your cam from tighe, pretty sure they have it on their website?, without the specs you can't dial it in :(

Edited November 14, 2011 by Clapped out

[Evan G]

I'm dialing in a 474 tighe cam. i set up my micrometer on the lifter and none of my measurements were the same as there website.

 

i rang up tighe today and found out the cam is 2.5degrees advance. (if you use the stock markings)

 

advance cam will give you torque and less power in higher rpm

 

retarded cam will give you more power up top.

 

i belive i had my previous cam installed 3 teeth out. (roughly 60 degrees!) this gave me MEGA torque but a redline of 5 grand.

 

 

good basic idea how to dial in a cam

http://www.rollaclub.com/board/topic/46468-ke30-ascf-1200-junior-sedan-build-speedway/page__p__498786__hl__andy43__fromsearch__1#entry498786

 

and a more complex idea

http://xtremecarzone.com.au/index.php?showtopic=805

 

a decent cam degree kit is around $180 mark from ebay.

 

let us know

[Evan G]

also did you run in the cam?

 

i think if your cam timing was out youll lose performance not just die/backfire

 

have you replace the coil? none of the eye terminals are near the spark outlet of the coil?

 

edit - has it always been like this? what did the muppets do when they dyno tuned it?

 

sounds ignition related to me but. id run another stock dissy and coil with a simple consistant power to it and a negative feed from the points, just to test it out

Edited November 14, 2011 by Evan G

[Figjam14]

probaly worth a shot, trying a different coil, i got a msd one( was around 200) and it free revs fine but as soon as its on the dyno breaks down and shit after 5000, a mate of ours had the same problem with a datto

[GJM85]

Yeah the cam was run in. I'm thinking the cam needs degreeing. I've touched all other bases I think. It made 44.2hp on the dyno so i'd say it has a pretty serious power deficiancy aswell as the blow back.

 

If it is ignition i'd be really surprised.

The setup is a GT40, no resistor, the CD multi spark ignition and the 3k dizzy. I've tried 3 others before the CD went in, 2 electronic and 1 points dizzy. Same problem.

 

The spark in this thing would kill a small child.

Edited November 14, 2011 by GJM85

[Evan G]

The spark in this thing would kill a small child.

 

thats the problem! it could be jumping spark in the dissy or arc on the poles on the coil.

 

just needs a hair line crack to arc out.

 

 

on my 4k it would die/sputter at 3grand or under load. spark from the coil output was arcing to the neg side of the coil

[altezzaclub]

As soon as you...... put load on the motor it just coughs and farts

 

1- Have you had the car running fine before, and this problem developed-

 

2- or have you had this problem since you assembled the motor??

 

3- Does it backfire up the carb?? That would take a fire in the inlet manifold, which means an inlet valve leaking or being held open by the rocker. or opening into a burning cylinder.

 

4- .or is it just not firing a cylinder every now and then? So the spark isn't getting to the cylinder or the mixture is too lean to ignite??