427 so compression test readings

[trularin]

Ernie, I always knew you were a night bird

I agree with the too much HP. You can create a car that has only one prupose. For the street, it is different than if you plan to drag race.

I kept my engine conservative ( well... sort of ) so I could drive it without heat, fuel and wear factors to deal with on a daily basis. Tinkering every week or so is fine for me.

Just my $0.02

[HSSS427]

[IMG] [/IMG]

Not quite what I had hoped for, but some room for improvement. Ed, the dyno operator suggested:
1 - ditch the Stelling & Helllings and over oiled K&N - 20 HP difference in the runs with and without the air cleaner
2 - Too much advance timing - get it to 36 deg max
3 - Take the carb jets down 1 or 2 steps
4 - Change the accelerator pump cam for a bigger shot

Next step would be a cam shaft with more lift. Got an Isky with .525 right now.

Scott

[MOTORHEAD]

Lean that puppy out!!!
Notice how your torque drops as the mixture goes rich, starting at about 3000 rpm?
Is this HP @ rear wheel?

[HSSS427]

Yes, these are "rubber to the road" numbers done on a Dynojet. Thanks for the advice. Since I'm just trying to learn - why lean it? Dumb question, but why is it that too much fuel causes the torque to drop?
Thanks!

[MOTORHEAD]

Well, for one thing, notice the dyno operators 3rd suggestion," take the jets down(smaller) one or two steps" to lean out the mixture.
Ideal air/fuel ratio is somewhere around 13/14 parts air to one part fuel for max power/efficiency. Your carb starts out at 14/15:1 off idle, but goes starts going rich above that. Notice how the mixture leaned out some when the air cleaner was removed. Mixture headed in the right direction (more air without aircleaner restriction) just not enough! The right mixture burns more efficently= higher BMEP (brake mean effective pressure)= more "PUSH" on the piston=more torque and more HP. Mixture is the most important factor in producing max power for any given set of engine parameters.i.e. compression ration, cam specs, etc.
If this doesn't produce enough power, I would "dial-in" the cam (check the cam timing) The lift you have should be sufficient, but the timing could be off. Did you set the valve lash to the proper specs?
On the dyno you could hold a steady RPM, say 4000, and have someone move the distributor and watch for increase/decrease of rpm. Peak out the rpm in this manner and lock down the dist.
Then go back and check your initial timing and max advance. Your timing marks might be erroneous, which is not uncommon.
Good luck, and if your engine blows up, we will dissavow any knowledge of this communication!

[HSSS427]

Thanks Motorhead.

I think I'll do another dyno session and in addition to having them re-jet the carb using the dyno, we can also set the timing as well per your suggestion.

I think the base timing is set at 30 deg, and I'm probably getting too much mechanical advance. I've got an MSD AL6 with an MSD billett distributor where you can change out the springs and stuff to change the advance curve.

Next dumb question - How do I use a timing light to determine what kind of mechanical advance I'm getting right now, thus helping me figure out total advance?

I'm sure I can find the answer on the web or in a book, but CC seems to be a much better source.

I've also got a friend who's offerring me a free Crower cam with the following specs: 255 duration intake, 260 duration exhaust, .591 exhaust lift, .579 intake lift. If I change to this, what else am I then going to have to adjust/change to get the desired results? Concern per the original post is that my compression is "supposedly" at 9.5:1. Will I need to shave the heads and/or change pistons to up the compression in order to get the cam to be effective?
Thanks!
Scott

[MOTORHEAD]

Firstly, its "I see said the blind CARPENTER, as he picked up his hammer and SAW"!
Secondly, forget the cam change until you find the true culprit. It's still a lot of work, and you don't know if it will do you any good at this point.
Thirdly, if your"base" timing is 30deg btdc, I don't think it would start/idle. If by "base" you mean "static" or "initial" timing, it should be somewhere around 16-18 deg btdc(I'll have to ck my manual to be sure) That, plus advance (mechanical, vacumn, or comb of both) of approx 20 deg = max advanced timing of 36-38deg. Do you have readable timing marks on your damper? If so, mark your initial and max marks with a contrasting paint.
Install timing light,start eng, let warm up and stabilize to correct idle speed. Your timing light should now show the "initial" timing mark under the pointer. If you have specs on your dist, it should tell you at what rpm max advance occurs, I would guess around 4000rpm. Run the engine to that speed and hold it there. Your max advance mark should now be under the timing mark. Increase rpm slowly and see if the max timing comes off the mark, it should not.
BUT.... as with all things, when you are trying to isolate a problem, you MUST start from a KNOWN point. In this case it is the timing marks must be verified before anything else !
You must find true TDC, and compare that with the marks on the damper & pointer. Do you or someone you know, know how to find true TDC???
Once that is done, you can check cam and ignition timing.
IF all the above does not produce the desired improvements, THEN the next step is to go into the engine, and since you don't know for sure whats in there, if it were mine, I would tear it down completely, and start from scratch!
Let me know about the TDC thing. Maybe you can get whoever helped you with the leak-down test to give you a hand with the TDC and timing checks.
Good Luck,
Ted R.

[HSSS427]

I decided first to just re-check the timing as is. I has about 42 deg total all in somewhere in the 3000s. The base/initial advance was well up into the 20s. I backed the distributor around till I had initial at 18-19. It sure seemed to idle a bit rougher at this level, but it was ideling at about 900 rpms. Is this to be expected?

Now I'm going to check for TDC and see if the marks are correct and also see what bushings and advance curves are installed in the MSD distributor.

Will post findings shortly.
Thanks!
Scott

[HSSS427]

Don't know if this is part of the problem, but have a post in to MSD to see what they say. Rust and little metal particles flying around inside your distributor doesn't seem like a good thing to me.

Determined that the BLUE bushing is what's installed with the 2 heavy silver springs. ID'd the bushing color by process of elimination as it looks rusted also. Appears the builder just left the out of the box set-up in the unit.

So all this apparently equals about 21 deg mechanical advance with the slowest advance curve. On the MSD chart it shows all in at 5500rpm. So looks like I had mid to high 40s total advance, but it wouldn't all be in till 5500.

I think I'm going to try the following:
Black Bushing = 18 deg mechanical advance
Light Silver and Light Blue springs = all in at 3200rpm
Initial timing = 18
Total advance = 36

Still have to verify the timing marks are at TDC. Motorhead - what method do you use for determining TDC? The most common I see is to use a piston stop in the plug hole, bring the cylinder up to it with normal rotation, mark that on a timing wheel (I'm assuming I can just mark the harmonic balancer vs using a degree wheel), crank the engine the other way till the cylinder hits again, mark that spot, split the difference and that is TDC.

I need to check the valve lash as well on the driver side. Did the passenger side, but got honey do'ed after that and the engine cooled off, so have to finish up.
Thanks!
Scott

[MOTORHEAD]

YIKES!! Looks like battery acid got in there! Probably was anti-freeze! Your right, thats not good !!
The way you have described finding TDC is the correct way, just make sure you turn the engine by HAND!!.

[HSSS427]

"What you're seeing is caused from ioized air inside the distributor cap as a direct result of the high powered CD ignition. The ioized air will attract moisture which over time can cause some corrosion like you're seeing. You can help this by venting the distributor cap. Drill a couple of 3/8" holes on the side of the cap between the towers at rotor height. Go ahead and clean off the 8 paddle reluctor wheel, but the pickup should be replaced. Over time, the rust can cause the pickup to become magnetized in a way that would adversely affect the performance. The part number for the pickup is 84661. "

Ordering a new pickup from JEGS - $17.99. Think I'll just get a new distributor cap and rotor while I'm at it.

Then:
- validate TDC
- Install new pickup and rotor
- Lash valves
- New air cleaner
- Set timing

Then, back to dyno to jet carb and test and adjust above. Interested to see what HP/Torque I can pick up on the cheap.
Thanks!
Scott

[mr0077]

Scott, that's interesting info from MSD, 'cause I found the same thing inside my distributor, and others here in the local club have had a lot of corrosion-looking stuff inside the caps. Gonna drill mine ASAP, though it's not as bad as yours is/was.

And on a followup note, I had earlier posted that I had 140 psi across the board on my motor...Cracker's reply comment hurt my feelings ( ), so I had the cam dialed in, and found two things: first, my GAUGE IS RONG (my motor guy got 165 psi before he did anything...not all that bad), and second, he got 185 psi for the lowest reading when he finished (better). I'm picking it up this pm, so I'm expecting a noticeable (seat-of-the-pants) improvement.

On your timing, I think you're on the right track with the springs, bushing and settings. Let us know how it goes.

BTW, you can use a 55 Chevy standard distributor cap on the MSD billet in an emergency (or permanently?) .

[HSSS427]

007, your reply makes me feel more optimistic. And don't let Cracker bother you - his bark is much worse than his bite! I owe him a lot as his was the first Cobra I drove and he helped me through the whole process while buying mine. Heck, he's even willing to give me a cam for free. Now if I could get the same deal on his 650+HP side-oiler then I'd be all set!

Headin' for the car to do the work shortly. Just hope I can get the bushing off as it looked to be as coroded as the pickup. New Cap, rotor and pickup on the way from Summit - along with a cam degreeing kit.

Will post ASAP, but out of town and country for 2 weeks starting Monday so it may be a while.
Thanks!
Scott

[HSSS427]

Hmmmm....pulled the distributor to get the blue bushing off - it was rusted on pretty good - TIP - check yours and make sure you've got some oil or grease on it to keep it from rusting on like mine.

Screwed up and re-installed the distributor 180 deg off - tried to crank it and got some immediate nasty rifle shot back-fires. Hoping I didn't blow out a power valve on the carb. However, recalled doing this on my mustang about 25 years ago, so figured it out pretty quick. Got the car to TDC and then installed the distributor with the rotor at #1 cylinder wire connection. Started up as usual after that.

Now have blue (light) and silver (light) springs on with black bushing. According the MSD instructions I have this should give 18 deg mechanical advance, all in by about 2100 rpm.

Put the timing light on and got the initial timing down to 18-19. She is not happy idleing at around 900 - 925rpms. The car really idles better with a high 20s initial advance. Ran up the RPMs and it seems that it's basically on track with what the MSD chart says. So I've got total advance of 36-38deg all in at the low 2000s.

Based on the engine, it seems it is set up to want a lot of advance so I may bump up the initial.

Lashed the valves to .018 hot. Seem to have more oil leaks that usual, and the oil temp really got up higher than usual.

Took it for a spin and didn't really feel any improvement and if I had to guess it was worse.

Well, I'll keep plugging. Need to get the carb jetted leaner and probably do that and get a final timing set-up during a dyno session.

Thank God for beer and garage refrigerators!

[mr0077]

Scott, have you checked TDC yet? I'm wondering if your damper has a slipped ring. I run my timing at about 36 total, all in by 2800. I've tried it from 10-12 initial all the way to 20 initial (using the various bushings), and it did fine on all of them, but I settled on about 14-15 initial with a nice lopey idle at about 800-850. I tried a faster curve (all in by 2300 or so?) and my motor didn't like it.
Update us when you get back from your travels.
Ken

[HSSS427]

I eye ball checked TDC when I had to re-install the distributor and it was close, but I guess close can still make it a hand full of degrees off one way or another. I actual have a cam timing kit on the way from Summit, so will try to get more precise when I get back.

007, what kind of cam are you running? I've got an Isky in the car with the following numbers:
- Isky part# 351390: Grind EE390, Solid lifter,
- Cam Lift=.298
- Valve lift=.525
- Duration=300
- .050 Duration: Intake = 250, Exhaust = 250
- Lobe Center=108
- Lash=.018

I've gotten suggestions to get a higher lift cam, which I'm looking at, but wondering if there's something about this cam that may like more advance. I also have only 9.5:1 compression so that's a factor toward more advance as well.
Thanks!
Scott

[mr0077]

I've got a Comp Cams 282S, 0.330" lobe lift, 0.581" valve lift (with 1.76:1 rockers), 236 degrees @ 0.050", 110 degree lobe separation, I'm running about 0.018" lash also (vs. the 0.022" recommended). My engine guys think a bigger cam might help, but only worth maybe 50 horses.
When I drove the car it sure SEEMS like I'm getting better power, won't know for sure or how much 'til I get to the dyno.

[CJ428CJ]

Scott,

I have the same Isky cam you have and mine likes tons of initial advance as well. I run mine at about 20 initial and 38 total.

Chris

[HSSS427]

Thanks for the info. What kind of compression is your engine and do you have any dyno info? Just looking for comparisons to see what I might adjust or change.
Thanks!

[CJ428CJ]

Scott,

My compression is about 10.25:1. I've never run a compression check with a gauge to see what kind of numbers I'm getting. I haven't put it on a dyno yet either. Maybe this summer. I just double checked my cam numbers and my cam is a bit different from yours though. I'm running the Isky 351360. .530 lift, 240@.050 duration on 108 LC.

Chris