Hi all,

I just rebuilt my first engine myself. Quite a learning experience I must say
I have a few questions now that I have it running. But before I get too far let me share some specs:

The engine was originally an all stock L98 block. Still using the stock crank and rods but installed a cam with 224/224 duration and .525/.525 lift. High flow oil pump, arp bolts and some other goodies when I redid the bottom end. Pistons are hypereutectics with about 10.9:1 with the 58cc heads.

The top end is the 58cc L98 aftermarket heads produced by GM in the early 2000s I think, basically the zz4 heads from what I've read. I did some mild/moderate porting on the intake and exhaust ports and installed LT4 springs to accept the bigger cam and added some 1.5 Crane gold RR.

Sitting on top of the that is an Edelbrock performer EPS intake and a Holly Street Avenger 570. I'm using a mallory distributor and have the timing set to *12 BTDC.

The engine fires up great and idles great. Revs fine in park/neutral. However, going down the road feels like it has no power. I've adjusted the idle mixture screws but off idle is really not the problem. It just feels like anything over 2500-3000 has no power at all. I'm running heads to just a Y pipe so its really loud now but I can't tell if its detonating or anything. I'm afraid to really get on it cause I don't want to hurt anything possibly running too lean.

My friend suggest we play with the jets on the holley to see if it helps any. Do you guys think I should even bother messing with the 570 or get something else. I've been thinking a 650DP might be a good choice once properly jetted. I'm open for any advice at this point.

Thanks,
Jon

 

A 650 would probably be a better choice, and I would think the jets are too lean on your 570. You might be able to get it running with your 570, though.

 

Which distributor exactly?

How did you set the timing?

 

I originally set the timing by rotating the motor until the damper lined up on the 12 mark BTDC. Then I dropped in the distributor and made sure the rotor was pointing at cylinder 1. The motor fired up and after adjusting the idle a little, we used a timing light to set it exactly to 12 degrees BTDC. I was off a few using my method, it was about 9.

The Mallory distributor is part number 29212 I believe. It was one a had on the car a few years ago. I put a replacement cap and used the stock gm cover on it, but retained the distributor and coil from the mallory.

Thanks.

I retarded the timing some and put some fresh premium in today. Car ran a little better but still feels like it has no power and stumbles a lot as you roll into the throttle.

 

I did some digging around in the garage and found I have an adapter plate for a square bore to a spread bore carb, or whatever its called. I'm thinking about taking the quadrajet off my 83 and test it on this motor. Obviously I wouldn't have any of the electronic controls to hook up but it should work right? I think I read somewhere these quadrajets flow pretty well, its gotta be more than the 570 does.

Also, the manual I found for my Mallory distributor was just for the coil. I'll pull my distributor off tomorrow to see what that exact part number is.

 

I'm just a rookie too, but did you check to see what your total timing is?

 

It sounds like the timing is not advancing as the revs climb

 

That P/N is just for the coil. What's the distributor?

 

You need to check to see if this is the case before you start bolting things onto the car. You need to rule it out. Mechanical advance mechanisms can and do get stuck.

Throw a timing light on it at idle and have it revved up to 3500 or so and see if it moves. five7kid may be on to something with you maybe having the wrong distributor... like one that a computer controls the timing advance and not a mechanical advance mechanism perhaps.

 

That's one thing I've not checked, total timing. I'll pull back out the timing light and do that as soon as I get a chance. Looking at the bottom of the distributor the Mallory P/N is 8548201. I can't find my manual but I did find a package of springs that came with it.

 

I agree on the timing issue, sounds like to need to advance it a little more. If the vacuum advance or whatever your using is working it needs some more time. You can't always go by cam card your engine will let you know how much it needs.

 

That distributor will work.

 

Get a timing light. No reason to try adjust it if you don't have the right equipment.

Okay...

Now that you have a timing light, with the vacuum advance disconnected and plugged, engine idling, set the initial timing at 12 degrees BTDC. Reconnect the vacuum advance, adjust idle speed if necessary, now see how it runs.

 

That's exactly what I did at first. Set it 12* BTDC using the timing light. Car idles and revs great in park. Once driving it falls flat on its face. I took my distributor off and took it apart to check everything. I'm wondering if my mechanical advance is working... I still haven't checked total timing as I've had to work a lot this week. I'm off the weekend so I'll be checking it then.

Another thought, this one maybe a big no brainer... The car sat in the garage with gas in the tank for about a year. Just a little though. Instead of siphoning it all out, I just added some premium to it. Think that could cause this bad of a problem?

 

Just hold it at 4k RPMs for a minute and see if the timing mark moves.

 

News!

You guys were dead on about the timing being the issue. Turns out my distributor is only giving around 12* or so mechanical advance. So this time I tried setting my total timing with the timing light. I put it about 34* or so total advance. After setting it there I checked the initial timing again. It read something like 22* without the vacuum connected. Took it for a test spin, car ran like a bat out of hell, well, compared to how it ran before it was a huge improvement.

Should I bump the timing up say a little more to 36* total? I guess that would put my initial somewhere around 24* which sounds like a lot to me. Car starts fine though and seems to really like that extra timing at idle.


~Jon

 

sounds like the timing mark is off. shouldnt even be running with 22* inital timing

 

Yes, but if that were the case then the total timing would be way off as well. Plus I've turned the motor over by hand a few times to check top dead center and it lines up with my tab.

Maybe it's my light or my dizzy, one way or another I just need to spend more timing looking at it to figure it out I guess.

 

Sounds like your advance springs are too tight. Put some lighter springs in to give more MA, then lower your IT.

 

whats your curb idle speed, with it at 22* initial i have to imagine you cant get it below like 1200-1500 rpm.

 

22 BTDC at idle is fine.

34-36 total mechanical is typical for SBC's.

 

22* at idle with the vacuum can hooked up yea, but 22* intial cant be right.

 

Although I had an Olds and not a Chevy, 20* initial without the vac advance was/is the stock setting.

When I was running the CCC stuff, I ran my Olds initial at 22-23 with the ECM grounded ( equivalent to having the vacuum advance unplugged ) and with the ECM connected, it was well past the highest mark ( 24 ) on the timing tab at idle.

Some people even run great on the street with their timing locked out ( like 36* ), so I don't see why anyone would think 22* initial would be too much with the right setup.

 

Sure it can. As long as you aren't getting starter kick-back, and you can adjust the idle, it'll be fine. Give the engine what it's happiest with.

 

i guess none of mine have been happy with with anything close to 22*. i always wind up with about 12-15* initial, then tune the mech advance curve from there.

 

My car is around 20 BTDC base timing. Runs fine. It wont run below about 14.

 

w/ a 525 lift cam your gonna need more intial timing, usually 16-20 intial is gonna be rite. and you want the mech to start moving rite off idle immedietly. but it needs to be all in 3000 rpm or so.

 

Just thought I would post some followup since its been a little while since my original post. I finally got a REAL timing light and started playing around. I set my initial timing at about 20. Checked total timing and it was a bit shy of 36 so I upped the initial to about 22. Car feels really close now. It looks to me like total mechanical advance isn't coming in until about 3500 or more rpms so I'm going to change the springs in the distributor out.

I've got some different color springs that came with the Mallory distributor. I'm guessing the springs that are softer or smaller have less tension and let the timing come in sooner? The car still has some hesitation or spots where it feels flat, some are due to the smaller carb I'm sure.

Thanks again for everyone's input!

-Jon

 

Usually come with heavier springs when you buy them.
Most seem to like the med or one light+1 med spring.
Youll have to play with it to see whats best. As said give the motor what it likes. All the advance in "right now" isnt always best.

Bushings you can play with too (adv bushings)
Springs will probably get you there though.