Hood clearance and electronic ignitions

[lnirenberg]

2 totally unrelated questions:

How much extra clearance does an LT1/BB hood have over a stock base engine hood?

I am considering converting my stock ignition on my mildly modified base engine to an aftermarket electronic variety. Any direction or suggestion as to what brands & parts anyone has used would be appreciated. I assume the conversion would require a different set of plug wires and plugs?

 

[Vettehead Mikey]

Regarding your ignition system, save your money and keep what you've got.

The stock system puts out more than enough juice to do the job. A different system will not increase performance one bit.

 

[hzl6cm]

I added an Crane system to my '70 (I think that it is an XR6000 unit but I don't see that on their web site, I see an XR3000 unit that is similar, here is a link to their web site: http://www.cranecams.com/index.php?show=browseParts&lvl=5&prt=161 ) - it has a control box that I mounted on the inner fender and uses the original points to trigger the ignition (it has very low power going through the points so they last basically forever). It's a high performance system that automatically adjusts dwell etc. based on the requirements of the engine. I installed it several years ago and haven't touched it since then. The one big advantage I have noticed is that I used to get quite a bit of pinging on lighted 4th gear acceleration, even when using octane enhancers, now with the new system I run 91 octane premium with no octane enhancers and there is no pinging at all.

I know a lot of people with British sports cars are running Petronix electronic ignition with good results. One advantage of these is that they fit entirely in the ignition cap so the unit is hidded. Jeggs sells these for a GM distributor for $74.99, perhaps some of our preferrred Corvette supliers sell them also. Here is a link that shows these units: http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=2273&prmenbr=361

Kevin

 

[goertz]

I've heard good things about Petronix too, and am considering one for my '69. they just screw right in place of the points, one wire goes to the negative side of the coil, and another goes to the positive side for juice. supposed to work great, and no need for a stupid ignition box to be bolted to any part of the car. As far as the hood question, I'm really not sure, I would guess it was purely asthetic, as it seems to me that the area where the air cleaner sits is about the same hieght. of course with an l-88 hood, that's a different story.

 

[Jack]

Crane's more recent conversion called "XR-1" ... self-contained; all fits inside your distributor ... use your wires & plugs ... under $80 for conversion kit.

"Breakerless SE" is another conversion ... self-contained; all fits inside your distributor ... use your wires & plugs ... under $140 for conversion kit.

I just got a another lot of new tach drive HEI distributors w/ performance coil & module ... self-contained as factory GM HEI but has mech tach drive ... use HEI wires & your plugs ... 4 TDHEI distributors available ... under $205 for complete distributor.

Each of the above tend to burn the fuel mixture a bit more completely than points ... usually w/both quicker start & smoother idle ... but NO noticeable increase in speed.

Click on my name & Email me through CAC for more TDHEI info.
JACK:gap

 

[lnirenberg]

I have an MSD electronic setup in place of the points. They were on the car when I got it. As to electronic ignition, I am beginning to think (something I should have done before I posted) that I am barking up the wrong tree. In hindsight I should have stated my problem before I proposed a solution of sorts. My problem is my idle is all over the place. When we were stuck in what seemed like perpetual winter the car started with the electric choke in the closed position and ran at about 1000 rpm until it warmed and then settled nicely around 700-800 rpm. Now that the weather is hot it obviously is starting without any choke and running around 700-800 and when warm is going up to about 1000 rpm. The car has a functional aftermarket AC system so that takes the idle down about 100-150 rpm with load but I think that 1000 is still is too high and I'm not sure what makes the idle go up when warm. Any help?

 

[WARVET]

If your idle is all over the place, I would start by checking your vacuum lines. If there is a leak then it could be messing up your idle.

 

[lnirenberg]

If your idle is all over the place, I would start by checking your vacuum lines. If there is a leak then it could be messing up your idle.

I will check the lines again but the idle isn't really all over the place, it holds steady once warm at about 200 rpms higher than on a summer "cold" start up. I'm reluctant to turn the idle down as I am a cold weather h. sapien by breeding. I have been known to reluctantly put the ttops back on when we get those hot and humid days so that I can run the AC. I don't want the revs to get into stall territory just because I'm trying to stay cool.

 

[Craig -1965]

Regarding the ignition systems, , I have a Petronix system on my 65, 327/350 and it's the cat meoow...... Plugs, set the timing, adjust the carb, looks stock......... Tough day at the office.........

 

[goertz]

how about adjusting the idle down, then put the throttle solonoid on, so that when the A/C compressor kicks on, the idle kicks up? I'm like you, if it's hot, the top is up and the AC on. T tops and convertables are great, when it's 75 degrees out, and the sun isn't beating on me.

 

[Vettehead Mikey]

Each of the above tend to burn the fuel mixture a bit more completely than points ... usually w/both quicker start & smoother idle ... but NO noticeable increase in speed.

With all due respect Jack, a spark is a spark is a spark. If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. The stock system does an excellent job of lighting the fire.

The non HEI systems you named still rely on the stock coil to provide the energy, so there is no 'hotter' spark to be had.

The big drawback with the pertronix POS is it's habit of failing without warning.

 

[craig32]

The stock system does an excellent job of lighting the fire.

It has always been my assessment that 'you can't beat the factory' GM makes parts for Corvettes. Aftermarket companies make parts for everybody. Who do you think did all the research, and who do you think is trying to copy it? I'm sure other parts will work, but hey, the original lasted how long? Just my opinion, I could be wrong.
Craig

 

[lnirenberg]

If your idle is all over the place, I would start by checking your vacuum lines. If there is a leak then it could be messing up your idle.

So, I finally get some time to spend on my idle problem and I check every line again with no luck and as I am about to throw in the towel I notice that one of the caps on the vacuum tree coming out of the back of my manifold isn't on quite straight. I get a better look at it from the other side of the car and shzam!!! its cracked and sucking air at a steady space. I'll blame the flowmasters as I probably should have heard it. A quick trip to the parts store and $.30 later its idling like a champ 750 rpms steady. Go figure, I never seem to think of the simple things first. Lesson learned.

 

[pgtr]

I am considering converting my stock ignition on my mildly modified base engine to an aftermarket electronic variety. Any direction or suggestion as to what brands & parts anyone has used would be appreciated.

I've very happy w/ the Pertronix - it was the cheapest at the time (10 or 15 years ago). There are a number of other conversion kits available for the GM distributor as well as the other posts above indicate - any should work great. THere are also complete distributor swaps too (obviously more expensive) including GM HEI w/ tach drives...

I assume the conversion would require a different set of plug wires and plugs?

Nope - not at all. Same everything else...

 

[pgtr]

With all due respect Jack, a spark is a spark is a spark. If it lights the fire, a hotter spark won't make any difference during combustion of the fuel and air. The stock system does an excellent job of lighting the fire.

Then why did GM switch to electronic ignition by 1975 (and offered it optionally on Corvettes before then) ??? Answer: A spark is not a spark - and the fed mandated improvements in emissions including the ignition system in 1975 which forced their hand.

The non HEI systems you named still rely on the stock coil to provide the energy, so there is no 'hotter' spark to be had.

Not true. Same coil will produce higher voltage based on the more discrete like switching (and saturation time) of an electronic control module vs a mechanical points based switch.

The big drawback with the pertronix POS is it's habit of failing without warning.

Actually this is arguably true of ANY electronic based ignition system including GM's own HEI or even a modern computer triggered system. While it might take a decade or two and mileage approaching 6 figures - when they go out - they do go out! It's a relative rarity however mixed in with the statistical noise of other show-stopper failures any car is prone too w/ extensive mileage/time/usage.

 

[Chiller]

Hood Clearance

What ever happened to this question? I'm curiuos to see what the answer is because I might need more hood clearance later on.
Chiller

How much extra clearance does an LT1/BB hood have over a stock base engine hood?

 

[Vettehead Mikey]

Then why did GM switch to electronic ignition by 1975 (and offered it optionally on Corvettes before then) ??? Answer: A spark is not a spark - and the fed mandated improvements in emissions including the ignition system in 1975 which forced their hand.



Not true. Same coil will produce higher voltage based on the more discrete like switching (and saturation time) of an electronic control module vs a mechanical points based switch.



Actually this is arguably true of ANY electronic based ignition system including GM's own HEI or even a modern computer triggered system. While it might take a decade or two and mileage approaching 6 figures - when they go out - they do go out! It's a relative rarity however mixed in with the statistical noise of other show-stopper failures any car is prone too w/ extensive mileage/time/usage.

Sorry, Mr. Know It All, you're just as much an a-hole on this subject as you are the glass fuel filter discussion. You're not fishing me in.:eyerole

 

[Chiller]

The last time I checked the goal of this site was to help one another out. People express there experiences and knowledge on the subject. Of course some people have more to bring to the"table " then others. It's nothing personnal! May we get back to the questions?
Chiller

 

[Vettehead Mikey]

The last time I checked the goal of this site was to help one another out. People express there experiences and knowledge on the subject. Of course some people have more to bring to the"table " then others. It's nothing personnal! May we get back to the questions?
Chiller

True enough- but I'll be darned if I set myself up for an attack like John got on the fuel filter topic. I don't need cr*p like that.

 

[lnirenberg]

Leave it to Chiller, a marine currently stationed in Iraq, to bring a little sanity to this discussion. I'm sure there aren't many of us that would want to take his place and I would venture to guess that what he is dealing with day to day makes these CAC squabbles seem pretty inconsequential bordering on stupid.