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My 70 442 daily driver with a rebuilt 455, Holley 650, electronic ignition. Car runs like a dream, both at idle (550-600) and at high RPM. Just put 300 miles on it at a nice cruising speed of 70 MPH. In hot weather or putting on lots of miles, it will usually diesel. Solved it by turning off in drive. Checked plugs (NGK XR4), insulators are a nice tan color. I have noticed some carbon blowing out the exhaust tips onto the garage floor on a cold start. Reading some posts, there seems to be several causes. Where do I start?
What octane fuel? What is the engine temp? Try retarding the ignition timing 2 degrees. Any chance of carbon buildup? Do you know the compression ratio?
As Sugar Bear said 93 should do it as far as dieseling, but she is still going to ping. At least my car does. She is a 10.25:1 350, pings at 2000 RPM and up on an incline with 93. Better with an octane booster but still there slightly. I just back off the gas as possible in those situations. Definitely at her worst in hot weather.
Old school octane rating system was different. 93 today is 98 in muscle era. And a 1970 442 required 100 octane minimum.
Here below is the reality for a Toro and your 442 as well.
Only 2 ways to really resolve this issue, detune the engine as Sugar Bear mentions, or buy race fuel which is what old school gas is considered today. And of course it's ridiculously expensive.
... but it is still going to ping. At least my car does. It's a 10.25:1 350, pings at 2000 RPM and up on an incline with 93. Better with an octane booster but still there slightly. I just back off the gas as possible in those situations. Definitely at its worst in hot weather.
You should probably do something about that before you melt a piston crown. Backing off the gas is not an acceptable solution if you're going up a hill.
Thanks, I'll try the Lucas octane booster since I can't get 93 anywhere.
The Lucas should help. I was using two bottles per tank before I gave in and retarded the timing a bit, but I was having detonation as well as minor dieseling. Seems to be under control now.
Ok, I’m not sure where to start but here goes;
Sugar bear- you don’t just back the timing off arbitrarily and 🤞hope that it does what you want it to without checking it thoroughly first. And have you ever seen what retarding the timing can do to ex temps? It can raise them, potentially making it worse.
69CSHC- if you’re getting pinging, FIX IT. Check your timing there etc. Next would be is it too lean there and so on. And you’re talking about 2 different rating systems for fuel. The US has used the R+M/2 rating system for decades. However most other countries use the RON system.
Finally to the Op, try XR-5’s, borrow a friends tube camera and check what piston is in there.
Next do a compression check, check timing with and without vacuum advance. Do a methodical check of things.
I’ve built dozens of iron headed 455’s with 10:1 or so compression, and they run fine on 91. You most likely have a simple tuning issue.
Last edited by cutlassefi; Aug 5, 2024 at 06:16 AM.
Ok, I’m not sure where to start but here goes;
Sugar bear- you don’t just back the timing off arbitrarily and 🤞hope that it does what you want it to without checking it thoroughly first. And have you ever seen what retarding the timing can do to ex temps? It can raise them, potentially making it worse.
69CSHC- if you’re getting pinging, FIX IT. Check your timing there etc. Next would be is it too lean there and so on. And you’re talking about 2 different rating systems for fuel. The US has used the R+M/2 rating system for decades. However most other countries use the RON system.
Finally to the Op, try XR-5’s, borrow a friends tube camera and check what piston is in there.
Next do a compression check, check timing with and without vacuum advance. Do a methodical check of things.
I’ve built dozens of iron headed 455’s with 10:1 or so compression, and they run fine on 91. You most likely have a simple tuning issue.
What AFRs have you seen work well for higher compression iron heads at WOT and at part throttle under heavier load? I'd assume they like to be on the richer side.
I agree. I have the rebuild docs that I will share with you. From JE Pistons: Displacement: 469 cu. in.; Piston type: dish; Bore: 4.19; stroke:4.25. dish depth: .068; comp. dist 1.750; comp. ratio: 10.0 to 1. I am not a re-builder and don't have a clue about the numbers. I have more docs if needed. But, I think a simple tune should do the trick. Please let me know about the engine from what I have provided. Thanks
Make sure you are reading your spark plugs correctly.
A lot can be told about your timing from the ground strap.
Different areas of the plug tell you different things. It's not all about the center electrode.
I agree. I have the rebuild docs that I will share with you. From JE Pistons: Displacement: 469 cu. in.; Piston type: dish; Bore: 4.19; stroke:4.25. dish depth: .068; comp. dist 1.750; comp. ratio: 10.0 to 1. I am not a re-builder and don't have a clue about the numbers. I have more docs if needed. But, I think a simple tune should do the trick. Please let me know about the engine from what I have provided. Thanks
Switch to manifold vacuum for timing advance. This will allow you to lower your idle speed adjustment a bit, which will help with your problem.
I would like to know more about this. I have a cammed 455 that has too high of a curb idle with a big drop to drive idle. It is on ported directly (the TCS tree is gone). Why would manifold advance cause what you say?
To OP, I had dieseling, so I installed an idle stop solenoid on the quadrajet. Upon loss of ignition power, the solenoid falls, and the throttle closes to 500 rpm in park. This is enough to cut the air/fuel off to the engine as well as the spark and cuts down on the dieseling. The ISS is what I adjust for slow idle speed.
I would like to know more about this. I have a cammed 455 that has too high of a curb idle with a big drop to drive idle. It is on ported directly (the TCS tree is gone). Why would manifold advance cause what you say?
To OP, I had dieseling, so I installed an idle stop solenoid on the quadrajet. Upon loss of ignition power, the solenoid falls, and the throttle closes to 500 rpm in park. This is enough to cut the air/fuel off to the engine as well as the spark and cuts down on the dieseling. The ISS is what I adjust for slow idle speed.
With manifold vacuum, you get full vacuum advance at idle, which is not the case with ported vacuum. The extra advance generally smooths out idle and requires less throttle opening to achieve the same RPM. Having less air/fuel entering the cylinders lowers cylinder pressure and makes auto ignition less likely.
With manifold vacuum, you get full vacuum advance at idle, which is not the case with ported vacuum. The extra advance generally smooths out idle and requires less throttle opening to achieve the same RPM. Having less air/fuel entering the cylinders lowers cylinder pressure and makes auto ignition less likely.
With manifold vacuum, you get full vacuum advance at idle, which is not the case with ported vacuum. The extra advance generally smooths out idle and requires less throttle opening to achieve the same RPM.
After doing this on my car, the RPM doesn't drop nearly as much when going from P to D even with the AC on, the idle vacuum increased quite a bit so the power brakes worked better, and the idle smoothed out a lot.
After doing this on my car, the RPM doesn't drop nearly as much when going from P to D even with the AC on, the idle vacuum increased quite a bit so the power brakes worked better, and the idle smoothed out a lot.
Ok, I’m not sure where to start but here goes;
Sugar bear- you don’t just back the timing off arbitrarily and 🤞hope that it does what you want it to without checking it thoroughly first. And have you ever seen what retarding the timing can do to ex temps? It can raise them, potentially making it worse.
😁 Cutlassefi the professional engine builder thing exudes through your pores. If you didn't tell us what you did for a living we would still know.
Yes off course what you are saying makes sense. But you've been a pro so long you are overlooking car guy stuff.
There is a right way a wrong way and what works ...
Originally Posted by cutlassefi
69CSHC- if you’re getting pinging, FIX IT. Check your timing there etc. Next would be is it too lean there and so on.
Understood and will do. As far as I know the timing is to factory spec, verified it years back. But will check again.
Carb has had issues since day one for me (10 years). New generic Rochester replacement just before I bought her. (Had a holley before that, original long gone.) Runs much better than when I got her. After many adjustment sessions. But still occasional mini backfires through exhaust system. Very random, could try to record and forward to you. Once in a blue moon she will pop stall. (Get on the gas from a dead stop and she turns off.)
My mechanic ran a smoke machine on her recently... no leaks ...
You should probably do something about that before you melt a piston crown. Backing off the gas is not an acceptable solution if you're going up a hill.
Understood. I avoid putting her in compromising positions for the most part. The issue is only audible in 3rd gear. She is generally babied on the street and highway and 2000 rpm (50 MPH) is usually max for me anyway due to perpetual traffic on the parkways/expressways. The occasional opening up is always level and brief. At the track I would add race fuel, either 100 if it was very low on fuel. Or 110 to blend with the gallons I already had. Blending it to about 97 octane resolved all issues. Track performance great, zero ping on ride home. Jersey can be hilly and wide-open.
Originally Posted by BangScreech4-4-2
The Lucas should help. I was using two bottles per tank before I gave in and retarded the timing a bit, but I was having detonation as well as minor dieseling. Seems to be under control now.
Jeez, my fill ups are a 100 dollar event as is with just one bottle. Good thing she is an occasional driver. 35,000 miles put since 2014.
My baby getting the best the other day.
I so do not want to retard the timing, but I will if no choice. (Professionally and correctly Cutlassefi.) Previous owner just put highest octane available. So that light chatter has been going on for a while... But he also loved and babied her.
My ride diesels with 91 octane. My 67 dieseled with 89 octane. But the 67 and its 9:1 330 never pinged, even with the timing advanced. My 66 442 never pinged or dieseled, because timing was pulled back .... All 3 received a steady diet of high test from Ultra 94 till phased out then 93. All un-rebuilt to my knowledge. Our factory engines do not appreciate modern gas. Been dealing with it since the mid 1980s.
