Compression Too High?

[Wolf Tickets]

I've got a 440 that was rebuilt to a good street blueprint by my local shop, Action Machine in Seattle. They say it should be 9.35:1 and run fine even on mid grade gas.


The problem is that I've had to limit my total advance to not more than about 26 to keep from pinging. I've danced around the exact total with changes in outdoor temp. Added a fan shroud which helped a bit. I don't have a temp gauge but the Stant radiator cap with a temp gauge in it never reads over 170 after a hard drive and shut down (then climbs after sitting for a while).

I've got the FBO limiter plate at 14 degrees and my initial somewhere between 10 and 12 (always adjusting these days trying to find the best spot). I'm all in by 2800 but 'all' is only 24-26 degrees so that shouldn't be too much/fast, right? I've attached a picture of the graph I made of the current curve. It's 2 gold springs from FBO. Also a picture of the graph of my old curve - I had one silver and one stock (mp elect distributor, the spring that wasn't the giant loop garage door spring) and that had a better curve, starting sooner and pulled harder from idle. Same limiting plate for same total.

Note the first picture is my old curve, the 2nd one is my current curve, all in by 2800

IT's great on the street but really lacks a top end and never gets better than 11mpg on the freeway without ever pressing the pedal more than 1/8" and keeping it at 60mph.

1973 440 out of a T&C wagon (it got 18mpg and was still fun in that LOW-PO 215hp/340tq setup!!)

Current Setup:
Stock heads
HP exhaust manifolds
Performer RPM intake
comp camp xe262
compression test at 180psi (on third crank over. It basically went 140, 160, 180 and didn't go higher than that.)
3.23 gears
26.6" tires (295/50/15)
holley street avenger 770 stock jets
MP performance electronic dist (basically identical to the stock 73 dist)
FBO ECU and Coil (eliminated ballast resistor)


THANKS a million for any input you can lend. This forum is a goldmine!!!

 

[4mulas]

Was the cam degree’d , maybe 0 isn’t zero on the damper.

 

[khryslerkid]

What heads? What #plugs? What octane gas? Is it running rich?

You're running almost the same setup as I (same compression too) and I'm running two 600s. I've yet to hear a ping. I've run non ethanol 89 to 10% 93.

 

[Kern Dog]

He stated that he had stock heads.
180 cranking compression is borderline with 91 octane. Is 91 the best you can get in Seattle?
People will tell you that camshaft timing is a factor. I say it is but not a big one. I was running nearly 11.0 to 1 with aluminum heads and having detonation problems on 91 octane. My cranking #s were in the 195 range. Forum guys tried helping and I resisted the best advice.....LOWER the compression by changing the pistons. Some suggested using a bigger cam with a later intake closing point. THat is a crutch. It might help at low rpms but as the rpms climb and the cam gets more efficient, the pinging was still there but at a point where I couldn't hear it.
Being a stubborn ***, I chose to swap in thicker head gaskets. Yeah, it did help but I may have lost some power in the process. A dished piston with quench pads would have lowered compression but retained quench....ultimately making more power.
For you, colder range spark plugs may help. You may not get all of your improvements from one thing. Cooler intake temperatures, higher octane, colder spark plugs, slower distributor advance rate, headers....
Why headers?
They flow exhaust better. The flow allows for cooler underhood temperatures.
The 383 in my "Jigsaw" Charger is at 9.2 to 1. I was out and about yesterday and it got hot. Not boiling over but close. 89 octane gas....Not a hint of detonation. I was hammering on it a LOT and not a single knock. Iron heads, 280-474 cam and headers. Timing set to 19 initial and 33 total.

 

[Don Frelier]

I would say with some certaintly it likely needs more fuel.
Get an AFR meter and install it.
You should be able to run closer to 35 degrees total.

 

[Slap Stick]

What are "stock jets" in an aftermarket carbatooty?
As mentioned you need to find the a/f ratio.

 

[Outsider]

Sounds like something isn't quite right with your overall combination. My GTX has 180+ cranking compression, cast iron exh, 4 spd w/ 3.54 gears. 34 deg total, 14 initial and the rest by 3k, and then vac adv. Union 76 Premium pump gas without ping. Shouldn't be a heat related problem in our mild climate, (except for this unusually warm week). 12-13 mpg on freeway seems about normal for these RBs with a mild performance cam.

Some thoughts; cooler plugs if yours's aren't already black and fouled. Carb...? Too tight a convertor if AT, need a bit more gears with that cam?

 

[Curiousyellow71]

A 262xe is a small cam and builds a lot of compression. It should be used on a motor in the 8's. The narrow lsa of 110 isn't helping.
Compression of 180 seems high though.
Plugging numbers into wallace racing I get this. I doubt it's as accurate for a XE due to the asymetric intake

 

[lewtot184]

i have two of those FBO plates and they aren't even close to being accurate. that 262 cam closes the intake valve too early.

 

[beanhead]

The first thing "I" would do is confirm the balancer is accurate..

Then make sure you're not lean under load...You can do a quick test of this by temporarily richening the carb (even if you go a little too rich, just don't get crazy) and seeing if it still pings.

Beyond that a couple of things need to be verified. And I know it's not what you wanna hear because it's a good bit of work, but....you need to know the CC of the chambers, gasket thickness, piston depth @ TDC, and piston type. For all you know it could be 11 to 1 with a steel gasket and iron heads. It would help to know the installed cam timing as well. It could have been installed with too much advance, and coupled with the early intake closing of that cam = pinger.

It's perfectly possible for flat-tops with no notches to knock at 9.25:1 with the pistons a mile down in the hole and a short duration cam. It would happen on some of the later factory RV engines when they tried to meet emissions by dropping the pistons down...and that was with 8:1 at best.

If you didn't build the engine there's no way to know what's inside there; even experienced shops make mistakes.

 

[beanhead]

What are "stock jets" in an aftermarket carbatooty?
As mentioned you need to find the a/f ratio.

LOL

 

[Wolf Tickets]

Was the cam degree’d , maybe 0 isn’t zero on the damper.

Thx 4mulas,

The machine shop tells me they tested everything before sending it to the shop for install. I am not familiar with what leads to a damper shifting, but the machine shop suggested that it's not likely on a new build (which I just put down in the notes as one more thing to learn about!!!)

Thx for the tip, though. I never got any notifications after positing this, and today, after googling "440 180 psi ping" the 2nd result looked familiar...it was my own question and all these great responses!!

Take Care

Ben

 

[Nate S]

Many good ideas here. I’d start with the fundamentals. Get the numbers from the shop. Piston compression distance, deck height (or distance down to pistons at TDC). Head cc. Gasket thickness. Let’s calculate it out first and go from there.

 

[Wolf Tickets]

What heads? What #plugs? What octane gas? Is it running rich?

You're running almost the same setup as I (same compression too) and I'm running two 600s. I've yet to hear a ping. I've run non ethanol 89 to 10% 93.

Thx Khryslerkid,

Not totally sure what all the machine shop did to the heads, but they're the stock ones from 73. I believe they cleaned up the exhaust ports as those had some big restriction for NOX emissions stuff.. The shop did say I should be able to run on 89, but I haven't bothered anything less than 92 which is the best I can find in Seattle.

2 weeks ago I got 5 gal of 110 leaded to try mixing, but before doing that, I decided to try the VG octane booster which, mixed with my 18 gal tank, should have yielded 95 or so octane. With this I felt good with 12 initial and 14 mechanical but that was the most I could do without pinging. It did seem to run way better though. I turned the timing back down after burning off that tank.

My plan was to mix the 5 gal of 110 with a full tank and see how much timing I could run with that (If I remember the math works out to 98 octane or something like that).

I changed the plugs the same week. NGK XR5 is what I had in and they didn't look bad, only one had a little more carbon that the rest but none were terrible (See picture of the worst one).


Thanks very much for your input

Ben

 

[Wolf Tickets]

He stated that he had stock heads.
180 cranking compression is borderline with 91 octane. Is 91 the best you can get in Seattle?
People will tell you that camshaft timing is a factor. I say it is but not a big one. I was running nearly 11.0 to 1 with aluminum heads and having detonation problems on 91 octane. My cranking #s were in the 195 range. Forum guys tried helping and I resisted the best advice.....LOWER the compression by changing the pistons. Some suggested using a bigger cam with a later intake closing point. THat is a crutch. It might help at low rpms but as the rpms climb and the cam gets more efficient, the pinging was still there but at a point where I couldn't hear it.
Being a stubborn ***, I chose to swap in thicker head gaskets. Yeah, it did help but I may have lost some power in the process. A dished piston with quench pads would have lowered compression but retained quench....ultimately making more power.
For you, colder range spark plugs may help. You may not get all of your improvements from one thing. Cooler intake temperatures, higher octane, colder spark plugs, slower distributor advance rate, headers....
Why headers?
They flow exhaust better. The flow allows for cooler underhood temperatures.
The 383 in my "Jigsaw" Charger is at 9.2 to 1. I was out and about yesterday and it got hot. Not boiling over but close. 89 octane gas....Not a hint of detonation. I was hammering on it a LOT and not a single knock. Iron heads, 280-474 cam and headers. Timing set to 19 initial and 33 total.

THANK YOU Kerndog for all that info!!

The point about pistons Vs Head gasket thickness for comp. ration alternation is very interesting. I'm basically stuck with the setup the shop built EXCEPT one of the head gaskets is leaking coolant a tiny bit so they need to change that for me, so I was thinking they could put a slightly thicker gasket in at the same time and do the other head too. I'd love to be able to make a case that would get them to fix it in the best way, which sounds like dished pistions as you suggest. And I guess regardless of who's paying, the time to switch the pistons would be when the heads are of anyway.

Both the machine shop and shop that put the engine in suggested manifolds because they wouldn't leak after daily driving, as I drive the car in town all the time. I also wanted to have the car be as quiet as possible given it's relatively mild build. After riding in my buddys GTX with headers and a bigger cam, I can't see that my car is much quieter inside. So maybe I need to sell the manifolds and get some headers?

As far as temp goes, I don't have my gauges done yet, just a mech. oil, but I got a radiator cap with a temp gauge in it and that never reads over 180 even on the hottest days we've had. I know it's measuring at the top of the rad and not in the pump housing so it's probably a bit lower than actual.

Thanks again for your help!!

Ben

 

[Wolf Tickets]

I would say with some certaintly it likely needs more fuel.
Get an AFR meter and install it.
You should be able to run closer to 35 degrees total.

Thx Don. I'll do that and report back.

 

[Wolf Tickets]

A 262xe is a small cam and builds a lot of compression. It should be used on a motor in the 8's. The narrow lsa of 110 isn't helping.
Compression of 180 seems high though.
Plugging numbers into wallace racing I get this. I doubt it's as accurate for a XE due to the asymetric intake

View attachment 1127927

Thanks Curiousyellow71

The machine shop read off some of the numbers to me on the phone and I know the effective CR was in the 7's based on their test before sending it out.

Ben

 

[Wolf Tickets]

i have two of those FBO plates and they aren't even close to being accurate. that 262 cam closes the intake valve too early.

THX lewtot184

I did notice that I was getting more total than I should have (with the plate on the 14 slot) by 1 or 2 degrees and right then started wondering about exactly how accurate the plate was!! I'm planning on an EFI setup sometime so I figure the old style distributor will be replaced then.

Ben

 

[Wolf Tickets]

What are "stock jets" in an aftermarket carbatooty?
As mentioned you need to find the a/f ratio.

Hey Slap Stick

Good Question. 78's primary and secondary are what I'm reading online, but I don't have the part number of my exact carb in hand....I'm realizing that knowing that a/f number will be really valuable.

One question and this might be totally unanswerable: would running hotter on the freeway suggest the primaries are too lean? After cruising with VERY light pedal, never coming near the secondaries, for 20 min or more, I notice the engine is hotter than just sitting in traffic. I've got a 7 blade fan and 3 core 26" rad (from the AC equipped wagon) and even added a fan shroud. It's never overheating, just up at 180 where it's 160 in traffic. It just occurred to me that lean burns hot, and normally cruising on the freeway should be the best cooling the engine will ever see. But what do you think?

THX!!!
BEN

 

[Wolf Tickets]

The first thing "I" would do is confirm the balancer is accurate..

Then make sure you're not lean under load...You can do a quick test of this by temporarily richening the carb (even if you go a little too rich, just don't get crazy) and seeing if it still pings.

Beyond that a couple of things need to be verified. And I know it's not what you wanna hear because it's a good bit of work, but....you need to know the CC of the chambers, gasket thickness, piston depth @ TDC, and piston type. For all you know it could be 11 to 1 with a steel gasket and iron heads. It would help to know the installed cam timing as well. It could have been installed with too much advance, and coupled with the early intake closing of that cam = pinger.

It's perfectly possible for flat-tops with no notches to knock at 9.25:1 with the pistons a mile down in the hole and a short duration cam. It would happen on some of the later factory RV engines when they tried to meet emissions by dropping the pistons down...and that was with 8:1 at best.

If you didn't build the engine there's no way to know what's inside there; even experienced shops make mistakes.

Thanks Beanhead

That makes sense. I'll order the AF meter and check the #1 cyl for tdc against the balancer.

Sounds like I should get a jet kit and see what is in there now and try one bigger, just to see what that does. I really like the idea of an AF meter so that should be fun. Ultimately, I REALLY like the idea of an EFI setup as watching the real time AF and timing numbers on the screen in my buddy's GTX was quite satisfying.

That's facinating to hear about the piston depth on the later RV engines. The only good part about this stuff not working perfectly yet is learning all of this great info about engines while troubleshooting.

As far as the Machine shop, I hear that. The engine had a tiny coolant leak from day one. I popped the hood at the gas station talking to a guy there and he and I both smelled coolant. Over the next few days it started using a quart a week and when I got it back to the shop, they said it was leaking from one of the head bolts (my first realization that a rebuilt engine, even from a shop that countless people have recommended to me, can be imperfect). The shop that installed the engine pulled the head bolts and redid the sealant on them. The leak was much smaller but still present. I finally got some good pictures and took them to both the shop and the machine shop and we could see that the coolant was leaking right at the head gasket. There's also a small oil leak coming from somewhere inside the bellhousing. Ugh.

They're going to take care of it so I'm not furious, just worried (what else am I going to discover?)

Thx for your help!!!

BEN