Another 87 octane/aluminum heads question

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redlined

redlined

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Odessa Tx
It's not an A body but it is a small block, and a somewhat odd combo. I have a '90 360/727 w/4.10 gears in an '86 Ramcharger 4x4.

It's fed with an unmodded swapped in '89 factory TBI. The current engine combo consists of an AirGap intake, shorty headers, mildly ported 72cc 308's, can't recall the cc specs but flat tops .015" in the hole, .038" gasket and a short roller cam. 192/203 @.050'', .459"/.471" lift, 114 LSA. Calculated static is 9.33:1. It's been four years since I screwed it together, can't recall the dynamic CR or the IVC on the cam. Seems like calculated dynamic was around 8.2:1

I run 4* more initial timing than spec on the TBI in ambient temps of up to 115 degrees, a 195 T-stat and 87 octane with no rattles. It has fresh air to the air cleaner and the aforementioned unheated AirGap. The engine temp stays rock steady, new radiator, HD fan and all that.

Here's my issue. I requested the machine shop cut the bowls on the 308's when the new seats were installed and the Chevy idiots cut the bottom angle off the seats. Being pressed for time I installed the heads anyway, crossed my fingers and made the planned trip from Texas to Moab Utah without issue, and have only put about 5000 miles on the engine altogether.

My concern is that since said Chevy idiots reduced the cross section width of the seats they'll eventually worm loose and kill the motor with repeated heat cycles and increased spring pressure.

I want to chunk the 308's and just bolt on a set of Eddy heads, a gain of about a point in compression to 10.3 or so, but with better quench and thermal characteristics. Also going to ditch the factory TBI in favor of an aftermarket setup, that will give me control of the timing curve.

I plan on putting quite a few miles on it in the near future. The thing sucks gas to the tune of about 10mpg on a good day and filling the 35 gallon tank daily with 93 would get painful.

To finally get to the point of this long windedness, think it'll still burn 87 octane with 10.3:1 and a careful tune? Think maybe with a longer cam?
 
Almost 20 years ago I did a 451 Stoker with Edelbrock heads,and a 500 AFB.Compression ratio was 10.1 actual. I drove the car cross country on the Hot Rod Power Tour and as a test ran it over 1000 miles on 87 without pinging and plugs looked good.After that I would mix 87/91 or 93 depending on the part of the country.Only because of thinking I might hurt it.Drove that car 30,000 miles in 2 years. It's still running today.Aluminum heads with 10.1 should be no problem.Tune-able EFI should help too. Cam will be up to you.
 
You make it too easy with all the detailed numbers! Kinda have to guess with the cam for IVC/ICA, but guessing 240 advertised duration, I get 9.35 for SCR and 8.2 for DCR, so those numbers agree.

Upping the SCR by 1 whole point would increase DCR by about the same. So 9+ DCR does not sound any good at all for regular fuel.

BUT, your higher elevations are helping and lowering that DCR by right at 0.5 points, and even more going to Utah. So, if you will be staying at Odessa's 2900' elevation and higher, then that will help. And conventional thinking is that the AL is good for at least 0.5 points in DCR. (Racer Brown says 1 whole point on his site.)

Since you don't have a great quench gap to preserve (it's at .052" right now), then I might consider the Edelbrocks with the milled 'open' chamber at 65 cc's. Throw in a .051 gasket and now your SCR is now 9.75 and DCR is 8.6 at sea level and 8.1 at your elevation. Or stick with the closed chamber heads and current head gasket and hog 5 cc's or so out of the chambers..... but I am not sure where to take it out of those heads.

IIRC the SpeedPro's have 65 cc chambers in the closed configuration so that might be a head to think about since you just want the AL material, not the highest flow numbers.

Seems like that is in the ballpark to make work with the proper care. Probably a bit of cam retard and thicker head gaskets and timing will get your there. A larger cam would help but you ought to stick with the 114 LSA for fuel economy. Dunno if there is a roller cam with longer ramps to make the ICA later; that used to be done with flat tappet cams. I had a 190@050" advertised intake duration cam in a 351C that had an advertised intake duration of 254 on an LSA of 114 just for that reason: better fuel mileage with a higher CR engine. (It had a DCR of 8.3 with iron heads and would ping a bit on regular, even at 1000' of elevation.)

IMHO, you need to communicate with AJFormS as he has run low octane fuels on DCR's in the mid to upper 8's IIRC.
 
What are you exactly saying about the seat width, that they hard seats on the intake side?
Are you saying they cut in bigger 2.02 valves, larger throat cut and seat? That should not effect whether the pressed seat will stay in the head. Idk what you as re worrying about.
Or are you saying it has a 2 angle valve job..
Be clearer.
 
MOPAROFFICIAL said:
What are you exactly saying about the seat width, that they hard seats on the intake side?
Are you saying they cut in bigger 2.02 valves, larger throat cut and seat? That should not effect whether the pressed seat will stay in the head. Idk what you as re worrying about.
Or are you saying it has a 2 angle valve job..
Be clearer.
Click to expand...

Kept the stock sized valves in the 308's and cleaned up the ports since my plan was smooth, high velocity flow at low RPM's combined with the short cam, with as much compression as I thought I could get away with. A torque motor in other words. It worked out pretty well, the little 360 hauls the 5500lb truck around with some authority, although it's done by 5000rpm. That was expected as well, and since the TBI is rev limited to 4800 it all comes together nicely. It rarely sees WOT anyway.

As for the seats, it's just what it sounds like. I had new ones installed along with new guides. They called and said the heads were ready, and I'd told them beforehand I'd do the final assembly myself. When I got to their shop and looked them over they'd left a big step in the bowls where they'd cut the old seats out. I asked them if they had the tooling to machine cut the bowls to remove that step, thus leaving me with only some minor hand blending to do.

A week later they called and again said they were ready. I went to pick them up and saw that the idiots had cut the entire bottom angle off the seats. So much for my three angle valve job. I raised hell, but having a scheduled trip coming up I didn't have time to dick around with the fools any more, and wouldn't have let them do any more work if I had. I paid the bill and left, never to return.

I'd considered just going bigger on the valves and keeping the 308's, but I'm not sure there's enough meat around the bowl on the exhaust side. It has stock sized 1.88''/1.60''s, a Magnum ex. valve is only 1.625".

I wasn't through with the blending and guide work in this pic but you can see what I'm talking about. They cut a boatload out of the bowls. Idjits.

RC3606.jpg
 
nm9stheham said:
You make it too easy with all the detailed numbers! Kinda have to guess with the cam for IVC/ICA, but guessing 240 advertised duration, I get 9.35 for SCR and 8.2 for DCR, so those numbers agree.

Upping the SCR by 1 whole point would increase DCR by about the same. So 9+ DCR does not sound any good at all for regular fuel.

BUT, your higher elevations are helping and lowering that DCR by right at 0.5 points, and even more going to Utah. So, if you will be staying at Odessa's 2900' elevation and higher, then that will help. And conventional thinking is that the AL is good for at least 0.5 points in DCR. (Racer Brown says 1 whole point on his site.)

Since you don't have a great quench gap to preserve (it's at .052" right now), then I might consider the Edelbrocks with the milled 'open' chamber at 65 cc's. Throw in a .051 gasket and now your SCR is now 9.75 and DCR is 8.6 at sea level and 8.1 at your elevation. Or stick with the closed chamber heads and current head gasket and hog 5 cc's or so out of the chambers..... but I am not sure where to take it out of those heads.

IIRC the SpeedPro's have 65 cc chambers in the closed configuration so that might be a head to think about since you just want the AL material, not the highest flow numbers.

Seems like that is in the ballpark to make work with the proper care. Probably a bit of cam retard and thicker head gaskets and timing will get your there. A larger cam would help but you ought to stick with the 114 LSA for fuel economy. Dunno if there is a roller cam with longer ramps to make the ICA later; that used to be done with flat tappet cams. I had a 190@050" advertised intake duration cam in a 351C that had an advertised intake duration of 254 on an LSA of 114 just for that reason: better fuel mileage with a higher CR engine. (It had a DCR of 8.3 with iron heads and would ping a bit on regular, even at 1000' of elevation.)

IMHO, you need to communicate with AJFormS as he has run low octane fuels on DCR's in the mid to upper 8's IIRC.
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There's no quench at all now with the .038" gaskets and open chambers on the 308's. In truth I'm kind of surprised it doesn't rattle since the factory issued PCM's timing curve was programmed with lower compression and EGR in mind.

I'm going to retire in a couple years, throw the thing on a trailer and go wheel the country for a while. It may see altitudes from Death Valley to 13,000+. I was limited on cam specs with the factory TBI, the current stick makes about 20" at idle and seems to cause no issues. With aftermarket TBI, a simple Holley Sniper setup most likely, I won't have that limitation and could bleed some low RPM cylinder pressure with different cam specs.

Another question. The '90 LA is somewhat of a hybrid, using basically the Magnum roller cam setup with the LA rockers. I'd like to keep the LA shaft rockers, I'm wondering about pushrod tunnel clearance issues with Eddy LA style heads and the Magnum style roller cam. Any problems there that a little grinding wouldn't fix?
 
Darter6 said:
Almost 20 years ago I did a 451 Stoker with Edelbrock heads,and a 500 AFB.Compression ratio was 10.1 actual. I drove the car cross country on the Hot Rod Power Tour and as a test ran it over 1000 miles on 87 without pinging and plugs looked good.After that I would mix 87/91 or 93 depending on the part of the country.Only because of thinking I might hurt it.Drove that car 30,000 miles in 2 years. It's still running today.Aluminum heads with 10.1 should be no problem.Tune-able EFI should help too. Cam will be up to you.
Click to expand...

You remember right off hand what the quench measurement/head gasket was?
 
redlined said:
There's no quench at all now with the .038" gaskets and open chambers on the 308's. In truth I'm kind of surprised it doesn't rattle since the factory issued PCM's timing curve was programmed with lower compression and EGR in mind.

I'm going to retire in a couple years, throw the thing on a trailer and go wheel the country for a while. It may see altitudes from Death Valley to 13,000+. I was limited on cam specs with the factory TBI, the current stick makes about 20" at idle and seems to cause no issues. With aftermarket TBI, a simple Holley Sniper setup most likely, I won't have that limitation and could bleed some low RPM cylinder pressure with different cam specs.

Another question. The '90 LA is somewhat of a hybrid, using basically the Magnum roller cam setup with the LA rockers. I'd like to keep the LA shaft rockers, I'm wondering about pushrod tunnel clearance issues with Eddy LA style heads and the Magnum style roller cam. Any problems there that a little grinding wouldn't fix?
Click to expand...
Ah yes, I was thinking 302's with the quench. I suspect the altitude has a lot to do with your running OK.... the effective DCR is around 7.7 at 2900' elevation. And it sounds like you don't have a lot of timing in.

Going to Death Valley? Then I'd find a way to lower the DCR with the Al heads and keep it in the low 8's max and Al heads. But again, communicate with AJFormS; he has run 87 IIRC on higher DCR's. And IIRC MoparOfficial here races some pretty darned high DCR's on iron heads. So there is a body of experience between those 2 to tap into.
 
You dont want it to taper off ..you want seat then straight up into the bowls on the exhaust ports.

Your pics aren't well focused btw.
 
redlined said:
My concern is that since said Chevy idiots reduced the cross section width of the seats they'll eventually worm loose and kill the motor with repeated heat cycles and increased spring pressure.
Click to expand...
IMHO: The main retention force ought to be the interference fit pressure between the outer edge of the seat and the head.... which should not be directly related to the width under the seat.

A narrower seating area MIGHT allow the seat to work up into the head more easily and I suppose that could effect the interference fit. Can you tell how much of the seat's ID has been removed?
 
redlined, Sorry I don't. I would guess somewhere in the .020 to.030 compressed.
 
Ramchargers are awesome, had one for a decade. Never let me down.

You haven’t complained about power needs. Why tear a young engine open? I’d suggest you leave the top end shut until you start seeing signs of problems where you need to change the heads.

Instead, work on the new fuel injection. There are many brands and styles. It’s going to take some time to tune.

The tune is going to dictate if you’re going to have problems with the your new heads anyways, if you run lean and try to move that heavy truck with a lot of throttle, you will detonate. If you run on a razors edge of higher compression and combine with low octane, the tune and timing need to be precise.

There are a lot of fuel injection systems out there now. I run megasquirt, and I can tune fuel and ignition timing on-the-fly.
 
T56MaxTorq said:
Ramchargers are awesome, had one for a decade. Never let me down.

You haven’t complained about power needs. Why tear a young engine open? I’d suggest you leave the top end shut until you start seeing signs of problems where you need to change the heads.

Instead, work on the new fuel injection. There are many brands and styles. It’s going to take some time to tune.

The tune is going to dictate if you’re going to have problems with the your new heads anyways, if you run lean and try to move that heavy truck with a lot of throttle, you will detonate. If you run on a razors edge of higher compression and combine with low octane, the tune and timing need to be precise.

There are a lot of fuel injection systems out there now. I run megasquirt, and I can tune fuel and ignition timing on-the-fly.
Click to expand...

It definitely doesn't run lean, AFR runs 13.2 at 2500rpm according to the wide band o2. I built it with low/mid range torque in mind, no complaints on power. It is thirsty though at 10 mpg, the lack tunability being the reason I want to upgrade from the factory TBI.

Question. How would I see signs of a seat getting loose? Oil pouring out of a tailpipe from the hole in a piston, a dead miss and one hell of a knock?
 
nm9stheham said:
IMHO: The main retention force ought to be the interference fit pressure between the outer edge of the seat and the head.... which should not be directly related to the width under the seat.

A narrower seating area MIGHT allow the seat to work up into the head more easily and I suppose that could effect the interference fit. Can you tell how much of the seat's ID has been removed?
Click to expand...

My thinking with the narrower the cross section of the seat is [1] the hotter it will get due to reduced contact area with the head, less heat sink area in other words, and [2] less overall rigidity of the seat itself, more prone to losing said interference fit on the OD. I have my doubts as to the proper fit anyway from what I've seen of that shop's overall knowledge of machine work. They may fit tight, may not. I don't want to find out the hard way.
 
Did you measure the ID of the seat ring before you assembled the heads?

The “recommended” replacement ex seat for those heads is 1.6875 OD/1.4375 ID.
These will usually leave a noticeable step where the seat ends and the casting starts.

If they were installed with a normal amount of press(about .005-.006), you could still open the ID up a bit and not have issues with them coming out.

In operation, the hot exhaust gasses blowing past the seat actually make the seat tighter in the head.

Here’s an old J head(actual T/A head) that someone installed the wrong size ex seats in(1.750 OD), and you can see the cross section is fairly thin.
They’d been in there for years, so I left well enough alone, I just blended that nasty step at the bottom of the seat away.

69BC78CB-326E-4EDA-BAE6-1C1DC2658EBF.jpeg


825AC2D7-C496-4017-95C1-2E33306D6A26.jpeg
 
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Keep in mind that thermal transfer is directly effected by the surface-to-surface pressure. So most of the heat is going to transfer where the pressure is greatest: around the outer edge of the ring, where the interference fit is located.

Now, the shop's skill is an entirely different matter LOL. And yes, a seat falling out is normally followed a short later with the symptoms you describe....

If you are really are going down this road with the higher CR and going to below sea level, then certainly aluminum heads can help. But you are counter-acting all that help with the higher CR. And unless you change to .028" head gaskets, then your quench gap with a closed head is not going to be worth much at over .050". So you are in a tight 'performance corner' here and need to look elsewhere for relief.

IMHO, for this and the fuel, you need to look more into the cam, and go with one with:
- A wider LSA like 114 which will help lower the DCR and reduce overlap for better economy
- Keep the intake opening later and the exhaust closing earlier to help reduce overlap for economy.
- Make it an old style sloooow ramp cam. 60+ degrees difference between advertised and .050" lift durations is where you need to be to drop that DCR.
- That was not uncommon to find in the mid-70's when guys were putting in smaller cams after the Arab Oil Embargo in high compression engines. Crane had a series of 'HE' (hydraulic economy) cams for this problem; I have a cam card for one with over 60 degrees between .050" and advertised lift: .050 durations of 190/200, and advertised of 254/264, on a 114 LSA (This was for a 351C). I see that Racer Brown has some profiles that are in the mid 50's degrees of difference, and Erson has some RV cams with a spread over 70 degrees, so maybe give them calls and explain the situation, once you settle on the heads and can get some real SCR numbers computed.

Edit to add: Dang, I read you current cam specs one more time.... missed all that! Looks just like I was telling you to do above LOL.

May I ask under what conditions the AFR is running in the 13's? If this is at 2500 RPM and cruise conditions, that is too rich for decent economy, carb'd or TBI. Folks get hung up on staying with stochiometric AFR all over the operating range, but that is only needed at more open throttle conditions. For moderate cruise at 60 mph on level ground, your AFR should be in the 15's; no problemo with the engine running OK. Heck, Chrysler Lean-Burn engines ran up in the 18-19 AFR range!
 
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IMO, for stock-ish motors the part throttle cruise can be really lean....... but I don’t care for getting them leaned out to the point where they’re kind of “surging”.
It may not be hurting anything, but I can’t tolerate that feeling.

Chrysler Lean-Burn engines ran up in the 18-19 AFR range!
Click to expand...

I’d have to say that some of my least enjoyable driving experiences are from sitting behind the wheel of some lean burn equipped Mopar.
You keep pushing the pedal down when going up a grade....... and nothing happens....... until the trans finally kicks down.
Just awful.

From what I understand, the new GDI stuff is more like 50:1 at part throttle cruise.
 
PRH said:
IMO, for stock-ish motors the part throttle cruise can be really lean....... but I don’t care for getting them leaned out to the point where they’re kind of “surging”.
It may not be hurting anything, but I can’t tolerate that feeling.

From what I understand, the new GDI stuff is more like 50:1 at part throttle cruise.
Click to expand...
Yes, 15-16 won't surge at least form my experience.

That 50:1 number is pretty wild! I have not kept up with that.
 
nm9stheham said:
May I ask under what conditions the AFR is running in the 13's? If this is at 2500 RPM and cruise conditions, that is too rich for decent economy, carb'd or TBI. Folks get hung up on staying with stochiometric AFR all over the operating range, but that is only needed at more open throttle conditions. For moderate cruise at 60 mph on level ground, your AFR should be in the 15's; no problemo with the engine running OK. Heck, Chrysler Lean-Burn engines ran up in the 18-19 AFR range!
Click to expand...

The 13.2 is at part throttle cruise on the highway. I can clear the memory in the PCM, which also wipes the fuel trims, and it will jump up in the mid 14 range for a while, but after a few hundred miles it's back to 13.2. One thing I haven't done is recalibrate the wide band since the initial install, it's possible it's lying to me a bit, but given the 10 mpg it's not stretching the truth much.

The narrow band o2 that the PCM uses to derive an average fuel ratio doesn't give a specific reading on this 30 year old system, but it does switch rich/lean/center as it should at cruise, I've watched it on my Snap On scanner.
 
Think I'm just screwed on the 87 octane. Calculated CR with a 63 cc head is 10.36:1. Not that dynamic means a helluva lot in the real world but it comes in at 9.4 with the current cam and a 63 cc head. Paid over $350 for the cam, hate to just pitch it over the fence.

Seems my best option would be to find another set of 308's, a shop that knows what the hell they are doing and stick with my current setup. Replace the heads, add a decent fuel injection setup and go with it.

It's hell when you get so old and fat that you have to pull all the sheetmetal off just to work on the sumbitch lol.

RC36015.jpg
 
Actually dynamic means much more than static in the real world. That is what the engine really sees, not static. And if you like the cam, which is going to be your friend for fuel mileage, then the 308's may be the best change to make. If you are at 8.2 DCR now, it is not going to be too hard to get down into the low-mid 7's to be able to run the lower grade gas.

I'd look once more at the aluminum..... since with that, you gain at least 0.5 point higher in CR with the same resistance to detonation. I would look at the 65 cc Edelbrocks and englarge the chambers some, and thicken the head gasket. With the open chamber and a gasket of at least .051" thick, you are out of the supposed piston-to-head gap range that is more prone to detonation (something like .060 to .080" gap). You can even go larger in gap with Cometic head gaskets.

As for the PCM and the AFR, has the narrowband O2 been replaced? If it ever saw leaded fuel, it could be compromised. If its readings are off, then where the PCM adjust to will be off.

Of course, moving a vehicle-shaped cinder block through the air with 4.10 gears is only gonna be so good on fuel mileage LOL
 
nm9stheham said:
Actually dynamic means much more than static in the real world. That is what the engine really sees, not static. And if you like the cam, which is going to be your friend for fuel mileage, then the 308's may be the best change to make. If you are at 8.2 DCR now, it is not going to be too hard to get down into the low-mid 7's to be able to run the lower grade gas.

I'd look once more at the aluminum..... since with that, you gain at least 0.5 point higher in CR with the same resistance to detonation. I would look at the 65 cc Edelbrocks and englarge the chambers some, and thicken the head gasket. With the open chamber and a gasket of at least .051" thick, you are out of the supposed piston-to-head gap range that is more prone to detonation (something like .060 to .080" gap). You can even go larger in gap with Cometic head gaskets.

As for the PCM and the AFR, has the narrowband O2 been replaced? If it ever saw leaded fuel, it could be compromised. If its readings are off, then where the PCM adjust to will be off.

Of course, moving a vehicle-shaped cinder block through the air with 4.10 gears is only gonna be so good on fuel mileage LOL
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Dynamic calculators don't take VE at various rpm into account, they are a best guess.

Yep, new o2 for the TBI when I did the build. The old worn out, bone stock '82 360 got 10 mpg too. Back in the dinosaur days of TBI they made a resistor assembly that plugged inline on the o2 wiring to alter the value of what the PCM sees. That would make it read too lean or fat overall as needed to fool the PCM into adding or pulling fuel from it's trim tables.
 
Well that is true, but what DO you have to go by besides DCR? No computational method that I aware of accounts for VE.....so don't ignore the best tool available even if it is a best guess; it's been used for decades now, and folks have gotten a reasonable handle on how to apply the results. Without that, all you can do is experiment. The Wallace one allows you to look at 'effective' DCR that accounts for altitude.

I was wondering last night if your PCM looks just at a TPS or does it have an MP sensor? With your low density altitude, any MP sensor would read low all the time. I would assume the PCM would have a way to look at and figure out the static pressure and correct for that, but maybe not.
 
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