AMC 360 propane engine build help please

[GaWag]

I have been running propane for several years now old junkyard motors. It runs well. Just no oomph.

I even was running propane the first year MC came to the ECI in Uwharrie and showed off his mini bike skills in camp. That was an interesting sight!

I currently run D60's front and rear, 5.38's welded, Atlas II 5.0, TF727 with reverse manual valve body and an IMPCO 425, VFF30, Model E lock off. Just had may mixer setup gone through by Precision Sales and Service here in Birmingham. www.alternatefuel.com, Buddy Gamel is awesome to work with!

Here is what I want to do, I want to build the motor to really run with the propane. This means I need a 10.5 or 11 to 1 Compression ratio. I've done some research and I know I need to do oiling mods, I found out from Buddy that propane does not need an interference valve job and that's about it.

I am working with an 70's/80's AMC 360. I have late 70's and early 80's heads to chose from. I have not been able to find a build sheet anywhere to do this. Of course I want a lot of torque early off idle and still be able to get as many RPM's as I can get to spin my 42's. This mixer will flow enough for 325 HP. I don't mind going more, Buddy has a dual mixer setup that will obviously double the flow.

I would like to use as many Bulltear products as I can afford. Been eyeing some pistons and filter relocation stuff. I can do everything else in this world auto related but spec out an engine. I can do the work but need the help picking the pieces.

All help is welcome and appreciated!

Steve

[jeepsr4ever]

Hey buddy that was the 4th year I went down there. What a blast!

[GaWag]

Hey buddy that was the 4th year I went down there. What a blast!

Yes it was!

[Revelc]

Bulltear forged pistons. Call and tell him what your working with and he can help you out.

My build isn't propane so that changes things but my guess would be the following
High compression Pistons with floating pins
Edelbrock Performer ( for torque retention )
MSD or DUI dizzy ( I don't know what kind of ignition you need for propane )
Hot coil and 6a box
3-5 angle valve job with gasket matching
High flow water pump.
Bulltear timing cover, gears,
Oiling mods ( not necessary unless you wind it up to and over 5,500 RPM )
I just run an extra quart just in case.
No clue about throttle body/carb. I would guess something capable of flowing 650 CFM
Electric fans and aluminum radiator
Manifolds with a free flowing exhaust.
High torque starter
I like my cam in my 401 so far. Not sure how it will jive with 11.5:1 but it has some gumption at low RPM and carries power up to around 5,000
It's a crower stage 2-3
http://www.crower.com/camshafts/amc-...m-276-hdp.html

None of this probably helped but I thought I'd try.

[msalaba]

I have almost the same setup as you, except 5.86 gears, t-15 and D20.

Search my name and Dan58 as I know we have discussed this before.

I have been running the Ipmco 425 for about six years. And have been asking the same questions for about as long. From what I have learned, build the engine for what you want as if it were gasoline. I run a stock rotating assembly with late bridged rocker heads. I had the heads shaved about 0.040. The important part is hardened exhaust seats as propane is a gas and does not have the cooling properties of atomized gasoline.

I run a summit K8600 cam. It has pretty good off idle torque and runs out of power ~5500 RPM, but will still spin up to 6000. I would recommend a cam with similar specs. Any more mild and you will run out of high R's and more wild and you'll start to lose off idle torque.

The most important part of a propane build is the ignition system. You don't need high dollar components, but a MSD 6AL box with a SS coil helps (more spark energy) as propane is a little more difficult to ignite. I run a motorcraft dizzy, but a MSD pro billit is a lot easier to adjust.

The following table may be appropriate when setting up a base timing map:
Propane engines seem to operate better with slightly advanced (as compared to gasoline) ignition timing profiles at
engine speeds below 1500 rpm, approximately the OEM timing advance at 2000 rpm, and approximately 5 to 10°
retarded from OEM at 3,000 rpm.

• Propane engines with compression ratios in the range of 8.0:1 to about 8.5:1 should have initial timing
around 8° btdc with a total of no more than 48°, all in by 3,000 rpm.

• Engines with compression ratios from 8.8:1 to about 9.2:1 should have an initial timing of no more than 6°
btdc and a total of 38 to 42° btdc, also in by 3,000 rpm.
• Engines with compression ratios from 9.3:1 to about 9.6:1 should have an initial timing of no more than 4°
and a total advance of 38° btdc, by 2600 rpm.

• Engines over 9.8:1 (and no more than 11.0 to 1) should have the initial timing set at 4° with a total timing
of 32° btdc by 2600 rpm.

All of these timing advance curves are based on crankshaft degrees, NOT camshaft degrees. Also, if pre-ignition or
detonation is encountered, retard the timing until the detonation disappears. Then re-curve or re-map the distributor
to compensate for the timing.

Hope that helps...

[msalaba]

Oh, one more thing.

No one manufactures a set of pistons other than factory replacements. For high compression, you will need to order a custom set.

[GaWag]

OK. My current ignition is the stupid stock brain box and a TFI upgrade. I was thinking I might do away with both and go HEI. That would work too? I do have a
N edelbrock performer intake after of fact I have a few. Lol. So high compression pistons, deck the head to get my compression where I want with the pistons, (scorpion roller rockers?), couldn't I use the stock exhaust manifolds and match the openings to flow then go 2 1/2 into 3? What about oiling mods on the crank? I've heard cross drill and no cross drill because of it being soft.

Thanks very much guys!

[msalaba]

The Duraspark II with Motorcraft dizzy is superior to an HEI unit. With the TFI upgrade you will have more spark energy than with the HEI unit. The Motorcraft dizzy is good to 5500 RPM. If I didn't get a MSD 6AL box for free, I would still use the Motorcraft Dizzy with the Duraspark II box. The only difference I have noticed with the 6AL box is easier cold starts and a little better top end. I do like the soft rev limiter as I don't have to worry about valves floating.

When you did the TFI upgrade, did you remove the resitance wire so the coil receives a full 12VDC?

The edelbrock performer intake is the #1 low dollar performance upgrade that I have found. Make sure it is dual plane.

To up your compression, you need custom pistons. You specify the compression you want. Have your blocked milled to a 0 deck height. Have the heads shaved just enough to true them up. Then you shouldn't have to worry about machining the intake manifold and resizing the push rods.

Roller rockers and oil mods are for high RPM race engines. Don't worry about it. Stock parts are more than adequate for an engine that spins less than 6k.

I run true duals with an H pipe. That was mostly for the sound. If I wasn't having a mid life crisis, I would run either 2 or 2 1/2 into 3" with a flowmaster.