Building a fresh 360ci engine for mileage & power

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BigBlockMopar
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Joined: Sun Sep 02, 2007 3:29 pm
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Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Thu Aug 06, 2015 6:36 pm

Recently I bought a fairly fresh smallblock Mopar 360ci engine and started working on rebuilding it for my daily '73 Dart, in favor of the current 318.
The plan is to built an efficient running engine that can put out some good mileage and power.

The current 8.6:1cr engine/drivetrain combo in the Dart (see signature) cannot provide a better mileage then around 11mpg on daily (summertime) commuting. Winter mileage is a sad 8mpg orso. It gets 15mpg on highway trips (summer).
I've spend a lot of time reworking the ignition timingcurve, mixture adjustments, cool air intake and oil weight tests, but the car just doesn't get any better mileage. The car is certainly fun to drive and the engine, with it's 22" vacuum at idle it's very responsive.
But I hope to get some considerable better mileage with a more efficient, high cr 360 engine.


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The engine came with high compression '107' KeithBlack pistons and by using closed chamber swirlport '302'-heads, a static compression ratio of 10.5 to 11:1 is possible. Still have to decide where I want to end up with the CR. Will need to do some dynamic compression calculations soon.

The engine wasn't complete. I had to locate a crank, heads, camshaft, rockers and a number of other items to make it complete.
I've just purchased a freshly reground crank @ .010" under, and also ordered a XE256H CompCams camshaft along with 1.6 ratio roller rockers. Had/have some worries if the 'Extreme Energy' camshaft might built too much cylinder pressure which would increase chances of pinging with the 'mild' cam.
Although I do like the lopey idle of a higher duration cam, it didn't make much sense (with mileage in mind) to choose a bumpstick with it's active working rpm-range outside the engine's daily rpm-range.
Also would rather have liked to install a roller cam in this engine but didn't want to blow the bank on this build yet. Maybe sometime.


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I've had the heads milled and new bronze valve guides installed. I just start working on portmatching the intake ports.
Plan to portmatch the exhaust ports after that, and polish the chambers as smooth as I can with the tools I have.
Also plan on smoothing the bulky portruding valveguide boses in the ports for added flow/less resistance.

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Last edited by BigBlockMopar on Sat Dec 16, 2017 6:58 pm, edited 3 times in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.


storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Building a fresh 360ci engine for mileage & power

Post by storm » Sat Aug 08, 2015 2:26 am

Keep us posted on this build, I enjoy this type of thing.

I am surprised with your mpg out of the 318. My old Pontiac 400 could easily get over 20 (imperial) mpg in a 1977 Trans Am (having said that it was running a (petrol) Quadrajet) and that was with 8.4-1 compression and 17" vacuum at idle.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
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Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Sat Aug 29, 2015 6:27 am

IMO the 318 in my Dart has some camshaft or intermediate shaft wear, which does a funny thing with the timing at low rpms.
When setting the idle-advance at say 15°, it will decrease to about 10-12° for the first few 100 rpm's as the engine rpms go up, after which the mech.advance will kick in and start increasing timing again.
I think the intermediate shaft is probably riding up on the camgear or something causing this timing issue.
Also the stock camshaft could be installed a bit more advanced I think, as the engine really comes alive above 2000-2400rpm.

Since my daily commutes are also pretty much all 15-20min. Stop&Go driving with a cold engine, mileage doesn't stand much chance.


Today I delivered the rotation assembly at the machine shop to have it balanced.
Still working (tediously) on the first heads, polishing and grinding away at/in the ports, removing protruding metal which could hinder flow and contouring them.


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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:00 pm, edited 1 time in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Sat Sep 05, 2015 5:19 am

Picked up the balanced crank and piston assembly from the machineshop yesterday.

Also have 1 cylinder head pretty much 'done'.
A lot of time went into this head alone already.

Smoothed out the intake and exhaust ports and blent castinglines and ridges.
Tried polishing the chambers to a mirrorlike shine (to prevent carbon build up and reflect combustion heat back into the mixture) but that didn't quite work out as easily as I hoped for, given the tools I have. Also at some point I get impatient and just want to move on.

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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:01 pm, edited 1 time in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Wed Mar 23, 2016 6:30 pm

Engine progress update.

Got both heads all done. Ground away internal casting roughness, blended valveports and valveguides. Refinished the seats. Reworked the headchambers, removed all sharp edges to prevent detonation, smoothed and unshrouded the valves.
Also purchased new valves and polished them to a shine.

In the engine block I removed any sharp castingflash and drilled, smoothed the oil pump and the internal passages in the block for less resistance.
Decided to cut and reweld the oil-pickup-tube, as the one I have was ment for a rearsump oilpan but I'm using a center sump pan.

Then (finally) came assembly time.
After lightly polishing the counterweights of the crankshaft, a thorough cleaning was done with brushes and brakecleaner through all the oilpassages.

Because of the hypereutectic KeithBlack pistons being used, all the top piston rings were checked and regapped wider from 0.020 to 0.025".
The sides of the rods were polished as well to remove the sharp machined edges that could possibly cut into adjacent material.
New .010" main- and rodbearings were cleaned, prelubed and installed in the engine block and rods.

After the crank and piston-assemblies were installed everything was torqued down to specs.

Unfortunatly it was only then that I noticed there was a 0.025" difference in the engine block's deckheights.
On one side of the engine, the pistons are 0.010" above deck, and the other side has the pistons 0.015" below deck.

But I think I can compensate that difference by using regular and thinner headgaskets on either side of the engine, and maybe a light cut on one head.
The regular FelPro headgaskets are 0.039" compressed, and I've ordered a pair of gaskets that are 0.028" compressed.
The heads cc'd at 60-61cc.

Quick calculation netted a 10.82cr or 11.21cr, depending on which headgaskets are used on which side.




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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:05 pm, edited 2 times in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Building a fresh 360ci engine for mileage & power

Post by storm » Wed Mar 23, 2016 9:32 pm

Great work.
Do the valves suffer from shrouding at all? It looks like the exhaust valve at lease would.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Thu Mar 24, 2016 7:49 am

Yes the exhaustvalves are shrouded quite a bit.
I beveled the edge to the flat part in the chamber, and enlarged the chamber around the valve slightly to the headgasket edge.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Sat Aug 13, 2016 6:19 am

Update:


Modified and mounted a windage tray from a later model smallblock;
And fabbed a baffle inside the new oilpan to prevent oil-slosh on hard cornering/acceleration and braking.

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Welded a toothed timing wheel from a 5.7 Hemi engine to the crankshaft pulley and balanced it (by hand to about 1-2grams);

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Installed and degreed the camshaft along with timing chain tensioner.

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Made a sturdy bracket for the cranksensor;

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For testing the crank sensor, I mounted the pulley-assembly on the lathe and spin-tested it, while checking it's signal through the Megasquirt ECU and a laptop;

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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:08 pm, edited 1 time in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Sat Aug 13, 2016 6:29 am

To compensate for the engine block's left and right deckheight-difference, I installed two different thickness headgaskets.
Would be better to have the block decked ofcourse but that would've cost me another 2 or 3 weeks of time.

At one side of the block, the pistons are out of the hole at 0.015", while on the opposite cylinderbank the pistons are below deck at 0.010".
To 'correct' these numbers a bit I installed a 0.028" MrGasket headgasket on one side and a regular FelPro headgasket at 0.048" on the other.
Calculated cr difference is now just about 1 tenth.

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Spend a lot of time deburring / prepping / correcting/ cleaning / shimming a set of cheap-ish 1.6 rockers;

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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:16 pm, edited 3 times in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

storm
Posts: 565
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Building a fresh 360ci engine for mileage & power

Post by storm » Sat Aug 13, 2016 6:16 pm

Excellent stuff, I enjoy watching and reading engine rebuilds that bring old tech into the 21st century.

A pair of these would be good http://www.edelbrock.com/automotive/mc/ ... m-sb.shtml
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Sat Aug 13, 2016 6:23 pm

Would really like to put a set of aluminium heads on this engine, if alone just for the weightsavings.
But currently a pair of fresh new heads are not in the budget unfortunatly.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

fpvmustang
Posts: 33
Joined: Thu May 05, 2016 3:28 pm
Location: Quincy Ca. USA

Re: Building a fresh 360ci engine for mileage & power

Post by fpvmustang » Tue Aug 16, 2016 3:17 pm

I recognize that tooth logger you going to do efi?

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Tue Aug 16, 2016 7:17 pm

Yes correct.
At first I will control, adjust the timing curve and later on I want to do vapour injection.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

fpvmustang
Posts: 33
Joined: Thu May 05, 2016 3:28 pm
Location: Quincy Ca. USA

Re: Building a fresh 360ci engine for mileage & power

Post by fpvmustang » Tue Aug 16, 2016 7:27 pm

cool I'm running vapor injection with magic jet injectors. ms3x

BigBlockMopar
Posts: 344
Joined: Sun Sep 02, 2007 3:29 pm
Location: Netherlands
Contact:

Re: Building a fresh 360ci engine for mileage & power

Post by BigBlockMopar » Wed Aug 17, 2016 5:38 pm

Nice coincidence, I'll be using Magic injectors too.
Are you running dual fuel with gasoline for starting and switching to LPG after warmup, or just plain LPG?

I like to run LPG-only, as I don't want to 'revive' all the gasoline fuel parts in my car for just those 5 minutes of runtime every day.
If cold starts will be an issue, I want to try using both the 'normal' Convertor and 425 setup for cold starts, and switch to injection when the engine has warmed up a bit.


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Last edited by BigBlockMopar on Sat Dec 16, 2017 7:20 pm, edited 1 time in total.
https://www.bigblockmopar.com
'73 Dodge Dart - 360ci - 11.3:1cr
MegaSquirt + HEI 7-pin timing control - Edelbrock AirGap - Cold Air Intake
IMPCO E / 425 mixer - A518 OD-trans - 3.55 gears - 225/50/17" tires.

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