Better acceleration?

[BillGrissom]

3.7L isn't small for current engines. One change is to modernize it with MPFI. One company began fabbing a custom aluminum intake for that. You would also need an engine controller. The Holley Commander 950 I play with allows that, but is older (UI software requires Win XP). Holley (and others) have newer controllers. Some use Megasquirt. Cheaper might be a TBI on a 4 bbl intake, but doesn't fix the fuel maldistribution problem of a straight-six. For boost, I might wait until electric-motor superchargers get better and cheaper. Some of the >$500 ones today actually work, but cheaper Chinese ones don't. MPFI works fine with boost, as long as your MAP sensor can read >1 atm.

Your note of 3000 rpm at 75 mph reminds me how bad my 1985 M-B 300D is geared. It runs 2800 rpm at 60 mph. My 1984 300D is even worse, running 3000 rpm at 60 mph. When getting on the freeway, you count the shifts and keep waiting for that last shift as the engine starts whining, then realize that is the tallest gear. Every owner complains about it. You think that exquisite German engineering could have used 4 gears more wisely. I think 1st gear is so low you could tow a tractor if the wheels don't slip. Anyway, I wouldn't change the diff gears unless you want to make your car a drag-race toy.

 

[273]

3.7L isn't small for current engines. One change is to modernize it with MPFI.

Why modern 6 cyl make 250-300+ hp with mild cams is head flow. Plus a 6 cyl only has 6 sets of ports to make the hp, /6 has terrible stock head flow even ported ain't that great. But still a cool little engine.

 

[Dale Davies]

The head was milled .001 but no port work yet. Not sure what the tear end in but am pretty sure it’s stock base level 1965 for the original 170 engine.

I’d probably go supercharger over turbo if I had the cabbage, just because I’m a little old school. But either would probably mean new everything past the crankshaft, so no.

You could grab the supercharger off a 3800 SC Series 2 Grand Prix for a modest price. The General made a ton of those engines and they are turning up at wreckers now. Might need to fab a drive snout to extend for the belt drive.

 

[Dale Davies]

So I was finally able to get my Valiant out for a real road trip for the first time since the rebuild, and really since the first time since I've owned it. We had a blast, running about 650 miles on mostly paved and some gravel highways and roads in the Oregon Cascades mountain range. Dry clear weather, mild temps. around 4000' elevation average. The motor purred like a kitten (well, a kitten with solid lifters anyway), comfortably cruising 75mph at around 3000rpm. Good mileage, no leaks at all.

I had real issues with climbing moderate to steep grades and with acceleration in general. So I'm wondering what I can do to get- what, more power, or more torque, or whatever- especially at higher rpms. I run a 225 with a Holley 390 4bbl carb, slightly larger cam, Clifford intake and headers, 2.5 single exhaust, and, yes, a manual 3-speed stock 1965 transmission. Thanks in advance!

What is the piston deck height. Slants generally have the piston down about 0.150". A blower would build cylinder pressure for more torque.

 

[volaredon]

With standard "rebuilder" pistons (I forget now the brand, may have been "sealed power") AND a 0.030 block shave my pistons on my 74 block are STILL 0.180" in the hole, I was pissed at that. With 0.70 more off the head, my engine measured out at exactly 8.4:1. When all the service manuals of the day claim they left the factory at that level.
If I'd have known that my pistons would top out that low in the hole I'd have had the block cut 0.100. that would still have put this engine with these pistons at 0.110 down.

 

[Dale Davies]

With standard "rebuilder" pistons (I forget now the brand, may have been "sealed power") AND a 0.030 block shave my pistons on my 74 block are STILL 0.180" in the hole, I was pissed at that. With 0.70 more off the head, my engine measured out at exactly 8.4:1. When all the service manuals of the day claim they left the factory at that level.
If I'd have known that my pistons would top out that low in the hole I'd have had the block cut 0.100. that would still have put this engine with these pistons at 0.110 down.

Measure first and double check. Custom pistons with a taer compression height may be the answer to get a zero deck or close. With the milling already done the head needs to be cc'd to calculate the static CR. Better with a zero deck and a bit of a dish if required to keep cranking cylinder pressure compatible with pump fuel. With the small bore, I see no reason to be afraid of 10:1 CR. You probably want to be able to run 87 gasoline as I cannot foresee a big drop in fuel costs anytime soon.

 

[RustyRatRod]

With standard "rebuilder" pistons (I forget now the brand, may have been "sealed power") AND a 0.030 block shave my pistons on my 74 block are STILL 0.180" in the hole, I was pissed at that. With 0.70 more off the head, my engine measured out at exactly 8.4:1. When all the service manuals of the day claim they left the factory at that level.
If I'd have known that my pistons would top out that low in the hole I'd have had the block cut 0.100. that would still have put this engine with these pistons at 0.110 down.

But now you have the EXPERIENCE to see what we all talk about all the time about Chrysler engines is true. The blueprinted spec on compression was always lower than advertised. Usually, by a good bit. I remember the very FIRST one I blueprinted. It was a 70 340. I kept measuring over and over because I just KNEW I was gettin it wrong. So I called an older friend who worked at his family's machine shop and he came over and measured with me (I was 17) and he verified I was right and told me then none of the manufacturers engines ever measured up to spec and that most times, Chrysler was the worst out of them. But honestly, at a TRUE 8.4:1 and with the right camshaft, that engine should be pretty snappy.

 

[Dale Davies]

But now you have the EXPERIENCE to see what we all talk about all the time about Chrysler engines is true. The blueprinted spec on compression was always lower than advertised. Usually, by a good bit. I remember the very FIRST one I blueprinted. It was a 70 340. I kept measuring over and over because I just KNEW I was gettin it wrong. So I called an older friend who worked at his family's machine shop and he came over and measured with me (I was 17) and he verified I was right and told me then none of the manufacturers engines ever measured up to spec and that most times, Chrysler was the worst out of them. But honestly, at a TRUE 8.4:1 and with the right camshaft, that engine should be pretty snappy.

With that compression, a turbo would be the easiest to mount and pipe up. 8 to 10PSI boost would wake that six up real good. EFI would be helpful for ignition timing and fuel mapping.

 

[RustyRatRod]

With that compression, a turbo would be the easiest to mount and pipe up. 8 to 10PSI boost would wake that six up real good. EFI would be helpful for ignition timing and fuel mapping.

It would be a nice compression for a turbo.....or a Torqstorm.

 

[Jim Kueneman]

Something does not sound right to me. My wife's Dart is similar... 0.060 off the block, 0.010 off the head, oversized valves, Oregon Cams 2106, Offy dual 1 barrel, Dutra duals with the "Y" back around the transmission cross member. Running the mountains up to 7000 feet in Az we have never thought it needed more power for acceleration. It easily runs as good as any modern 4 cylinder car we have.

 

[volaredon]

Measure first and double check. Custom pistons with a taer compression height may be the answer to get a zero deck or close. With the milling already done the head needs to be cc'd to calculate the static CR. Better with a zero deck and a bit of a dish if required to keep cranking cylinder pressure compatible with pump fuel. With the small bore, I see no reason to be afraid of 10:1 CR. You probably want to be able to run 87 gasoline as I cannot foresee a big drop in fuel costs anytime soon.

which I did those measurements. Though I didn't get the parts back between the bore job and the milling of the block face, dry assemble and send back for them to finish. The 30-thou mill on the block deck was a wild guess on my part as to what I was gonna need milled off of the block, to get where I wanted this engine to be, and I tried to compensate once I had the block assembled and measured for piston position/ and then had the machine shop CC the head after the valve job, but before telling them how much I wanted it milled..... then I CCd the head once I had it back in my hands. The machine shop came back with 60cc chambers unmilled, and when they called me I did a quick calc in my head as I was driving when they called and that's how I came up with 70 thou off the head. The chambers came out (1) at 48cc, (1) at 49cc, and the rest at 50cc after that 70 thou "head shave".
I got this engine as a basket case at a swap meet, originally bought for the super 6 stack that was part of the package, was a "gotta buy it all to get what I was after"situation, and as such it was missing the pistons and rods.
I then bought a set of NOS /6 connecting rods from a popular die hard /6 racer over on the other/6 site, and upon dropping e block crank and head off for machine work I bought the 0.020 over pistons that the machine shop said it would need and the pistons I ended up with were the pistons I ended up with....

 

[volaredon]

I'm just glad I measured it out, first engine I've ever gone to that extent with on an overhaul, was quite surprised to discover that had I not done so/ and not had the block deck and head machined even to the extent I had them machined, that I was gonna be so far under "blueprint" spec for a /6....
And with all the machining I did have done, that it brought me exactly (and barely) to the factory blueprint spec and no more.

 

[Dale Davies]

which I did those measurements. Though I didn't get the parts back between the bore job and the milling of the block face, dry assemble and send back for them to finish. The 30-thou mill on the block deck was a wild guess on my part as to what I was gonna need milled off of the block, to get where I wanted this engine to be, and I tried to compensate once I had the block assembled and measured for piston position/ and then had the machine shop CC the head after the valve job, but before telling them how much I wanted it milled..... then I CCd the head once I had it back in my hands.
I got this engine as a basket case at a swap meet, originally bought for the super 6 stack that was part of the package, was a "gotta buy it all to get what I was after"situation, and as such it was missing the pistons and rods.
I then bought a set of NOS /6 connecting rods from a popular due hard /6 racer over on the other/6 site, and upon dropping e block crank and head off for machine work I bought the 0.020 over pistons that the machine shop said it would need and the pistons I ended up with were the pistons I ended up with....

Deck height is well known for most engines. Machine shops can measure it easily. Stroke is easily measured as well as con rod length. So, deck height minus 1/2 the stroke minus con rod length gives the remaining for piston CD. At this point off the shelf pistons or custom pistons is the decision to make. The machine shop can measure the bores to determine the oversize of the piston required. This is then when cost becomes a big part of the decision making. Also you can look to the bore diameters and piston CD's of other engines that may be used at less cost than ordering custom pistons.
People looking for more displacement for their Buick/Olds aluminium 215 V8s have for years bored them out and put larger diameter sleeves in to use Pinto 4 cylinder or 305 Chev off the shelf stock replacement pistons.
The point with this is to plan your build up front before laying your hard earned money on the parts counter. This way you get what you want or need instead of what someone with a glowing box in front of them tells you what is best for you.
You could build an engine using a 170 block, 198 crank, 225 rods and I think Neon pistons are used. This gives 205 or 210 CID, is lighter and may make more power.
A turbo is possibly the easiest to get mounted and plumbed. Otherwise a good used 3800 supercharger should work. Displacement is close. You could take all the SEFI components off the 3800 to make it all work. Tuners have the software to tune the GM ECM for your application. Could turn your engine into a sleeper.

 

[Jim Kueneman]

So it sounds like you are similar to us. We want to drive these cars everywhere we go. Think about all the aftermarket stuff that is being suggested here and is that worth a few extra ponies in a hill or passing. Turbo/ Supercharger adds junk that will be the first thing to fail. My opinion on “upgrades” like that is they are downgrades on reliability and being able to fix the car on the side of the road with simple spare parts in the trunk. Same with EFI. I did that on my Coronet and have used carbs since for that reason alone. I can carry a fuel pump and carb kit and fix it on the side of the road if necessary. What do I do with the Coronet, buy a spare FITech unit and carry it with me? No one will have parts on the road for aftermarket stuff.

 

[Dale Davies]

So it sounds like you are similar to us. We want to drive these cars everywhere we go. Think about all the aftermarket stuff that is being suggested here and is that worth a few extra ponies in a hill or passing. Turbo/ Supercharger adds junk that will be the first thing to fail. My opinion on “upgrades” like that is they are downgrades on reliability and being able to fix the car on the side of the road with simple spare parts in the trunk. Same with EFI. I did that on my Coronet and have used carbs since for that reason alone. I can carry a fuel pump and carb kit and fix it on the side of the road if necessary. What do I do with the Coronet, buy a spare FITech unit and carry it with me? No one will have parts on the road for aftermarket stuff.

True enough. But to get the torque up to where it should be, something needs to be changed. Those engines should not have trouble climbing hills, even in Oregon.
Was the cam degreed on installation? Was the timing mark location verified at true TDC? Either being not correct could be the source of low power.

 

[Charrlie_S]

You could build an engine using a 170 block, 198 crank, 225 rods and I think Neon pistons are used. This gives 205 or 210 CID, is lighter and may make more power.
.

My personal opinion of doing this, is it's a waste of time and/or money. Just use a 225 motor. Easy/Peasy
Unless you are racing, and the low deck slant gives you an advantage. Slant Six racing rules allow the low deck engine to run the next lower weight class, then the same vehicle with the high deck engine.

 

[Dale Davies]

My personal opinion of doing this, is it's a waste of time and/or money. Just use a 225 motor. Easy/Peasy
Unless you are racing, and the low deck slant gives you an advantage. Slant Six racing rules allow the low deck engine to run the next lower weight class, then the same vehicle with the high deck engine.

I do believe you missed your flight. My point was piston CD and piston availability to get the CR up for street, not racing. A well built and tuned 225 should perform well and get good fuel economy.

 

[273]

A well built and tuned 225 should perform well and get good fuel economy.

Depends what the individual considers performing well ? Most people hopping up a streetable NA /6 is gonna get around modern NA 4 cylinder power levels of 140-180 net hp not modern 6 cylinder hp if that not enough some kind of power adder or bigger engine is needed.

To me a /6 is more on par with a 4 cyl.
/6 has size compared most 4 cyl so 1000-3000 rpm gonna be stronger even though torques ability to create hp is dramatically reduced at lower rpms eg.. 25% @ 1313 rpm 50% @ 2626 rpm compared to 100%+ from 5252 rpm and up. Most modern 4 cyl have better head flow especially with 4 valves per cyl but /6 does have 6 sets of ports to help make up the difference and most 4 cyl now have variable cams but /6 size will allow a larger cam as a compromise.

 

[volaredon]

Well I didn't say what I did, to take away from the OP and his project, as much as a real world "how my build went" to (maybe) give him an idea what to expect.
Or what to stay away from, as the case might be.
I still do have thoughts of adding a home brew turbo "just because".
I have my engine in and running/ but have yet to drive it but compared to "before" I don't see any way it could be worse than what I started with.
As things have it, some parts found me that I wasn't looking for, and now my build is changing, I am doing what I said I wouldn't, to a point. I've grown tired of the BS about "dump the 727 and (in my opinion/experience) downgrade to a 904". Well the 727 is coming out but the truck is growing a 3rd pedal. Yeah my /6 is in a D150. That will never see a dragstrip. Not an A body. So my needs, expectations certainly may not be your expectations out of your engine.
I was hoping that with all the block deck and head face machining would have gotten me closer to 9:1 CR, it's definitely much better than it ever could have been if I would have just been happy with "just shave it enough to square up the gasket surfaces". When he told me he was "done" and my stuff was ready to go pick up, I asked about the machining of the block, and he said "it only took 6-thou to clean up". Well I had told him from the get go that I wanted at least 30 taken off so he had to put it back into the mill and shave it again.....
And the same guy who twisted my arm and convinced me to take the 8330 OD off his hands, also has said on here more than once that many "stock replacement" pistons are intentionally made"short" to make up for the chance that the CR might just increase slightly because of an overbore, when in actuality that difference would be quite slight to begin with.

My question becomes with the comments above about deck height being commonly "findable" info for a machine shop, and Chrysler engines being so notorious for action CR coming up way short of "advertised" where the tolerance stack up becomes?
Is the deck taller than spec? Are stock original pistons shorter than spec? Is the head chamber oversized compared to what is called for?

 

[Dale Davies]

Well I didn't say what I did, to take away from the OP and his project, as much as a real world "how my build went" to (maybe) give him an idea what to expect.
Or what to stay away from, as the case might be.
I still do have thoughts of adding a home brew turbo "just because".
I have my engine in and running/ but have yet to drive it but compared to "before" I don't see any way it could be worse than what I started with.
As things have it, some parts found me that I wasn't looking for, and now my build is changing, I am doing what I said I wouldn't, to a point. I've grown tired of the BS about "dump the 727 and (in my opinion/experience) downgrade to a 904". Well the 727 is coming out but the truck is growing a 3rd pedal. Yeah my /6 is in a D150. That will never see a dragstrip. Not an A body. So my needs, expectations certainly may not be your expectations out of your engine.
I was hoping that with all the block deck and head face machining would have gotten me closer to 9:1 CR, it's definitely much better than it ever could have been if I would have just been happy with "just shave it enough to square up the gasket surfaces". When he told me he was "done" and my stuff was ready to go pick up, I asked about the machining of the block, and he said "it only took 6-thou to clean up". Well I had told him from the get go that I wanted at least 30 taken off so he had to put it back into the mill and shave it again.....
And the same guy who twisted my arm and convinced me to take the 8330 OD off his hands, also has said on here more than once that many "stock replacement" pistons are intentionally made"short" to make up for the chance that the CR might just increase slightly because of an overbore, when in actuality that difference would be quite slight to begin with.

My question becomes with the comments above about deck height being commonly "findable" info for a machine shop, and Chrysler engines being so notorious for action CR coming up way short of "advertised" where the tolerance stack up becomes?
Is the deck taller than spec? Are stock original pistons shorter than spec? Is the head chamber oversized compared to what is called for?

A machine shop has or should have a caliper big enough to measure from the near side of the main bore to the deck surface. Add half the bearing bore diameter to get deck height. Factory has the specs on what it should be. This will tell if and by how much the deck has already been cut.
Well known that the slant engine deck height is quite a bit below the deck. Another engine known for a low deck height is the Buick 3.8l V6 engines, like 0.080" to 0.100". Very poor for quench and efficient combustion. That is the way the factories designed them.
What could a slant achieve for fuel economy with quench and 10:1 CR and port fuel injection? 25+ I would venture.

 

[Charrlie_S]

I do believe you missed your flight. My point was piston CD and piston availability to get the CR up for street, not racing. A well built and tuned 225 should perform well and get good fuel economy.

My point is/was there are easier/cheaper ways to increase CR on a slant than swapping pistons and rods. Just mill the deck and/or head. Close to 11-1 can be obtained with No special parts.

A well built and tuned 225 should perform well and get good fuel economy.

Agreed. Even a well built 170. I have a 64 Valiant (strictly street)170 9.5 CR mild MP cam, high flow exhaust (stock manifolds). Holley 1 bbl carb, HEI ign with a recurved dist. 3.23 rear, 3spd stick. It will smoke the tires, and gets upper 20's mpg. I actually have a little too much CR for the mild cam used. Need mid to high octane gas. Should have a little more cam or a little less compression. Tuning was a bear.

 

[Slugfarm]

I have to say I've been really enjoying the discussion going on in this thread. I wasn't really sure what to expect when I posted up asking for advice but the replies have been great. I'm no mechanic (I'm more of a driver but am putting feelers out locally for somebody to learn from) so a lot of this stuff is way over my head, but I do know how to learn so I've been hitting the Slant6 Forum and Google to help me decode what y'all are talking about. Regarding my engine, it's a rebuilt mid 70's with a bigger cam (I still don't know if it's been degreed but I think so given the rep of my mechanic) with about 1000 miles on it. The head was milled about .1 but it hasn't been ported. I'm pretty sure the pistons, rods and stuff are all stock. I'm taking it in to the shop next week and they're going to give it a look over, fix some electical stuff, and among other things install a rebuilt distributor I got from @halifaxhops that I'm hopeful will improve response time and acceleration. Given what I've been learning here I think my most accessable path right now is to head up the freeway to Wildcat Auto and pick up a new head that I can hopefully find someone to show me how to port out, and get some larger valves. This car is my daily driver and I don't want to lose it for weeks or months while the work gets done on the head that's in it, since I'll probably be relying on the mechanic to do the teardown and buildup. Second step when the money comes in probably should be pistons, rods and rings, right? And some day, when my ship really comes in, a Torquestorm and a rear end to go with it. Hell, a guy can dream....

 

[273]

I have to say I've been really enjoying the discussion going on in this thread. I wasn't really sure what to expect when I posted up asking for advice but the replies have been great. I'm no mechanic (I'm more of a driver but am putting feelers out locally for somebody to learn from) so a lot of this stuff is way over my head, but I do know how to learn so I've been hitting the Slant6 Forum and Google to help me decode what y'all are talking about. Regarding my engine, it's a rebuilt mid 70's with a bigger cam (I still don't know if it's been degreed but I think so given the rep of my mechanic) with about 1000 miles on it. The head was milled about .1 but it hasn't been ported. I'm pretty sure the pistons, rods and stuff are all stock. I'm taking it in to the shop next week and they're going to give it a look over, fix some electical stuff, and among other things install a rebuilt distributor I got from @halifaxhops that I'm hopeful will improve response time and acceleration. Given what I've been learning here I think my most accessable path right now is to head up the freeway to Wildcat Auto and pick up a new head that I can hopefully find someone to show me how to port out, and get some larger valves. This car is my daily driver and I don't want to lose it for weeks or months while the work gets done on the head that's in it, since I'll probably be relying on the mechanic to do the teardown and buildup. Second step when the money comes in probably should be pistons, rods and rings, right? And some day, when my ship really comes in, a Torquestorm and a rear end to go with it. Hell, a guy can dream....

I'd start with tuning, carb and timing and timing curve make sure your get everything it's got now.
Then yes pick another head have fully done port milled valves etc.. and have the have the piston height volume checked while it's a part but unless cr not crazy low I wouldn't overly worry about piston/block milling, porting gonna give most of the power upgrade rest seems decently done.

Cr is importing but spending huge sums of money to gain a 1/2 to full point of cr is questionable that's like 2-3% power gain, now if you need a couple of points it's more worth it, but still a big investment to rebuild a good engine for a little extra power. I'd probably live with it until it needs a rebuild. if it's too low.

 

[Dartsun]

You don’t need to goto wildcat for a slant head. You can get one local, they are still at the wrecking yards. I’m local if you want some help.

 

[Slantsix64]

Nitrous it