Opinion on Clifford mods for Slant 6 motors

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Dave Haertel

Dave Haertel

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Ok, so I'm considering a 74 Dart with an original 225 and 904. This appeals to me because I think this could be a really fun project to go from the ground up. Motor is seized as it was stored with no intake or exhaust manifold for years. Car is going to have to be trailered to even get to me. In the end I believe that the motor is rebuildable.

Clifford says that with the following things I can end up with over 400 foot pounds of torque and 325 HP.

> mill .110 off the cylinder head, port & polish the cylinder head and polish the tops of the valves.
> Install our 270 mechanical cam, springs, retainers and valve locks.
> Bolt on our Weber Twin kit with headers and you will have a minimum of 320 ft lb. of torque.
> Go with .060 pistons and our 270 mechanical cam, you could end up with 400 ft lb. of torque and 325 hp, but we have to use Chrome rings or you will no seal

So their Weber twin kit is basically a dual 2 bbl carb setup and they have headers that'll hook to 2.25" pipes out the back/sides.

So, the million dollar question is, does anybody have experience with Clifford and are their claims mostly accurate? Or is this a big marketing thing and you can get improved performance but nowhere near the numbers they're suggesting?

They're talking around 3 grand without any crank or piston/cylinder work just to get this far, so obviously this could easily be a 5,000 dollar or more motor to get there, but if it does get there, it's a numbers matching slant 6 car that could really perform well.

Thoughts? Advice?
 
Numbers will vary.What I will say you can have a very good running Slant for 5 grand.But don't forget a total package that includes a converter,tranny work and a rear set up to handle the extra horses.
There are some good running Slants on this board.
 
Darter6 said:
Numbers will vary.What I will say you can have a very good running Slant for 5 grand.But don't forget a total package that includes a converter,tranny work and a rear set up to handle the extra horses.
There are some good running Slants on this board.
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Thanks, any suggestions for the rest of the power train? I was thinking the 904 could probably be built up at the same time if I pull the motor and tranny together. I could then look for an 8 1/4 to go on the back, new drive shaft/yoke. Would you suggest another tranny? Being that it was original, I was thinking it would be nice to have original motor and trans in the car. Not that this is a highly value or highly sought after car but it appeals to me to have the original stuff, even if it's modded.
 
No way... not even close. I built something similar in my Yellow Duster without using Clifford items.

I would say it was between 200-225 hp. Milled the head, Megasquirt TBI, cast iron exhaust manifold, Erson 270 cam, 3.73 Gears, home port job. Best time was high 15's, driver skill could be improved.

My suggestion is to home rebuild the bottom end, get the heads gone through (Mill, Seats, 3 Angle). Purchase the Aussie Hurricane intake manifold, Oregon Cam Grinders (Regrind), and only purchase Clifford Headers.

Results will vary.
 
Boedighw said:
No way... not even close. I built something similar in my Yellow Duster without using Clifford items.

I would say it was between 200-225 hp. Milled the head, Megasquirt TBI, cast iron exhaust manifold, Erson 270 cam, 3.73 Gears, home port job. Best time was high 15's, driver skill could be improved.

My suggestion is to home rebuild the bottom end, get the heads gone through (Mill, Seats, 3 Angle). Purchase the Aussie Hurricane intake manifold, Oregon Cam Grinders (Regrind), and only purchase Clifford Headers.

Results will vary.
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I was afraid a good bit of it was marketing. If I go your suggested route and just their headers, where do you think it could get torque and HP wise? Or is that what you're saying gets 200-225?
 
They tranny freshened look at spending $600 to $1000 (Depends on your area) The 904 is a stout tranny. A good converter another $600 or so.The rear is again what the price is in your location and gear ratio depends on the terrain you drive in your area.Local roads,hilly,or open highway.
All this also depends on how much of the work you will be doing yourself.
 
Darter6 said:
They tranny freshened look at spending $600 to $1000 (Depends on your area) The 904 is a stout tranny. A good converter another $600 or so.The rear is again what the price is in your location and gear ratio depends on the terrain you drive in your area.Local roads,hilly,or open highway.
All this also depends on how much of the work you will be doing yourself.
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Part of the allure of this possible project is that it's not very expensive and I'm looking to go through something from top to bottom, so I would say almost everything with the exception of actually rebuilding the trans I would at least try to do myself. I've been told that the 904 though is actually the easiest to rebuild so who knows, I may actually even give that a shot, worst case scenario, I box it up and truck it down to a transmission shop and say here you go!
 
There are a few articles out there, Hot Rod did one of them showing a real recipe for 300hp out of a slant 6, dyno tested.
 
My first build netted me 158 rear wheel HP. That was mild head work with a.100 shave.Comp cam @.425 lift. Clifford intake,Edelbrock 500 CFM carb, headers,2/12'' single exhaust ,stock bottom end and 3.73 gears in a 67 Dart. The dyno operator took a guess at about 210 HP at the crank.
 
I would take a look at slantsix.org and see what some of the really knowledgeable slanters have done and recommend and do lots of reading. What are your goals for the car? Drag race, road racing, nice peppy driver, street and strip, occasional strip? Whatever your plans are, be sure to do some measuring after taking the head off and before disassembling the block like how far down in the hole are the pistons? What is the combustion chamber volume? That info will help you decide on how much to deck the block and/or Mill the head for increased compression. As they will tell you at .org the head is the biggest bottleneck on making power in a slant.

You can certainly do better than buying Clifford’s high price stuff as someone else has mentioned. Ask @slantsixdan about Clifford sometime!

I’m personally doing a beefed up slant in my wagon - blocked bored 30 over and the deck cut 90 thou with the head cut another 10 thou. Will be using a single 4 barrel or possibly a FiTech FI with a set of long discontinued Clifford Early A long tube headers designed to work with PS. With the cam I selected with the help of the guys over at .org I should have about 10 to 1 C.R. and a Dynamic C.R. of about 8 to 1.
 
65 Dartman said:
I would take a look at slantsix.org and see what some of the really knowledgeable slanters have done and recommend and do lots of reading. What are your goals for the car? Drag race, road racing, nice peppy driver, street and strip, occasional strip? Whatever your plans are, be sure to do some measuring after taking the head off and before disassembling the block like how far down in the hole are the pistons? What is the combustion chamber volume? That info will help you decide on how much to deck the block and/or Mill the head for increased compression. As they will tell you at .org the head is the biggest bottleneck on making power in a slant.

You can certainly do better than buying Clifford’s high price stuff as someone else has mentioned. Ask @slantsixdan about Clifford sometime!

I’m personally doing a beefed up slant in my wagon - blocked bored 30 over and the deck cut 90 thou with the head cut another 10 thou. Will be using a single 4 barrel or possibly a FiTech FI with a set of long discontinued Clifford Early A long tube headers designed to work with PS. With the cam I selected with the help of the guys over at .org I should have about 10 to 1 C.R. and a Dynamic C.R. of about 8 to 1.
Click to expand...

This will just be a peppy driver for me, so honestly 250 HP would probably suit me just fine but if I'm going to dump some cash into this, I figure I might as well get as much out of it as possible. I'm all for researching, so its all good information and I'll definitely do some digging around. I'm glad I did go ahead and post this because the Clifford stuff did seem like just a bit of hype. And the fact that you can't really find many dyno pulls with the Clifford suggestions makes me even more sketched out about it. They certainly sound awesome and look good, but the proof's in the pudding so to speak.
 
we have a stock re ringed short block ( block milled .120 ), erson cam ( cant remember the spec's ), Ported head, Aussie intake, Clifford header.
it by no means is a race car. I am still working bugs out ( way to low of a stall converter ) and too much carb. it is still a very Fun little ride. has decent Pep, best part for me is it was a father daughter project that got me more 1 on 1 time with my daughter.
 
vitamindart said:
we have a stock re ringed short block ( block milled .120 ), erson cam ( cant remember the spec's ), Ported head, Aussie intake, Clifford header.
it by no means is a race car. I am still working bugs out ( way to low of a stall converter ) and too much carb. it is still a very Fun little ride. has decent Pep, best part for me is it was a father daughter project that got me more 1 on 1 time with my daughter.
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I love the fact that you get to do a father daughter car, mine are still too young but I'm looking forward to that in the future for sure.
 
Honestly if I had a slant and wanted to keep it, it would be turbo time. A smallish turbo will do 320hp all day and be way fun.
 
You'll hear the name "Clifford" come up, but be very careful before you decide to spend any money with Clifford. They have a long and ugly reputation for being a bunch of clowns; see for example here, here, here, here, and here. Much of what they sell is inaccurately described, and a lot of it is not even slightly cost-effective. The good news is that you don't need to go to Clifford to get hot rod parts for slant-6s; there are lots of other, better options. See for example Dutra Duals and header options discussed in this thread and this one, Erson custom cams, HEI ignition upgrade, Mike Jeffreys windage trays, Hurricane intakes, other exotic intakes. Hi-perf engine buildup here, high-perf parts and build info here. (some of these links may be broken while we're waiting for slantsix.org to come back up)

As for Clifford's recipe they sent you, No. Unless the goal is to just funnel money to Clifford, you don't just blindly take some prescribed amount off the head and do other such mods. That way lies sadness, despair, and wasted money. Instead, you measure and figure out where you are with your particular parts—combustion chamber volume varies a lot, for example—and then you do the calculations to figure out exactly where you want to be with the specific (pref non-Clifford/non-Comp) cam you'll run, the gasoline you can get, the altitude you're at, the kind of driving you'll be doing, etc, you talk it over with people who actually know what the eff they're talking about (not just trying to make the cash register ring) and then you have your answer as to how much to mill off the head and/or block.
 
slantsixdan said:
You'll hear the name "Clifford" come up, but be very careful before you decide to spend any money with Clifford. They have a long and ugly reputation for being a bunch of clowns; see for example here, here, here, here, and here. Much of what they sell is inaccurately described, and a lot of it is not even slightly cost-effective. The good news is that you don't need to go to Clifford to get hot rod parts for slant-6s; there are lots of other, better options. See for example Dutra Duals and header options discussed in this thread and this one, Erson custom cams, HEI ignition upgrade, Mike Jeffreys windage trays, Hurricane intakes, other exotic intakes. Hi-perf engine buildup here, high-perf parts and build info here. (some of these links may be broken while we're waiting for slantsix.org to come back up)

As for Clifford's recipe they sent you, No. Unless the goal is to just funnel money to Clifford, you don't just blindly take some prescribed amount off the head and do other such mods. That way lies sadness, despair, and wasted money. Instead, you measure and figure out where you are with your particular parts—combustion chamber volume varies a lot, for example—and then you do the calculations to figure out exactly where you want to be with the specific (pref non-Clifford/non-Comp) cam you'll run, the gasoline you can get, the altitude you're at, the kind of driving you'll be doing, etc, you talk it over with people who actually know what the eff they're talking about (not just trying to make the cash register ring) and then you have your answer as to how much to mill off the head and/or block.
Click to expand...

That’s why I love this forum. I was afraid of just getting hype from them and it appears that’s exactly what I got from them.

All that aside maybe I need to think about things differently, you’ve given a ton of data to digest so it’s going to take a while.

As for the car and my desire for it, this seemed like a chance to do either a resto mod or juicy driver with a numbers matching car that was affordable. Seems now a days a numbers matching rust bucket starts at 20 grand. Again I know this isn’t a hugely rare car but I thought it would be nice to be able to use this as a learning experience as well to start with and end up with something that might retain a little bit of its value.

I’m on the ocean, East coast, do you recommend anyone on this side of the country that could be a guide for this?
 
Best advice I could possibly give: start by defining, in specific detail, exactly what-all you want the car to do (or not-do, or do differently). In terms of real, practical function, not in terms of how many horsepower you think you want it to have (that number is good for bench-racing, and nothing else).

Be sure to factor in that a car that goes faster also needs to steer and stop better, and these cars mostly don't steer or stop well in stock form, so a good chunk of your money-time-effort budget needs to go for stuff like that. A higher-perf engine also requires more in the way of a cooling system, a sturdier transmission and rear axle, etc. Y'might want to see here to get some ideas about accounting for non-engine aspects of your build.
 
slantsixdan said:
Best advice I could possibly give: start by defining, in specific detail, exactly what-all you want the car to do (or not-do, or do differently). In terms of real, practical function, not in terms of how many horsepower you think you want it to have (that number is good for bench-racing, and nothing else).

Be sure to factor in that a car that goes faster also needs to steer and stop better, and these cars mostly don't steer or stop well in stock form, so a good chunk of your money-time-effort budget needs to go for stuff like that. A higher-perf engine also requires more in the way of a cooling system, a sturdier transmission and rear axle, etc. Y'might want to see here to get some ideas about accounting for non-engine aspects of your build.
Click to expand...

Dan hit the nail on the head with this comment.

I will say that I did run the Clifford headers and intake on my slant for a couple of years and they didn’t produce the results I expected. Building a slant for power is awesome but you will not go fast with just bolt ons. In my opinion if you want power then throw a small block in it but if you really want to keep the slant six then you may need to lower your expectations or prepare to spend the money on serious machine work and trick parts along with a powe adder.
 
slantsixdan said:
Best advice I could possibly give: start by defining, in specific detail, exactly what-all you want the car to do (or not-do, or do differently). In terms of real, practical function, not in terms of how many horsepower you think you want it to have (that number is good for bench-racing, and nothing else).

Be sure to factor in that a car that goes faster also needs to steer and stop better, and these cars mostly don't steer or stop well in stock form, so a good chunk of your money-time-effort budget needs to go for stuff like that. A higher-perf engine also requires more in the way of a cooling system, a sturdier transmission and rear axle, etc. Y'might want to see here to get some ideas about accounting for non-engine aspects of your build.
Click to expand...

This is all research at this time, that’s the reason for the post. I’m not sure what to do with the car to be honest. My 71 340 right now is my daily, but this popped up on my radar at 1200 dollars for a solid original with an already good interior.

I’m not worried about the rest of all that extra stuff, suspension and drive train because all of that will depend on what I do with the motor. I don’t anticipate going and buying an original /6 only to swap it out to a v8, I’ve already got a non matching swinger with a v8. The reason that this appeals to me is two fold, 1 the entry price and 2, I could take my time and really learn how to do everything myself for the first time.

I’m not really hung up on the horsepower either, the original idea for the post was opinions on Clifford’s suggested build and their reputation as a company. Obviously that has been answered already that they’re not the direction I need to go but to build this motor I need to know the correct direction so that’ll mean researching the other options.

If this becomes too massive an undertaking then that’s what it is, but having a blank canvas like this to start with is very intriguing.
 
OK, my 2 cents worth, and worth every penny.
You mentioned about an opertunity to learn about doing it yourself. The slant is ideal for this. I have done several slants, both for racing, and for mileage. Building is different for these desires, but there are some mods that work for either/both. So, decide what you want to do. Raising compression is the main mod. How much, is determined by the end goal, as is the cam. As for clifford, the only things I would get, would be headers (for a race car) and/or intake manifold. Everything else is available elsewhere, at a better deal.

Edit: For 1967 and newer "A" bodies, Clifford is not the only source for headers.
For 66 and older, Clifford is the only source, as far as I know, and they do not fit with a 170 engine, or a 225 with power steering.
 
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Dave Haertel said:
This is all research at this time, that’s the reason for the post. I’m not sure what to do with the car to be honest. My 71 340 right now is my daily, but this popped up on my radar at 1200 dollars for a solid original with an already good interior.

I’m not worried about the rest of all that extra stuff, suspension and drive train because all of that will depend on what I do with the motor. I don’t anticipate going and buying an original /6 only to swap it out to a v8, I’ve already got a non matching swinger with a v8. The reason that this appeals to me is two fold, 1 the entry price and 2, I could take my time and really learn how to do everything myself for the first time.

I’m not really hung up on the horsepower either, the original idea for the post was opinions on Clifford’s suggested build and their reputation as a company. Obviously that has been answered already that they’re not the direction I need to go but to build this motor I need to know the correct direction so that’ll mean researching the other options.

If this becomes too massive an undertaking then that’s what it is, but having a blank canvas like this to start with is very intriguing.
Click to expand...

If you just want to use the slant as a learning tool then I think that’s a great idea. Every gear head should tear down a motor and rebuild it at least once in their life and since you already have the slant and drivetrain then there ya go. I’m not to sure how easy it is to find oem replacement parts for those engines though. I know for small blocks it’s very easy to find spare cranks and connecting rods and things like that. It could be easy for the slant six also I just have no knowledge on that.
 
Charrlie_S said:
OK, my 2 cents worth, and worth every penny.
You mentioned about an opertunity to learn about doing it yourself. The slant is ideal for this. I have done several slants, both for racing, and for mileage. Building is different for these desires, but there are some mods that work for either/both. So, decide what you want to do. Raising compression is the main mod. How much, is determined by the end goal, as is the cam. As for clifford, the only things I would get, would be headers (for a race car) and/or intake manifold. Everything else is available elsewhere, at a better deal.
Click to expand...


Thanks Charlie, and I definitely want to tear down and rebuild way more than 1 motor in my lifetime, but this would seem like a solid first one to start with, provided that I can get enough good information on what I'll need to use to get there. If I'm budgeting between 4 and 5 thousand for an engine build, I'd like to get it to the point where it's at least a snappy little engine, I mentioned 300 hp because I've been watching a good bit of YouTube on these and that seems to be the mantle that everyone wants to hit. If it's 250, or more but not 300, I'm fine with that. To that point if I'm nowhere close to 250 that becomes a decision that I have to make. If I wanted to spend crazy money, I know there's a turbo scene for these motors and it could make a good bit more hp than 300 but I don't think that's the direction I want to go with this.

SO, if I was lowering my aim to say 250HP for a fun regular driver, and putting a nice converter and new build in the transmission and a rear that will support the additional HP, what would be your suggestion for this build? I've got someone that would love to do the head work on this so if I can get the rest of the parts in mind, I can start to price it out.

I think in either case, I'd convert everything over to newer on the front end, tubular upper and lower control arms, discs, probably just rebuild the whole thing soup to nuts, kind of like what I did with the 71 that's my daily.
 
[QUOTE="doogievlg, post: 1971883722, member: 5562”] I’m not to sure how easy it is to find oem replacement parts for those engines though. I know for small blocks it’s very easy to find spare cranks and connecting rods and things like that. It could be easy for the slant six also I just have no knowledge on that.[/QUOTE]

I see people on this forum offering complete slant engines or parts all the time for little or no money From their V8 swap
 
Seems like am awful lot spent on a slant to hit 200hp n/a. Its a labour of love and enjoyment for me if i do some refreshing and goodies but i dont expect massive hp returns on my money spent.

A turbo will really be the easiest bet for hp, even a simple draw through with no intercooler
 
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