The newest "building a slant six" thread

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Cruisingram

Cruisingram

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Not looking for serious HP here, low end torque is a very good thing, probably will never see the north side of 4k, and even then only when passing on Saddle road. I got a two barrel manifold coming, have a 38 Weber. got a 225 /6 that is bone stock. I will have to look at what year again to remember, early 70s I think, could be older. I just want to do the old tried and true thing- intake manifold, exhaust, cam. I don't want to grind on heads, put a lot of money into building the snot out of this thing. The 225 replacing the 170 alone will help a lot! I have an auto transmission and it is going into my wife's 68 Dart four door. The main mods to the car will be this motor, AC and good brakes. After that, it is done and ready just for transportation in style around the island. So I am just looking for a good slam it in and go cam, and if it is worth it to buy some headers or go with the Rustyratrod just open up the stock manifold and go 2-1/4 exhaust. Looking through all the cam discussion really didn't answer my question on my particular build.
 
The exhaust mannyfold I have on the car now is the one Freddie opened to 2.5". It has the 2.5" TTI exhaust on it as well. The 2 1/4" mannyfold is on the 170 still.
 
Oh, thanks for clarifying. So I can open up my stock exhaust manifold to 2.5? I am looking at headers, and I have that old Slant six power book, I think we all know about that one right? It has a set of headers and a 4 barrel on it, and I believe in that book they put an "RV cam" in it LOL Not super interested in buying 400 buck and up headers, seems to be a few offered in the under 200 range though.
 
Cruisingram said:
Oh, thanks for clarifying. So I can open up my stock exhaust manifold to 2.5? I am looking at headers, and I have that old Slant six power book, I think we all know about that one right? It has a set of headers and a 4 barrel on it, and I believe in that book they put an "RV cam" in it LOL
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You should get Doug Dutra's new book too. Really no new info in it, but there's a lot of good stuff all in one place.
 
Cruisingram said:
Not looking for serious HP here, low end torque is a very good thing, probably will never see the north side of 4k, and even then only when passing on Saddle road. I got a two barrel manifold coming, have a 38 Weber. got a 225 /6 that is bone stock. I will have to look at what year again to remember, early 70s I think, could be older. I just want to do the old tried and true thing- intake manifold, exhaust, cam. I don't want to grind on heads, put a lot of money into building the snot out of this thing. The 225 replacing the 170 alone will help a lot! I have an auto transmission and it is going into my wife's 68 Dart four door. The main mods to the car will be this motor, AC and good brakes. After that, it is done and ready just for transportation in style around the island. So I am just looking for a good slam it in and go cam, and if it is worth it to buy some headers or go with the Rustyratrod just open up the stock manifold and go 2-1/4 exhaust. Looking through all the cam discussion really didn't answer my question on my particular build.
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You said you ‘don’t want to grind the head’ does that mean you don’t want to do any porting or you don’t want to have the head / block cut to raise compression? For a low rpm street motor the stock valves and ports are fine, but every slant can use a bump up on compression.
When you rebuild your slant it is not likely that you will be able to find a replacement stock metal head gaskets. The typical FM composite slant head gaskets have a compressed thickness of around .036 so you are loosing compression right out of the box when you rebuild a slant.
Measure piston recession, cc the combustion chamber and use an online compression calculator to help you get to the target.
Getting the static compression up to 8.5 to 1 is the best way to increase low end torque.
Perhaps the second best thing to do to increase low end torque is to re curve the distributor. Bringing in the mechanical advance sooner can do wonders for a torque curve.
 
If I were building for what you want to do. I would get the compression up to about 8.5 to 1 (actual measured), as the first thing. In general, everything you mention doing, will hurt low end torque, if you don't raise the compression. Within limits there is no downside to raising compression, and is the "best bang for the buck".
 
You are going to get a lot of opinions but the things mentioned in posts 7 & 8 are good basic things to do. Both of these guys have many years of /6 racing and driving experience.

There was a slant 6 dyno article in Hot Rod mag a few years ago. Number one power adder was a bigger carb. Your Weber is right on.

Opening/enlarging the exhaust is also very good. You will feel the timing changes that John mentions in #7.

Is there even a single machine shop on your island? Milling the head. 080-.100 is a good thing. Charrlie told me about 5 yrs ago there is no downside.

Once you get your basic plan, consider contacting Oregon Cam for recommendations. They can regrind your stock cam. (lift in 1968 was .395)
 
Rob, did the hogged out mani really pep it up or was it installed in conjunction with the 2.5 head pipe? Curious to what just the 2.25 super six head pipe on a bone stock 1.9x ish outlet would accomplish on a stock build. Only thing I'd do is an Oregon cam ground to "RV" torque specs along with that carb and maybe a 2.93 or 3.x rear.
 
Shoots, I was going with bolt on hoping not to have to remove the head, but it sounds too important to miss! So I am going to end up with a composite gasket, so what's the consensus if how much I should take off without having to do a lot of tdc finding and cc'ing? I would like to take head off, take to shop, have it decked, take home slam together with can
 
Take .080 off and slam it together. The rockers can take .100. TDC is not affected. Everything will drop ~.100 but should not affect anything. Quote us the price your paying for that mill job.
 
I took 0.030 off my 225 and still wound up with the pistons at .180 in the hole. Am gonna be shaving the head too. Not yet sure how much, 0.060 is looking like the number at the moment though.
 
I would say start by advancing the timing as much as it will take. I would also hog out the mani like RRR posted. And port match it as much as possible on the manifold side maybe? That might not matter much considering.
 
pishta said:
Rob, did the hogged out mani really pep it up or was it installed in conjunction with the 2.5 head pipe? Curious to what just the 2.25 super six head pipe on a bone stock 1.9x ish outlet would accomplish on a stock build. Only thing I'd do is an Oregon cam ground to "RV" torque specs along with that carb and maybe a 2.93 or 3.x rear.
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It made a noticeable differrence with the 170 and I retained the stock size pipe.
 
pishta said:
Take .080 off and slam it together. The rockers can take .100. TDC is not affected. Everything will drop ~.100 but should not affect anything. Quote us the price your paying for that mill job.
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The head I'm running right now was whacked .155" and I used the stock pushods.
 
Cruisingram said:
Shoots, I was going with bolt on hoping not to have to remove the head, but it sounds too important to miss! So I am going to end up with a composite gasket, so what's the consensus if how much I should take off without having to do a lot of tdc finding and cc'ing? I would like to take head off, take to shop, have it decked, take home slam together with can
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While you have the head off, I would have the MS clean up the valve seats, maybe do a minor bowl clean up and definitely put new valve stem seals in.
 
pishta said:
Take .080 off and slam it together. The rockers can take .100. TDC is not affected. Everything will drop ~.100 but should not affect anything. Quote us the price your paying for that mill job.
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That's what I did. .080 cost me $80 by a very good machinist. Replacement head gaskets are about .040 and original steel are about .020 so down on compression without doing anything.
Valve job, hardened exhaust seats, I did some pocket porting. A little porting on the intake and exhaust manifolds, gasket matched, bigger exhaust. Still looks bone stock and runs on 87 octane.
Little inexpensive things that add up.
 
Okay, soon as this thing on the engine stand, I am removing the head and taking it to the machine shop. Who has the best link to the best cam they think would be best for this motor again? Oregon cams I have heard?
 
Cruisingram said:
Okay, soon as this thing on the engine stand, I am removing the head and taking it to the machine shop. Who has the best link to the best cam they think would be best for this motor again? Oregon cams I have heard?
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You are doing a daily driver, low rpm motor, so just stay with the stock cam.
More duration will simply move the HP and TQ peak higher and cost you low rpm torque and low rpm HP.
It is very important to keep track of the lifters and get them back in the same holes. Do change out the timing chain.
Use the money saved by keeping the cam on: recurving the distributor, HEI ignition upgrade and a good coil and sparkplug wires.
 
I know nothing about slants except my uncle had one in a 71 Duster work car back in the early 80s:)
 
my68barracuda said:
You are doing a daily driver, low rpm motor, so just stay with the stock cam.
More duration will simply move the HP and TQ peak higher and cost you low rpm torque and low rpm HP.
It is very important to keep track of the lifters and get them back in the same holes. Do change out the timing chain.
Use the money saved by keeping the cam on: recurving the distributor, HEI ignition upgrade and a good coil and sparkplug wires.
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Thanks for that- I want it to be a hydraulic camshaft and not a solid camshaft like I have in the 170. I have the motor in the garage and have not even looked as to what year it is yet, though I know it's pre-1970.
 
Cruisingram said:
Thanks for that- I want it to be a hydraulic camshaft and not a solid camshaft like I have in the 170. I have the motor in the garage and have not even looked as to what year it is yet, though I know it's pre-1970.
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How do You know it's a pre-'70 if You don't know the year? You need to clean the pad off at the pass.frt.deck surface adjacent to the alt bracket, & get the stampings written down.
If indeed that is an earlier than '70, the factory cam is tiny! I have Dynosim modeled the OCG 2106R against the OE cams. & the "penalty" of the 2106R is really only below 1500rpm, from there it is all the OCG unit, peak hp at 3500-4K & a ton more in the 4-5K range. Hardly "hot street" territory, & really should idle fine.
 
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