The 170 is the original slant six. The slant six cylinder head was designed to feed a 170 and then just bolted onto the 225 which is, in effect, just a stroked 170. When it comes to high RPM operation, the valves are sized better for the 170 than the 225, the ports are sized better for the 170 than the 225, the internals are lighter on the 170 than the 225, all of which makes it easier for a 170 motor to spool up to a higher RPM and live healthily at a higher RPM. Yes, a 225 can be built to live happily at high RPM, but it takes a bit more work and money to get it there.

If I were building a high-rpm motor that I was planning on boosting, I would look long and hard at just starting the build with a 170 instead of building up a 225.

Already have all of the valve train ready with 1.7/1.44 bigger valves, and trying to figure-out what I should keep or get rid of from the Comp Cams kit that came with firmer springs. Already have pushrods, but will take the advice posted here and given by Ken at Oregon cams and will get thicker ones. The idea with going with those specific valves is to keep stock geometry and keep clearances along with flow rates at highest efficiency while giving me more lee-way to do crazier stuff to pistons, rods, and the rest of the valve train.

The intention from the start of this thread was to get advice on the largest cam that will work with a ported, polished, and big-valve head, bored/honed block, new pistons, and new rods; and then how such an engine would act on the street from people's personal experience, and what parts they did or not not like from that experience. I got carried away with my first post, so some of that probably got buried down in that.

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1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

"and the whole thing needs to be balanced."

I was getting ready to suggest adding engine oil.

Kenny Rogers comes to mind, "got know when to......"

I'm going off to chase some unicorns, but can't decide on what color of glitter.

You know, I think it was your build along with a bunch of what Lou and DI posted about their own builds that inspired my current obsession.

I think I may need to reconsider the 250+ci and go closer to the recommended 238ci if it kills my top end so much... my initial thought was that if it builds more torque AND you can spin it faster it will make more power, too... but if you can't spin it, then there is no extra power, just torque.

Yeah, the exhaust was just for fun, a single is all that thing needed, but it does sound pretty nice at lower RPM when it cruises.

The .500+" lift is also something I picked-up on here from another racer who suggested (at the time) to not bother with a cam with less lift for serious performance... mind you I'm talking in the 250-300 range for "serious"... it good power for a Slant, and that's all I want right now... also to put stock 340's to shame.

Lou, how are you and your son liking that Erson 280 duration cam in your motor? What does it do on the street? Based on the feedback from CJ above, I think it's pretty safe to assume it's still more than smooth enough by my standards.

I'm not looking for wheel stands, but if I can get that weight down to around 2,800lbs with me in it and get that motor to 270ish hp, I would be happy. With an electronic rev limiter, a line lock for the rear, Ford's TruTrac, and some pre-heated sticky 255's out back, I may get lucky and get to where I need to be, no? Mind you, I don't mind the rear sliding-out a little for fun without the nice smokey burn-out... although those burn-outs sure are fun!
Well, and that was my logic, too. I've seen a few people on here stating that a 750cfm or even an 800cfm gave them more over-all top end and shaved ET's with a wild enough engine build (which is what I'm going for), however I think that the effeciency of a carb at that level is a bit inefficient for practical daily use... hence if I need more carb, I would rather just go EFI for more air, fuel, power, AND MPG.

The Edelbrock 500 is currently on my stock engine with small valves, hence why I need to run it pig rich at lower speeds/engine RPM.... it actually picks-up a bit and I can manually move the choke out a bit once there is more air.

To be fair, the carb on there now is only on there because I wanted headers, and if I'm doing headers, I might as well do a new intake manifold. I'm well aware that it's not currently matched properly, but I will say that I drove the original 110hp beast, and properly matched or not, the pig-rich 140ish-hp beast still seems faster in all respects, especially at highway speeds... yes, Honda Civic-fast.

Am I getting maybe 16 mpg and my exhaust dumping unburnt fuel? Sure! Oh, well, I put less than 1K miles on it in over a year, and it will be matched a heck of a lot better with the built motor, am I right?

The header wrap I soaked in my bathtub for a day, and itched for the following 2 weeks, but hey, perfect header wrap and I got to bolt stuff on an older car back when I had free time, so that was fun. What's the point if you are not having fun?

The fact that I can bolt-on a toe hitch to the back and pull a light U-Haul trailer full of car parts every so often just adds icing to the cake.

_________________
1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

I get the sarcasm, but seriously, lots of people run stock bottom ends... I was just stating that I am not and that my reciprocating mass will be reciprocating quite well and with new cylinder rings doing their job.

It's not the same as bolting a cam into a stock bottom-end with a stock 170 head, expecting something impossible.

For the engine oil, planning to run Mobil 1 as per Dan's advice in another thread. ... already doing that with the stock motor.

I don't get the reaction, though.... yes, I'm planning to build a car most people don't build, and the few that do (and there is a list with times), have been able to accomplish my goals.

I was only looking for advice on what, specifically in terms of the cam; just like how Lou and CJ were able to do without mocking somebody who has done a lot of research, but wanted answers not readily available after tens of hours of reading through these forums... but whatever floats your boat, I guess.

I suppose I just prefer unicorns to people... not so sure that glitter and rainbows will help me lower ET's though.

Additionally, while I'm not sure of the accuracy of this source, if it is correct, the '72 Duster is one of the lightest A-bodies to begin with: http://auto.howstuffworks.com/1970-1976 ... ster13.htm

I also want to point-out that Slantzilla ran a very low 12 with his nos and engine build at 3250 lbs... why is something like a 13 unobtainable with less weight and without the 80-shot of nitrous? I'm not expecting the motor alone to get the job done.

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1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

2500 lb early "A" 170 cid, lots of spray, "DONE", "CHEAP".

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

You are the other bane to my existence on here with your 'early' A-body I could not find for sale at the time, especially for $100 lol.. but hey, next best thing is that '72 in terms of stock weight.

How did that 290 duration .460" lift cam help with your performance? Any regrets by not going with something smaller?

I'm sure I did read about it at one point, but how long did the stock pistons last?

How did your 170 compare to your 225 Signet with the nitrous? IS there replacement for displacement with these engines based on your experience?

What was your best experience in racing with a completely NA setup? Was that setup streetable by your standards?... I define "streetable" as being able to get from point A to point B without stalling or any major organ damage, your opinion may vary.

_________________
1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

I would have to check my notes, but I don't remember that cam.
It depends, on how much spray. I had one motor, that had over 400lbs of nitrous thru it, at about 150 hp shot. Had another motor that had three passes on it. Don't think it was related to the amount of nitrous, as it was the same as I had been running. I think it broke a ring, as I didn't see anything with a bore scope. Haven't taken it apart, yet.
PS: all my motors have had stock pistons. My 170's have run better then my 225's. The 170's have been in a 3250 lb car, while my Signet with the 225 weighs about 2650 lbs. BUT the 170 had a fogger system, while the 225 has a plate. The Signet/225 is just now running a little quicker then the Barracuda/170. My current setup in the Signet/225, in my opinion, is totally streetable (even though the car isn't). It has gone mid 14's NA in the 1/4 mile, and low 9's in the 1/8.
The Barracuda/170, if I remember correctly (been about 15 years since NA) was mid to high 16's in the 1/4.

The biggest problem with the 170 is getting compression(cannot do more then a cleanup cut on the deck), and piston to valve clearance (any cam bigger then about 260-265 adv dur, with a milled head, needs valve notches), the 170 is a zero deck motor

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

The Erson 280 is way too small for what you are trying to do. The Oregon cam I recommended above is substantially larger than that, and you can go bigger if you like and still be streetable.

Make sure you degree the cam at 99-101 installed centerline. You read that right, and I am not kidding. Anyone else installing your cam or doing your motor work should use this for sure, no doubt, no head scratching. It works.

I also advise, if using stock-type ignition, to have DI build a recurved dist for your application. This will save you lots of time dialing in an advance curve.

Happy building,

Lou

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Home of Slant6-powered fun machines since 1988

67-69 "A body would be better

I am running a racer brown ST-21 in my 225 engine. lift .520, and 254 dur at .050 and my last 170 engine had the Mopar performance cam that is very similar.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Racer Brown ST-21 would be a great cam for what you are trying to do. Might want to run 10.5:1 static comp and pump gas premium will be fine with that cam. Degree cam at 100 centerline.

Lou

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Home of Slant6-powered fun machines since 1988

stock rods with polished side beams then grind all to same weight, drill all oiling passages to clean and smooth passages, do doug`s positive oil feed to oil pump/ cam gear modification ,it work to save pump gear, also run in both gears by hand before installing to make sure edges are smooth and not sharp. stock piston with extra clearance will live under all condition except lean or too much timing.

Thanks again guys for all of your AWESOME input!!

I've been a bit busy the last few days, but am I ever glad I remembered to come back on here!!

I'll definitely take all of this advice, as clearly all of this greatly changed my perspective on what can and can't be done on this motor... originally, I even forgot that the 170 WAS the stroked motor, so I was looking to stroke the 225 even more to get to that 250+ ci... would it be worth messing with the forged stock crank for me? Probably not in all honesty.

I'll definitely research more on Doug's method to save my oil gear, in addition to ports I need in the transmission to get fluid away from the clutch packs faster (based on another thread).

I'm going to have Oregon grind a ST-21-type cam based on the specs provided, and yes, will be shooting for 10.5:1 if it still lets me run pump gas... I figure if I ever want to run race gas I just boost the timing a few degrees, right?

@Charrlie_S
I have no idea where I got that 290 duration from then... I think I was trying to do too many things at once and a few wires got crossed... more than usual.

@everybody again
I'm guess I'm now down from my initial 250+ ci idea to a reasonable 232, but I will definitely talk to the engine builder to see if sleeving my iron block is even possible... it would certainly open a world of possibilities if we really can open-up that block that much... if it's even remotely on budget at the time I get around to it.

Also, I'm thinking of running some sort of forged piston and rod along the lines of what is found here: http://www.campbellenterprises.com/slan ... istons.php

Anybody have a good source of either rods or pistons, possibly in a lighter version that can still be solid enough?

Would it make sense going with 198 rods and running 2.2 turbo pistons today with the parts listed above being available?

I guess the real question I should be asking is what have some of you done, or have heard of being done, to make the entire assembly spin faster? I understand that due to the design of the engine it may not produce much more after 6,000 RPM, however surely being able to spin that engine up faster would help keep it in the power band better with an aggressive cam designed to move the power curve up into the RPM range?

Also, is there any point in messing with the forged crank to either add stroke or make it lighter?

Thanks again!

_________________
1972 Plymouth Duster:
- 225ci
- Offy 4-Barrel Intake
- Weber 38/38 DGES
- Clifford headers
- Split 2.25" dual exhaust
- Pertronix digital ignition conversion
- Black-out custom digital gauges
- Front disc brake conversion
- Viper Blue

If I were trying to build a slant that would spool up faster, I would run a 170 or run a 1980s era cast crank motor. The cast crank engines introduced during he 1976 model year had lighter internal components and head. The cranks were lighter and the timing gears were lighter.

If you are trying to keep your original forged crank 225 and make it spin up faster, just get your rotating assembly balanced, run different pistons with thinner rings for reduced drag, run lightweight synthetic oil, and mill the block and head to achieve the dynamic compression ratio you want. There aren't many tricks you can do with a slant six crank beyond balancing, offset grinding the journals, or cutting and rewelding the crank for increased stroke.