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Discussion Starter #1 (Edited)
Hello to all,
I'm a new member to the site. i have a 69 Cougar with a 351W, fat cam,Edelbrock dual quad manifold,0.30 over bore, aftermarkek Aluminum heads. Heres the question, I would like to end up with a 351 stroker, reusing the heads and intake (they are very low miles less than 2000). I would either build using existing block or purchase new block. I have been told by some that the heads are not a good fit, and others they are. Here are the specifications on the heads I am using are the following;
1.94" intake, 1.54"exhaust stainless swirl polished valves 180cc intake runners 58cc chambers Hi Performance springs (.550 lift hyd roller)
Thanks
 

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It all depends on what you expect form the engine when you're done. Your heads are fine for a stroker - but not to very high RPM. It's all relative. State your goals, and be as specific as possible.

David
 

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Discussion Starter #3
Hello David,
The car is a strickly street car, I don't really see the car doing anything radical, My day of heavy hot roddin our past. Take it to car shows & the local drive-ins. hope this helps.
 

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Alright, so if I can interpret correctly, you want what you have, but a bit more 'push' when you hit the go pedal. When the stoplight goes green, you want to squirt across the intersection, but not much farther. You want to pass cars on the highway by just thinking it - not by having to mash the pedal.

If all that is a good description, then build your stroker and use the heads you have. The effect is that the stroker will use the capacity of the heads at a lower RPM than a smaller engine would. This may be what you're looking for. Snappy, tons of power, but only limited use and RPM. Similar to a warmed-over version of a factory big block.

My '69 Cougar convertible has a similar setup as a strong streeter or 'power cruiser'. It uses a 351W stroked to 427, TFS TW 170 heads that flow about like AFR 185s, and a mild cam (for a stroker) that has a mild but noticeable idle. It idles at 750 to 800, and though it can run hard to over 6000, I rarely take it over 5500. Tell me if that's what you're thinking or something else.

David
 

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Yes thats exactly what I'm thinking, did you dod the build yourself, or have it built. who did you use for a supplier of parts
 

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I do my own planning and building. Parts come from all over to be suitable for the specific build. Some recip assembly kits are OK for the basic short block, but many include the sexy part of the month rather than what you're really after, and a build for a power cruiser is different than for a 600hp track car. That said, there are options for picking parts, buying semi-kits, and full crate short blocks. Your budget, time, and skills will govern that choice.

David
 

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Discussion Starter #7
I agree, the motor thats in now, was a mild build. I also did the planning/build, and did not go the kit route. Being that this will be my first stroker, I want make sure it's right the first time. Thanks for your input.

Russell
 

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built about a hundred of these windsors over the years... the 408 is a great combo... square motor 4inch bore by 4 inch stroke makes 400 plus .030 bore is 408... anything bigger wears faster because of piston load in my opinion... big heads build horsepower... stroke builds torque which is what moves a object....
 

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David: what stroke/bore combination did you use for your 427 short block and are you completely happy with it? Is it a stock block or aftermarket? I'm going the same route and can't decide whether to go bore over stroke or stroke over bore. Options are: 1. 4.040 bore and 4.10 stroke , 2. 4.040 bore and 4.17 stroke, 3. 4.60 bore and 4.10 stroke. I can go 4.30 or even 4.020 also as my block has never been bored and has little taper. I just want to pick the right combination that will survive street use and a little track time as well.
 

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David: what stroke/bore combination did you use for your 427 short block and are you completely happy with it?
Totally happy with it. I did careful planning to get the result I wanted, and it fit very well. Not that other options wouldn't have worked similarly, but it fit my vision. I used 4.04 bore (2nd-build stock block) and 4.17 stroke. I already had some ultralight Llemmon cap-screw rods (cap-screw rods have less clearancing, but more importantly have few cam clearance issues with typical street cams), and they plugged right-in with some shelf SRP dish pistons. 10.6:1 with 61cc chambers and it's a mule. Don't let anybody razz you about rod/stroke ratio - it's not a bleeding-edge engine, and there are millions of factory engines with worse R/S ratio that have gone millions of miles. That is backed-up by the reality that with 10s of thousands of these things built, and how they are typically used, I don't know a human that has actually worn one out. A solid 393 or 408 would probably do about as well, but I like the '27s grunt. It was that or a turbo 255ci with the same power. Old school won this time.
Is it a stock block or aftermarket?
Stock early '70s block. Any year 351W block will do. No need to be picky about that part. Remember what it's purpose is. Pick a block. Do a visual for core shift. Do a quick check for cracks and dimensions for ordering parts. Clean it up, but don't tank or boil the block or machining until you're done clearancing for the stroke and 90% of your blueprinting, because you'll just have to clean it again anyway. A cheap steel crank is plenty for a street app under 6500 - especially if light/ultralight parts are used. Take it in for tanking, bore, squaring and zero-decking (or whatever you planned), build it carefully and drive happy.

David
 

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Thanks David, your combination is the one I was leaning toward. I want the low end torque as well. My block is a very sound '95 roller and it will receive the full-on machining and prep package as you mentioned. What length rods did you use? I am already leaning toward Scat or Probe H beams with cap screws. My heads are are Dart Pro-1's, 195 cc intake runners, 61 cc combustion chambers. What did your block deck height come out to after milling and what is your piston deck height? I like to get as close to 0 piston deck height as I can. What is the volume of your piston dishes? Guess I'm trying to replicate your lower end build, if you don't mind. No sense in trying to figure it out on my own if someone else has already done it!

Thanks!
 

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I checked my build notes, and here's what I used on that engine and how I got it:

  • Cast steel 4.170" stroke crankshaft - checked for straight and index - minor knifing
  • 6.125" ultralight I-beam cap-screw rods @ 557 grams matched to .5 gram (Probe has a very similar rod #10667)
  • SRS 12360 pistons (1.280" CH, 22cc dish, 4.040" bore) 545g matched w/pin and rings to .5 gram
  • Hastings 2M5523 plasma-moly rings (1/16" torsion high-tensile iron, 1/16" reverse torsion, 3/16" flex-vent std tension oil)
  • Bore finish 4-step with torque plate (hone 100g, 280g, 500g, 320g brush finish)
  • Decked .011" to square & zero deck
  • Balanced assy (pulley to flywheel) to 1.5 gram, no added weight
I did it for the use - efficient power with reliable long life. There are plenty of other choices you could make, but that's what I used to finish the package. I show 116 hours for this build (that's everything - planning, ordering, blueprinting every last part, multiple mock-ups, head work, spring changes, etc.) So, although a relatively inexpensive build, I did everything with the same attention to detail as a pro-level engine because that's just how I work, and I don't have surprises that way. My philosophy is if you build it like medical equipment, it will perform 1st time, every time, for a long time, compared to... a tool from Harbor Fright. It's just my time, and I enjoy it. Some call me anal. That's fine.

My personal opinion - I avoid heavy parts whenever possible. This build has no need for killer rods, and especially sexy H-beams that weigh about 1/4 pound more per rod. In reality, H-beams have rather few applications, and usually only ones that require extreme tensile or compressive strength. We don't have that issue here, and you will generally have higher actual strength and durability with the lightest parts you can use, as the strength to weight ratio is better. Using stronger rods means heavier, and heavier means more stress on the crank, so that needs to be stronger to take it, etc. It gets to be a losing battle if you're not careful. I love ultralight. Think of them as aluminum rods that don't stretch or grow. ;)

Calculating your parts is actually easy. To determine for zero deck, measure your block for deck. Let's say it's 9.500" to make it easy.
9.5 - 1/2 stroke - rod = compression height. So, my combo is 9.5 - 2.085 - 6.125 = 1.290. If you can square the block to 9.490" (and most can), then you are at zero deck with a 1.280 piston. Yes, you could run longer rods, but remember what you're building. With a 6.250" rod, your piston only has 1.155" CH. That means less stability, greater chance for 2nd ring flutter, or the oil rings will go thorough the wrist pin hole if you space the rings apart, or the top land will get scary thin if you space them up. Not good compromises for a long-life engine - or even a power package for that matter. The gains in R/S ratio are lost in off-temp ring sealing or gained back by adding 1 psi to your tires. Not worth it - in my opinion. Same reasoning for opting-out of low-tension oil rings on this street engine.

BTW - there is no fear of using an early short-deck block or if you have to cut more to square your roller block. That's what gasket selection is for. I have a set of .050" head gaskets just for that, so I can use the short 9.480" '69 block I have and still get the same quench as a later block. HTH

David
 

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Thanks again David, I'm going to take note of all of this and incorporate it into my build. I'd actually rather use I beam rods. They only reason I mentioned H beams was I was under the impression that they offered more stroke clearance. If that is not the case, then I will opt for the less expensive, lighter I beams.

As regards the block, I already purchased a later model so I could use a roller cam without having to use a thin cam conversion. I will use the formula you showed to arrive at my deck height, it should be close enough. I like a 0 deck height so I can set my quench with the head gasket. I have been doing this for years on Harley engines as well as my current 351w in my Mustang. Thus I can use more CR with less detonation. How's your motor run on pump gas there at sea level?

What brand crank are you using and what brands for this type of application do you recommend?
 

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It's very happy with anybody's 91 octane at optimum timing. My particular combo uses 111° LSA with the short timing for really snappy low-end without det. The dynamic cranking compression is scary at 205 psig - and the engine loves it. One of the quickest revving strokers around. If you run a hotter cam (remember what you're building), then you may need to bump the static CR if a tighter LSA can't get it. Yes, I've run it on 87 octane, with a noticeable tendency to det at throttle tip-in, so the compression and cam combo is dialed perfect for premium, but usable with a couple degrees softening in the initial timing curve for interstate cruising with 87. Always build to your fuel.

The crank was a try-out from a buddy that pulled a pallet of offshore cranks in for testing. Something like $200 cranks a few years ago. If you find a cast steel 4.170 crank it will probably be the same crank, no matter who is selling it, as the prime sources are usually the same. Since we didn't know what these things would do, I changed springs and ran it up. "If it's gonna blow - I wanna know", so I hit something like 7200 RPM with it and called it good for this purpose.

While we're here; a couple tips for stroker building - you will (of course) clearance everything, but your main focus above standard builds will be the rods and crank throws and weights. The slick way to do the rod clearance without machining the block first is to use rod centering springs. You don't want to do all that pretty machining and finishing, just to throw razor needles from your carbide cutters to embed into your pistons and bearings, or scratch-up the fresh finish.

So, go to the hardware with your calipers and find a spring that fits your piston pin bore and is about 4" long. You use the new crank and a couple rods with a couple of these springs for clearancing one throw at a time. The springs will hold the pin end perfectly centered in the bore as you rotate the crank on a set of old bearings to clearance. Just grind and chew as necessary. Minimal work at exactly the right place for just the right clearance for your exact parts, and faster than any other method I know. Couldn't be easier. Funny, because that's often the scariest part for a first-time stroker, but one of the easiest jobs in the build.

Same with the cam - just slip it in, and spin it with the rods at minimum clearance to check that all is OK. If you have any interference, then you'll have to set-up your degree wheel and timing set to verify you have clearance at proper cam timing. You usually wont have to go that far on a street cam with cap-screw rods.

You won't forget the clearance at your oil pump pad. ;) But, expect to do several partial mock-ups as you go to verify everything, such as the crank weights to the piston pads after final machining. It gets really tight there, and you can expect a touch of crank weight edge cleanup.

David

Hard to see in this angle, but here is the 4.170" crank with the SRS pistons at BDC:

When I came-up with the idea to use these, it totally changed how I build strokers. While I may not be the only one using them in the last couple decades, I haven't heard of many besides folks I've told. Spread the cheer:

 

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Great information David, I was wondering how to mock up the rotating assembly before boring the cylinders. Sounds pretty easy. The cam won't be too radical but larger than what you are running. Lifts around .544/.565, duration's around .231/.235 @ .050, LSA is 110, I believe. This is a Howard's off the shelf grind. I my go with a Cam Research custom grid as well, haven't decided yet.

As regards the crank, Coast High Performance sells the whole Probe rotating assembly including SRP pistons, light weight forged I beam rods and a cast steel crank, rings and bearings for a pretty dang good price, so maybe that's the simple answer!
 
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