302/347 crank-- winter project

[itsaMustangtoo]

I just bought a 347 stroker kit to replace the 302 in my Cobra Clone I have seen some kits in PAW ,but they say you need to use an 83 or later block with a 1 piece seal ?? Are the cranks different or can I use my 2 piece seal block ?? I can get a later block if need be ,but I would prefer the one I have. I am not going to tear it down if it will not work. I have not yet recieved my kit , but what would the difference be?? I also picked up a new pair of aluminum heads and ordered my new comp cam

 

[Blue Thunder]

My 332 is still for sale, and it's fairly powerful.

 

[Dano78]

I'd have to see the cranks side by side to be 100% sure but the older (pre-'80) cranks have a flange just behind where the rear main seal is located. The later cranks may not.

The other thing could be the deck height. The '83 block may have a taller deck height that may better accomodate the addtitonal stroke. I never really deal with any post-'80 blocks to verify if the deck height is taller than the 78-79 blocks or not.

I do know that there are two different kinds of stroker kits out there. One that blows oil and one that doesn't. The main difference in each kit is the rods and pistons. The oil burner kits are the ones that have the oil rings located over the wristpins and using a 5.400 connecting rod. Typically they use Keith Black, Mahle, Probe or JE/SRP Piston. Yeah they mention that they include "ring supports" but you just can't polish a TURD.
The best setup is one that uses a 5.315 connecting rod and prodominately Probe Pistons (they make pistons for both rod lengths) are used. Rumor has it that JE/SRP offers a piston for this rod too, but I have yet to find a part number for them. The difference with this piston/rod combo is that the oil ringland is no longer over wristpin thus eliminating the possibility of oil consumption sometimes found with the longer rod and pistons.
I know you already bought a kit, hopefully the short rod one, but this was more or less 'food for thought' since stroker talk was about.

Best bet is to contact the kit's manufacturer and find out exactly 'why' you would need those particular shortblocks.

 

[Putter]

Keep us posted on what you do find out. Iwould like to do a stroker also, and have a pre 83 block.

 

[Blue Thunder]

I do know that there are two different kinds of stroker kits out there. One that blows oil and one that doesn't. The main difference in each kit is the rods and pistons. The oil burner kits are the ones that have the oil rings located over the wristpins and using a 5.400 connecting rod. Typically they use Keith Black, Mahle, Probe or JE/SRP Piston. Yeah they mention that they include "ring supports" but you just can't polish a TURD.
The best setup is one that uses a 5.315 connecting rod and prodominately Probe Pistons (they make pistons for both rod lengths) are used. Rumor has it that JE/SRP offers a piston for this rod too, but I have yet to find a part number for them.

I don't run the 5.4 rods, I use eagle H-beam 5.5 rods with full floating wrist pins and spiralocks. I run lightweight forged pistons from JE specifically made to run a 5.5 rod with 3.25" stroke and with valve reliefs for the canted valve TFS track-heat heads. The JE pistons are the best combination of strength and weight and use a very effective oil ring support plug for the pin area. I have between 4 and 5 thousand miles on the 332 motor and it has never burned oil at all.
The rod to stroke ratio with a 5.5 rod and 3.25 stroke is 1.69:1, which is identical to the stock 302, and is therefore perfect for the 332 stroker.

A 347 has a 3.4" stroke, which means you can't get a good rod to stroke ratio from it, there's just not enough room. (The 3.4" stroke with 5.315" rods yields only a 1.56:1 ratio) One reason for the oil consumption problem you mentioned is due to such poor rod to stroke ratios, which causes excessive piston to cylinder wall side-load and leads to piston skirt wear and cracking, loss of engine efficiency and ultimately engine failure. (For this reason, I never recommend the 347" combination unless the car is strictly to be used for the strip, where street longevity isnt an issue.)
Even the stock 302 has a fairly low rod to stroke ratio, but Ford engineering found it to be acceptable for street use, so I try to stick with that number as the bare minimum. (The 289 is a slightly more efficent and more durable engine than the 302 for no other reason than its superior rod to stroke ratio. Although the ribbed rod caps help, too.)

It's not the oil ring crossing through the piston pin that causes problems, but rather inferior product quality of most stroker "kits", where the seller is trying to throw together an inexpensive package for the masses.

Lastly, if you want to build any type of stroker, it's important to know that the newer style (late 81 and up) 302 blocks are a *lot* lighter than the older blocks, due to Ford reducing the mass of the webbing in the main bearing support areas. They wanted to save money in the casting process as well as try to lighten the 302, to make the new Fox body cars handle and perform better. Years of various dyno testing and racing the small blocks has revealed that the older blocks can deal with roughly 700 hp before the block splits between the crank and cam and the crankshaft exits through the oilpan. The newer 302 blocks can deal with perhaps 450hp before the same thing happens. (And that's with a stock 3" stroke) A mainstud girdle(a billet STEEL unit, not aluminum) will help eleviate the block weakness, but when investing a lot of cash into a stroker motor, why start with a weaker block?

I would suggest getting the steel stroker crankshaft designed for the older block, complete with the rear oil seal flange, and also running a steel mainstud girdle to hold everything together. An older block with the girdle is pretty well bulletproof. I would also suggest not buying any "kits" unless you can call them and modify the kit specifications, otherwise you're going to get some cheap stuff that won't be anywhere near as durable as a custom selected setup.

 

[itsaMustangtoo]

I know the older blocks are meatier, which is why I wanted to use mine. It does not make good sense to increase displacement and power in a weaker block. The kit I purchased uses the 5.400 " stroke, I beam rods and Kieth black forged pistons. I know the short skirts will slap and longevity is an issue,but my clone does not see the strip and street use is limited. I appreciate the suggestions and help. I will keep you posted. I plan a trip to the dealer and machine shop in my search for the truth. If I cannot use this kit I will probably just punch out my 302 and rebuild it ,topping it off with those alum.heads & new cam.

 

[mines80]

How did you get the 5.5 rods?

Blue Thunder, how did you get the 5.5 rods, where they custom? I want a set, but want a 3.4 crank. Doesnt give me much pin height, I know. But using only in a circle track motor. And trying to locate a early 302 block, Mexican, with a the taller deck height. (8.229) Lemme know about those rods.

 

[Dano78]

First off you'll never find a Mexican 302 block with a 8.229 deck. At least not here in the states. The mexican block was only imported for 1-2 years ('68 & '69) and from my understanding, they were all 8.206 blocks. The '68 Mexi block I have here is an 8.206 deck.

If you want the taller deck block you'll need a '74-'77 302 block. Those are the only 8.229 deck blocks that I've ever seen. In '78 Ford reduced the deck height back to 8.206 from then on out.

If you're running circle track why run so long-armed? Shorter stroke bigger bore would be much better for roundy-round.

 

[mines80]

Mexican blocks

Dano78, no way man. Mexican blocks were used for a while, I know through the seventies, might even find a few in early 80's trucks and vans. Yeah its the big thing about running a short stroke and big bore, I'd love too. But you got to buy a $1500 block to do that. But I think on small tracks, aint that big of a deal. Mostly the big NASCAR tracks. Hoping to go .060" over on a nice Mexican block I found. C8AM-6015-B. Wonder if I can go bigger than that, want to unshroud that valve as much as possible, let her breath! And wonder if using off set dowels to help that too? Never hear of guys using those much anymore. But this is my build idea. Light 3.4 crank, 5.5 rods, .060" flat top pistons (at least) N351 heads with studs, roller cam, 14-1 compression, Victor Sr intake and 750 H.P. carb. Turn it 7400 rpm, need about 600 HP. But want to either get some good steel caps with studs, or a nice billet aluminum girdle from someone, DSS has a nice one. What do you think?

 

[Dano78]

All sounds good but I'm not sure how far you can really take a factory casting as far as overboring. I know aftermarket blocks can go much further. I've only had a couple .060 blocks that I've run, and they did run a little hotter. I fear with your compression and power output expectations heat might be your worst enemy. Staying FAR away from post-'79 blocks would be of good advice too. Those block will not handle the power at all.

A good head/intake/cam choice will more than make up for the lesser gains of a few cubic inches.

 

[mines80]

Are you good with casting numbers? I'm getting a C8AM-6015-B block, hearing some stuff about them and SVO, Holman Moody? I'm pretty sure its a standard bore, might be even all original 1968 block. But it did have 289 heads on it. But I think Ford was putting alot of 302 blocks in cars that had "289's" in them when they got low on 289 blocks in 1968. I may or may not use that much compression and roller cam. Would rather run a flat tappet and 11-1 compression like I am now with my Chevy. But at the track I'm running now, I have to weight as much as a guy with the other combo. And the N351 heads are a good head, 10 degree valve angle. With the right about of valve to piston clearance, I can run a set of pistons without reliefs with those heads. Appreciate the back and forth on this, not too many Ford guy out here, and none that know anything about Mexican block history. Keep in touch.

 

[Dano78]

C8AM-6015-B

C8 -- 1968
A -- Ford (all car lines)
M -- Performance Operations, later known as SVO Service Parts
6015 -- Basic part number for cyl block
B -- Design Change Designation

This is the same casting # I have on my Mexican 302 and is the most typical number I see. There is a D1ZM-6015-AA Mexican Block that I know of but have yet to see one in person.

Supposedly the Mexican 302 has a higher nickle content but that is still left up to debate. However they do sport the larger, thicker main caps just as the Hi-Po 'K' code 289s as well as the extra main webbing. They are also suppose to be a little heavier or at least the same thickness casting as the more desirable pre-'73 302s and 289s. Even if the nickle story is untrue it's still the best for factory casting you can get.

1968 was a crazy year. You could get either a 289 or a 302, like as you said, until the 289 surplus dried up. However, '68 was suppose to be the premier year of the 302. Even after that it was not uncommon to have a 289 casted block with a 302 rotating assembly (casted 2Y on the crank, 1Y for a 289). I've got what some argue to be untrue, two early 6 bolt bellhousing 289s casted- one in Dec of '64 and the other June in '65. Casting numbers don't lie. Poeple will say the 6 bolts didn't exist untill late '65 for the '66 model year. Obviously I have proof otherwise...

With your cam, these days if you can afford roller lifter cams, go that route. The EPA fools have seen it their way to ruin motor oil directly affectin flat tappet camshafts. The EPA has the oil industry remove all remaining zinc and phosperous (sp?) from todays engine oil citing that " newer engines don't require them. What about the old stuff, i say... ? There are additives you can use or there are several aftermarket perf. oils that have the zinc and phospherous in them. Flat tappet cams rely on these ingredients, especially during initial break-in period. I use Brad Penn (the 'Green' oil) which my cam grinder is a retailer for. If you can go roller, I would. Just stay away from factory style dogbone lifter-keeper setups, as these are terrible with high-lift applications causing the dogbones to bind and fail. Comp and Crane are probably your best bet and make a roller retrofit kit that works nice.

Don't know of too many SBFs that would run without valve reliefs. Maybe the '74-'77 blocks with stock style pistons because the pistons are so far down in the bore caused by the increased deck height. I'd be sure to check valve clearance anyways. I was running a .498/.512 cam and had to enlarge the flycuts in my pistons - also due to using larger sbc valves aswell.

 

[Dano78]

Also wanted to add-

If you are serious about going 347ci might I suggest using a 5.315 rod rather than the mainstream 5.400 rod. The reason for this is to relocate the wristpin out of the middle of the oil ring lands. Granted companies claim their 'oil ring supports' remedy the oil ring breakage/leakage issues, i just find it hard to want to chance it in an application such as yours. If you can affor H beam rods, that'd be the best for the rpm/hp output you'd like to achieve. Most H-beam rods are good for the 900-1000hp range. For you it'd be extra insurance but not all of us have cash to burn, so it'd be understandable.

Pistons- Probe and i believe SRP or JE make pistions that work with the shorter 5.315 rods in lots 'o' compression combinations.