C5AE rods

[Mdixon300f100]

So in preparation for the 240 I’m picking up next weekend, I decided to strip down the 240 I picked up last year that’s been sitting on the stand in the basement. It appeared to be a stock engine, although I couldn’t read the casting # on the block. The guy said it was a “70s” era 300. The pistons are flat top with 4 valve pockets, bores measured 4.038 with cheap harbor freight vernier calipers. The rods are small pin variants with C5AE casting # and no spit holes. If this other 240 has the same rods I may decide to hold off on the turbo build and go in another direction...

 

[pmuller9]

Nice!
The 1968 and earlier 240s used the Ford 289 V8 pistons and is the reason for the 4 valve reliefs.
Those are indeed the "Good Rods"
What would you do instead of a turbo project?

 

[Mdixon300f100]

I was thinking about utilizing the 240 crank honestly, it’s a little scratched up but maybe offset grind it for a few more cubes. I figure with those rods, the shorter stroke, and the head it could handle 7k. Maybe not, but food for thought. Fun to run while I build something else anyway. I’ve always loved the sound of a high revving 6

 

[Mdixon300f100]

I was really surprised to find them in there. Someone had been in the engine before, the #1 piston looks different from the rest, and the head had a D shaped chamber. Cam measured .392 lift at the valve. Center sump pan. It had been in a storage container for 20yrs buried under years of junk. As you can see the rod bearings r wiped, but the mains appear ok. I still have to clean everything, and press the pins out of the rods at work this week.

 

[pmuller9]

The 240 crank can easily handle 7000 rpm.
The crank has a lot of journal overlap making it a very rigid unit with low torsional harmonics and is nearly indestructible compared to the 300 crank.
The rod angle is a crazy 2.13 so very little piston side loading and reduced "G" forces at TDC.

You could do a high rpm turbo engine.

You would need a solid lifter cam and some really good valve springs.

 

[Mdixon300f100]

Well, isn’t that great to hear :rolflmao: Maybe I’ll set my sights on the rest of the turbo plumbing at this years swap meets while I assemble a block. If this next engine is still near factory bore I may be ready to begin.

Check out the thread “another turbo 300 in a f150” on the turbo page, I have that head.

 

[pmuller9]

Check out the thread “another turbo 300 in a f150” on the turbo page, I have that head.

It doesn't look like the stock spring locators were machined flat.
If the locator is left in place the inner spring will be compressed further than it should and the spring pressure will be more than expected.
With shorter stock valve lengths they could go into coil bind.

I do not like the soft pushrod guides for long term use that he originally used.
Are those the ones that came with the head?

I would like to see the port work.

That was a great buy. The rocker arms alone was worth the money.
What rocker arms are they?

 

[Mdixon300f100]

I’m planning on having it worked over by the local machinist after racing season starts around here. Right now he’s tied up with other customers, but was enthusiastic about it when I went to talk to him. They’re aluminum Harland sharp rockers. Can the Teflon guide insert be replaced? The inner springs appear to be sitting flush with the outer springs around the seal, although I haven’t taken anything apart yet to take measurements. What’s the best course of action for pistons? I’m assuming custom, but it’d be nice if there is a stock item that works. I’m also thinking my carb is way too big, I believe it’s 750cfm, another swap meet bargain I couldn’t pass up.

 

[pmuller9]

The 1.6 ratio Harland Sharp rockers are perfect.

In order to get the rocker roller tips centered side to side on the valve tip ,we use the Comp adjustable pushrod guides and weld them at the proper center to center spacing.
I thought that a 1.940" spacing would work for everyone but I was wrong due to variations on the rocker stud spacing.
You need to install the pushrods and rockers, then center the roller tips and measure the pushrod centers where the guide plates locate on the pushrods.
BigBlue94 just went through this exercise starting on post #123 in the following thread.
viewtopic.php?p=615486#p615486

The 300 head combustion chamber should have around 76cc which means you need a flat top piston without valve pockets to get an 8.8:1 compression ratio with the pistons at zero deck height.
You will need to CC the chambers.
The piston CD or pin height is 1.600" +/- .010"
Ford 302 V8 pistons fit those dimensions but all have valve pockets.
At 7000+ rpm with boost I would recommend a forged 2618 alloy piston.

You shouldn't need more than a 600 cfm carb for this project.

 

[Mdixon300f100]

Does the combustion chamber shape allow for a 5cc dome piston? That could compensate for large chambers as long as it doesn’t cause interference.

 

[pmuller9]

Does the combustion chamber shape allow for a 5cc dome piston? That could compensate for large chambers as long as it doesn’t cause interference.

Sure.
A 5cc dome would be about .035" high or about the thickness of the head gasket so it wouldn't actually go into the combustion chamber.
Not sure if you want a compression ratio higher than 9:1 with 20lbs of boost with pump gas.
If you run E85 then it would be no problem.

 

[old28racer]

Just so you know this is what a set of Comp SBC adjustable guide plate welded together looks like.

 

[Mdixon300f100]

Does the combustion chamber shape allow for a 5cc dome piston? That could compensate for large chambers as long as it doesn’t cause interference.

Sure.
A 5cc dome would be about .035" high or about the thickness of the head gasket so it wouldn't actually go into the combustion chamber.
Not sure if you want a compression ratio higher than 9:1 with 20lbs of boost with pump gas.
If you run E85 then it would be no problem.

Quess I need to order that cc’ing kit that’s been in my cart on summit for 6 months. Hard to accurately determine anything without it. Ok I’ll update later. Thanks for the info. I don’t want to get ahead of myself yet, I still need a block

 

[Mdixon300f100]

Would something like this work?

https://www.amazon.com/Speed-Mercury-Fo ... B00E1J4OCG

I’m a little concerned about the valve reliefs pictured, kinda negates any quench if one lands in the quench area. Maybe turning the .045 off the top eliminates that?

 

[pmuller9]

You don't want to cut any off the piston top for turbo application. You need all the thickness possible.
Speed-Pro pistons are heavy plus the skirt coating do not stay on the piston.
We have tried most of the skirt coating and the only thing that stays indefinitely is anodizing.
Either anodize or stay with a bare aluminum skirt.

If you go with an "off the shelf" piston they will have valve pockets for the V8 heads.
Look through this list and filter for the 1.599" to 1.610" Compression Height pistons.
https://www.summitracing.com/search/par ... =Ascending

The problem is non of the above pistons are designed for boosted application.
I would consider a set of BWE 2618-T6 alloy pistons. I spoke with Bruce earlier this year for pricing and a set of flat top pistons were $105 each and pins for $18 and $30 each depending on use.
He also offers an anodized skirt with a ceramic top heat shield for $40 both processes for each piston.
http://bwepistonrings.com/pistons.html

You can also compare prices with Ross pistons and RaceTec pistons.

 

[sandboxer]

What would the best material be to machine one’s own rods from billet?

 

[Mdixon300f100]

From my understanding forged billet that’s then machined is not as strong as stamped forging with cleanup machining. Something about the way it structures the steel it the shape of the forging, rather than a round or flat bar stock that’s machined after the steel structure is formed.

Regardless probably the same thing the pros use...

 

[pmuller9]

What would the best material be to machine one’s own rods from billet?

Most rod manufactures use some form of the 4340 steel alloy with the 300M being one of the best.
Timken Steel also supplies some of the best steel alloys for rods.
Some of the manufacturers have their own heat treating process.

It would easier if you could purchase forged blanks from one of the suppliers.

 

[CNC-Dude]

Many of the companies such as Crower and Carillo and most others have their own proprietary processes and material they use for their connecting rods, and treat those intellectual properties as "trade secrets", so finding much details about this may be very difficult to obtain. And you might find yourself subject to being the victim of misinformation more than getting useful info. But I know of a guy that made his own rods out of stainless steel for a straight 8 Buick saltflat race car and had good results.

 

[sandboxer]

Great information all.
Thank you