Engine Rebuild - Rod Length

In the old days, which is where I am from, rod ratio was important. The current crop of engine builders, and they have big credentials, say it isn't as important as they once thought.

A 377 with 10.5 to 11.:1 cr and smaller port heads like the CHI would be pretty close to what you are asking for.
The issues with current pump gas are minimal and you are only looking at a 1/8" stroker on the crank.

Personally I feel if you want those rpm and durabilaty forget about the hydraulic lifter and go with a solid lifter cam, titanium valves, screw in rocker studs. Hydraulic roller camshafts are not for the long run. They break a lot of parts. They add more compexaty to the valve train and provide more failure posabilaties.

About the only thing you have to worry about when going over 7000 is oil supply and drain back. The Cleveland will pump a lot of oil into the valve covers.

That isn't all bad though since the fix for valve springs breaking in competion was to submerge them in oil in the covers. Apparently Cleveland springs run hot enough to induce failure at those constant rpm's...and you should sleeve the lifter bores.

The rod ratios aren't something necessarily that you specify. They are a result of the stroke you have derived, because of crank, piston and rod availabilaty. The ratio becomes what it is because that's what you can get.

The closer you get to 1.5:1, the more the piston wants to go through the side of the bore. Even with a thick bore race block that isn't a great idea.

While it has been pretty much proved that the stokers run pretty strong, no one has really proved a NASCAR type of race durabilaty out of them. Strokers have been around for a long time. They were once installed in the "rabit". That being a vehicle that ran away from everyone in a race but had no expectations of finishing the race.

It was there to stress out and break as many of the competators as possible to give the team memeber that they wanted to win with less competition.

Just my 2 cents worth.

Supporting what Doug has written, back in the days when men were men (and sheep were scared) I built the solid lifter motors with a good quality 6" rod, the hydraulic cam motors kept the oem rods which were 5.78". The solid lifter motors were expected to turn more rpm, and it was universally believed 20 to 30 years ago that the engine worked better at high rpm with the longer rod.

You'll "read" in books that the stock connecting rods are good for high rpm, but that is to be taken with a grain of salt, everybody normally replaces them after their first oem rod fails, learning that the "books" aren't always 100% accurate. Its a costly lesson. My point is this, since it would be prudent to purchase a set of quality rods anyway, you might as well plan on buying them 6" in length. You'll want a set of good rods made from 4340 chrome moly, dowled bolt holes, with beefy 7/16" cap screws holding them together. The "H" beam rods are prettier, but the "I" beam rods are lighter. Oliver and Crower are two sources for true race quality rods.

For a camshaft talk with Mark McKeown. He says he can spec a solid lifter roller cam that doesn't require any more adjustment than a hydraulic roller cam.

You want low end torque, but a motor that will rev until 7500 rpm, plan on specifying a wide flat torque curve. If you will be using iron 4V heads plan on running the Parker Funnel Web, Holly Strip Dominator, Blue Thunder or Edelbrock Torker intake manifolds (in that order). The Funnel Web requires the use of intake port stuffers, which improves the shape & air flow in the 4V port.

Oil system mods will consist of bushing the lifter bores so that the clearance between lifter and bore is only 0.0007" (that's not a misprint). This controls where the oil is going and insures it is flowing to the crank instead of flowing out between the lifters and their bores. A high pressure oil pump spring keeps the relief valve built into the pump closed insuring all the oil being pumped is supplied to the block. A heavy duty filter (Fram HP1) insures the higher oil pressure doesn't burst the oil filter cannister. At least one 5/8" oil drain back line between each valve cover (or head) and the oil pan because the oil drain back holes built into the block are small. A heavy duty oil pump drive shaft to prevent it from snapping at high rpm, and beefing up the pin that secures the distributor drive gear to the distributor shaft (or else it will sheer when used with the heavy duty shaft). Finally, you'll redesign the crankcase evacuation system to evacuate the crankcase instead of the top of one valve cover, and you'll run breathers in both valve covers, thereby making the air flow through the engine in the same direction as the oil. This aids oil drainback.

That's how you do 7500 rpm (and above) with a Clevo.

cowboy from hell

George, don't forget to tell him to balance. 7500 rpms without a good balance job can be scary. And make sure all the parts are to the print. Don't want an out of tolerance wrist pin ruining all these expensive parts.

Yes, a 7500 rpm motor calls for dynamic balancing AND a little head porting would be in order too, at least on the exhaust side.

George,

Thanks for the advice, I already made the decision to use a solid roller cam.

For the top end I have C302B heads, roller rockers and will use the Weber IDA's.

quote:

Originally posted by Joules5:
George,

Thanks for the advice, I already made the decision to use a solid roller cam.

For the top end I have C302B heads, roller rockers and will use the Weber IDA's.

Oh dear! I think I have corrupted Julian terrably! Sorry Julian but it isn't really bad here on the dark side once you come over.

quote:

Originally posted by PanteraDoug:
...it isn't really bad here on the dark side once you come over...

quote:

Oh dear! I think I have corrupted Julian terrably! Sorry Julian but it isn't really bad here on the dark side once you come over.

Just as long as you don't try to tell me you are my father

Back to the discussion, specifically the C302B heads which I now have in hand and got a screamin' deal on complete with roller rockers, girdles and rocker covers. Oh and some headers (which will serve as the base for making a set of 180's) and a manifold for a 302, which will go on ebay.

The exhaust ports have been ported ('D' shape) and although I don't have flow numbers I measured them at 120 cc, whereas the intake appear stock (I measured them at 200 cc), but I've seen 212 cc quoted for stock, so maybe that is what they are, certainly no more.

The question is will this work well with my intended application of high revving 10.5:1 351 cubic inch motor running 48 IDA webers and 180 headers or should I be thinking about porting the intakes?

Thanks for all advice,

quote:

Originally posted by Joules5:
...should I be thinking about porting the intakes...

So long as the intake ports have been "cleaned up", nothing protruding to disrupt gas flow, especially just below the valve seats, the answer is no. For the valve lift you'll be using with this motor (around 0.600") I'm sure those heads flow more than enough.

Use the force Luke...

cowboy from hell

Since these are used heads you really have no way of knowing what work was done to them.

From what I have seen, the c302's are usually ported heavily. What I find interesting is that the finished products I have seen are tailored to the headers on the car, more then cleaned up around the valves and the intake ports wind up resembling the B351's.

You can't know what they flow unless you put them on a flow bench and test them. That is what I would do.

They should be just about perfect for what you want.

Incidentally, Hall's small port Weber intake is made for the A heads. The intakes are going to be wider then your C3's. You should flow the intake and head together to determine if anything needs to be done on the mismatch. I presume that is the manifold you will use.

Forget about using the big port manifold. It will get messy at the bottom of the intake ports to match to your heads.

You would need to make an aluminum plate "gasket" to close the 5/8" or so at the bottom. Otherwise it won't mate up to your heads at all.

The Australian 2v manifolds by comparison will have the top of the ports around 3/4" too low.
They would need some type or adaptor plates also.

The small port Hall would be the best choice unless someone like CHI had a Weber set up, but I don't think they do.

Welcome to the Dark Side L..., ah Julian.

Doug,

The used Webers came with the big port manifold for cast iron heads and I offered it up to see how the fit was, yes there is that 5/8 inch gap at the bottom. I considered using the money I would spend on a new manifold towards a TIG welder and welding it up, but finding time is the biggesst challenge. There's always epoxy filler I suppose.

I guess in reality I'll have to bite the bullet and buy the Hall small port manifold or better still one of Panterror's castings with CNC porting.

Thanks,

> The exhaust ports have been ported ('D' shape)

Do they look something like these:

http://www.bacomatic.org/gallery/album06/C302_ported_exhaust

> and although I don't have flow numbers I measured them at 120 cc,
> whereas the intake appear stock? (I measured them at 200 cc), but
> I've seen 212 cc quoted for stock, so maybe that is what they are,
> certainly no more.

That 212 cc number probably comes from my Cleveland aluminum head guide
which is floating around the net in one form or another. That number
comes from a 1980's Ford Motorsport catalog. I've uploaded pages from
a couple of those catalogs here:

http://www.bacomatic.org/gallery/album22

They have additional information that may be of use to you. The C302's
were also sold without port throat machining (under a D302 part number)
which may account for your small intake port volume and I've also seen
ported C302's that came in around the cc's listed for unported heads.
As others have suggested, have the heads put on a flow bench. You won't
know what wether the intake needs ported until you do. You'll also need
that information when it comes time to spec a custom cam and/or run
simulations. Note the flow numbers that Ford published here:

http://www.bacomatic.org/gallery/album22/highport_small

are taken at 25" Hg, not the usual 28" standard. You can convert those
numbers to 28" but, in my experience, the numbers will still be very
conservative. I had a set of A3's flowed that had only a port cleanup
and they flowed way more than what that chart suggests.

> The question is will this work well with my intended application of high
> revving 10.5:1 351 cubic inch motor running 48 IDA webers and 180 headers
> or should I be thinking about porting the intakes?

Do you mean 7500 RPM shift point, a 7500 HP peak or just be safe to
rev to 7500 RPM. Do you have a particular RPM range and horsepower
goal in mind? Stock displacement, high revving and gut wrenching
torque (presumably at low RPM) typically don't go together. However,
C302B heads and the IR intake will do a lot for bringing the working
range in at a lower RPM.

> I'm looking at the engine rebuild for the '74 and need some education on
> advantages and disadvantages of longer rod length. I assume a longer rod
> is better from a less stress perspective e.g. stroker engines
>
> What about keeping a conventional 3.5" stroke but using a 6" rod and
> piston with lower compression distance, any advantages?

The advantage is indeed less stress on the sidewalls. There can be
a power advantage too but it isn't that large and is highly dependent
upon the rest of the build. The downside is the engine is slightly
more prone to pre-ignition since the piston dwells longer near TDC.

Dan Jones

Everybody knows you have to be able to turn 7500 RPM to go over 200 MPH with stock gearing. Being able to do that is just plain mandatory. It is like being able to go from zero to 100 and back to zero again in under ten seconds. It is just baseline cool is all. It ain't a super car less it can do that. :P

I have used .125 x 4" (maybe 3.5", I forget) aluminum bar stock and make a plate that covers the bottom of the intake port on the manifold.

You have enough material to use some 6-32 Allen socket bolts to hold it to the manifold and eliminate the possibilaty of warping.

No one has proved or disproved flow loss with this type of mismatch of ports.

I would presume there would be some but maybe not enough to worry about?

It's always cheaper to use what you have then start anew.

I have all these bicycles that I don't use. Those tires and wheels sure do look skinny on the Pantera but who cares? They were free.

Dan,

Thanks for the input and links.

I'd like the engine to be able to see a 7,500 rpm shift occassionally, not just one of those 'bench race' 7,500 rpm engines.

The exhaust ports look like yours, actual photo posted below and they are approx. 1.568" x 1.568". The intake ports are 2.136" x 1.32" and I'll post a second photo of those.

Doug,

Thanks for the tip, but if I was to use what I have I'd TIG weld up the manifold ports to get a reasonable match. Time being what it is, I suspect I'll just get on of Kelly's IR manifolds.

Intake Ports