Road Racing Engine "for the street"...

[ChainDrive]

Hey All, This is my first post here, but I'm a regular on FBBO - known as GRabinov911. I copied this post from over there because lotsa folks there suggested I talk to you guys. Thanks in advance.

Post 1: OK so a buddy of mine ran the Silver State Classic (in a 65 Mustang) and I can't get it out of my head!

My 1970 Plymouth Roadrunner resto has been going along great and the car runs well on the stock 383 (only 50k miles) and the 3.23 rear end. I've got it all set up with Firm Feel suspension parts because I'm a handling geek - not so much because I thought I needed then, but maybe I do...

I just bought, magnafluxed and sonic checked, standard bore, 1978 440HP block to use to build a new motor for the car. Again, not cause it NEEDS a new one, but because I've never built a car engine before (done motorcycles) and I've always wanted to. I have a local machine/hot rod shop to help me with the build. They are used to building hot rod "drag" engines, and they build some pretty hot inboard boat engines.

Question: If I want to build my 440 for roadracing, or going really fast (about 100mph average) in a relatively straight line over a long distance (90 miles), what do I tell my hot rod shop guy about cam selection, compression, carb specs, etc.? I'm guessing this is a somewhat different engine than one build to run for 11 seconds from idle to 8,000 rpm, more like a boat engine which runs high rpm under heavy loads for long periods of time...


Post 2: I'm back with the Road Racing Engine thread. My stock 440 block is now at the machine shop with a Mancini Racing internally balanced 493 stroker kit sitting next to it - a complete short block rotating assembly ready to go together. Now we're talking about cams and types of cams. The shop is a fan of Crower cams (they say they like the billet they are made from) and recommends going with a hydraulic roller setup. I'm not opposed to either for any reason that I know of. I don't mind the ease of maintenance of a hydraulic. I don't mind the limited RPM (6,500 or so) because I don't expect to be above there anyway with my setup (now a 3.55 TrueTrac rear end, 727 auto trans / 2,500 RPM stall converter, 27-28" tire) . Crower doesn't have a stock Chrysler 440 hydraulic roller cam in their catalog, but the machine shop suggests going with a custom grind.

I spoke to them about the oil clearance issue and they have no problem with that because they build boat motors all the time. The problem is, the shop guy keeps telling me: You're not gonna find a cam that is good for sustained "high RPM" road racing and still comfortable on the street. To refresh your memory, what we are trying to build here is an engine that will hum along comfortably at 4,000 to 5,00 RPM, which is what it takes to go 100+ in a 3.55 Roadrunner for an hour or more.

Now I didn't tell him I need maximum horsepower at 4,000 to 5,000 RPM. I just need SUSTAINED operating at 4,000 to 5,000 RPM with enough horsepower to maintain the high speed over varied highway terrain. I know that I can keep my Roadrunner at 100+ MPH on just the stock 335HP that my 383 makes (less, since it DEFINITELY doesn't make 335HP in its current condition). So that means that as long as the motor makes 300 to 400HP between 4,000 and 5,000RPM. I'm good to go.

It can't be THAT hard to come up with a cam profile that will do that and still be streetable right? (I'm planning on standard Edelbrock performer RPM 84cc heads, my existing Schumacher tri-y headers, good ignition and some big carb.). It'll probably be closer to 450+HP in that range I'd guess. Obviously the car will spen more time on the street trolling around than on the "track" at 100+MPH.

Here's a proposed grind based on a Lunati cam from Mancini:

Item# LUN60304LK
$218.95

Product Description
Hydraulic. Hot Street cam, likes 2800 converter, Hi-Rise type dual plane intake with 850cfm carb, headers, 10:1 compression and 3.73 gears. Likes up to 200HP nitrous.

Advertised Duration (Int/Exh): 276/284

Duration @ .050 (Int/Exh): 234/242

Gross Valve Lift (Int/Exh): .513/.533

LSA/ICL: 110/106

Valve Lash (Int/Exh): Hyd/Hyd

RPM Range: 2200-6400


Anyone care to check my calculations and my logic? Be gentle!

Thanks

Greg

[72BBSwinger]

Your logic is good. Even if you went with the biggest hydraulic roller Lunati offers in that engine power would still peak at probably 5500 rpm. And that lunati is what I would run anyway. I would also have the heads at least taken apart and checked for guide clearance and the valve job quality, don't run them out of the box. Keep compression at about 10.1 to allow for inconsistency in fuel quality. Their was a pump gas 505 just built recently with ebrock heads, .600 lift solid roller on pump gas made 650/650 with peak hp at 5800. That type of engine can live a long happy life at those speeds. Maybe run an oil accumulator and a oil cooler for good measure.

[Ron Sutton]

Mancini Racing is a great shop with a stellar reputation. Those guys know their stuff, so you're in good hands.

Crower is known in engine builder circles for making parts stronger & more durable with better alloys. Their cam cores flex less under high rpm & high spring loads in racing situations. I don't think you'll need that, but it won't hurt either. Crower also makes some of the toughest roller lifters, valve springs, cranks & rods.

I agree with Swinger. Your logic of power need, rpm range & 100 mph Silver State Challenge run is sound & will all work together. (I'm planning to run that event with the car I'm building too.)

The cam selection:
Duration @ .050 (Int/Exh): 234/242
Gross Valve Lift (Int/Exh): .513/.533
LSA/ICL: 110/106

I would consider this a "moderate" (as in between mild & aggressive) street cam. It is really hard for someone else to tell you what camshaft profile you will like to drive on the street. The cam profile determines the engine's "personality" & driving characteristics. Duration & lobe shape play the biggest role in this. So the "correct" cam choice is personal for each individual.

This cam will have a definite "lope" to it, sound "racy" & build all the power you need. It's not going to drive super smooth at 1200-1500 rpm, like an LS will. But 2000-2200 & up are going to be awesome in this 493" torquer engine. It is going to be a powerful & fun engine. You "could" go smaller on duration & still achieve the power you want, and smooth out the ultra low rpm powerband, but you would give up power from 3000 & up. What is important to you? Only you can decide that.

This is a very personal choice ... kind of like suspension ride quality. What one car guy/gal says is "too rough & stiff for comfort" ... another car guy/gal feels it "has too much body roll" for their handling goals. A lot of PT folks have stock LS in their cars (with durations in the low 200's at .050"), while others have cams with 10-20-30 degrees MORE duration than you're running.

I see you have a 2500 rpm stall converter, which tells me you're not going to drive it at 1500 rpm anyway. So your combination matches up. I personally like your combination & suggest you go with their cam recommendation. If you drive it for 6 months & decide you need it smoother at 1200-1500 rpm, changing the cam won't be the end of the world. Most people's PT cars are never "done" anyway, as we all continue to work on ways to improve them & personalize them for our tastes.

[Scott Parkhurst]

Street/road race engines are more about cooling/lubrication than compression/cam.

You are in good hands at Mancini's. Have them look into kickout pans with trap doors. Extra capacity and the assurance that the pump pickup will always be in the oil is what you're after. Stef's and Canton make amazing stuff. The Milodon unit with the swinging pickup has proven it's worth for decades.

Cooling-wise, make sure you've got an awesome radiator/pump combo. There are plenty of good pumps out there that can move a lot of coolant, and plenty of custom-crafted radiators too. Get that good stuff and keep that 440 cool. That will help keep the clearances perfect inside it..

The cam needs to be a good match for the heads you're running and your target rpm range. Crower makes great stuff. Roller lifters are more expensive but deliver more performance. They need to be lubricated properly, and Crower's "Hi pressure oiling" or "hippo" lifters are great. The shaft-mounted rocker setup is plenty stable.

You should have no trouble enjoying this kind of racing.

[ChainDrive]

I'm gonna like it here! I tried to craft my question intelligently and I can't tell you guys how much I appreciate the thoughtful, educated and honest replies. Each of you guys offered a slightly different insight, and each is clearly based on expertise. Thanks Gents. Right on...