Starting 408 build - thoughts or suggestions?
 

I'm starting a new engine build. Planning on a 408 stroker. I currently have a 351W bored to 40 over that is 325hp 350tq at the rear wheels. I would like a little more. My goal for this engine is still to have a street drivable 500hp.

Right now, I am in the planning stages. I have a 79 351W block that I'm planning on using. I currently have a Tremec T5z that will likely need to be changed for the increase in power. I also have a 9-inch rear with 3.73 gears.

I am currently looking at the following items. I'm not stuck on Summit, but their free shipping and large selection makes it easy.
Scat Crank stroker kit - Click here
AFR 205 Renegade Heads - Click here
Edelbrock AirGap Intake - Click here

I haven't researched what springs are on the AFR heads or if I will need to change them. I suppose it will depend on the cam I get.

I am planning on TB EFI. Maybe MSD, maybe FAST. I haven't really researched them enough yet to know the differences. I don't have a fuel return line yet, so I'll have to plumb one into the cobra.

Haven't decided on the distributor or cam yet. I have an MSD 8478 distributor that I finally have tuned in, but may try a different brand. I do have a Mallory-brand 6AL ignition box.

My current non-roller-block has a small base circle cam, comp standard roller lifters, and a dog-bone conversion. I can do the same setup with the new engine or go with the link-bars. I've heard good and bad things about both setups. The link bar lifters are >$500 now.

I'm looking for about 10:1 compression. Will keep RPMs under 6k. Mostly a street car with once a year around the track at Harris Hill.

Whew... Any thoughts/comments/suggestions?

There is no replacement for displacement. Is there some reason you are only stroking it to 408 CID? Lots of builders are getting 427 CID from the 351W block.

You might want to check out other heads, too...my favorite builder has some pretty good things to say about the Twisted Wedge brand, IIRC.

Cheers!!!

Dugly :cool:

Here is a great cam for that build-
COMP Cams: Xtreme Energy™, XR294RF-HR: Cam & Kit

It seems like the 427 is too big a step up from the 351. I've heard some people complaining about it being too much for a stock block.

I've also heard about the TW 11R heads (I think that's the code). Do they flow as much as the AFRs?

The 294 cam states it requires 4.10 gears. I have 3.73 gears. Would the XR288RF cam work as well? Both of these also say not for E.F.I. I'm planning on the EFI system. Will it work or not?

Both of those cams are small base circle. I guess since they have the link bar lifters, I wouldn't need the dog bones, but the pushrods may not be the right length.

Looking at those kits, they have the cam, lifters, pushrods, timing chain, springs and retainers. Looks like a big price saving for the kit. Don't the heads come with springs and valves already installed. Will I need to switch out the stock springs on the heads?

Thanks! Tom

I was going to build a 408, but ended up with BBF. If interested, I have a set of sbf AFR 205 Outlaw heads that might suit you well. With heavy duty springs & the works ready to go. Also @ half the price you'll pay for a new set. Drop me a note if interested.

Just so you know, I can meet or beat Summit's prices, and if you have a question about something you buy, I touch these parts every single day.

For a lower priced 408, it's hard to beat a Scat 9000 series crank, I-beam rods, and a set of Probe forged pistons.

As for heads, I would give an AFR 205 the nod.

On the cam, don't read the description that any cam manufacturer gives as to what gears are needed, what rpm range it's for, etc. How do they know what displacement you're using? Or heads? Or intake? The same cam in a 351 is going to act TOTALLY different than the same cam in a 408 or 427. I'd be more than happy to recommend a cam for you if you wish.

The link bar lifters are not over $500....more like $385 for a nice set of Morel lifters. With that being said, if your block is already set up for a lifter spider, it's a lot cheaper to go with a set of OEM lifters. In an application like this, either would work perfectly fine.

I would suggest giving an engine builder a call, whether it be me, Keith, Barry, whoever, and making it a one-stop shop, so you know everything will work together without issue. I've tried every head that you've mentioned (including the new 11R heads on a 408), different cams, carbs, intakes, you name it.

Do you want to sell your old motor?

I will, once I get the new one built. I have quite a few other projects going, so this is going to be a slow build. Once the new one is built, I will wait for the next winter, then do the install. Then I will post the old one for sale.

Brent, I will definitely give you a call. I just finished teardown of the new engine and am going to take it to the machine shop to have it cleaned and fluxed. Thanks!

Good to know - I have a "slow" build going too, so maybe our stars will align. Will you be in San Marcos? I'll be there, and we can touch base....

I will be there!

Any recommendations or comments on intakes for a 408? I would like to keep it street drivable without having to keep it above 4000k to get any power. I understand that the stroker kit will give me more power down low. But I'm not sure what else to look for.

The cam I'm considering is:
Hydraulic roller
Advertised Duration: 280/288
Duration at 050: 228/236
Lift: .565/.565
LSA/ICL: 112/106

I can barely squeeze the Airgap under my hood but have to use a 1inch tall 11 inch diameter air cleaner. I'm not sure if that is enough flow for the 408. So I am considering going with a different (shorter) intake. Performer RPM, Weiand Stealth? The Vic Jr is a single plane which I've heard are less tolerant on the street.

Any comments?

Brent would know best, but with the extra cubes and a light car, I take with a grain of salt the perceived negative effects of a single plane on the street.
Particularly if your rear end is on the taller side.

Sounds like your going to have a fun project on hand.

Enjoy,

Didn't I recommend a cam for you? Unless you want a pickup truck hp and torque curve, the duration is too short on that cam, and I would run more lift.

Rpm air gap or victor jr either one would work just fine.

I don't even know what that means...

Thanks, tho. I talked to a few builders and custom cam manufacturers. They thought this cam would make the engine a little more street friendly. I can always change it later if needed. I'll go with the AirGap since I know it fits.

I'll call you when I'm ready for the AFR heads. It will likely be a few months.

Texasdoc,
I'm far from an engine expert, but I faced a similar dilemma regarding intake height versus air cleaner size on one of my cars. I decided that putting an undersized air cleaner on a high performance engine was not a good choice. I went with a shorter intake and a bigger air cleaner. Maybe one of the experts will chime in on this.

Yeah, I'm going to try to figure out if I can do a drop base so maybe I can get a 3 inch filter in there.

It means that the engine would be more suitable for a truck with that cam.

You can not read or listen to the advice that a cam manufacturer gives you about a camshaft. I promise that I've built more 408 Windsors than any cam hotline operator.

I'm sorry for sounding a little crass, but I'm coming off of a weekend blessed with a stomach virus, so I'm not in the best of moods.

Anyway, I've built a whole lot of 408's, from pickup truck engines to race engines. The cam that you picked is way short on duration, and will probably peak somewhere around 4800-5000 rpm.

If that's what you want, then that's great, but IMO a performance engine should not be that short winded (but does not have to be radical either).

The last 408W that I did used a set of Trick Flow 11R heads, a Victor Jr. intake and a cam with about 12° more duration. It peaked at 5600 rpm, had a very flat torque curve, but still sounded and performed nicely, making about 510 hp.

I also built a 408W using a similar cam to the one you picked, for a guy's pickup truck that he was using to tow a car hauler. It peaked at about 4800 and made about 390 hp.

The biggest mistake that people make when searching for cams is that they read the description under the cam specs, "Power range from x rpm to x rpm". That may be true, but it's only true for one specific engine size, and it's usually the smallest size in the engine family. What they don't tell you is that a 408 needs a LOT more cam than a 351, and that even changes depending on the cylinder head and other parts of the build.

Keep in mind that a drop base may allow you to run a bigger filter, but it will not change the size of the gap between the top of the carburetor and the lid on the air cleaner. If that gap isn't big enough to allow air that has passed through the filter to freely make that 90 degree turn into the throat of the carburetor, you may still be limiting the air flow to some degree. I offer this opinion as a retired aerospace engineer, not an experienced engine tuner.

You can use more duration with that 112 lobe separation and not sacrifice driveability. Something in the 235/245 range would be about right.


Also, that manifold will give you a better average horsepower, but you will sacrifice peak horsepower.

The last Engine Masters we did with a 408 we got 635 average with a dual plane, and 690 with a single plane. But, since we were racing dynos, after all......