Cam and Springs for a totally street 383 build

I finally got decent core parts to get started on a /6 to 383 swap in my Dad’s 1966 Coronet post. He’s the ‘customer’ so I have to make it what he wants. Just like a lot of us here (I assume) we’ve all over-cammed engines and also put together great parts, but parts that don’t work well together. Even though my Dad is requesting a couple contradictory things, I think I have a decent plan. Below is the short list. By Dad’s request this is a mostly stock appearing and very easy driving 383... i’m thinking an honest 350hp is a reasonable expectation.

-1965 A383HP block and steel crank. (I already have the block and crank) Shop is going .030 and a I’m planing to use 2315 flattops (compared to silvolite’s) due to the slightly higher compression height.
-Heads (I already have these) Fresh worked 915’s. New 2.14/1.74, bronze guides, hardened seats. Bowls slightly cleaned up, Crane double springs, slight .010 surface cleanup. All chambers cc @ 77-78cc.
-Intake (I have this) DP4B
-Exhaust (I have these) stock 383/440 HP manifolds and the TTI 2.5” H pipe.
-Tranny (I have it) a freshed up stock 727.
-Converter, i’m planning a 10.75” factory hi-stall from Patty.
-Rear (I have already) is a 3.55/grip
27” radial tires.

3 Questions are:

-Are the 2315’s my best option?
Using the stock deck (the stock flattops were .024 in the hole plus adding the difference of the slightly shorter 2315, .020 shim gaskets and my heads i’m calculating about 9.3:1 which is perfect.

-Cam. My dad MUST have some sound to it. I’m thinking either a comp 270mag, a comp 268xe or maybe a voodoo of similar spec. He does not want the summit 6401, we had that in the above mentioned short block years ago and he hated it because it idled to smooth.

Springs- the crane spring that are on the heads are 135# seat and 335#@ .550. Should I swap to a set of standard 440hp springs? This engine will likely never see above 5000rpm.

I know the Achilles heal is the manifolds and the heads are overkill... but it allows room to grow.

Thanks for all the help the people on this great board have already provided and will provide in the future.

Maybe a thumper?

I think your cam choices are dead on, but I would use the springs recommended by each manufacturer (just in case). There are some really good piston guys on here, so hopefully someone else will chime in. Maybe "flow extrude" or whatever the F.A.S.T. guys call stock manifold porting? Sound like a very good & well thought out build.

Consider the Diamond 51903 piston. Your 2315's are okay, but valve to piston clearance could be an issue. Deck the block to get your CR where you want it. It might be a tough balance to get both a decent CR and quench with your 915 heads. If you used alloy heads, you could use the Icon IC687/KTD.

The "idle" that your dad wants usually means more over lap, and exhaust manifold motors dont like much overlap. So that is a bit of a conflict, but the cams your looking at are still pretty small. If you're serious about the 5000 rpm shift, put the 268xe in it knowing that your leaving a bunch of potential on the table and your not going to reach 350 hp.

Maybe the Crower 271 cam.

Based on some other threads I've read I see the 2315 flat tops can have clearance issues, but even with the 2.14 intake valves I have it looks like I'll be OK if I stay in the 225*-ish @.050 duration range and only .475"-ish lift. Sound about right?
I'm favoring the comp 270 cam, I put the comp 280 in a $bc400 years ago for him and he loved it. His most recent car however had a 451 I built about 12 years ago. It had the .557" solid purple cam, a late 50's iron 2x4 manifold on it and about 11.5:1. We put it in his 65 coronet with a 10" converter and 4:30 gears. It had vintage 45 year old L-60 bias on the rear and 40 year old F-78's on the front that we found new with tags at a swap meet. All that with just 10" drums and the jelly jar. The car was utterly terrifying. I drove it only 2 times and that was enough.
That was his cruise car for almost 15 years, it never went over 60mph, he just wanted/needed that "sound" when he pulled into the cruises. Now that he's in his mid-70's I think the build I'm speaking about above will be a better/safer cruiser for him in his new 66 post car.

A 9.5-ish 383 with 915’s and a 270H will do what you’re looking for.

Thanks PR, I’m leaning towards that cam as well. One question though, comp indicates a different lifter for pre-1967... it’s like .020 taller. I’ve never seen any other cam company reference this. Does it have something to do with the pushrod length? The originals I have for the engine are the ones with that smaller lifter end ball...

HotRod777 said:

Thanks PR, I’m leaning towards that cam as well. One question though, comp indicates a different lifter for pre-1967... it’s like .020 taller. I’ve never seen any other cam company reference this. Does it have something to do with the pushrod length? The originals I have for the engine are the ones with that smaller lifter end ball...

Click to expand...

The 67's have a smaller pushrod/lifter ball/cup

As Russ stated, the 67 and earlier motors used pushrods that have one end smaller, which fits into the pushrod cup.
Besides having the smaller diameter tip on one end, they’re also about .060 longer

You can use either lifters in any year block, you just have to make sure the lifters and pushrods are for the same year application(67 and earlier, or 68 and later).

I use the 68 and newer in everything.

If you’re using the 67 and earlier lifters and you need a non-stock length pushrod, they’re more difficult to get.

Just an update on progress. I have the long block assembled with the Comp 270 cam and forged flat tops. Ran into an uh-oh moment along the way, but it will be a either a good or a bad thing. When disassembling the short block (that I re-ringed back in the 90’s) I was always assuming that the pistons were stock original. Well, they were stock bore and appeared factory stock, but it turns out there was something different. The ‘stock’ pistons were .024 in the hole. Assuming they were stock spec and stock compression height, I was expecting the forged slugs (which are slightly shorter then stock are) to be about .035 or so in the hole. That along with a .020 shim gasket would work out (on paper) to be around 9.6:1. However when I pushed #1 in and tightened the cap and rotated it around and up... it’s WAY closer to the deck. After all 8 are in they are all ‘only’ .016-.018 in the hole.
The good news, with the .020 shim, I am right at the ‘perfect’ quench... the bad news is i’m going to be at 10.4:1-ish.
I’m going to try to run it on 93 gas, 35 total timing and a cold plug. I’ve convinced myself that with that, along with the good quench, cam installed straight-up, a new 26” 2-row 1” tube aluminum radiator and 160° thermostat I’ll be OK. Also, the 3.73 that I ended up with and the factory wide-right gear 10.75 converter will help not loading the engine. I think this is really going to wake up the small-ish 270 cam...
BTW, I did clay it and seen no valve indents.
.040 Fel-Pros are on hand in case it’s a disaster... nothing a Friday night and a 12 pack can’t cure.

Your stock pistons were probably 0.002" in the hole. The 2315 pistons are usually in the 0.015" in the hole range. Personally, I don't think it would work at 10.4:1. Good news is that it is unlikely to be that high. Not sure what your actual 915 chamber size is, but unless there has been a lot of machine work on them, they'll probably be in the 80 cc range.

BSB67 said:

Your stock pistons were probably 0.002" in the hole. The 2315 pistons are usually in the 0.015" in the hole range. Personally, I don't think it would work at 10.4:1. Good news is that it is unlikely to be that high. Not sure what your actual 915 chamber size is, but unless there has been a lot of machine work on them, they'll probably be in the 80 cc range.

Click to expand...

My old 383 build in a 4000 pd b body had a Comp XE274 with closed chambered heads with Kb 162’s. It had 9.1 comp with a steel shim head gasket. With 3.73 gears and a 11” turbo action 2800rpm converter it still was/is pretty quick.



My old 516 heads were 82-84 cc, and those were milled a tiny bit. I have heard many of the closed chamber heads were this way, unless you take .020 or more off

Can I just throw this out there, in regards to your clay valve/piston check. First, I apologize if you already know this..if you have the hydraulic lifters in there as you rotate the crank the spring pressure will immediately begin to depress the lifters, farther than they will under normal operation(no oil pressure). You won't get an accurate check unless you: use lightweight 'checking' springs, use a solid lifter with the same cup height as the hydraulic you intend to run, or disassemble and shim the hydraulic lifter on the valve you're checking..it isn't the max lift but where that big 'ol valve is when the piston moves through TDC...again sorry if you're already on top of this, just trying to help prevent the dreaded death smack!

A bit delayed but here are the results. The slant pic was Friday afternoon of Memorial Day weekend just after getting home from filling it up with Hi Test, the V8 pic was Monday afternoon (Memorial Day). This was a big project for 1 long weekend and it was just me and my Father, he always was a gear head but he’s 74 now so he’s not able to lay down and crawl around under the car anymore... so I’d say it was 1.5 guys, 3.5 days, 2 30 packs to accomplish:
- slant 6 out
- 904 out
- 7.25” and leaf springs out
- K frame out
- Bolt in connectors in
- K frame in
- 8.75 (3.73 grip) and HD springs in
- 727 w/10.75 convert in
- 383 w/comp 270 in
- TTI 2.5 manifolds to tail pipes in
He was driving it by 4pm Monday.
Still chasing a few bugs but overall it’s a huge success.
The comp 270 is a very nice surprise. It sounds really good and is just ‘small enough’ to NOT be lazy out of the hole. So many cam choices end up only coming alive above 20mph and 2500rpm... the 270 doesn’t have that noticeable band come in... it’s just respectably strong from a dead stab.

way to go
my installs rarely went that smooth
I would not run 160 stat if mostly around town as it does not get hot enough to evaporate condensation and other bad stuff
after break in do a compression test and report back
then tune your timing curve and carb
what did you end with as far as valve springs?

Great job between the two of you !!

Install looks fantastic.

Glad to hear it’s just what you were after.

Very nice. That 270H is a really good pic in my book and glad you/dad like it.

Thanks for the follow-up post.

I put in a set of spring from EBay, listing says 110lbs at seat. They have run there springs into the 11’s.
$80 for the set. They are working fine.
I welded up the T-bar to limit it to about 17° in the distributor and I am running 17° initial with 1 light and 1 medium spring. The 650 AVS2 is out of the box rods and jets. Idle screws out 1 turn. It had a bog/sneeze if you snapped it open quickly... I moved the pump up to the top hole and tightened the flap a 1/2 turn and it’s perfect. Next time I have the plugs out I’ll check the compression.