I am looking to make a 427 for my Dad. He's not looking for anything crazy. He wants something he can drive every day if he wanted to and have lots of low end power. I think a little better than 400 HP would keep him happy. He wants to keep it looking fairly stock as well. This is my plan so far

215 heads (427/390 heads) I will give them a light polish.
factory forged crank
forged KB pistons ~10.5:1 CR
427/390 intake, I will give it a light polish as well
Comp 11-601-8 Thumpr roller cam .558/.542 lift, 291/311 duration, 107 LSA
650 Holley (He has the carb, but I told him to go bigger, he probably won't rev past 5500 or 6000 so he should be ok)
He wants to keep the stamped rockers so he can use stock valve covers

 

has anyone used this cam, how did you like it? He likes a lumpy idle I'm not sure if maybe this would be too lumpy though.

 

For the same money you can build a 454.

I haven't heard anything good about that cam.

 

Dad wants to keep the 427. Have you heard bad things about that cam? what would you recommend then?

 

I didn't realize you already had a motor.

I have read on this forum that those cams sacrifice quite a bit of power to get the lumpy dle. I'm sure if you search CF you'll find a lot of info.

 

I think that is an oxymoron. Big Blocks are crazy.

 

haha good point. I just meant he doesn't want a 700 HP car that can't idle below 1500 and makes no vacuum.

 

427/390 intake is spread bore,holley carb is square bore,change one or the other.

 

427's make great street and race motors and 427/390's are great starting points. You've got a good plan already with the forged pistons and good strong bottom end. Make sure the block is honed with TQ plates and with a finish to match the rings you select.

You won't be decking the block (so as not to lose the #'s) so plan on using a thin steel shim headgasket to keep quench decent. That's how GM did it. Pistons down in the hole .020" or so and a thin gasket gets you around .040" quench. Typical replacement gaskets are thicker and you end up with .060" plus. Hopefully the KB pistons are made with the correct pin height to keep you at .020" or less.

The heads are something you want to pay attention to. The bowl area of the head just under the valve is critical. You might do some reading to understand the measurements. You want the bowl to be in slightly smaller than the actual seat to provide a venturi effect. Somewhere in the 88-91% range for something like this depending on which valves you use. If you have 2.19"s installed in the heads be very sure to check radial piston/valve clearance. Stock pistons sometimes can't handle the larger valve without a little work. The KB's probably can, but ck anyway.

The Thumper line of cams aren't all terrible...you just need to make sure they are what you want. The one you selected has more intake lift than exhaust which is very common today and a good idea. Same concept as adding 1.8 rockers on intakes only (which I do quite often). It has 14* more exhaust duration which adds to the strong sound everyone likes and helps it *hang on* at higher rpm. It's also something folks do with N20 cams to help with the added exhaust. Typically opening the exhaust earlier can reduce TQ a little..but not terrible. The tight 107* LSA will help the midrange and add even more overlap that will make it sound killer...but it will be pretty *thumpy* as the name implies. It won't rattle the windows out of it, but it won't be super smooth either.

I like cams with at least .600" lift for oval port street toys, but it's not critical.

The stock rockers are going to need to be checked very closely for binding on the stud with that cam. Should work, but it will be close. But also understand that added spring pressure that you're going to need isn't going to make life any easier for them. You might at least look into a set of stamped *long slot* rocker arms or some rollers. You can get them under stock covers with a little work.

The intake has been mentioned. Using an adapter to put the Holley on the spreadbore intake isn't the best approach. If you're locked into that intake then maybe a good Q-jet would do better? They can work great.

Is this an auto or stick car? Headers or stock manifolds? Gears? A/C?

JIM

 

Its actually a spread bore holley so that isn't an issue. Its a stick car. He wants to run manifolds to keep it stock looking. It has 3.55s with a 4 speed. It doesn't have A/C right now but probably will in the future.

With the ***** Thumpr cam and .020 thick gasket the CR is 10.6 and Dynamic CR is 7.04

I was also looking at the magnum 280 roller cam which would bump the DCR to 7.28
.566"/.566", 280/280, 110 LSA

 

Help us out a little and throw up the .050" numbers on the cams as you post them. It's a lot easier to figure out what it's likely to do with them.

That Magnum 280 is a 224* single pattern cam. Typically you see them doing well in stuff that doesn't rev super high...but with near stock ovals I'd add some more exhaust duration. You're in one of those weird spots. The heads won't be choking it....the intake and carb will definitely choke whatever the heads are capable of flowing. So the choke is out past the intake port. With the stock manifolds we have a restriction right at the port, so reversion is a real worry. I'd use a mid 220's to a 230'ish @.050" dual pattern cam with a relatively wide LSA (maybe 110 or so). The smaller Thumpr aren't so bad on overlap with the tight LSA that they have since they are not too big. You might look at some of the Isky and Crane HYd Rollers also.

JIM