Corey_68

I'm boring and stroking the 454 into a 540 with forged crank,rods, and pistions. I have 2 sets of heads in my dads shop, rectangle port and oval port. I realize one is better for hp and one is better at tq. They are both iron and was going to have them ported. I'm looking at about a 10.5.1 compresssion because of the iron heads. What cfm shhould I be after? I'm looking for 650hp on the motor and most likely run a 200hp-300hp shot of N20. I want a cam that's stout be srill drivable. I'm not worried about vaccum because I will run a vaccum booster to compensate. Any Ideas on what cfm to port them to and what cam? The engine will bebacked by a Richmond 6 speed.
Thanks guys...

gkull

510 ci is about the limit. Their are a few bad 500+ inchers on the forum. I would use 2.3/1.88 or bigger valves in ported rect port as a minimum. With 260+ degrees at .050 with just under .800 lift from a solid roller. I use to have a 510 it runs real well with a 1150 dominator carb. It's still running today in a prostreet machine.


[Modified by gkull, 4:49 PM 10/4/2001]

StrayDog

Just my 2 cents ,,,,,BUT a 268 Comp Cams Extreme energy will give you a 6000 + RPM redline & a mountain of axel twisting tourque......I have a 427 .30 over in my 66 , she is a street driver with 9.8 compression & Endlebrock alum heads , I have a hydralic cam , but tYpe unknown pulls strong to 5,800 RPM , as basicly driveing in the 1300 / 5400 ball park , thinking about a 262 extere energy in my situation,,,,,,,,,,,,,you have MEGA cu inch , but dont go overboard with DURATION torque is what feels good,,,,just my thoughts........


[Modified by StrayDog, 3:49 PM 10/4/2001]

Corey_68

Gkull,
What do you mean when you say 510ci is the limit?

Flareside

I was wondering the same thing. Maybe he meant the limit for stock iron heads?

-Joe

ML67

Hi Thad,

I may be able to help you out, but first I'm curious how you plan to get 540" out of a 454. If you are talking about a standard 454 passenger block, this will safely take a .060" over bore, and *possibly* up to .120" if you have a perfect block, although w/o block filler you may get some ring flutter due to cylinder wall flex.

If you're running a Bow Tie block (as I am) this will safely take a 4.625" bore due to the siamesed cylinders. A 4.5" bore x 4.25" stroke is the common 540 configuration.

Know that torque will NOT be a problem with a 540, so I think you will be better off w/ the rectangle port heads. Of course if you want to build a low rpm torque monster with modest valve timing, oval port heads are better.

As to a camshaft, I'm partial to solid roller cams. I accept they take more care than other cams, but are IMO well worth the extra work. Just keep the lift sane if you plan to run it regularly on the street. Another good feature of solid rollers is they do not lose as much "streetability" as a flat tappet cam of similar duration. Comp and Crane among others offer several street rollers that do not require killer spring pressure, thus eliminating reliability issues associated with said springs. Additionally, Comp has a line of solid roller lifters that incorporate an additional oil groove on the lifter body to aid in low rpm oiling.

What are you planning to run for an intake manifold? What is your desired rpm operating range?

I run a Comp XR292 ground on a 112 lobe separation angle, installed at 108 intake centerline (4 degrees advanced). It has 254 degrees of intake duration at .050". My idle rpm is 850 and vacuum is ~ 10 in Hg. My heads and intake have been heavily massaged by Bernard Mondello, Corona, CA. My peak chassis HP is 560 @ 6300 rpm.

I think 10.5:1 CR may be pushing it for pump gas with iron heads, although valve timing, ambient temperature and altitude also come into play. You can tolerate more compression with a bigger cam. Aluminum heads are certainly more forgiving of high compression than iron heads.

As gkull said, there are several forum members running 540's of various configuration. They may have a different slant on component recommendations for you.

I can say I enjoy my setup very much -- although the line between control and violence is easily crossed!

Good luck with your project.

Mark

norvalwilhelm

I agree with George and others who say that 510 is about the limit. A .060 over and 1/4 inch stroker equals 498. Like earlier stated it will go .120 over but that is pushing it. The retangular heads will work with this much cubes. The rectangular heads will accept 2.250 and 1.90 valves easily and with porting will flow 325 about the same as Brodix stock heads. As for the compression I ran 11 1/4 with a crane cam with around 264 @ .050 duration on 108 lobe centers. For good top end charge and mid range I don't like 112 lobe centers. Keep the lift around .620-.640 on the intake and less on the exhaust. The rectangular heads exhaust fall off after .500 so increasing the lift does nothing but overwork the valve train. The intakes will flow to .700 but by .600 they are almost done. I have flow specs for the heavily reworked rectangular heads with 2.250 valves.

Corey_68

I appreciate the info guys. I'll be using a Mark VI or V block with the siemesed cylinders. Even at .120 will this thing run hot?

ML67 what radiator are you running in your car?

ML67

I run a factory C/B radiator with a Stewart Stage 1 water pump and 160F hi flow thermostat. I also use the factory clutch fan and shroud. For fluid I use 1 gal Dexacool, 2 bottles Water Wetter and balance DI water. Temps stay in the 180-190F range around town driving depending on ambient temperature, and creep up to about 200F on the highway.

And I don't run a front license plate.

Good luck,

Mark

Corey_68

I checked the block in my dad's shop and it is infact a Mark IV block. So this can be bored .120 without any problems of flex, or overheating? I'm just a little concerend because the biggest I bored a 454 is .80.

Corey_68

ttt

427Hotrod

I'm with the other guys.....

.125 over on a regular MKIV block is good race only stuff. Usually requires block filler. I've seen some .100 over on the street, but I'm not sure the issues with cylinder wall stabilty and ring seal are worth the larger bore size.

I used a Merlin Block to build mine which can also go 4.625.

I used Brodix 2-Xtras. They have 365 cc ports and 2.30/1.88 valves. After talking to everyone I could find, it's almost impossible to overhead or cam one of these things. Ok , maybe not but they are very forgiving. Bigger is better!

I had a custom solid roller done with .672/.675 lift, 262/274 @ .050 on 112 LSA. It idles cleanly and also holds 10" of vacuum. It peaked power at 6100 rpm and torque at 4600 rpm. 702 HP and 687 ft lbs at the crank.

10.44 compression.

I know Mark and I could both gain from additional cam timing. These are actually very mild for these engines. It's amazingly smooth and driveable. It's going to be tough to keep the nice street manners and still make ridiculous power as well as have long valvetrain life after you go past this point.

If you are using a regular block just build a 496 and put some kille rheads on it. You'll love it.

I know of a 496 with Merlin oval ports that have been ported to flow around 310 cfm and a flat tappet cam that made 650+ hp. It has only dyno time and is for sale. Was professionally built. Guy decided to not finish the project.


jim

Corey_68

What is the difference between a Mark IV 454 like I have and a Bow Tie Mark IV like let's say Mark has in his '67?

GDaina

Difference is Mark IV ar not simese cylinder blocks, while Mark vI are siamese. Alos with the mark VI, you will have to address cooling issues....Electric fans and a good radiator will take care of that.

I would be hesitant to take any BB past .030". Just my preference, I guess.

Solid lifter roller is the way to go. Others have mentioned, mega cube motors make lots of torque. Give u an example, Im running a 1/4 stroker in a 502 block giving me 533 cubes, Doug Nash 5 speed. Starting in 4th gear at a light, I can smoke the tires off the rims. I cruise all around town in 5th gear,w/3:55's, turning 1000rpm. I can approach and go up a steep hill turning 1000R's in 5th, without downshifting, and nail it and the 68 responds without bucking, or spitting, and no need to down shift.

I am running square port heads, 2.25 intake 1.9 exh. comp cams AR288 street roller, solid roller.

Merlin522

Don't forget, a lot of this has to do with your goals. Most street engines just simply won't see the kind of rpm that would require the square ports. I'm using them because I wanted to go all out, but we certainly could have gotten by with oval ports. Also, if you are going to be in high rpm situations all the time, it would actually be better to use more bore & less stroke. That's one of the reasons I decided to go 522. We could eake out a little higher rpm without hurting things..

ML67

The Mark IV (2 & 4-bolt) designation refers to the generation of big block Chevys (396/402/427/454) used in Corvettes, passenger cars and trucks and available from 1965 – early 1990’s. GM updated the design to Gen V specifications (1 piece rear main seal, different deck cooling passages, elimination of mechanical fuel pump boss, different front cover, etc.) and more recently to Gen VI specifications. The updates are largely detail changes aimed as far as I can tell to eliminate the propensity of Mark IV’s to leak oil. I believe either/both the Gen V & VI blocks also use taller lifter bosses for increased strength, particularly in light of the fact that GM regularly use hydraulic roller lifters which are taller than flat tappet and solid roller lifters.

The Mark IV Bow Tie block was originally designed as a dependable 500+” engine for race applications such as Pro Stock drag racers and offshore boat racers. The Mark IV Bow Tie block’s cylinder walls are siamesed, IOW there are no water passages between adjacent cylinders, unlike the 360 degree cooling passages of the passenger Mark IV. This casting can be bored up to 4.625”. Externally the Bow Tie is identical to the passenger Mark IV blocks.

I agree w/ Jim and others in limiting the over bore of a passenger Mark IV to +.060”. Coupled with a 4.25” stroke crank gives a very strong and reliable 496” engine.

Hope this helps,

Mark

ML67

One more point about cooling -- I ran both a 427 & 454 Mark IV passenger block in my Vette prior to the Bow Tie 540. I never had cooling problems w/ the passenger blocks, and was concerned about the ability of the factory cooling system to handle the extra cubes and attendant heat of the 540. I'm happy to report that for 7+ years running the 540 I have found virtually no difference in operating temperature in any of the engines.

FYI

Mark

Corey_68

Thanks for the info guys. With your advice along with my father's, I'll limit the bore to .60 over. Since torque will not be a problem with 496ci's I plan to go with the rectangle port heads rather than the oval (I a have a set of each in my dad's shop). What size valves should I go with? 2.30's? Will they fit? I'm building the motor to handle up to 7,000 rpm's but most pf the miles will be on the street rather than the track. It will be a weekend car and will have 3.73 or 4.11 gears backed by a stick (a 4 speed for now, later a Richmond 6 speed).
Thanks again.

Flareside

What type of block is required for a 496? Can a 427 block support it, or must it be a 454? Has anyone put a 4.25 crank in a 427 block?



[Modified by Flareside, 2:51 PM 10/8/2001]

gkull

For chevy iron rect. port heads 2.25/1.88 are about the biggest without extensive porting. Generally you only bore what is required to clean up the cylinders. Like if it has never been bored you jump to .030 Then up the line with each rebuild. Whenever you jump to the max bore you turn the block into a throw away item on the smallest of problems or just bare ware with time. Like scuffing a cylinder that honeing can't take out. I have had sleeved blocks - so sometimes blocks can be repaired.

I was joking about .800 lift. That is not of any concern in a prostreet car. That causes periodic spring changes and you have to have heads that flow up into those lift ranges.

You just need to buy 4.25 stroker crank with all of the goodies.