J. Swisher

I am in the final planning stages of my 468 big block project and was wondering if some advice could be given.
Bottem end consist of stock rods polished and peened, with arp rod bolts installed. Compression ration will be 10:0 to 10:25 courtesy of SRP +.060 forged pistons.
First question is I am looking at either using a Comp cams XE274H specs on this cam are advetised duration 274in. 286ex., at .050 230in. 236 ex, lift is .552in. and .555ex
or XE 284 H specs on this cam are advetised duration are 284in. 296ex., at .050 240in, 246ex, lift is .574in, .578 exhaust.
Comp cams 1.7 roller rockers will be used.

Next question is Rectangle or Oval Port cylinder heads.
The Oval Port head Im look at is:GM Performance Parts Aluminum #12363390. the rectangle port head im looking at can be seen here it is the http://www.worldcastings.com/docs/catalog/pg17.pdf. It is the 320 cc version.
The intake and carb will be an edelbrock performer rpm and an 870 Holley street avenger.
Exhaust will be hooker headers and magnaflow exhaust.
The car has a 2800-3000 stall converter in it, 3.55 gears in the rearend and the car will be used for a little bit of every, except as a daily driver, so I can err a little on the rough side.
Just like to say thanks to everybody for all the great help Later JOSH

69 N.O.X. RATT

It all depends on how much power you want to make, and the rpm range you want to make it in.

J. Swisher

Im hoping to make the most availble power in the 1500-6500 rpm range with peak hp coming on around 6000 rpm, thanks JOSH

69 N.O.X. RATT

The G.M. heads are a very good choise for that power and rpm range. I would go with a bigger cam than either of the ones you listed. I have a similar set up to what you are building. I have an Air Gap intake, Edelbrock Oval RPM heads 10.25 compression etc. The big difference is my cam. I have a solid roller 242 and 248 at .050 and .646 / ,653 lift. My car made 450 rwhp (6100 rpms) and 470 rwt (4100 rpms) all exhaust in place. If a roller is out of the question I would at least go with a solid flat tappet 244 at .050 or so. :chevy

bence13_33

Personally I have become partial to solid flat tappets. IMO a solid flat tappet cam is one of the best bang for buck cam choices you can go with. The nice thing about a solid lifter cam is that it gives you more options. For example I was drag racing a Monte Carlo down at the track. He had me by about 3 car lengths. When I hit third gear I started reeling him in hard. I was approaching the finish line and was tachin 6500RPMs in 3rd gear....I decided to keep it in 3rd crossing the traps so as to not lose momentum. I ended up revving to 7000RPMs. Try doing that with a hydraulic lifter cam...I dare ya :D.

Another thing I have grown to like about the solid lifter cam is setting the valve lash. Comp Cams recommends .022" lash hot. You can go +.006" or -.006" depending on what you are going for. If you lash your valves tigher (.018") it gives you more effective lift thus giving you more top end. If you lash the valves looser (.024") it gives you less effective lift but more bottom end.

Just thought I would throw the idea your way. I'll never have another hydraulic cam in the 'Vette again.

norvalwilhelm

I am also a fan of bigger cams and for the buck a flat tappet solid is hard to beat. I set my solids in the spring and don't touch them again until the car goes away in the fall. They do not need constant maintenance.
For heads big is not better. I had a set of wild rectangular port on a 460 and the motor was a dog below 5000rpm. I would go with the oval port. It would run like crazy from 5 to 7500 but who drives in this range most of the time?
My best cam was 256, 264 @ .050 with 106 lope centers and .648 lift. My present roller at 244 @ .050 is too mild. Produces lots of vacuum but no top end.

bence13_33

Norval:
So you used to rev your 454 to 7500RPMs? I've been thinking about getting a good set of aluminum R-Port heads and revving it to 7000RPMs (possibly higher if it could take it). So do you think my motor could take 7500RPMs? It was balanced and has forged pistons and 4340 H-Beam rods w/ 7/16 rod bolts....but it only has a Cast LS4 crankshaft and 2 bolt mains.

69 N.O.X. RATT

Norval

You might want to inlude your sig with the drivers view of your motor :lol: other wise you might scare the poor guy :chevy

bence13_33

69 Ratt:
Nah, I've seen his motor before. I actually wish I could afford to slap an 8-71 street blower on my car. Norval helped me out a lot throughout my 454 build up.

norvalwilhelm

Shane. My 454 saw 7500 too many times so I got a rev limiter. I wouldn't be without one. Comming out of the hole even with slicks the thing use to get away from me and before I could shift the tac needle was pointing straight down. I could even be higher then 7500. This is not recommended continue practice for the 454. I set my rev limiter at 7000 and regularly took it there.
With the blower I lost my desire to hear it rev. Now I set my rev limiter at 5600 so don't mind bouncing off it.

norvalwilhelm

Forgot Shane. I have a steel crank, 4 bolt mains and all studs. The studs add strength to the block but make it a pain to work on
Here's the picture 69 N.O.X. Ratt

Shane has seen it before.

427Hotrod

As everyone is saying....lots of ways to go about it.

First off...forget the hydraulic. I'm with everyone else. Hydraulics are for your pickup truck. For the toys use a solid. They don't require as much work as people whine about and they make more power than with less hassle.

Most people spend half their lives trying to make a hydraulic act like a solid. They "zero" lash it etc to make it rev higher without pump up. Well, now all they've done is make it unable to do the one thing it accell's at... keep the valvetrain quiet. Now it's noisy and slow!

Plus big block valvetrains are heavy. You don't want to mess around and have trouble.

If you are willing to have it "thump" a little, you definitely need to go up on cam. I've had great luck with several different ones.

There is a Crane # 134691 that is about pefect. It's .580/600 and 290/300* adv. I can't remember the .050 numbers but it's around 256/260 or so. 110 LSA. It will idle pretty decent and twist well past 6500-7000 rpm when needed.

The Crane #134671 is very similar but has .600/.620 lift and 310/320 adv. It's pretty hairy but has a top end that is unreal. It never stops pulling.

I've used the Crane # 134781 at .567/.590 and 314/324 adv. on 108 LSA. Sounds tough but nowhere as strong as either of those other cams in a 10.5 comp. bigblock. Too much cam without some more compression.

The Comp 294 Magnum cam is 294 adv. and .579/605. It's on 110 LSA too I think. Very strong cam. Close to the first Crane but not quite there.

I've also used the Comp 306 and 310 magnums. They are both pretty rough and will need lots of gear and rpm to make them happy. Probably not what you want.

If you go with a street roller, the Comp 288 adv/244/244 @ .050 and .623/.623 is a great street cam. It will idle with 14" of vacuum and pull past 7000 rpm. Very driveable. There are several different ones but on this cam I think the non split pattern one is the best.

It will pull almost as hard as some of the other solids I listed, but have much better manners. Not absolutely necessary, because the others will behave fine. I've run many more, but these give you a ballpark idea.

On heads, again several ways to go. First, I doubt you want rectangular ports with your gears. I did back to back tests in the past and found that with lots of work I could make it run as fast with rectangulars if I revved it past 7500 rpm and went up to 4.56 gears instead of 4.10's. Not a good plan!

You could find a really good porter or do it yourself and make 550-600 hp easily with GM iron oval ports. The easier way is to use the GM aluminum ones. But they also need some bowl work to perform well. There are scores of 10 sec. big blocks around with GM iron ovals.

I'm also a big believer in the Merlin iron oval ports when cleaned up. They have a much better ex port but are HEAVY!

I would also look at the Pro Action heads. I've recently seen some and for the $$$ are absolutlely the best looking out of the box heads I've ever seen. Ck with MountainMotor here on the Forum....he was getting some great deals on them.

Best bang for the buck is to get a good solid flat tappet like everyone said. Invest in some good springs and retainers and use a set of roller rockers. You'll have lots of trouble free miles.


JIM

69 N.O.X. RATT

Bence: I know you have seen Norval's motor, I meant for J. Swisher. :chevy

Jughead

NOW..has a pump gas 732 HP 540" Merlin/Brodix,
Chassis Dyno'd at 615.7 at 6200 RPM! All motor!



Yikes, Jim! :eek: 615 RWHP!!!!

J. Swisher

well thanks for all the help from everyone. Well after alot of thinking and asking the engine shop that did the machining, I settled on a Comp Cams 294S Magnum and the Gm performance parts aluminum oval heads with a small amount of cleanup work done to them (port matching, and some bowl work). Thanks again for all the help.

427Hotrod

I've got the whole car apart right now(body off) doing the Dana IRS install and frame reinforcing.

Plus the engine is apart too for "Phase II"......

He He He...........

Last version was the test setup....now we're gonna make some pump gas POWER!!

Jim