Well, just when I thought it was safe to finalize plans for a mild street 454 stroker project, I received some very damming advice from an experienced and trustworthy engine builder here in town.

During my discussion with him today concerning my planned combo, he immediately shot down using GM 063 closed chamber ovals that I was wanting to use for a mild street application. The reason being that those heads would essentially "smother" the engine due to the greater pumping action of the bigger 4.25" crank and longer 6.385" rods vs a stock 4" crank & 6.135" rods even at low rpm. However, he went on to say that he would build it however I wanted, just that mucho horsepower would be sacrificed.

This was to be my mild street combo:

454/489 c.i.
Skat Cast rotating assembly
GM 063 closed ovals (light cleanup w/standard valves)
Flat top pistons (about 9.8 CR final)
VooDoo 276/284 Hyd.
Edelbrock RPM intake
Jet Performance 750 Q-Jet Carb
1 3/4 headers
TH400 w/2400 converter
3:31 gears

I realize the superiority of most aftermarket heads over the old GM 063's, but I'm not trying to shoot the moon for all the horsepower I can get. Now, I am at a point of trying to persuade myself that if I go ahead and use the 063's anyway that I can still have a solid 500 horse engine to drop into my 67 Chevelle that would be fun to drive on the street or at the strip.

Do I really need aftermarket heads for my mild combo or proceed with a light cleanup on the old 063/s? I am trying to save money on this project by using what I already have.

Thanks, Charles

I'd built it. If for some reason you want to go with say the Brodix racerite Ovals down the road, you can always do it or do like Crankitup and go with the Edelbrock heads and you'll have a mid 11 sec. performer at least.

Onlu shortcoming I see in the build are what pistons to use. With 063's, you will want flat tops. Later on changing to open chambers will net lower compression. With running 3.31 gears, it will be a torque monster.

I would use your heads but not untill I had somebody who knew what they were doing increase the valve sizes to 2.19/1.88,unshroud the chamber, and open up the bowls with a Serdi seat and guide machine or equivalent. then I would at the minimum blend the bowls or better yet full port job. Those heads wiil work really good if you work them right.

Hi Charles, here's a copy of previous post on a unit built for a member up here. This unit has ALL factory components included except for the stroker. It has the low-rise intake, the cast exhaust manifolds, and a Q-jet carb. It is an honest "sleeper", believe me! I'm not certain why other shops have issues with these size builds and HP numbers?

A mere 1HP/Cu.In. gets you to 500!! "Piece of cake" for most BB's. Remember, this following unit HAD to be "stock-appearing", if you don't have that type of limitation, I see all types of possibilities with an aftermarket intake, carb, and slightly larger cam. We can hit the 500 HP number with a 4.000" stroke on "pump" without these limits!!!

(Quote) 1972 LS-5 Stock-Appearing 1/4” Stroker.....

this is another 100% original appearing unit but with a 4.250" stroke/long-rod in place of the 4.000" piece. This was done like the others due to the fact the 454 damper/flex-plate combo must be maintained. This unit appearance-wise has nothing to do with racing, only for car shows!

The unit came off the dyno Saturday, March 10, 2007 for another forum member's ride.

I'll give you the components used first, and the final numbers at the end. Remember this is NOT built as a “race” unit, but as just another 1972 "factory-appearing" LS-5.

1-Factory 2 B.M. "289" 2 B.M. block using ARP fasteners.

2-Eagle 4.250 "4130" forged/dependent balanced, factory balancer/flex-plate

3-4340 Scat +.250" bushed rods (had to be modified to clear factory oil pan).

4-Probe pistons, domes machined to 9 cc's for corrected C.R. @ 9.5:1, S/P 1/16, 1/16, 3/16, S.T. file-fit ring pack.

5-Comp Cams (Custom) H.R. 230/236 @ .050" x .550"/.550” x 112L/S on Steel/Cast gear blank (–9) and a set of 854-16 H.R. retro-lifters

6-Factory #241 114cc heads, SBC intake valves 2.125" x .343", stock 1.720" x .375" exhaust valves. Incorporated some very mild in-house porting.

7-A set of Comp Cams 928 springs (145# @ 1.940" / 340# @ 1.400"), 741x10* steel retainers, 611-8 intake locks, and 77104 Lunati exhaust locks.

8-Comp Cams Pro-Magnum’s, to fit under the stock valve covers, and a set of Comp's 3/8 pushrods.

9-G.M. stock cast iron low-rise intake #6263753 and stock (modified) Q-jet carb. We did not do any carb modifications of our own, the customer had the carb sent in finished. If you have any questions about it I will have him contact you individually or on the site! The carb worked flawlessly "from the box". Anyone considering using the Q-jet pay very close attention here, you may want to contact his vendor. I believe it’s a “Carbs Unlimited” piece.

10-Factory "low" valve covers, with single thick gaskets, period correct!

The first set of numbers at the 9.5:1 C.R. came off at 471 HP @ 5500 and 523 Ft. Lbs. @ 4200, with open headers (1.750”), another true BB "pump-gas special" that may well run on 89 octane. Customer should be able to run all the timing up front at 34*/36*. We shall see!

The unit was delivered, out the door, at 463 HP @ 5700 RPM and 541# Torque @ 3600 RPM with his cast exhaust manifolds. It gave up only 7-8 HP from the headers. One of the best features here is the fact it maintained 17” vacuum idling at the recommended factory RPM!

I would add this here, this may be one of G.M.’s worst intake manifolds ever produced, right along with the “stock” LS-6 piece! I have a similar manifold here from an early 396/350 which uses the Q-jet but appears more “race” oriented. The carb, also a Q-jet, sits about 2 inches higher. This test is upcoming, but on a “bone-stock” 396. These are my own opinions however from numerous test results!

This particular build can be used as a guideline for anyone interested in keeping with the G.M. factory look along with some really substantial HP gains from the “OEM” LS-5.

(Add) Thanks Stan, it was my pleasure and I was also very pleased with the final numbers. Should have a real good “seat-of-the-pants” feeling in that 4000# car with those torque numbers!!!!

Thanks, Gary in N.Y.

P.S. The HP/Torque numbers were first recorded using open headers, the second set of numbers are with the customer's cast exhaust manifolds and mufflers. Back on another previous LS-5 stroker, I had stated I believed we could get to 500 HP with some additional modification, this unit confirms it is possible while still appearing “bone-stock”.

Double P.S. I also believe it would be entirely possible to “see” 500 HP on a stock stroke (4.000”) 454 LS-5, BUT would not see the Torque quite as high with the stroke difference! It would take some slightly additional compression and just a tad more camshaft. The slightly higher C.R. MAY enable similar Torque numbers even with the shorter stroke. Would take more testing to prove! (End quote)

Thanks, Gary in N.Y.

P.S. Finsh your build "your" way. This type of unit above will have "zero" tuning issues with ALL the timing in "up-front". It will be another
"maintenance-free" unit fun to drive!

Charles,since you doing a light cleanup on the heads i would also use manleys swirl polished undercut raceflow valves that have better flow to complement the head cleanup especially if you are running headers and a good flowing ex system.

Dont worry, your 498 will perform very well with the 063's if the machine work & assembly is done correctly along with dialing in the timing & fuel calibration later on after you fire it up.

Yes you could make more hp with much more exspensive heads but again the 063's will do well with your setup . This is especially true with the cleanup you mentioned,if you install Manley Raceflow undercut valves for better flow,along with headers ,good breathing mufflers,and 2.5-3 inch mandrell pipes throughout the ex system.

Scott

gnicholson hit the nail on the head. 063's are very similar to 215's and 290's. One former member here had a 468 with reworked 215's on a Chevelle that ran 10.30's. A good machinist with a Serdi can do some impressive chamber work with valve unshrouding and really pick up moderate to high lift flow.
Sounds like an engine builder trying to sell some heads to me...

the only thing I see not-so-hot about your combo is what GRN69CHV said about changing heads later. You can't really use domed pistons with those heads and have a streetable combo, it'll ping itself to death. Any heads you get later will have larger chambers and need domed pistons. But, it'll be a torque monster now and you can deal with later, well, later.

All that aside, it would really be worth your while to have a knowledgeable head guy fix up your heads as gnicholson suggested. your engine really needs that, but it needs to be a good head guy who understands how good the Chevy heads can do.

Use those heads, if you can afford it at all, get the larger valves installed with some port work and cleanup, and you'll probably never want to change them! No offense to your engine guy, but those will work very well....and down the road, even if you use flat tops, you can get a set of Edelbrock aluminum heads that are milled to 100cc chambers. But you'll be happy with the 063's, the engine will NOT suffer with them.

I am running some ported 063's with big valves that flow pretty well.
My 454 with a little 223/231 @ .050 hydraulic f/t runs mid 12's @ 107-108 MPH with 3.31 gears and those heads.

Thanks for the positive reinforcement folks. I think I will consider some additional port work and larger valves in those 063's. I just might sequeeze out that 500 horse goal with some fine tuning, etc.

I still cannot understand the basic principle of why the installion of larger valves achieves better breathing. It seems to me that the port size pretty much governs the flow limits of an engine, not valve size in the chamber. Doesn't increasing the valve size also introduce a new issue.....shrouding?

Charles

Doesn't increasing the valve size also introduce a new issue.....shrouding?

You have to relieve the chamber once the seats are cut for the larger valves

To support the complication with a future head upgrade. I had closed chambered heads that let go (breach in the valve seat - so be sure your porter dude doesn't F this up!). I upgraded to Merlin oval ports. They come 119cc. In order to keep the performance I wanted, I had to mill them down to 113cc. ouch.

But, it sounds like you don't want to race the car, so anything around 500HP should satisfy street life. I say build it the way you initially wanted to with the GM heads.

I bought a new pair of Merlin cast-iron oval jobbers w/ 2.19"/1.88" valves b/c I was afraid of getting hosed locally rebuilding my good -781's w/ big valves and such.

And then I pistoned my 496 to get it at 9.5 to 1 and then used shims instead so I'm about at 9.8 to 1!!

If I had this to do over, I would do onna two things!!

I'd either buy a set of Canfield 310 aluminum jobbers for weight savings OR W/P's, (I wanna say VR's(??)), 290 cc cast-iron jobbers..

All this said, Ed got his 468 into the low 10's w/ a set of -215's so I figure -063's CAN BE MADE TA RUN FINE TOO!!!

pdq67

The short answer to your question about why you should use bigger valves; first of all the b block chevy is under valved anyway especially the stock 206/172 sizes in the stock oval heads.Going to bigger valves gives you a good increase in seat area which helps low and midlift flowand the larger throat area produced from the machining and bowl blending helps mid to high lift flow. The larger valves will produce more shrouding but your hopefully qualified machinist should have swept the chamber with a radiused cutter during the machining operation.The port itself doesn't become a restriction untill around .500 of lift which means if your running a small cam larger valves and a good seat and bowl job should suffice. Anything approaching .600 or more would benefit more from a full port job. On a modest performance street motor of 550 hp or so the main benefit to aluminum heads is the 75lbs. of weight you'll save

Gnicholson, that explanation makes sense to me about improved low & mid lift flow due to larger valve seats. I think I get it now.

With the large valves and light port work done to the 063's, and referencing my street combo in my original post, is 500 horsepower realistic?

Thanks, Charles

I think it should make about 525-550 with the head work described earlier minus the full port job. I feel this is a consevative estimate. With a correctly specced roller cam that is still streetable and good port work you should have close to 1.3 hp per cubic inch which is about 630 hp if you want to dream about a more powerful combo. As it is it should be plenty fast. Just get a guy who can do the heads right. The seat angles , throat diameter,etc are important to good flow and velocity.