[cobalt327]

Unless the combo is spec'ed out to have its power peak and cruise RPM high, relatively speaking, the rectangle port heads will be giving up power under the curve to the oval port heads, like the 049, etc.

If the idea isn't to take advantage of the CR that can be had w/the closed chamber heads, I really don't see any advantage in running them, other than (in this case) the rectangle port heads having good valves already in them and ready to bolt on, and the 049's presumably needing work.

In any event, don't try to open the closed chambers up to use unaltered open chamber pistons.

[ericnova72]

[QUOTE=cobalt327]Unless the combo is spec'ed out to have its power peak and cruise RPM high, relatively speaking, the rectangle port heads will be giving up power under the curve to the oval port heads, like the 049, etc.

[QUOTE]
Where alot of times I would likely agree with this, he did say 4-speed, a '65 Chevelle is relatively light, he wants it fairly rowdy, and is considering running a solid cam. I say set the compression ratio where it needs to be to use the head on pump gas, rev 'er up to 7500 and let it sing - instant wood

[cobalt327]

Originally Posted by ericnova72

I say set the compression ratio where it needs to be to use the head on pump gas, rev 'er up to 7500 and let it sing - instant wood

What I 'saw', was a guy who, w/the exception of the rectangle port heads, had a combination (a hydraulic roller, 780 vacuum secondary carb and a dual plane intake w/a cut plenum good for 6800 RPM(?)) practically MADE for the 049's.

But, as long as the OP is aware of the requirement to spin hell out of it if he uses the 291 heads- go for it, I suppose. Seems like chasing one's tail to use a pump-gas-friendly CR w/a cam that'll try to make power @ 7500 RPM just to use those heads...

The 4.56 gears and a 4 speed WILL be a hoot, though!

[techinspector1]

Stop it already with the 10 to 1 business...."spoken in a Jewish dialect"
Bore the block +0.060" and install flat top pistons having a compression height of 1.645" such as KB202-060. The stack will measure 9.780". Cut the block decks 0.020" for a zero deck. Cut your heads to achieve 106cc chambers and change springs to handle 0.700" valve lift. This will result in a 9.000:1 static compression ratio. Use an 850 carb on a RPM or Stealth intake manifold. Use long tube 1 7/8" headers with an X pipe right after the collectors. Use a solid roller cam with the same timing events and lift as a CompCams 11-700-9. I don't care who grinds the cam, but use the timing figures shown here....
http://www.compcams.com/Cam_Specs/Ca...?csid=508&sb=0
Use this head gasket for a squish of 0.041"....
http://www.summitracing.com/parts/FPP-1071/
Use these pistons or similar with 3cc relief....
http://www.kb-silvolite.com/test/kb_...tails&P_id=113

WARNING: Big block Chevies will not tolerate a flat tappet cam. That's my opinion.

RPM HP TQ
2000 167 439
2500 215 451
3000 273 478
3500 347 521
4000 418 549
4500 481 560
5000 527 553
5500 550 523
6000 544 476
6500 500 402
Peak volumetric efficiency 94.5 @5000
Peak BMEP 181.5 @4500

[ericnova72]

Originally Posted by cobalt327

What I 'saw', was a guy who, w/the exception of the rectangle port heads, had a combination (a hydraulic roller, 780 vacuum secondary carb and a dual plane intake w/a cut plenum good for 6800 RPM(?)) practically MADE for the 049's.

But, as long as the OP is aware of the requirement to spin hell out of it if he uses the 291 heads- go for it, I suppose. Seems like chasing one's tail to use a pump-gas-friendly CR w/a cam that'll try to make power @ 7500 RPM just to use those heads...

The 4.56 gears and a 4 speed WILL be a hoot, though!

The way I'm thinking is having a high compression ratio to go with big cam and high rpm isn't as all-fired important as every average person seems to think if the engine is big enough, and a 468 is. A little low end torque lost isn't a big deal when the engine is this big and will allow getting hooked easier on a tire that fits in a stock wheelwell. Power below 3500 will be of no consequence when launching with a 4-gear, and will still be more down lower than that than you really need.

Yes the 780 Holley is marginally too small but also not a deal breaker, use it until you can replace it or add a HP-type main body. Should be plenty responsive tho'....

Rectangle port dual plane is also not that bad, going for a shift 4-600 rpm past peak puts you right at 7400 or so for the shift and at a 6800 rpm power peak. It will need a 1" spacer at least.

Totally agree it will never fly with a hydro or hydro roller cam, NO WAY, but I am not afraid of solids in a BBC as long as a face-oiling lifter is used and zinc additive or race high zinc oil is used and the operator is willing to do a correct cam break in by removing the inner valvespring or using a stock spring during the break-in. OP could consider nitriding the cam if you really want insurance, still cheaper than Hydro roller and you have to have the rpm capability to make this whole package work. OP doesn't have a hydro roller, just was considering it at first but wanted thoughts on the engine and said in a later post was also considering a solid.

I'm no fan at all of the oval port heads, the average guy can't port good enough to really get them to work, it takes a pro to do it. The Rectangle port, on the other hand, I have personally had a hand in or been near 3 engines almost verbatim to what I have laid out, and they will make your sphincter pucker. Too many people have been spoon fed that oval port bilge by car rags for so long everyone thinks it is the only way. This isn't a 4500lb 4x4, it's a light Chevelle and the OP wants it kind of rowdy.

It'll be just fine at 10-1 comp on pump gas, no worries there. It will be just fine with a 3.90 rear gear, 4.56 will likely have you driving over the tach in the 1/4 unless you are running a 29" or taller slick.

Not looking to start an argument, the OP just wanted opinions and this is mine. "If your gonna be a Bear, be a Grizzly"

[Guy Hiltz]

I'm no fan at all of the oval port heads, the average guy can't port good enough to really get them to work, it takes a pro to do it. The Rectangle port, on the other hand, I have personally had a hand in or been near 3 engines almost verbatim to what I have laid out, and they will make your sphincter pucker. Too many people have been spoon fed that oval port bilge by car rags for so long everyone thinks it is the only way. This isn't a 4500lb 4x4, it's a light Chevelle and the OP wants it kind of rowdy.

Now theres a statement that I can agree with 100 %.
I'm on my 2nd set of rect port heads,the 1st were on the 454 LS-6 crate motor that was in my car when I bought it,those were the 188 heads,and they worked real nice,lots of bottom end.Now I've got a set of Brodix Race Rite rect port heads,and they work even better than the factory ones did.And you dont need to rev these 454 + motors to 7500 rpm to make power.I've got a UDHarold,(Harold Brookshire),custom grind solid roller cam in my 468.I asked for a cam that worked from 2500-6500,and thats exactly what I got,it makes peak HP around 6400 rpm.And I can guarentee you that it will indeed "make your sphincter pucker".
Guy

[Fastest65]

Hey you guys have been a huge help..thanks man.
The SRP piston that puts me right around 10.0-10.2
will be great. Should have pinging/knocking becasue of
low octane and be able to run premium with no problem.
Cool...thought I was out of luck. And a little leary to start
grinding away at new pistons due to lack of knowledge.
With your guys brains what is your opinion on the 11-430-9
Compcam? I have the Gen 4 block. With my 291's, compression
with the piston, 780cfm, Stealth, headers, good MSD HEI would
this cam be nasty enough? I don't have to worry about vacuum
with a 4spd. I do want nasty as hell. Want to go the hyd flat tappet
or hyd roller not solid.
Thoughts

[ericnova72]

I would not even consider a hydraulic flat tappet in a BBC, as you cannot get a hydro flat lifter with a face oiling hole that I know of, and without that face oiling hole BBC's are hell on flat tappet cams.

Can I ask why you took the solid flat tappet cam out of the picture?? They are not the pain to maintain that all the oldtimers and know-nothings think they are, valvetrain parts and valvesprings have come a long way since the 60's. You might have to adjust them twice a summer if all you do is street drive it, you will probably spend 4x as much time waxing the paint.

If you have to go hydraulic roller I think the 11-430 is too small, it will not be very "rowdy" at all. You need to go to at least the 11-450-9 or maybe better yet the 11-460-9 if you want it noticably rowdy.

Problem is that BBC valvetrains are heavier then the hydro portion of the lifter can control easily. You will have to be very specific on matching the valvespring pressures to what is needed or you will go into valve float earlier than you want. If you don't pay attention to valve spring selection you could run into valve float as early as 55-5700 rpm. Regardless of what you do you are going to have a struggle preventing float showing up above 6200-ish rpm due to valvetrain weight and the fact that the hydro portion of the lifter can only handle so much spring pressure.

Using Titanium valvespring retainers will be manditory to reduce weight. So will full roller rockers.
I would suggest a stud girdle too, to help stability.

[cobalt327]

Therre are other ways to oil the lifter/cam interface than a hole in the foot of the lifter, like correctly grooving the lifter bore. Tool shown is from Comp.

AFA the whole "OEM rectangle head vs OEM oval port head" has been beaten to death- anyone who cares to can find a couple dozen builds and dyno runs to do their own comparison as to where the power curve/RPM "break even" point between the two is.

I don't see anything mentioned about the crank, I'm guessing it's a cast OEM piece. Before I'd be spinning this deal up to 7500 RPM, I'd be stroking it a quarter inch and have 600+ ft/lb @ </= 4K and be done w/it. Then you can worry about the trans/drivetrain and tires.