c3_dk

I agree, that is why a bit smaller runner would fit better (unless a 383 short block I coming up soon)

Again I agree, that is why under 64cc would be a better choice. Or install new pistons with the 64cc heads.

c3_dk

I was only trying to bump up your compression, I don't think you will be happy with this setup, not because it is NKB heads, but because your compression/performance will not be as you wish for (low compression and too big heads)

Just my 2 cents.......

jb78L-82

I am not a cam, engine expert but do know a few things...When folks say that a small bump in compression does not effect engine power much, I often scratch my head since collectively with some other small changes, compression increase can add up to more than a few ponies in a given engine...One example that comes to mind IN GENERAL is the 70 LT-1 350 with 11:1 compression (I know the cams are not the same, the 70 LT-1 had more intake lift) and the 71 LT-1 350 with 9:1 compression..370 GROSS HP versus 330 GROSS HP..40 hp is a lot to me...

mobird

Except my engine isn't the L-48, its the Goodwrench crate engine. Unfortunately, I don't know which one as some had an 18cc dish, some a 12cc, and some were flat tops. I was always told that mine had a 12cc dish, but after doing some more reading it appears that that may not be the case.

I may just pull the heads off this next week to see what I"m working with.

If it IS a 12cc dish, then I have 9.5:1 compression with a 4-speed and 3.55 gears, would the 268 cam be an acceptable choice? OR should I go down to the 262?

Thanks

mobird

A 383 is in my future actually. The plan is to do this top end build, then in a year or so start building the short block on the side. I can re-use the Performer RPM intake and the heads, and I'll be building a roller block so new cam anyway.



And I'm with you on getting the compression up, after doing some reading it turns out that there were 3 different pistons that went in the Goodwrench 350 depending which crate motor I have. I bought the car with the motor installed so I have no idea what it is, so I'm gonna get the heads off soon and see what pistons I have.

GOSFAST

Haven't read the entire post here but I would strongly recommend changing to a retro-hyd roller platform FIRST, then choose any other mods after that one. We make the same recommendation to anyone wanting to do a decent rebuild AND chase a bit of HP at the same time.

Through the years we've dynoed a high number of these SBC retro-type builds and have established the roller lifter platform by itself (with no other changes) will free-up in the neighborhood of 30 HP (nominal) to the final number.

We do flat-tappet builds but we get to checkfor any potential issues immediately after the dyno testing, BEFORE they ever get delivered.

Thanks, Gary in N.Y.

P.S. There's a number of reasons to choose the roller route, first, like I mentioned, the "free" HP, but the best overall reason is eliminating the fear/chance of "flattening" any lobes on the initial break-in period. Once a lobe goes "south" much of the monies one spends becomes wasted, and you will be doing all over again fairly quickly!! This is my own opinion from a strictly business standpoint where we need to stand behind EVERY build we do.

REELAV8R

Would be a good idea to cc the pistons before you buy the heads to see what you're a actually working with.
You can have your heads shaved .030 which would bump your CR up a bit.

I would say that the Lunati 268 is a bit too much for decent low end torque given your current plan. Operating range 1800 to 6200.
The RPM intake is not developed for low end torque either.
A 200 cc runner head is not for low end torque on a 350 engine either.

Using the components you have lined out you are building an engine that will come into the power band in the 3500 - 4000 RPM range and max out at maybe 6500 RPM.

There are varying opinions on this but I believe that a good high torque street engine requires good intake velocity. That means smaller runners and decent compression. Your compression at 9.0:1 is good with smaller runners and a smaller cam and a idle to 5500 dual plane intake manifold.

So to answer your question I believe that the Lunati 262 would be better suited than the 268 given what you have planned.

I built my previous engine with 180 cc runner heads 9.9 CR. Unfortunately the heads cc'd out to almost 200 cc's. That single item I believe slowed my intake velocity enough to not bring on my power until 3200 rpm or so.
I had a 2600 stall torque converter and a 3.08 rear end. So it always had to struggle to go between the torque converter stall and the 3200 beginning of the power band.
I used and am using a 270/270 advertised 219/219 @ .050 duration cam with a 108 LSA. The overlap is 54*. The cam easily runs to 6000 RPM even with the Edelbrock performer intake.
Not exactly a apples to apples comparison but the cam and the intake were not limiting the RPM capability. They were not however a good match for the 200 cc runner heads. Now I am still in the process of installing proper 180 cc heads.

Just a hobbyist though not an expert or professional in this stuff, so take my opinion for what it is worth.

worship79

Had the Goodwrench 350 myself. Also did a top end first and a 383 later. Still regret not doing it right the first time and putting all my money in a bad *** roller engine from the get go.

However, I learnt a lot though and had fun during both builds. So choose wisely and post plenty pics for us

tracdogg2

A lot of talk here on compression. All of it good. But two important points are being missed. Flame travel and quench. A dished and beveled piston have very poor flame travel and no quench.The dish and bevel create a ridge on the piston opposite of the spark plug and towards the end of the flame travel. This creates detonation.
Also no one is using dynamic compression ratios. Forget about static compression. In the real world it means nothing. For what you a wanting you need a dynamic compression in the 7.9-8.1 range With the Lunati cam that puts your static compression in the 9.5-9.6 range.
Those 200 cc heads will want more cam, more compression, and more rpm. More than you shortblock will allow. By the time the heads start working your cam is running out. Been there, done that, engine growing dust under the bench.
Mike

c3_dk

Agree Mike.
Here is how I made my engine.

REELAV8R

OP, have you thought about ISKY cams. You can stay flat tappet as you want and get a 108 LSA which gives great mid range power and extends the top just a bit.
Here is a 264/264 cam on a 108 with plenty of lift. Will work with 9.0:1 CR. Doesn't give any extra duration to the exhaust side but I figure a guy could experiment with put 1.6 rr's on the exhaust and 1.5 rr's on the intake to give the exhaust a bit more room to move out.

http://iskycams.com/cart/index.php?m...roducts_id=675

Or you could go with a bit less lift (less likely to wipe i believe) and use this cam;

http://iskycams.com/cart/index.php?m...roducts_id=270

Roller rocker is certainly much better IMO as well. However it sounds as though budget may prevent that at this time. The extreme and voodoo line of cams have a reputation of wiping more often. So the Isky may be a good option.

diehrd

Build it to the ZZ465 spec .. That is about all the power a 350 will give you and still have good manors and as a 350 should scream when ya stuff your foot in her


200 CC is fine on a 350 by the way GM used 210 heads on a ZZ motors 350 and 383

63mako

You ask to analyze your build then refuse to consider change. Lets start here, the bottom end of your engine is a 5600 RPM redline bottom end.
My analysis is your head choice is to big of ports and chambers. Compression is to low, cam is to big.
These heads:
https://www.summitracing.com/parts/t...0002/overview/
will bump compression to a better place and have a spring that works with this cam.
https://www.summitracing.com/parts/c...10-4/overview/
which are a better match for your bottom end, trans, rear gear and intended use. It will also have a functional rumble. A roller cam would be a much better option but looking at cost.

Taijutsu

There is too much info on building a SB Chevy. Like many you have an idea of what you want, but no clue on how to get there.
We have members that have earned their experience the hard and expensive way. Listen to them!
If you wish to reinvent the wheel, don't bother them. If you want some solid advice on what works and what doesn't, ask!

Do your homework and have a budget.
How fast do you want to go and how much are you willing to pay?
If you are getting into some serious power, plan on putting some money into brakes and chassis.

If you want similar results as someone else. plan on using the same parts.

JMHO

R

gkull

This should dispel any 200 cc myths. The motor has a 224/234 H-flat from summit and just changing through 10 heads made from 370 to 430 hp or so.

compression is a good thing. But if you are stuck with a static compression because of the lower end. You boost dynamic with cam choices. 110 lsa and lower bleed off pressure and 112 or 114 lsa build pressure with the same lobes

c3_dk

That gives (with 18cc pistons):

Static Compression: 9.7
Ratio Dynamic Compression: 8.14
Quench: 0.040 (I've used fel pro 0.015 head gasket)
Intake Valve Closing Angle: 58

cv67

not getting into whats "proper" but did take a goodwrench shortblock put a Isky 270 mega HFT in performer rpm, Eddy carb headers etc HEI usualy stuff. Ran good even in a heavier shortbed truck. This one had stock 882 heads also. With some gear and converter would have been much better.
If the OP has more gear a stick think it would run good. Textbook perfect maybe not but was lots of fun.

63mako

Nice.

REELAV8R

I would agree with the too big of ports and a bit low on the compression. However with those style piston tops a guy could run into trouble as tracdog2 pointed out. They offer no real squish and promote poor turbulence and flame travel. Too much compression and detonation may be the result.
I also like the specs on the cam, just don't trust the manufacturer.

Here is some good advice from a guy who certainly knows what he is taking about. It's a 383. Note the ideal port size that was determined overall for that displacement.
http://www.superchevy.com/how-to/eng...ons-measuring/

Some important excerpts from that article.

Fast81

IMHO - your parts combo will be a dog to drive on the street until you hit ~2000 rpm.
As stated above, your head ports are too big for velocity and too little compression for a 268 cam.

I did this same cam in a 9.75:1 355 with AFR 180 heads, RPM AIRGAP intake, LT headers, 700R4 with stockish stall, and 3.55 rearend and it was too soft below 16-1700 rpm to be a satisfying street driver...................BUT when it did hit 17-1800 it screamed all the way to redline @~6000 rpm. I'd go no bigger than 185 on the heads & stay under 262 on the cam for your stated use of the car.

just trying to help