could anyone give me an estimation?

[nelsonusmc]

Ok so I was wondering if I could get an estimation so hear is my setup.
355 sbc 4-bolt main 4-valve relief hypereutectic pistons cast internals
just under 10:1 compression
292 heads (came off a 69 z/28 camaro) that were ported to about 195cc
2.02/1.60 Manley street-flow valves w/3 angle valve job
Mr Quickfuel SS-750 carb
Comp cams xr294hr cam
Ported Edelbrock Victor Jr. intake
comp cams hydraulic roller lifters
1.6 Skorpion roller rockers
comp cams magnum push rods
double roller timing chain
Lunati Springs retainers and clips
Holley pro mechanical fuel pump
MSD Pro-Billet Distributor

Well this is my first engine build, a buddys neighbor ported heads at a local speed shop here in Indy and I had
him port my intake and heads and assemble them with a valve job. I told him my goal was to have 400 to the wheels.
Could anyone give me an estimation on what they think it will make?? Its going in a 74 vette and I am trying to decide
as to whether I want to put a T56 or Muncie 4-speed or T5, what timing I should use... its my first build so i don't know much
Thanks

[Ron Sutton]

Hi Nelson,

I think there is a contradiction on your heads. The GM 340292 "Turbo" heads were the 1st over the counter race heads from GM offered in the 70's, but never came on a production engine. Pretty good head for that era. They had good port wall thickness for extensive porting if desired. I found these heads to have a wide range of "possible flow" depending on the quality & amount of port work. So accurately "Guestimating" the flow you have is not possible ... and that will play the biggest role in the power potential of this engine.

If you have the funds (small amount) .... I'd pay a shop to flow the cylinder heads so you know what you have. This would play a role in some of your decisions I'll outline below.

Before I start with some suggestions, just know that I'd typically dial in an engine for optimum power on the dyno playing with the fuel curve, timing curve, cam timing & occasionally exhaust tuning. If you do that, just consider my suggestions a starting point. They will be close. But you may find 2-3% more power with your combo by fine tuning it on a dyno.

Some assembly suggestions:
1. Don't get carried away with bearing clearance. Keep the rod clearance around .002" & the main clearance around .0017-.002"
2. Consult the piston mfg for piston clearance. I don't have experience with hypereutectic pistons, but know they need smaller piston-to-bore clearance than forged pistons.
3. The "squish clearance" from the top of the piston to the the cylinder head surface is critical for power. Keep it in the .035" to .040" range. Adjust small amounts with your choice of head gasket. Large amounts require decking/milling the block or heads.

4. Pay attention to the piston-to-valve clearance or be prepared to grenade an engine. I suggest .090"+ piston-to-valve clearance on the exhaust valves & .110"+ piston-to-valve clearance on the intake valves.

5. As you phase the cam timing, check the piston-to-valve clearance.
* Reminder: As you advance cam timing, you are decreasing piston-to-valve clearance on the intake valve & increasing piston-to-valve clearance on the exhaust valve. As you retard cam timing, you are increasing piston-to-valve clearance on the intake valve & decreasing piston-to-valve clearance on the exhaust valve.

6. I suggest advancing this camshaft 4°-6°. If you get the cam where you want it ... and you find you don't have enough piston-to-valve clearance ... you'll have to make a decision to either have the pistons flycut for more clearance or adjust the cam timing to less than optimum.

Some tuning suggestions:
A. Set the total timing at 36° ... all in by 2500-3000 rpm.

B. Set the initial timing in the 15°-20° ... as long as your starter can handle it and start the engine fine. This higher initial timing will help the engine build more power at idle, run smoother & take off easier. It will also idle with a much smaller throttle blade opening which helps the fuel curve & reduces problems with run-on after you shut the engine off. If the starter struggles, back down the initial timing until the starter works fine and see if you're happy with the idle & take off. If not, you can always buy a HP starter & bump the initial timing back up.

C. Make the investment in 6 sets of cheap spark plugs right from the start. Buy 3 sets 1 step hotter than you plan to run & 3 sets of the heat range you plan to run. Don't buy $7-10 double-platinum, diamond encrusted, aerospace tested, Nascar approved, 19-prong spark plugs ... yet. You need them to be cheap so you won't cry when you throw them in the trash after a short while of running them. More on this below.

D. Start with the carb jetting on the rich side & start with a set of cheap, 1 step hot, spark plugs. Set the idle timing first thing after firing the engine ... then the idle rpm as the engine warms up. Next, tune the carb's idle A/F screws evenly ... and the idle rpm ... until you reach highest idle vacuum numbers at 900 rpm idle. As you make it idle better the idle rpm will go up. Keep lowering it to 900 rpm and adjusting the idle A/F screws until you max out.

*You can decide to lower or raise this idle rpm number later, depending on engine idle performance & your preference ... but always tune the idle A/F screws for the highest vacuum at your chosen idle rpm.

P.S. Buy 2 extra power valves before you start this process. Anytime the engine back fires while you're running the cold engine, setting the timing, tuning, etc ... usually blows the power valve (rips the diaphragm) ... and will make the engine run richer (equal to 6 jet sizes). So be prepared to check and/or replace the power valve when this happens.

E. After the engine is in the car, running, idle & timing set, confirmed no fluid or exhaust leaks, and you're ready to drive it ... take out the 1st set of plugs and "read them." If they are black or wet, don't fret, just yet. If they are white or light tan on the outer ring or center porcelain ... you may be on the lean side. Put in a new set of the cheap, 1 step hot, spark plugs ... increase the front carb jets by 2-4 numbers ... rerun the idle tuning sequence ... and go drive it.

As long as the car runs ok, drive it some and put some miles on it in different rpm modes below 5000. Come back home, pull the spark plugs & "read them". Assuming they are dark tan/brown or even black-ish ... the engine is rich ... and you will want to lean the front side of the carb jetting down in steps until they read ...
* Off white on the porcelain
* Dark brown/black (but not wet) on the outer ring
* No spots, dots or bubbles on the porcelain

Everytime you make jet changes, the idle A/F screws will need to be fine tuned again, but it is a small change.

***This is why you need several sets of cheap spark plugs. Once a plug has colored up from being rich ... you can not run the engine leaner & have the leaner reading show on the plugs. The plug stays the darker color from being rich. So you need new plugs every time you jet the carb leaner. Everytime.

P.S. Some old timers will suggest sand blasting the plugs clean & reusing them, but that's a PITA. Just buy $2-3 plugs & rock-n-roll. Use the "1-step hotter" plug sets first, then switch to the correct heat range for final tuning.

F. Then, when the engine is ready for higher rpm runs, you'll do the same procedure up to 6500-7000 rpm.

Getting down to numbers ...
If the ported heads flow only slightly better than stock, this combo could make as low as 410# of torque at 5000 rpm & 440 HP at 6000 rpm. It will pull strong to 6500 rpm & fall off hard after 6500 rpm. My suggestion for headers for this case would be 1-5/8" diameter x 34" length. I'd probably run the cam timing 4° advanced.

If the heads have been ported really well and flow close to the best I've seen with 195cc, this combo could make as much as 440# of torque at 5000 rpm & 500 HP at 6000 rpm. It would pull strong to 6500 rpm & fall off progressively after 6500 rpm. My suggestion for headers for this case would be 1-3/4" diameter x 32" length. For this scenario I'd run the cam timing 6° advanced ... piston to-valve clearance permitting.

Making the optimum header selection & cam timing decision are the reasons I'd have the heads flowed.

If you have other questions … or once you get it going, if you need more tuning help ... just ask.

[nelsonusmc]

Im still picking out my transmission, the car will mainly be a steet/strip. Would I be better off with a Muncie 4-speed, T5, or T56?? I was thinking about a M21
close ratio but I didn't know if it would
A. shift me down too low in my power band or
B. Id get even worse gas mileage
The only thing I think a 4 speed would be better at is there would be less shifting.

[Schwartz Performance]

The T5, T56 and 4 speed all have a 1:1 fourth gear so there wouldn't be more shifting unless you're going 140mph+.
It all depends on your budget and the end result you're going with. I don't recommend a T5. The 4 speeds are good, we built an LS powered 68 Vette with the stock Trans and it was fun to drive. But not having an overdrive wasn't the best for highway use.
The T56 is a great Trans but is more expensive and will require more work to install. Especially if you're going hydraulic over mechanical actuation.
That's my .02!!

-Dale

[Ron Sutton]

Dale,

What are your thoughts on 5-speeds. Do you like the TKO stuff?

[Schwartz Performance]

I personally like the T56 much more because they shift easy at "high" rpm (over 6k). A drag strip run or even an autocross is limited by them.
I'd like to drive one of the Legend transmissions to see how they compare though.

-Dale

[nelsonusmc]

Wouldn't a T56 do better on the high way with the higher gear? the 5th and 6th gear is lower than 1.00

[71RS/SS396]

I don't think that engine is going to be very happy with a 6-spd at normal highway speeds in 6th gear. With that cam and a single plane intake I think it's going to surge and buck just my $.02

[nelsonusmc]

Also I forgot to mention the heads are angle plug so with headers(I want side pipes) the hooker sidemounts can't be used with angle plugs but dog's headers can
http://www.summitracing.com/parts/dou-d380-c
My question is would they be too big for the power I'm making??