Thread: 355 build HP and Torque?

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Originally Posted by rollie715

I'm building a 355 and have just about decided on most of the components. I am impressed by many of the comments I have seen by others here particularly techinspector1 and was wondering if he or someone could run some numbers for me. The CompCam software using the following specs predicts this combo to be somewhere around 400hp, 462torque, but I think that is high. What do you think?

Some of these are based on my own spreadsheet calcs.

89 350 block w/ roller lifters
3.48 stroke
4.030 bore
Deck 9.013
Piston pin to top 1.561
Piston to Deck .012
Head Gasket GM 0.028
Quench 0.040
Vortec Heads 64cc w/26915 beehive spring set
KB142 Pistons 18cc D-Dish
Static Compression 9.03
Dynamic Compression 7.68
Cam CompCam 08-410-8 260HR IVC=56 ABDC
Edelbrock 2716 Performer Vortec EPS
Edelbrock 1406 600cfm carb
Full length 1-5/8" headers
2-1/4" dual exhaust

And what ever other variables I need to run a sim.
Thanks

Have the machine shop check the roundness and parallelism of the main caps. If any are off, then either align-hone or align-bore the main saddle/caps. Measure the block deck height on all 4 corners. If it isn't within a couple of thousandths, front to rear on both sides, then cut the block decks to square everything up. The heads will then sit squarely on the block and the intake manifold will sit squarely on the heads.

Use a 12cc dish instead of the 18cc and make absolutely certain that the compression height is at least 1.560". Shorter pistons with a 1.540" compression height will wreck your squish if you don't make allowances for it by cutting the decks. If you're using GM L31 Vortec heads, the chambers are likely a little larger than the advertised 64cc's, maybe 66-67. If we figure them at 66 cc's, then using 12cc pistons will put you at around 9.43:1. Then, if you use a camshaft that closes the intake valve at say.....35 degrees after bottom dead center, the resulting Dynamic Compression Ratio will be 8.30:1 and you'll like the motor a whole lot better. You have nailed the squish at 0.040", so the motor should run on cat-piss pump gas and make good power throughout the rpm range. Here is such a cam.....
HR-216/339-2S-12.90 IG Hydraulic Roller Camshaft for Chevrolet 1957-1987 V-8, 262-400
This cam has a smaller base radius than a standard cam, which will allow rod clearance at the cam if you want to rebuild the motor as a 383 down the road.

You'll want to get a couple of adjustable pushrods from the cam supplier to check for the exact pushrod length to use. You adjust the pushrods (one intake and one exhaust) to work with your combination of parts, lock down the adjustment, send them back to the supplier. They will measure them and send you the correct 1-piece pushrods to use with your combo. If you feel the need for more "rump-rump", have the manufacturer grind the cam with a tighter lobe separation angle but keep the same intake close point. The cam I spec'ed above is cut on a 112 degree lobe separation angle, so having a similar cam cut on a 108 or 106 degree lobe separation angle would give you some "rump-rump".

I would use only 1.5:1 rockers. More lift with higher ratio rockers can be more of a pain than you want to deal with. If you want to rollerize the rockers, Scorpion is a decent quality aluminum roller. Avoid using a rocker that has only a roller at the tip and uses a conventional slide ball fulcrum at the stud. Tests have shown that the benefit of roller rockers is in the fulcrum, not the tip. The conventional aftermarket roller tips are much too small to complete a mechanical couple with the tip of the valve. They won't be a negative influence, but they won't be a positive influence either. What I'm saying is to avoid those Fosdick Comp Magnum rollers, in my opinion, they're a waste of money. L31 heads used rail rockers. Is that what you are going to use? They were designed for use with a 0.430" lift cam, so pay attention in your mock-up trial assembly. Make certain that the dips made into the rocker arms on each side of the valve stem to keep the rocker centered DO NOT contact the top of the retainers. If they do, you will unseat a retainer, or retainers, during operation and you will not like the results. Pay close attention to the hole where the pushrod comes through the head if you plan to keep the rail rockers. With more valve lift, you may need to do some surgery on the holes to clear the pushrods all the way through the 720 degree cycle. You will also want to pin the studs. They are pressed in and will begin to pull out of the heads at valve spring pressures over about 260 lbs. Use the Mr Gasket kit.....
Mr. Gasket 806G - Mr. Gasket Rocker Arm Stud Pinning Kits - Overview - SummitRacing.com
You can, of course, pull the stock studs, mill the thickness of guide plates off the heads, tap the holes for studs and run the guide plates with conventional (non-rail) rocker arms. If you do that, pay attention to the holes where the pushrods come through the heads. You can use either rail rockers or guide plates, but not both.
Scorpion makes an aluminum, narrow body, self-aligning roller that will work in place of your stock self-aligning steel rockers. All you'll need to do is to pin the studs, install the rockers and check for pushrod clearance where the pushrod comes up into the head....
http://www.summitracing.com/parts/SCC-SCP1035BL/

Use the Edelbrock 7116 Performer RPM intake manifold (if these are truly L31 heads you're using and not some Fosdick aftermarket "Vortec" heads) and a rebuilt Edelbrock AVS carb, vacuum secondaries, 650 CFM.
Edelbrock has these on a broom list right now, so you can save a little on them......
#18259 Edelbrock Reconditioned #1825 Thunder Series AVS 650 cfm Off-Road Carburetor, Manual Choke
I will use nothing but mechanical chokes on anything I build. With a mechanical, YOU KNOW exactly where the choke plate is at any given moment. Mount a microswitch on the choke linkage that will illuminate a lamp on the dash, showing you when the choke is on. Use a drop base air filter housing, like off a Corvette 427, to fab up a 14" x 4" air filter arrangement. Stack two 2" filters if you can't find a 4" thick element. With a good breathing system on the top and good breathing headers on the sides, you'll have a real nice combo going for you in my opinion.

For ignition timing, I'd begin with 20 at the crank and 14 in the weights, all in by 2800. If the motor is a little hard to start (grunts back against the starter motor) with this much initial, interrupt the wire that powers the coil and mount a momentary push-off switch close to your left hand. Turn the key on, press the coil interrupt switch and hit the starter. When the motor has wound up on the starter, let go of the starter key and the momentary switch and the motor will be running with no long grinding on the starter. No muss, no fuss. Slick, no? Use a Crane adjustable vacuum advance kit to dial in the vacuum advance timing. If you play with this enough, you can get it right on the money for your combination.....
Crane Cams 99600-1 - Crane Vacuum Advance Kits - Overview - SummitRacing.com
Use whatever distributor gear the cam grinder recommends for his cam or you could frag the distributor drive gear on the cam. Here's a bronze gear and a composite gear for use with a steel billet cam core.......
http://www.howardscams.com/index.php/distributor-gears

All else looks good and although my DynoSim software is in Phoenix, I would reckon this motor would produce 425hp / 400ft/lbs. Since the cam comes on at around 1600 and the intake manifold comes on at around 1500, I would probably use a slightly looser converter than stock, something like 2000-2200 stall. You can run a 3500 stall on the street without much hassle and the car will be noticably quicker, so maybe a 2500-3000 stall would work better for you. I think most of the subtle stalls (2000, etc.) use a conventional size converter with re-worked internals. The higher stall units will use a smaller diameter converter housing. If you feel like you'd want the best performance at the cost of fuel mileage, then use a 3500 stall unit with a 10" diameter. With a 3.73 rear gear and some kind of posi arrangement, this would be a car that I personally would like to drive. Should be a dream.

For all you other guys, I have cleaned out my PM's, so you can get in touch with me if you need to.
Richard