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Old 11-08-2009, 01:07 AM
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500hp 327 sbc

I am rebuilting my 327 this winter, but i am taking the time to add stud girdles, thicker pushrods, an oil cooler, and a properly measured CR.

to recap: i was given this motor from my dad, but i was sitting for about 2 years. I did not have the knowledge at the time to freshen the motor up. It seams that the person that originally built the motor only intended to race a while and then have it die. at the time it had 462 heads with 1.94/1.50 valves, 3/8 rocker studs w/o girdle, no studs at all, and a stock 8" dampener. The guy put in a crane cams saturday night special cam. 4200-7200 oval track cam, 256/264 @ .050".

The whole long block is being rebuilt, .060" over, main studs, GM large journal forged crank, speedpro forged pistons, and possibly scat forged i-beam rods

This is my plan so far:
Sell my 462 heads and get RHS pro-action 200cc heads w/50cc chamers.
Speedpro flat top pistons, 2 vavle reliefs
Isky oval track cam, 200571, 3000-7600 .570/.580, 258/262 @.050
.015 or .020 thick head gasket (with .025 deck clearance)
Shooting for 11.5 - 12.1:1 cr, cam has intake valve closing point of 69 abdc.
Comp cams gold 1.5 ratio rocker arms 7/16 stud, arp pro series studs, stud girdle.
undecided - push rods at least .080 wall either 5/16 or 11/32
Engine oil cooler???
Good cooling system
Super victor intake W/ holley dp 650 (will soon get a 750 main body upgrade w/o choke tower)
Some kind of SFI approved dampener.

From what i read from Tech inspector's posts, and several cam tech sites, 165 PSI cranking pressure and 7.5-8.5 DCR is good for pump gas. with my short stroke and late intake valve closing point, 12.1 SCR gets me right around 8.4 DCR. plus i can advance or retard the cam timing to change the DCR a little.

I have already invested a lot into the car: Completely rebuilt rear-end with yukon axles, 4.10's, eaton posi. Upgraded fuel system, AN lines, mallory 140 gph pump. I currenly have summit 1.5" tube shorty headers, with dual exhuast that dumps before rear axle. I am hoping for 500 BHP with open headers.

A couple questions:

Would it be worth it to sell my reconditioned gm rods and buy some scat 5.7" i beam rod rated at 750 HP?

This will be my DD for the first few months, but then will turn into my weekend car. I have a sane car that i will use more frequently anyhow. I want to have the power available, but not be pushing things to the limit. Would an engine oil cooler help for longevity?

I am sacraficing all luxuries in the car to get HP to the wheels, no a/c, no heater, no computer. I have underdrive pulleys for crank and alternator since i plan on turning 7000+ rpm. I am not too worried about manifold vacuum or idle quality. I also happen to live in an emissions free county. most of my driving is on the freeway and farm roads. Not very much stop and go stuiff.

Tell my what you think, what might you do differently? Any things i am forgetting? I am looking for this motor to last a good while, but i don't intend to abuse it or let things go. I have all the time in the world (relatively speaking)

My car is a 1988 camaro rs, lookes beat up, faded paint, but hopefully will be fast!

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  #2 (permalink)  
Old 11-08-2009, 04:39 AM
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Have you considered stroking it to a 383?
Shane
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Old 11-08-2009, 06:39 AM
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First off that cam in a 327 will run more in the 4000 to 8000 range it is advertised for use in 350 cid engines so with your smaller cid the power range will move up.I think you would be far happier with a smaller cam somewhere in the 240 range at .050. Your stock rods are fine up to an 7000 rpm "Short Duration " blast but with the proper cam you won't need to spin it this high any way.As an example my 355 in my bu has a crane cam with 260 @.050 intake .557 lift, 268 @.050 .572 lift exhaust with well ported 292 turbo heads 13 t o1 compression 4000 stall converter and 4.10 gears it is used mainly at the strip.It will haul the mail at full throttle but it also idles at 1200rpm, is a dog below 3500rpm and I shift at 7800rpm.I would not want to do much street driving with it it would be a pain.The real truth is in a street hotrod engine smaller is better when it comes to cams and pump gas compression.
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Old 11-08-2009, 07:38 AM
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You may want to consider better pistons.The SpeedPro/TRW are old school,and are usually heavier than newer pistons.
Guy
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Old 11-08-2009, 08:07 AM
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c/r

If it was me i wouldn't go with 50cc heads and want it to be reliable and last a while. But thats just my opinion.
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Old 11-08-2009, 02:24 PM
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the cr is too high for pump gas
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Old 11-09-2009, 01:12 AM
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I wish i could get an aftermarket block and make a 454 sbc, but i can't. this motor was given to my from my dad, and it just happen to have all forged stuff and whatnot. I am using what i have, and believe me, i will move on the much larger CID engines 10 years down the road.

From the isky catalog, the cam is designed for 327-350 engines. The next cam down the list is meant for 350-400 engines. With desktop dyno2000, peak HP is at 6500, and peak TQ is at 5000. I am not sure how accurate this program in, but i can enter every bit of data on the engine. head flow charts, cam timing, cr, intake style, exhaust style etc. The isky cam, 201571 get me at 450 hp and 400 tq with mufflers, and a dual plane intake (air gap), and then shoots to 550 HP 470 TQ with single plane intake and large tube headers open exhaust.




I have considered a smaller cam, but i am ok living with a 1200rpm idle. The last cam in the motor was very close to this new one, 256/262 @ .050. Pulled like mad from 3500 on, That is what i like, besides, there is only one stoplight from my house to work. My friend has a camaro just like mine with a slighlty above "stock" 350, hyd. cam, "stock" 350 heads, idles at 700. It gets off the line, but overall there is less seat of your pants feeling.

Why would 50cc heads be worse than, say, 64 cc heads. I was originally going to get 64cc heads along with dome pistons, but someone on this forum said to stay away from domes, as they are more prone to detonation.

in reality, the is the same combustion space with equal CR and different domes/head cc's. I read that flame fronts don't travel as well around domes, especially large domes.

What pistons would you recommend? I don't want a $1000 set of pistons, but if a lighter piston will put less strain on my rods, the i am all ears.

What would you say a good, safe max rpm for scat 5.7 forged i-beam rods are? In the summit catalog, the rods are rated a 750 hp, but no max rpm is listed.

Thanks for the input.

Josh
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Old 11-09-2009, 06:23 AM
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Actually the stock rods with good bolts are good to around 8000 in short bursts I have no experience with scat but plenty of bad ones with eagle wouldn't use them if they were free.The 450 hp estimate is close the 550 is pretty far off however the curve shown on the desk top is usually pretty accurate. So the peak should be right where it shows it. Your trw slugs will work fine at this rpm.
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Old 11-09-2009, 06:31 AM
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Get longer rods and some better pistons. Longer rods will make a difference in an engine like this. 6.25" rods would help that thing sing in the higher RPM's. That cam is too big for what I would want to drive on the street in a 327, but it is possible. You still need to knock your static compression down to around 11-11.5:1, and run race gas when you plan to open up the throttle. You didn't detail the current curb weight, but a heavier car will need a slightly lower compression than a light one.
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Old 11-09-2009, 06:37 AM
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even with 93 octane youll ping with the comp ratio you got.
you might get away with backing the timing off a bit but then you defeated the porpouse of a 500 hp 327.
good forged lower end is a must!
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Old 11-09-2009, 07:23 PM
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A 177 cid supercharger would go a long way toward helping you reach your goal. It's a great replacement for cubic inches.
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Old 11-09-2009, 09:41 PM
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Before this rebuilt, i was running 11.7:1 CR with pump gas and 38-40 locked timing. NO detonation at all, my old pistons were speedpro 7000p with 14.3cc domes. But my cam had an intake valve closing of 74 deg ABDC. whats the deal??? I have heard both sides of the fence...???

How would you use 6.25 rods? wouldn't you need to get special pistons too? Also, the isky catalog on the cam recommends a rod length of 5.7-5.85. My current stock rods have arp rod bolts. My guess is that they have has several cycles of heating the wrist pin end to get the pin in, and then having the pins pressed out. does this hurt the structure of the rod? The top 1.5" of the rod is bluish in color.

car weighs 3400 lbs but i plan to strip it, and try my best to get ~3000lbs
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Old 11-09-2009, 10:24 PM
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You've been getting away with that compression ratio only because you are at a high altitude. It will be fine if you stay on the mountain, but it won't work if you plan to go anywhere closer to sea level. I wouldn'tbe trying to go beyond that 11.7-1 with the rebuild, however.

Your rods should be fine, heating for pin insertion will turn them shades of blue .

Yes, 6.25" rods (or any rod a different length than 5.7") will require a different piston, but you are buying new pistons, right?? The only added expense is a set of rods, and you are worried about the stockers, so... get new??

Do you realize you can use a 6" rod 350 piston to make a 6.125" rod 327?? 6.125" rods are readily available as a low cost sportsman type rod(I-Beam).

Your forged factory crank, 6.125" Scat rods, Use 6" rod 350 piston with 1.265" compression distance, equals a 9.015" stack height. I'd use KB Forged Head Relief series piston part # IC 9930 Flat Top 2 Valve relief 3.7cc relief volume uses standard width rings, then open up the 50cc head to around 55-56cc to get the compression ratio right. NOW YOUR TALKIN', power to 8000 rpm!!

Alternative KB premium Forged piston is # IC 702 bigger 4.9cc valve reliefs and takes narrower 1/16" rings. You can also do a 6" rod 327 using KB# IC 790 1.385 compression height, 4.9cc 2 valve reliefs 1/16" rings ,equals 9.010" stack height.

Don't worry about what the Isky catalog says about the rod length for that cam. Buy the cam based on the cams specs and the operational rpm range of the engine.

Last edited by ericnova72; 11-09-2009 at 10:29 PM.
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Old 11-09-2009, 10:37 PM
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The air density at 5300ft elevation is 16% less dense than at sea level.

Because of this factor, you may (or may not) be able to stretch it to a true 11:1

Using a supercharger or turbo charger to recover the difference in inlet air density difference beteen sea level and Denver's elevation is more effective than cranking up the cr.
+ the supercharger boost drive ratio (pulley ratio)can be adjusted if you go to a different elevation an/ or switch fuel octanes.

327's make a very good base for a street super charged motor.
500hp is easily within reach with a blown 327. All said and done, The engine will be much milder in nature, not so racey but with equal or much more power.

The engine is easy and straight forward to build.


A well done Weiand 177cid blown 327 would "R U L E".

Last edited by F-BIRD'88; 11-09-2009 at 10:47 PM.
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Old 11-10-2009, 01:18 AM
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As much as i have thought of the idea of a supercharger, i don't have $1800. That is the simplest one in the summit catalog. Also, i would like to stick to "all motor" power for now. Later on down the road, i plan on getting a fuel injected lsx 454. But that opens up a whole new can of worms.

I work at a restaurant, so i am on a "budget." I don't have a set spending limit, but i have to but this whole motor piece by piece. I will get good parts, but i won't rush things. I don't want to go all crazy with cnc porting and meticulous decking/surfacing work.

I have heard/seen some bad things about Keith black. Are there forged pistons better in relation to their hypereutectic ones?

So with the 350 rod/piston combo: Will the skirts clear the crank counterweights? Will all the clearances be ok without machining?

I guess i just can't get over the sound of 7000+ rpm. it is SWEET. I will move on to more sane things as i get older.
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