I am in the process of building up a mean 327 for my 88 rs. I need some advice on cylinder head intake runner volume. looking for close to 500bhp. and shifting point at about 7500.

I already have the block and crank ready, its a large journal forged gm crank, 2 bolt mains with arp studs, and .060 over bores.

I will get scat 6.125 i-beam rods with 6" rod KB forged 350 pistons, comp cams solid roller, 254/260 @ .050, Super victor intake, holley 850 DP HP series. 5 speed maual trans, 4.10's.

I am looking at RHS proaction for the sake of not spending too much on heads. would you get the 200cc or the 220cc heads. will have 11-11.5:1 CR.

i realize my bottom end will suffer some, but thats ok. to make best hp and tq and still have just a little bit of "streetability".

what do you think?

 

Sounds really cool!! I ran that cam (XR292) in my 11.5:1, 396 sbc with Dart 230 heads and was shifting at 7000 so you're in the ballpark to spin that motor a bit higher for sure. I would do AFR or TFS 195cc heads myself. They will be great out of the box and IF....IF you can afford it, get the CNC'd versions.. should be about $500 more.

Contact Pro Systems carbs about having a streetable race carb built. It'll run about $600, custom built for your engine specs. Mine was spot on right out of the box and that seems to be the story of all of the Pro Systems clientel. Quick shipping and personal tech support if ever needed.

Gooodluck!!

 

Looking at prices RHS heads don't seem like any big savings over other proven performance brands. You can buy Canfields for about the same money and AFRs for just a little more. Sure some CNC'd or higher end name brands start to run over 2000 a set but there is a lot of head to be had in the 1000-1500 range.
Canfield 200cc heads flow around 260cfm which would be right in your desired HP range. The AFR 195s will flow closer to 280 as they are factory cnc'd.

 

You can make the power with a smaller/more streetable cam. That cam is huge for a 327

 

I am in agreeance,as well as pointing out that I hope to hell you aren't planning on running a T5 with that combo!

I'd call some major manufacturers tech lines,give a general recipe for the soup your making,and get a few suggestions on the camshaft choice.

 

some good advise. but here is my reasoning: i need at least 11:1 cr, and the only way to do that with flat top pistons is a head cc of 56 or less. the only heads in the 180-200cc runner volume are ususally 64 cc. the rhs heads are 50cc out of the box.

I chose the cam because a chevy high performance article build a 500+hp 327 using this cam, bu ended up with about 553 peak HP.

If i get some afr 64cc chamber heads, will it be to big of a deal to mill them down to 56cc? i really don't want to have issues with my intake manifold lining up.

stock 5.7 rod 327 = 1.75 rod length to stroke ratio
New build with 6.125 rods = 1.88 rod length to stroke ratio.
also, a lighter rotation assembly to handle 8000rpm.


lol i was running my stock t-5 with this motor beforehand. motor was .030 over, 11.7:1, 462 heads, crane solid cam 4200-7200. only about a month and all the syncros were shot.

probably looking at getting a g-force t-5 with dog cut gears.

I am trying to take advantage of the bottom end.

 

may beable to find a slight dome style piston to bump compression if you are getting new assembly anyway.

AFR i dont think can get much below 58cc with an angle mill but manifold more than likley will need to be cut to match

I know some LT1 guys buy AFR heads and mill them to 58cc

 

i am trying to stay away from domes as much as possible. I had a big thread going on flat tops vs domes, and when it comes to high compression on street cars, flat tops are better for smooth traveling flame fronts. with the same compressions, flat tops will be less like to detonate.

that is also the main reason behind choosing the rhs heads. otherwith, i probably would have went with brodix IK200 or track 1's.

 

What headgasket do you plan to run? According to my comp math program with a zero deck and a .011" gasket(copper) you will get just about 11:1.

Also for what its worth running the numbers on desktop dyno with the AFR 195s with a 0.039headgasket so you get your quench area ideal and a smaller solid roller cam it is still putting our well over 500hp.

 

i have done a lot of DD2000 simulations, believe me. my block is still standard deck, but with 6.125 rods, i get .015 clearance. i will probably use the headgasket that gets me the best compression and best quench after i decide on what heads to get.

 

I want to be the first one to say that a carbed 327 with that size cam is not going to be very streetable at all - a 406 maybe... Problem is that with that setup you are going to make peak power somewhere about (or over) 7,000rpm - which is going to make the bottom end so doggy you might want to get it a leash and a water bowl; even with a manual trans. 4.11's might be too shallow with a combo like this.

 

Its gonna want 4.5x type gears for sure. As far as dome pistons vs flat tops, i like flat tops for the above reasons but in this case you need compression. Goin with those small 50cc chambers how will the piston to valve clearance be with that very large cam?

A dome with some valve relief may clear better

 

to me, streetablility is anything that runs on pump gas. Before this rebuild, the motor was already "unstreetable" - crane oval track cam 4200-7200 256/264 @.050. yes it idled at 1100, but it got me from a to b, and it was fun going from a to b. i don't like tame motors. Not to mention i take very good care of my motors. everyone has their hobby, this is mine. i do have 4.10 gears, but with my last setup and extreme cam, i still had no traction in 1st. That was even with bad compression, hence the reason for this rebuild.

As for piston an head combos:

my choice so far on pistons is KB forged head relief w/4 valve reliefs. Or KB premium forged w/ 2 valve reliefs. Should clear just fine... How much more does a dome top piston weight over a flat top? I am trying to keep my rotating mass light (within reason) and piston speeds acceptable for the factory forged crank.

 

You'd have to compare the weights as i'm not sure.

Sounds like the 2 valve reliefs will give you more compression over the four. I guess they are a 4.9cc valve relief, so given your assembly i get .010" deck clearance, assuming 9.025" deck. With 58cc chambers, that gives 10.4 to 1. 56cc is 10.6 to 1. I dont know how far down trickflow/dart/brodix/AFR can go but 56-58 cc should be doable. Those arent too bad for compression but I'd aggree, closer to 11 would be best.

 

What are you using for "pump gas"?Around here 91 is about as good as it gets,once in a while you see 93.But even with 93,your timing curve will have to be conservative,even with a big cam bleeding off cylinder pressure.
This combo honestly doesn't sound like much fun to me,but as long as you enjoy it I suppose opinions don't matter.

 

Canfield is out of business. I wouldn't touch any leftovers with a ten foot pole.

AFR's can be had cheap. 1040s (195cc, 65cc chamber, eliminator) are around $1300 plus shipping.

-- Joe