Ok I am a fairly new member, and need a little insite. I was given a 96z28 from a friend, since which I have aquired a m6, spec 3 clutch, and lt4 engine. The thing is the motor act's like it is trying to lock up when I try to start it. My plan's were to build a stout 396, but reliability and longevity issues have changed my mind. A 383 is now my goal, I have a set of brodix race rite 200 head's. I have talked to both AI and LE andeither have a cnc program for them AI said they would not be able to do them. Lloyd Elliot said even though he didn't have a program he could hand port them. My question is has anyone on here ever had any dealing's with him hand porting any head's. This is going to be mostly a street car that occasionally see's some track time. Do you think I can make some good power with the brodix or do I need to just have the stock casting's ported. Any and all suggestion's welcome, just a newbie looking for a little knowledge.
















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Do you plan to use the block from the LT4, or a Gen 1 SBC block? Are the Brodix heads Gen 1 SBC? I was not aware Brodix made a head for the Gen 2 LTx engines.

What kind of HP are you looking for at the flywheel? Will this be normally aspirated, or will it have (eventually) a power adder (S/C, turbo, N2O)?

 

There is a couple great threads ongoing on these forums about the topic. I will tell you my take on it. Why bother with a 383 just build a screaming bullet proof forged 350 that you can rev to 6500-8000?

The heads, all I can say is to shop around, prices vary and you might find a great deal somewhere out of the mainstream.

Why do people change connecting rod lengths or alter their rod length to stroke ratios? I know why, they think they are changing them. They expect to gain (usually based upon the hype of some magazine article or the sales pitch of someone in the parts business) Torque or Horsepower here or there in rather significant "chunks". Well, they will experience some gains and losses here or there in torque and or H.P., but unfortunately these "chunks" everyone talks about are more like "chips".

To hear the hype about running a longer Rod and making more Torque @ low to mid RPM or mid to high RPM (yes, it is, believe it or not actually pitched both ways) you'd think that there must be a tremendous potential for gain, otherwise, why would anyone even bother? Good question. Let's begin with the basics. The manufacture's (Chevy, Ford, Chrysler etc.) employ automotive engineers and designers to do their best (especially today) in creating engine packages that are both powerful and efficient. They of course, must also consider longevity, for what good would come form designing an engine with say 5% more power at a price of one half the life factor? Obviously none. You usually don't get something for nothing - everything usually has its price. For example: I can design a cam with tremendous high RPM/H.P. potential, but it would be silly of me (not to mention the height of arrogance) to criticize the engineer who designed the stock camshaft. For this engine when I know how poorly this cam would perform at the lower operating RPM range in which this engineer was concerned with as his design objective!

Yet, I read of and hear about people who do this all the time with Rod lengths. They actually speak of the automotive engine designer responsible for running "such a short Rod" as a "stupid SOB." Well, folks I am here to tell you that those who spew such garbage should be ashamed of themselves - and not just because the original designer had different design criteria and objectives. I may shock some of you, but in your wildest dreams you are never going to achieve the level of power increase by changing your connecting rod lengths that you would, say in increasing compression ratio, cam duration or cylinder head flow capacity. To illustrate my point, take a look at the chart below. I have illustrated the crank angles and relative piston positions of today's most popular racing engine, the 3.48" stroke small block 350 V8 Chevy in standard 5.7", 6.00", 6.125" and 6.250" long rod lengths in 5 degree increments. Notice the infinitesimal (look it up in the dictionary) change in piston position for a given crank angle with the 4 different length rods. Not much here folks, but "oh, there must be a big difference in piston velocity, right?" Wrong! Again it's a marginal difference (check the source yourself - its performance calculator).

To hear all this hype about rod lengths I'm sure you were prepared for a nice 30, 40, or 50 HP increase, weren't you? Well its more like a 5-7 HP increase at best, and guess what? It comes at a price. The longer the rod, the closer your wrist pin boss will be to your ring lands. In extreme situations, 6.125" & 6.250" lengths for example, both ring and piston life are affected. The rings get a double whammy affect. First, with the pin boss crowding the rings, the normally designed space between the lands must be reduced to accommodate the higher wrist pin boss. Second, the rings wobble more and lose the seal of their fine edge as the piston rocks. A longer Rod influences the piston to dwell a bit longer at TDC than a shorter rod would and conversely, to dwell somewhat less at BDC. This is another area where people often get the information backwards.

In fact, this may surprise you, but I know of a gentleman who runs a 5.5" Rod in a 350 Small Block Chevy who makes more horsepower (we're talking top end here) than he would with a longer rod. Why? Because with a longer dwell time at BDC the short rod will actually allow you a slightly later intake closing point (about 1 or 2 degrees) in terms of crank angle, with the same piston rise in the cylinder. So in terms of the engines sensitivity to "reversion" with the shorter rod lengths you can run about 2-4 degrees more duration (1-2 degrees on both the opening & closing sides) without suffering this adverse affect! So much for the belief that longer rod's always enhance top end power!

Now to the subject of rod to stroke ratios. People are always looking for the "magic number" here - as if like Pythagoras they could possibly discover a mathematical relationship which would secure them a place in history. Rod to stroke ratios are for the most part the naturally occurring result of other engine design criteria. In other-words, much like with ignition timing (spark advance) they are what they are. In regards to the later, the actual number is not as important as finding the right point for a given engine. Why worry for example that a Chrysler "hemi" needs less spark advance that a Chevrolet "wedge" combustion chamber? The number in and of itself is not important and it is much the same with rod to stroke ratios. Unless you want to completely redesign the engine (including your block deck height etc.) leave your rod lengths alone. Let's not forget after all, most of us are not racing at the Indy 500 but rather are hot rodding stock blocks.

Only professional engine builders who have exhausted every other possible avenue of performance should ever consider a rod length change and even they should exercise care so as not to get caught up in the hype.

ISKY Racing Cams - Do It Right. Race with the Legend. Camshafts, Connecting Rods, Valve Springs, Lifters
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SBC heads will not bolt onto an LT1 block without some machining so I'm not sure how far you'd like to go but the stock castings in the right hands will support plenty of HP (see signature).

A power goal will help us with helping you make a selection.

 

To answer your question about LE, he is one of the most respected porters used by the LT1 crowd.

 

LE is a legend around here. He can set you up with a custom cam and porting that will get you where you want to be. I would talk to him some more, tell him your goals then go from there. Just do a search on here for LE or Loyd Elliot heads and you will see.

 

The head's have already been converted from brodix, and my power goal's are around 500 to 550hp at wheel's.

 

With that power goal you're looking at some serious bucks. I'd go with an 18-degree head, single plane, big solid roller, FAST, 24x or equivalent, etc. Plan on $15k or so for the motor alone, not to mention the drivetrain needed to handle that kind of power.

That 500-550whp goal is a bit more realistic if you choose a heads/cam/displacement/nitrous build. 450whp is pretty easy if done right, but to get that extra 50HP requires a LOT more.