A guy I know bought an LT1 Z-28 with some obvious bottom end issues. The engine was shot but the rest of the car was clean and the price was right. Unfortunately the guy has more money than sense when it comes to these things. His priority was to get the car running as quickly as possible rather than doing things correctly.

He wanted to make a stroker out of it. However him and his brother (who pretends to run a shop BTW, RUN LIKE HELL) thought that they could just buy a stroker kit and put it together without any worry of balancing / clearancing, etc. When one of my other friends absolutely refused to build the motor in this way, they opted to buy another LT1 short block, probably of questionable origin and just make a heads / cam car out of it.

The owner of the car actually talked to me about it. He said that he needed to pass emissions and wanted advice. I suggested that the Hot Cam is very streetable and should pass emissions easily so long as everything else is intact. I told him how there are all kinds of different things out there but it might be hit or miss in the emissions department. I told him that if he wanted to be absolutely sure that he could pass, a properly tune hotcam was the ticket.

He wanted other information and suggestions. I told him that a good set of CNC'd cylinder heads from a reputable company would make a killer difference. I tried to explain flow and lift to him and explained how a set of 1.7 rockers might also help him make a little bit more if the heads were worth the aluminum they were made out of.

Well ultimately, he SOMEWHAT listened to my advice. He bought the hot cam, he bought long tube headers, a high flow cat, and 1.7 rockers. On the cylinder heads though he didn't listen to my advice. He didn't go with a reputable company, he bought some POS handed ported garbage off of e-bay! Just by looking at the heads I could have told him they were crap, but it didn't really matter, he already had them and there wasn't going to be any sending them back, he wanted the car running. BTW, he "didn't have the money" for CNC'd heads, yet he did have $1200 for 18" Z06 wheels and tires, even though the car had perfectly good wheels and tires on it. Yes they were the ugly stock wheels, but getting it to run right is always higher priority than cosmetics, at least in my book.

After many installation headaches, all of which caused by impatience and lack of education on behalf of the owner's brother who was doing the work, the car runs. He drove it for a while and yesterday decided to take it out and get the tune resolved on the dyno.

Now before all the anti-dyno people jump in here, do a little reasearch. A hotcam / heads / headers car will make 350+ on a dynojet if it's running right PERIOD. Sure there can be a range of variation from car to car / dyno to dyno, but it's certainly consistent enough for rough comparison purposes.

For a day's worth of tuning they got the car all the way up to 332 rwhp and 330 lb-ft of torque.

My car made more than that on STOCK heads and 1.6 rockers with a mail order tune done for a car with STOCK emissions exhaust. My math shows that he's at least 20 hp short, 20 lb-ft of torque short, and more like 40 hp short. Looking at the shape of the power curve, I have to chalk it up to the heads. Whoever ported them just hogged out the ports and destroyed the short turn. They don't have enough velocity to make any torque on the low end and they can't flow enough of the upper end to keep the engine fed. I honestly think he could make more power with a set of stock cylinder heads.

The worst part of the whole thing? The owner of the car is so un-informed that he's actually happy with the numbers. I can't wait until the track opens back up so I can see it run as poorly as I think it will. The truly sad part though is that even though the owner is un-informed, he can somehow drive a car at the track pretty well. He'll get a decent E.T. out of it, but his MPH will be abysmal. I guess as long as the owner is happy that's all that matters.

The moral of the story here is, if you don't know what you're doing with cylidner heads, talk to somebody who does. It is well worth the money to get a product from a reputable company rather than a hack job.

 

that's why I look at all the info about shops & who everyone uses on the forum. I'm going to have mine done by either percision or portpros. I just have to contact them to talk & decide after that.

 

Exactly, the cylinder heads makes or breaks an engine. That's why it kills me when people buy into this" I'm getting a stage I, stage II head, etc. WTF is that? Stage 45 can mean nothing. Heads are not a one size fits all. Get someone who will listen to what you want, or can tell you what you need if you dont know. Only then will it make the desired power. Spend it once, do it right even if it means saving a little longer. I've learned this lesson the hard way more than once.

 

Very good commentary "cuisinart"! The heads are the Key. If you can only spend in one area do it in the cylinder head. You won't be diappointed. I fixed some heads for a guy on this site that were done by "pro's", very scary to see! Let me know if i can provide some service.

 

This reminds me of the chucklehead who wanted to put high dollar aluminum heads on a stock L98 intake... more money than common sense... or simple pigheadedness... I donno.

I know my way around a car, but I also know my limitations... and since I have never delved into hipo engine parts, I would query... and listen... cause I DO NOT know enough to make these calls myself. These morons lack not only the knowledge base, they lack the common sense to make the right call.

They deserve what they get. Junk.

You are right, Nathan, that motor is at least 20hp down... Someone went into that head with a die grinder and widened the wrong part of the port... how stupid can you be? Hell, a simple hand port job, with port matching to the manifolds, and a little subtle deburring of the bowls and valve chambers would be worth a lot in lost horsepower.

As for Dynos... they provide a valuable service, sure, they are not 100% accurate, but, they create baselines and the ability to monitor the engines performance. Even if the dyno reads low, the exhaust sensors and engine sensors should be accurate... and a good tune will result.

I acutally OWN a dyno - for RC Car racing! It's a Competition Electronics Turbo 30 dyno... it uses a slave motor to apply load to the test motor. It measures the motor over 5 different amp loads... upto a 30 amp draw! The value of this? The dyno is very repeatable, so I can compare 2 motors on it with relative accuracy. Let the dyno cool between usages and all is well. We normally run 3 passes on the motor from a cool dyno, then let it cool again (mostly, the slave motor). Even with heat building in the 2 motors, it does not seem to have a huge effect on the numbers, sure, they go down a bit, but not much.

The slave motor is timed to zero degrees with a specific brush and spring combo for the brushes. This creates the standard. Sure, there are variables... but brush wear isn't one - unless the brush is toast! But comm wear is... There is also a specific armature to use, a stock 27 turn arm.

It's all about being standardized...

 

You should know by now, Nathan, that there are a lot of people out here with money (or credit cards ), but not that many who know what it takes to put a strong engine together.
Your buddy's story is not unusual at all.

Larry
code5coupe

 

Yep. Two years ago when it was uprgrade time, I felt I couldn't afford the full cost of heads/cam, longtube headers&new cats, cat back exhaust. So what I did was the heads and cam and later, I got muffler elims. Didn't port match the intake either @ porter's advice.

That dyno'd 352 rwhp and 336 rwtq. At the track I got 12.55's @114.9 mph in decent but not great air (60's in May but muggy).

You either do headers & exhaust and keep out of the motor or you do heads&cam and some exhaust (at least on the Corvette--F-body exhaust manifolds are definitely worse). Or of course, do it all as most do. But start research with the heads, build around those.

 

Dynos dont mean squat. Sorry, I just had to say that. By the way, sometime I gotta look up the name of the guy I purchased my heads from. He claims they were done by TEA by hand. I been meaning to find the paperwork and ask you if you knew him. If I find it here I will pm you with the info. By the way, I credit your site for teaching me alot about the LT1

 

Was the car a 350 cid still? Was it a automatic? Do you have any dyno graphs?

Dynos are really nice and repeatable but 1 number doesn't indicate how the car will preform. Autos w/ big stalls will show a lower number than a manual car equallly equipped.. SO you have to go in and look at it with a bit of experience.

The big advantage in a dyno is putting a degree or two here or there and watching what it does to the cruve gain, or drop, smooth or ruff.

It is a extremely valuable tool... Extremely valuable..

 

port pros.com the only way to go.

 

Obviously Nathan is a person that can tell the difference, the ones he saw probably WERE junk, but I wanted to throw out a couple things anyway. All CNC ports start off being mapped from one done by Hand. The winners demand that all 16 ports flow as good as the two best ones. That's the difference between CNC and hand porting. It's about the integrity of the porter more than anything. There's fewer and fewer good headporters these days thanks to CNC. A buddy of mine makes $2400 PER PORT because it's going to get copied and that's the understanding. Trust me, the best port isn't one that's magically computer generated by CFD. It's also the difference between a 30 hour head at $100/hr versus a $800 polish job. There are some porters out there still willing to do a good job for very little $, but some customers will always confuse shiny with fast. All that being said, if you're not getting new aftermarket or ported heads, ALWAYS pay the machinist a few hundred dollars to do a proper valve job and a bit of bowl work. Don't think the average machinists can't do a "decent" job". That's the "grass is always greener" deal. If they've even read a magazine in the last 10 years, they can always go off the 90% intake valve diameter for the venturi and 85% exhaust diameter for the exhaust venturi at the very least.

 

Alvin, it's a 6-spd car. I don't actually have the graphs yet. The guy's printer was broken, he's supposed to be e-mailing me the files so I make my own graphs with the winpep software and take a look.

Absolutely, but the CNC is all about consistency. Once you get a good "map" for each of the runners you can program this all into the CNC machine and have a very repeatable setup. Being said though, even the best CNC job will require some finish hand porting to make it complete, and you have to know what you are doing in that regard as well. The CNC just does the bulk of the work in a highly repeatable manner to allow the hand porter a very consistent starting place to put the finishing touches on without having to worry about the possibility of screwing it up while doing the more tedious aspects. As it is though I've seen two sets of heads come off the same CNC program, one set rocked while the other set sucked, it was just a matter of who did the finish porting. It is an acquired skill for sure.

There is of course also a lot in the valve job, that's for sure. When I worked at TEA I assembled cylinder heads, it was my job to cut the angles on the valves and assemble / flow heads. It's amazing how much of a difference you can get out of just a minor difference on the valve angles! These heads? They were already bolted on the car block by the time I ever saw them but as far as I could tell they were stock valves, and they likely had the stock valve job as well. About the only good thing about these heads was that they had some pretty big springs on them.

Apparently something threw a die grinder at them, put springs on them, and called them ready to ship. I wish I had taken some pictures, they really did suck. No two ports were even close and you could see grinding marks on the intake mounting face, IE it's like the guy was blind and had to feel around for the port, WITH THE GRINDER!

 

It sounded to me that your friend was concerned more over about bang for the buck. Mentioning his priorities to wheels, and heads being secondary. I think many get tied up in that idea, and disregarded the idea that good parts pays off down the line. For what I spent I know I could have purchased any other cylinder heads on the market. I didn't like spending that much for sure, but when they arrived and I inspected them, everything was right and they were a piece of art. With all said and done I don't know if I am making any more power than anyone with other comparible heads but I do know I have no worries about there longevity and the extra dough was well worth it.

 

Originally I took the heads off of my car because I thought I had a bent valve, turns out I didn't. I had done several weekends worth of computer work for TEA that the owner said he would just trade me for the actual CNC portion of any head work I ever needed done. So while I had the heads off the car I took him up on his offer and the CNC was done basically for free. Naturally CNC is only the first step. Well a friend of mine who I'd known since like the third grade was working there so he took it upon himself to do the finish porting himself. He did it as a favor to me on his own time rather than company time. He took his time and did it right, but again it was free.

When it came down to the valves though it was time to get serious. Since I already had all the other work done for free I could have just put stock stuff back on there, or I could spend a little money. I opted to spend some money and went with new stainless steel valves, undercut stems, swirl polished, etc. We discussed my camshaft as well as my other mods and decided how we would need to prepare these heads for optimal performance for my application. It was decided that anything bigger than 2.00 valves on my application would be a waste of money. Going with a 2.02 on an LT1 head produces some extremely high lift gains, but it costs mid lift flow. Since my cam would never see the required lift to see the benefit, we stuck with 2.00 valves and concentrated on maximizing mid lift flow. We also cut the heads for larger springs and installed titanium retainers, 10 degree locks, etc.

Ultimately my "free" ported cylinder heads cost me quite a bit of money, but every dime was well spent. As far as LT1 heads go these are top of the line and they were tailored specifically for my application, and it shows. It seems like my car always makes just a little more power than other people are able to get out of the same combo. As far as I know, nobody has been able to beat me on LT1 castings. There are people out there with better numbers with LT4 heads, but that would be expected. The time and attention to detail was well worth it. If I could do it over again I don't think I'd change a thing.