I am planning on building a 383 LT1. I am currently trying to decide exactly which cylinder heads will best match my goals for the car. Regarding my goals, the most important factor is that this is a 100% street car. I have not taken it to any track events, and although it would be fun to in the future, I want to build the car to fulfill my everyday needs. From what I understanding of engines, this means I want to maximize low and mid range torque, while maintaining a healthy top end. In the LT1 world, our selection of heads is somewhat more limited, so I have determined the following heads might match my goals:

1) AFR 195cc Street Heads
2) Trick Flow Genx 185cc 21 Degree Heads
3) Trick Flow 21 degree heads with 2.08/1.60 valves (with the larger valve job and valves the cost should still be reasonable)
4) LE/AI have good options, however I want to build the engine and then swap it into the car to reduce downtime, so I have to add ~250 to their prices.

I want to keep the total costs under about $1750. I plan on having all supporting modifications, such as 58MM TB, port-matched intake, headers, cutout/catback, etc. For camshaft, I am leaning towards a Lunati Voodoo 60121 221/229 .550/.565 lift with 1.6rr.

My main dilemma at this point is whether larger valves will hurt low lift port velocity. Llyod Elliot told me to build for as much flow as possible and use the camshaft specs to maintain low end torque. AFR says their 2.08 valve Competition ported heads to not reduce low end torque, just increase power everywhere. However, Trick Flow and TEA told me the 21 Degree TFS heads with 2.02 valves and some extra bowl work would be best to maximize low end power.

What is your opinion? Which heads do you think will best match my goals?

 

Usually advanced inductions or Lloyd has something kicking around that'll fit your needs. I would call both too see. Alot of time local guys drop their heads off top have them ported and don't come back for 6 months. Usually they'll send you that customers heads and redo a set for when they do stop in. This is how I got my le2's

 

Are you installing the heads yourself? If notbyou could be looking at 2k minimum for any set of heads and installation with new head gaskets,intake gaskets, header gaskets etc etc. I would say a ported setbof stock casting will fulfill your needs. Golen heads may even be appropriate for your dillena and o typically see them on ebay for 900-1000

 

Ported stock castings are your best bet, hands down. Avoid all of the hype of the aftermarket castings - ported stock castings (in the machine of the right porter) will outperform all of those as-cast. Unless you're planning on spending MORE money on having them hogged out they aren't worth the price.

 

I know there are some excellent stock ported options, but I think the 21 degree trickflow heads are pretty competitive especially considering they are only a 185cc runner, and do not require me to find another set of stock castings. But one of my main question is, if the TFS 21 degree head was fitted with say 2.08 valves and properly bowl blended, would that head work in a midrange build? I have been told different things on the affects of larger valves.

 

If a 100% street car I would not waste money on a bottomend you can't make use of and put more into the topend.

A proper 350/355 will make more lowend than you can use on the street.

You are buying into all kinds of hype and BS, this stuff is not so hard.

FWIW I have an over 2 ton street car that does 1.53 60ft times so I might have some experience here.

 

Dwayne,

I have chosen a 383 because this is my only car, so I need to build another block to swap into the car. Once building a separate shortblock, the 383 is a cheap upgrade. Regarding the heads, I have not bought in to anything, I am asking for help figuring out what will maximize what I would like to do to the car. If I had bought in, I could go give AI $2500 for a set of CNC AI heads, but I do not plan on buying into anything.

My main question is a technical one. Cylinder Heads can flow more air with either bigger runners or bigger valves. So my question is if you take a head with solid flow at a small runner size and equip large valve, how will the low and mid range of that engine function?

 

You don't need such a big valve. Without some spendy machine work you're just going to end up with valve shrouding. If you do a general Google search on your technical question you'll find a bunch of good tech articles.

For the record, I run a 2.00"/1.56" valve in my ported stock castings and am getting better than average results. The two big porters will both tell you that running a huge valve on a fairly mild setup is a complete waste.

I suggest you take a look at the combos that work and emulate them. There's no need to reinvent the wheel here - there's a few guys here who know what they're talking about.

Your view of a "cheap" upgrade by doing a 383 is false. More displacement requires more cylinder head and more camshaft, so unless you sink an equivalent investment into the top end then you won't be maximizing your potential.

And AIs 200cc heads are $1975.

 

A local guy took second in smallblock NA at Dragweek this year believe the car is 36-3700lbs around 400ci from the Dart block, with 23degree Dart(believe they started as 215cc) heads it turns 8500rpm. That uses 2.08 valves even though he has a LOT more room in the bore for a bigger valve. The stall in the thing is over 6500rpm.

All that extra displacement and rpm and it only uses a 2.08 valve. Does it really sound like that valve would be right for a low rpm smaller displacement build looking for lowend torque? Heck I think that motor idles at 1200rpm or so.

 

I myself like being original but in this case these two guys "dwayne and joe" have stellar results with both of their cars and would recommend talking to them and may've they would give you a build sheet. They know what works. I chose my own combo and needed a 150 shot of nitrous too get too where ram air got on motor. And my combo definitely didn't last long. These guys have been around the block and know what works and what doesn't. In my opinion if I was going too do a nasty strip build I would probably get a set of lt4 castings, send them too a.I too be cnc'd, then too Lloyd to have them handported. Those heads I believe would make as much power or more then a set of a.f.r 227's. They wouldn't be much fun on the street though lol

 

Unfortunately the nostalgia of being "original" and "different" wears off very quickly when you don't run the numbers you anticipated.

 

Not a lot left to reinvent on the LT1, I mean the basic architecture of it and such is over 50 years old. All people need to learn to do is separate what actually works from what "should" work.

 

If you're planning on running that camshaft I would recommend using ported stock head. No reason to dump big money into an aftermarket casting and/or giant valve and/or alternate degree head for this application. Lot's of people port factory aluminum heads. Advanced Induction are typically more expensive than Lloyd, but both are proven to perform. Over the years Lloyd Elliott has provided me with excellent service and products, so I prefer to deal with him. Call each and others if you wish, and decide which will work best for you.

-Dustin-

 

I know it's an old post, but what did you end up going with? maybe some build specs....??
I'm disabled and need some new reading material ,

 

You might want to contact "jahajazz" via e-mail (left click on screen name for e-mail option). He has not visited this site since October of last year.