rocketfinger

Just came from the shop where I'm going to have a hotcam knock-off installed. We figured 'as long as it's all apart, might as well change to the later opti, throw on some headers, have the heads done, etc'.

It's the 'heads done' part that I need advice on. We went over to the machine shop to inquire on a garden-variety valve job, back to stock except LT4 oval wire springs.

Turns out, the machine shop is a bunch of former TPIS guys, and their general recommendation is to CNC port my heads to the tune of $1200-$1400. I told them I was worried about hogging them out and losing all my low-end, they said in the old days with a carbureted motor that might have been a problem, but with the injected LT1 setup and a mild cam there is no need for concern.

I also suggested that I might just go with aftermarket heads at a later date, they said I'd still need to work those over to get the maximum gain and that there was plenty of power to be had in tweaking the stock heads.

I realize I was kind of getting the hard sell, but I'm wondering if that price is justifiable for the increase in performance and if there are any down sides I should know about beyond the cash outlay.

As usual, any input will be greatly appreciated.

cprgmr

They were absolutely correct. Have your existing LT1 heads worked over on the CNC machine. I sent mine to CNC Heads in FL for their stage III job with double valve springs, etc. It ended up costing $1,750.00, but there is real power to be had with these heads. You can opt for the single valve spring setup and that runs $1,500.00. Good luck! :)

Nathan Plemons

Sounds to me like the reason they would give you such a spill about hogging out the ports is because they do. Believe me you don't want that, you want the best flow through the smallest port to maintain your best velocity. This will give you more low - mid range and will maintain your upper end.

If they didn't tell you already figure out what the size of one of their ports is and figure out what their heads flow.

Total Engine Airflow did my heads and did a very good job. I would give them a call 270-782-6397 and talk to them about a set of heads. Compare port sizes and flow numbers with them because price would be pretty close. They pride themselves in getting smaller ports to flow better than their competitors huge ports.

Are heads worth it? Depends on what else you're doing. If you're doing a cam the heads will only compliment that. However if you've got stock manifolds it can choke you a good deal. Before I ever bought my heads I was talking to Brian Tooley, the owner of TEA, and asked him about my setup. He knew what I had and I asked him what I should do, he could have sold me a set of heads right there if he wanted to. Instead he chose to tell me the truth. He told me that heads would be choked my stock manifolds and I would be better off going with headers first. That's before I really knew Brian Tooley, long before I ever worked for him. I could tell he knew what he was talking about and he could have sold me bridge in Brooklyn but he chose not to.

rocketfinger

Actually I eluded to the loss in low-end in response to their recommendation to port my heads. I think I pretty well made it clear to them that losing that torque would **** me off plenty, but if we proceed, I'll make sure they don't just open them up.

Regarding port size, we didn't get down to that level of detail, but they did mention larger valves (obviously).

Regarding the stock manifolds, they may be gone even as I'm typing this. :yesnod:

Nathan, I knew you'd already basically been down this same road. In fact I have an electric WP based in no small part on your observations, and I absolutely dig it.

Sounds like this may not be too bad an idea after all...

AquaMetallic94LT1

You have several options for cylinder heads. You can send you stock LT1 heads to a head porter who knows how to port them correctly with good results. You can also go with AFR LT1 190 cc or 180 cc heads. The 180s flow virtually the same as the 190s so they would be the better choice since they have smaller port volumes. Canfield also makes or made - haven't checked lately - heads. You can also get stock LT4 heads and use the LT4 intake with them.

I suggest you get bare castings of the aftermarket heads if you go that way and have a good maching shop assemble them. The quality control on assembled heads is lacking these days. Several of us have had problems with them. Keep in mind that the valves and rockers don't line up real well on AFR heads which results in some rockers pressing to one side or the other of the valve. You really need shaft rockers to get proper geometry.

I have to disagree that the stock manfolds won't support the larger heads. The stock LT4 engine puts out 350 hp using stock manifolds. The LT4 hot cam with the LT4 intake and heads is supposed to put out 425 hp using the stock exhaust. I am using stock manifolds and got 350 rwhp with a coil wire that was loose in the distributor.

Nathan Plemons

Right, but with headers you can pick up about 15 horsepower, 30 pounds of mid range torque and about 3 mph in the quarter. I call that choked. I didn't say they would do nothing, but for best results out of a good set of heads you need to have the intake and exhaust to compliment them.


One thing to watch out for as well is valve size. Stock displacement LT1's don't benefit at all from 2.02 valves, don't go over a 2.00. With a 2.00 valve you'll see flow gains across the board, with a 2.02 valve you'll pick up one or two CFM up top and see a serious flow loss down low which equates to lower horsepower. You'd end up paying a good deal more just to be able to install these valves and it would probably hurt you in the long run. Not my idea of a good thing.

sothpaw2

I have to second that--I think you'll still get good results without the headers,
but Nathan's right, I think 10 hp w/ 20 ftlbs is a more reasonable number
if you still have bullet cats.

--I wouldn't do stock LT4 intake man + heads (unported) because it's too
expensive for what you get. I opted for CNC heads in FL. Seems like a
great place, I'll know more when my car is put together!