I just got a set of heads installed in my car that flows 260@.050, and 175@.050 on my hotcammed LT1. It is .040 over, and has about 9k on the rebuild. I raced a friend of mine, and the heads made absolutely no difference! I have PCM forless tuning with the cam, but it is not tuned for the heads yet. The valves seem to be set perfectly, starts right up with no misses, etc. I am also running on the stock throttle body as of right now, and have Mac headers, and an Off road pipe.

Do you think that it might just be that it isn't tuned for the heads yet? Do you think that maybe the stock TB, or the mac's are choking it? I am really upset right now, and I just want to get what I am supposed to out of these heads. I have a 306 with springs, retainers, etc but I didn't put it in because I wanted the drivability, and better gas mileage of the hotcam. Not to mention I spray, and the hotcam is great for nitrous, but I am tired of getting beat. Please let me know what you think.

 

did you see the flowbench test your self?? That is about 45-50 CFM greater flow than stock LT1 heads. What this leads me to belive is that whomever put them on just polished up the ports and didnt truley get 260 CFM out of them. we am doing a set of heads right now for my 383. they are stock LT1 heads ( non 561 castings) and we have finished the intake side. We ported them out a whole bunch and used 2.00 racing valves and we got 259 CFM on the intake at .500 lift. I think you got ripped

 

I wouldnt jump to conclusions. Racing a friend is not a good way to measure your before and after horsepower. He could have set his valves wrong, exhaust leaks etc. I would have it scanned...

 

I had it ported, and polished, then I took the heads to craig at GTP, and saw the #'s so I know that they are correct.

Rodrigues I think that you are right, and I am going to try to get it scanned as soon as possible. I think that the valves might not be just right. Hopefully it won't stay this way for long

 

valves too tight could be a problem. Basically 1/8 turn past clattering seems to work well. Just enough so that they stay quiet. I am sure that others might have a procedure for you as well.

A mail order tune has to make alot of "guesses" on certain things and that "might" be some of the problem. A dyno tune is always better. Any idea about KR or A/F ??? If either (or both) of these are not correct than the car will NEVER make the power that it could.

TOO many options for a mail orer tune to be perfect.

One more thing, Most people ASSUME that an LT1 head flows 215/145 on ALL benches so when they get it flowed and a ported head flows 260/175 they think that they have a 45/30 cfm increase. Not all benches are the same and a stock head flows higher on some benches. Ya might ask Craig what kinda flow #'s that he sees on a stock LT1 and compare to see how much GAIN in CFM that you have. Also those are peak #'s that you have mentioned. It is possible to flow good at .600 lift but not very good (or bad, or horrible) at low and mid lifts.

I am not trying to scare ya or make ya think that you got bad heads but I am just giving ya things to think about.

BEFORE ya tear the heads off, I would try and get someone to help ya check out the valve adjustment, and help ya check for KR and A/F ratio.

good luck

NightTrain66

 

I never seen a stock Lt1 head flow 145 at the exhaust port more like 175 stock. Did you heads even get touched on the exhaust side. Mine flow 258/198 at .550 lift. Just for comparison. My friend installed a pair of Lt1 heads ported by the same person as mine and he gained more than 4 mph in trap speeds. He has a cc305 cam which is very similar to hotcam. Get those heads verified.

 

Get the car to a dyno or dragstrip.
Why do you say the HOT Cam is a better bottle cam than the 306?

 

If the heads were flowed on the same bench as 96ZRDR and only flowed 175 cfm and a stock one flows 175 cfm on THAT bench, than you see what I mean about benches being different.

If it is a properly calibrated Superflow (not Flow Data, Quadrant Scientific, etc) a stock LT1 should flow close to 215/145. Some say 205-220 on intake and some say 140-150 on exhaust but other than the 561 casting they should not be that high unless the bench is another brand.

You can not compare flow #'s on diff benches.
FWIW GTP claims around 280/210 and they flow 255/185 on my bench.

Still, I would make sure that the car is tuned pretty well BEFORE ya start tearing into the heads. Maybe see what a stock head flows on Craigs bench and compare to your #'s. If there is only a 15-20 cfm increase and it is mainly at high lift and not any improvements down low, ya might consider some other heads. Also check with people about the porter and see how well their car runs.

Even good portwork by itself can be hindered by poor machine shop work, (crummy flowing or crummy sealimng valve job, not deburring after milling, wrong spring pressures, etc) and that is why most porters would rather get the machine work done by someone THEY trust (or do it themselves if they have the ability) to make sure things are done correct. Machine work can make good heads look bad or AWESOME, depending on the quality.

Once again, if others have had good success and if the flow #'s show a descent increase over stock ON THAT BENCH, I would focus more on tuning it.

good luck

NightTrain66

 

Heres the stock flow charts vs ported from the heads Lloyd ported for me

http://kak.com/camaro/heads.htm

139.9 @ .5, no where near 175

 

any luck with findin out the probelm or problems???

anything require tuning or is everything pretty close as far as
valve adjustment and scanning?

NightTrain66

 

I am going to have Jordon Musser double check the valves for me, and he is also going to see if my lifters are ok. One of them felt kind of spongy(may have just not been fully pumped up), and that might be causing the rockers to back off. But I am pretty sure that it will get looked at monday, and if that isn't the problem, then he will be able to tell me what is. I will let you all know what we find out.

 

Was I reading that wrong? Did someone say the HOT cam was great nitrous? WRONG!!! Just my opinion but I don't think the HOT cam is good for nitrous at all. I also second the opinion that there is no substitute for a dyno tune. Brian Herter has done wonders with HOT can tunes but there really are too many variables to get it just right. Get it on a dyno.

 

I found out what the main problem was. My car started ticking real bad, and I thought that one of the rockers had backed off. So I went to reset the valves, and every time I got it to zero lash, it would get lash in it again, and get loose. I did this about 8 times but nothing good was coming of it. So i eventually realized that the lifter was just collapsing (sp?). I got a set of comp R's so jordon and I are going to put them in tonight, and we should be finished with everything by tomorrow. We may go ahead and put in the 306 while we are at it too , but I will let you all know how it goes!

 

Well, when we pulled the car apart, jordon said that the lifters looked ok, but I am going with the Comp R's anyway. He also looked at the timing chain gear, and found that there was a hairline crack through the entire thing! So it is good that I decided to do the work on it. I ordered a cloyes double roller timing chaing, and a CSI water pump from jegs, because together they were only $215, and the LT4 extreme duty timing chain (that's weaker than the cloyes) was $299, and I will get more power with the electric water pump. I think that this little problem is the motivation that I needed to put in the 306, and get a couple other things straightened out. We will see how it goes though. I will let you all know on the progress.

 

Can someone tell me what "561" castings are and why they are not the ones to use??

John