mike100

Another diagnostic trick that doesn't require a lot of engine disassembly is to throw on lesser rocker arms (1.5's vs 1.6's) or put on the stamped steel ones in place of whatever nicer ones you might have to effectively lower the duration (not actually, effectively). The lift rate will decrease and the duration below .050 lift will increase in time due to different geometry and the actual duration at decent lift will decrease making the cam act just a bit smaller. If the car picks up time, you can then change or advance the cam. a bit less ignition timing here or a little more there might help too.

Weav's Vet

I have some pretty healthy springs because when I ordered the heads I wasn't aware that the 1.6 rockers were calculated into the lift already. (Live and learn I guess). Would going down to 1.5 cause issues there?

94vettelover2

You picked up 2 tenths after installing the AFR heads?If thats true,that sucks.Hope you get it sorted out.

mike100

lift, rocker arm lift speed will both be reduced and so will the maximum spring pressure achieved thru the cam cycle. you just have to make sure the rock arms swipe across the valve stem somewhat properly. maybe stock length pushrods match up to stock stamped rockers best. depends on the lift- I think you know what to check for...

you aren't gaining any mph so there seems to be a limitation other than the exhaust. so it's either the heads or induction system.

ON EDIT: does your engine have 7000+ rpm capability?

Weav's Vet

yep know all about rocker position on the valve stem.

induction system......that makes wonder one more time about this LT4 Edelbrock intake. I bought it because AFR recommended it or at least an LT4 GM. I have a ported LT1 intake. I may change them out just for fun to see if I gain lose anything there.

7000 rpm.....maybe once The motor has 98K on the bottom end. It's been spun to 6700 on the dyno and I about freaked out at that.

mike100

Maybe you're asking too much to go faster than 111 mph only spinning a 10:1 350 to 6000-6500 rpms.

I used to run a street strip 69 Camaro that only had 170cc intake runner volumes (old brodix street heads) 1-5/8's headers and I never got it over 111 mph either. That car was not as efficient in the wind as a vette and weighed at least 250 lbs more though (and it only had a 3 speed trans). To make up for it, I did shift at 7200 rpms and had a little nastier cam (244 @.050) non-roller solid lifter. It used to run 12.30's with tires.

Weav's Vet

This is my whole point of this thread. Correct me if I'm wrong please.

Advancing the cam shifts the rpm and power arch down, correct? If I advance the cam 2* that will move everything down so the motor can rev less to generate the same amount of power but at a different/lower rpm. I'll lose some top end but hell, what good is it where it is? I can't get to it in a 1/4 mile.

I don't mind doing the work. I would just like to be certain it would work this way and work better if I did do it. Asking to much?

mike100

I'd advance the cam and/or try going to 1.5's to simulate a lesser grind to see if the response picks up. With an automatic and not as much stall as you'd like to have, phasing the power band down 100-200 rpm should make the car faster. You may find that it still pulls 111 mph, but with the torque peak occurring a bit quicker.

Weav's Vet

Just out of curiosity, what is you guys opinion on a unlocked converter or a locked converter at WOT in 2nd and 3rd?

LD85

Did you flow the heads to see what your max flow was at that lift?

Do the 195's flow more at a lift higher than .565 ?

Pete K

[QUOTE=Weav's Vet;1574664051]Advancing the cam shifts the rpm and power arch down, correct? If I advance the cam 2* that will move everything down so the motor can rev less to generate the same amount of power but at a different/lower rpm.QUOTE]

Yes.
Possibly more power.

Pete K

Every car is different. My 87 did not like locking the converter at all.

383vett

My car is quicker by .15 to .20 when I lock up the converter after the 1-2 shift. My 406 with the Super Ram has a lot of torque and locking up the converter works with this combination. As Pete says, every car is different.

rodj

If you look at Lloyd Elliot's stuff;
he is claiming 400+RWHP on a LT1 with a 230/234 .592 lift cam on his ported LT1 heads

Weav's Vet

I did not LD

These are the numbers from AFR website for the 195 st elim. like I have.
280/218 @ .550




[quote=Pete K;1574666305]
Thanks Pete. I really think I'm going to do this but first I'm contacting Bullet to see if any advance is already ground in and to get their input on things.


I believe the stock setting for my car is 95 MPH. I'll have tuner change it back. The reason I had him unlock it in the first place was that the car seemed sluggish when it hit 3rd. That was before I changed heads. Converter is unlocked now in WOT in 2nd and 3rd.

Weav's Vet

So here are the things I can try to see if they help.

1 Change rockers to 1.7 for more lift simulating a larger cam
2 Change rockers to 1.5 for less lift simulating a smaller cam
3 Advance cam 2* to change rpm/power range
4 Lock converter back up at WOT
5 Dyno tune as is (400.00)
6 Change intakes
7 Change back to 1 5/8 headers
8 Build 383 stroker (this ain't happening, not now anyway)
9 Accidentally set car on fire.........

LD85

If the peak flow of your heads is higher than your cam lift, then install some higher ratio rockers, 1.7 etc, because you left some HP on the table there.

other than that, I agree with Mike100 that the exhaust flow could be inhibiting your results.


BUT, I would not expect "substantial" gains with a rocker mod other than the possibility of more MPH

Pete K

I agree. On the stuff I have put together over the years, over lifting slightly seems to improve.
If your heads are like my 1040 AFR's, it will like something closer to .600 lift.

Weav's Vet

So you agree that the 1 5/8 headers would be better? Is this what you meant LD?

Weav's Vet

If I get 1.7 rockers would these be good enough? These are Scorpion 1.7