[Mike S]

Hi guys. I need to find 20 or 30hp. Had a tuff time going 10.00 this weekend. It was 90 deg. and humid. Ran 10.03/132. Need to find a little more hp to run my 10.00 index easier in the heat.
I was thinking of a bigger cam. Right now it is a easy lob solid roller 278/282 at .050 lift is .640/.645 with 1.5 rockers. 108 ls installed at 106.
Heads flow 330 at .700. 12-1 comp. 455 stock block. I run mufflers if that matters. car is 3200lbs. Converter stalls at 4900. shift at 6400 and trap at 6800rpm. 60's usually in low 1.37's with a best of 1.35.
I tune it with weight and timing to go 10.00/133. Seems like everyone in my class mph's better than me.

Do you think I should try 1.65 rockers first? Any other ideas to pick up a little hp?

Thanks Mike

[slowbird]

What oil you using? Lighter is good for hp
What fuel? Q16 will pick it up.
Not sure if you have 9" rear but more gearing will help in the heat to get the rpm back to where the engine likes to.
1.65 rockers should help, dont think you need more duration at all but more lift will help for sure.
Just some thoughts i had, easly things to do and can be changed back easliy for when the air gets better.

[steve25]

The 1.65 rockers will certainly help , the question then becomes does the motor respond best to a full set, or just the 8 Intake rockers and for that you need a test & tune session and make at least 2 passes each way.
What's the motors compression?
For race only I would want to be knocking on 14 to 1 .
In a way the more compression you have the less weather effects things !

[charlie66]

Have you tried tighting up the valve lash to see if you can get some more out of it?
Maybe check the valve springs if you havent already..

[Skip Fix]

Rockers are sure an easier way to try over a new cam. Try more ratio on intake, exhaust them both and play with lash if you have not. But I doubt rockers alone will give you the HP you need. When I dynoed different ratios maybe 5 HP per bump from 1.5s.

I run 1.8 Crower offset trunnion BBC rockers on my 455. Seemed to have a decent valve tip pattern to me but Dave at SD did not like them. I have a couple of mock ups I can lend you if you want to see. They do need a shorter pushrod.

[pastry_chef]

IMO you have plenty of duration. I'd like more lift, lobe or rocker.
Where did the cam come from?

Victor intake? Any work done to the intake?
4150 or 4500?

[steve25]

Take a look at the engine masters video when they tested rocker arms and also increased ratio rocker arms!

[Jack Ferris]

I run (ran) a Comp 280-284 .440 110 SR in my stock block with 325 E heads. I managed to get 9.80's in my 3150# GTO at 4500 ft track(6800DA).

[J.C.you]

better intake and head package with more rocker ratio would go a long way.

[Skip Fix]

One last thought on my lower HP motors they often did not like tight lobe seps with a muffler system so if you do change cams might toss that around.

[pontiac494]

how restrictive is the mufflers ? seen cars pick up a lot and lose a lot with them.

[Mike S]

Compression is 12-1. Spott's help pick the Comp cam when the car was running 10.50's. I tried adjusting lash but never found any improvement or loss. The intake is a victor 4500 with just a port match. Heads cam from Kauffman years ago.
I am going to freshen the engine the end of this year. Right now it is pretty much tuned for what I have.

Just need a direction to go to start getting parts ready.

[Mike S]

I run a 3.5" x pipe and dynomax large mufflers.. In the summer I switch to dynomax 3.5" bullets right on the headers. I have to run mufflers for the class.

[ponjohn]

Can you get a 100lbs out of it?

[LMSRACER]

Quote:
"Right now it is a easy lob solid roller 278/282 at .050 lift is .640/.645 with 1.5 rockers. 108 ls installed at 106."

Do you know the advertised duration and the duration @ 0.200"?
The Lobe Lifts appear to be 0.427" and 0.430".
What is the Lash Hot?


Larry S.

[Mike S]

Found the .cam card. I was going by memory.
duration at .020 311/313 at .050 278/280 lobe lift .438/.439
valve timing at .050 INT- 31 BTDC 67 ABDC
EXH- 68 BBDC 32 ATDC

Lash is set at .020 hot on intake and exh.

Found the head flow numbers also

.100 81/59
.200 160/117
.300 226/169
.400 281/215
.500 302/242
.600 321/254
.700 328/257

[Mike S]

can't really get much more weight out of it. Might be a good reason for ME to go on a diet. I could stand to lose 40lbs.

[charlie66]

The only other thing i can think of if you havent tryed it already is palying around with the a/f and timing...

[LMSRACER]

[QUOTE=Mike S;5887660]Found the .cam card. I was going by memory.
duration at .020 311/313 at .050 278/280 lobe lift .438/.439
valve timing at .050 INT- 31 BTDC 67 ABDC
EXH- 68 BBDC 32 ATDC

Lash is set at .020 hot on intake and exh.


So, the Net Lift at the Valves is 0.637" Intake and 0.639" Exhaust. Your heads would like something in the 0.750" Area. Going to a 1.65:1 Rocker will put you at 0.703" Intake and 0.704" Exhaust.

A little more Stall Speed would help.

From there, it would be tough to recommend anything further without knowing ALL of the details of your combination.

In Theory, More Lift and More Stall Speed should be of benefit.

Larry S.

[pastry_chef]

Originally Posted by Mike S

Found the .cam card. I was going by memory.
duration at .020 311/313 at .050 278/280 lobe lift .438/.439

Comp RZ lobes?