[PAUL K]

Originally Posted by Dave Bisschop

I'm not suggesting everyone run out and slide 114 lobe sep cams in their engine. The reality is lobe sep isn't really what we should be looking at as overlap, valve opening and closing events is really what should be looked at and the lobe sep ends up being what it is, but of course when spec'ing a cam and choosing the lobes to run part of placing the cam order is to specify what LSA the cam should be ground on, trying to remember all those events off the top of your head for bench racing discussion would get a little confusing. About 95% of my customer base is street/strip guys, about 6-7 years ago when the economy was booming we had a lot more customers building higher end larger engines, but most still wanted pump gas as they wanted to drive their cars on the street.

We spent a bunch of time and money doing R&D on 535-541 pump gas combo's using Marcel's 541 shortblock as a test mule. In the end his engine with a set of our wide ports and a 276/286 @ .050" 114 lobe sep cam, ported 4500 Victor intake etc. produced 826hp on pump gas with 10.8 to 1 compression. He put the engine in his 81 Lemans street car and ran as quick as 9.68 @ 140ish mph with a race weight of 3920lbs (car still has PW, full interior etc.). The car was very difficult to get down the track with more aborted runs than good ones as he typically ran it at street legal events on 10" slicks, but when the track was good it did run a bunch of 9.70's-80's. Not a great true street combo so we are working on a new combo with a big hyd. roller that should still put the car into the 9's with good conditions but be a lot more street friendly.

Before the 541 Marcel ran a 10.6 to 1 468 with a set of 310cfm hand ported E-heads, 271/279 @ .050 .675"lift 112 lobe sep solid roller in his 81 Lemans which had a race weight at that time of around 3800lbs, the car ran consisitent mid 10's with a best of 10.43 @ 127+mph and he drove the car on the street a lot at that point.

A few years ago a customer with a stock weight, stock wheel well 66 GTO wanted to have a super low maintenance engine to run in the mid 10's. He wasn't concerned with pump gas and actually preferred to run race gas as he was worried about the quality of fuel at the pump so we built a 505 with flat top pistons and a set of our 340-350cfm E-heads and ported 4150 Northwind intake. For a cam we used a 252/262 hyd. roller .608"/.638" gross valve lift 114 lobe sep with 857 hyd. roller lifters (old style), Compression is a hair over 12 to 1. Intake is topped off with a Pro Systems 1000cfm HP 4150 carb. The engine effortlessly made 752hp on the dyno and shifted @ 5800rpm lays down 10.0's 10 teens and if he shifts it at around 6400-6500rpm runs into the 9's. This is right off the trailer and there hasn't been any need to do any tweaking since the car is only legal for 10 flat. He runs a TH400 4000 stall ATI conv. and 3.73 gears with a 28" tall slick, race weight is around 3500lbs. This same combo at 461-474ci using a stock block and 10.75 to 1 would easily run mid to low 10's also.

These are just a few I can think of off the top of my head. I wasn't disputing that you can run quick with the tighter lobe seps, but a street/strip car with wider lobe sep cams (read less overlap) will run cleaner and have a broader less peaky rpm range.

Thanks for posting, good info. I'm not surprised at all the big inch engine responded well to the wider LSA, also not surprised the higher compression engine liked it. Years ago we were running a 455 with an UltraDyne 271/279 .426 LL cam on a 110. When we switched to 108 LSA the car picked up a solid tenth and a half and almost 2 mph.

As far as the last combo mentioned you think a 462ish engine with 10.75 compression would run low ten's with a 252/262 cam?

[Dave Bisschop]

Originally Posted by PAUL K

Thanks for posting, good info. I'm not surprised at all the big inch engine responded well to the wider LSA, also not surprised the higher compression engine liked it. Years ago we were running a 455 with an UltraDyne 271/279 .426 LL cam on a 110. When we switched to 108 LSA the car picked up a solid tenth and a half and almost 2 mph.

As far as the last combo mentioned you think a 462ish engine with 10.75 compression would run low ten's with a 252/262 cam?

There are so many variables that will affect performance, your cam swap obviously showed that the 108 LSA was better suited to the rest of the combo. Does that mean if you had made other changes in the combo that the 110 LSA could have been quicker than the 108? When you did the cam swap did you keep the ICL in the same position? It all goes back to what you said earlier that matching the components is critical. With all the info out there it's fairly easy to get into the ball park, but there are a ton of "grey" areas that require tweaking to get things optimized.

I do believe that a 3500ish lb car all dialed in could run bottom of the 10's with the last combo. Will that happen first time out? I doubt it. Good discussion, if a guy could just do R&D all day everyday!!! Unfortunately that doesn't pay the bills.

[PAUL K]

Originally Posted by Dave Bisschop

There are so many variables that will affect performance, your cam swap obviously showed that the 108 LSA was better suited to the rest of the combo. Does that mean if you had made other changes in the combo that the 110 LSA could have been quicker than the 108? When you did the cam swap did you keep the ICL in the same position? It all goes back to what you said earlier that matching the components is critical. With all the info out there it's fairly easy to get into the ball park, but there are a ton of "grey" areas that require tweaking to get things optimized.

I do believe that a 3500ish lb car all dialed in could run bottom of the 10's with the last combo. Will that happen first time out? I doubt it. Good discussion, if a guy could just do R&D all day everyday!!! Unfortunately that doesn't pay the bills.

Yes, you are right about someone else paying the bills, while R&D is done!

We ran the 110 LSA for two seasons and tried changing the cam timing several times. It liked tight lash, 1.6 rockers over the 1.5s it ran best about 5 degrees advanced and was running 10.5 @ 127. We swapped the cam and installed it 5 degrees advanced and started with the tight lash. Off the trailer we went mid 10.3 @129. We played with that for a couple of seasons. It didn't make much of a difference moving the cam timing around but it still liked the lash tight so we switched to a UD 275/283 on a 108 and picked up again. Now the engine liked 103 ICL and the lash at .026. We played around with that for a while and ran 10.1 @ 131 mph. The engine was put to the side and after a few years I just freshened it and installed a Comp 280/284 .440 LL cam ground on a 105. I hope to get a chance to test it in my brothers 70 Firebird this year but we are into June already and still behind. I also degreed the old 275 UD so we can swap them easily in the car if we feel we want backwards.