Quote:
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.
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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?