Cam choice- LT1 or summit 8800?

Hipster said:

I hear ya, I was kind of referring to the go fast mindset not the hard parts. If the guy you watched took his time and flow checked along the way you might not be too bad off. I watched one video, no joke, the guy was telling people if the handle of the screwdriver fit through the port it's big enough as he was shoving his screwdriver through the exhaust port. Thought I was watching a horror flick. lol Not Chevy stuff but would be a good afternoon of trash talking posted here. Efi definitely more adjustable and some of these guys are whizzes with it.

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Their is some truth to what he is saying. One of the engine masters competitors tested 1.3:1 break in rockers on the exhaust of one of their engines and saw nearly 50 ft/lbs more torque at lower engine speeds. I feel exhaust port flow numbers on a bench and camshaft choice are highly overhyped. I see very little reason for a dual pattern cam, all it is doing is blowing low-speed torque out of the tail pipe when the overlap is correct for the application.

L31MaxExpress said:

I had a 1988 Monte Carlo with a factory TBI 305 years ago. Option code L03 on the RPO sheet. It was a roller cam engine with 081 heads. There were definitely some late production TBI V8 G-bodies. Whether they were test cars that made it into public hands or just very late production I am not sure. GM was even prototyping TBI on the Oldsmobile 307 at the time. I have seen a 1988 Cutlass 442 with factory TBI. It had the GM cast 307 TBI manifold on it. Atleast 2 that I know of made it into private ownership.

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Had a friend in High school with a Monte SS, 305 HO, bone stock, actually a pretty decent runner all things considered.

L31MaxExpress said:

Their is some truth to what he is saying. One of the engine masters competitors tested 1.3:1 break in rockers on the exhaust of one of their engines and saw nearly 50 ft/lbs more torque at lower engine speeds. I feel exhaust port flow numbers on a bench and camshaft choice are highly overhyped. I see very little reason for a dual pattern cam, all it is doing is blowing low-speed torque out of the tail pipe when the overlap is correct for the application.

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Totally agree there. Too much ex. duration can scavenge incoming intake charge and too much overlap can create reversion and suck exhaust back in for a dirty charge. Port matching to a header gasket is the direction this guy was headed and that's own reversion inducing disaster in itself. I'm all about a straighter shot in or out but for all his efforts he gained a couple tenths in the 1/4. Not worth it too me, but to each their own. Keith Black did some funky dome designs way back for Mopars, Step quench or step dome, on the non valve side you had to machine for quench and various configurations for domes on the other. The running joke was you'll feel better once ya get ya hands on some double d's.. Absolutely cavernous chambers with no way to get quench. Now everybody makes A/M aluminum with vortec style chambers.

I feel alot of it is overhyped, merely guidelines and testing tools. Flow bench numbers don't tell all either best only particilarly useful to compare before and after #'s on a particular port job., you can have a better developed smaller port that performs better, not on paper, but in reality. 190vs.200, 200 vs. 210 etc. but it's nice to know at what lift the flow falls off so you can close the valve before air flow falls on it's face. Nine times out of ten I do straight patterns. Free flowing exhaust and you've removed a big bottleneck already. Often said, we race cars not flow bench and dyno sheets.

This math is the part we were all missing for so many years. This is why hobbyists would throw a motor together with parts that should work and it would ping like crazy, or it would be a dog.

I built the engine in WCJr with flat top pistons and a .016" head gasket before I had this spreadsheet, and it just happened to hit the numbers pretty good. My static compression ratio is 9.7:1

Plugging in a .023" head gasket brings your DCR down to 8.07:1 and your static to 10.13:1.

Dynamic compression ratio works off of cam timing. A more radical cam will actually bring your DCR down. That's part of how race motors survive with 11:1 static ratios.

transitionbikes93 said:

Another summit 8800 cam guy here, I love mine. I am getting the heads pulled (again!) on the l31 I put in last year this weekend and they are getting some machine work done, and I will be running 1.6 rockers for 480/480 lift. It’s got a touch of chop currently with the stock vortec heads with the 1.5 rockers.
Also going dynamic EFI, just picked up a manual transmission to replace my 4l60 today so I don’t have to buy a $900 stand-alone TCM.

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You can use the duel computer set up if you wish to keep the electronic transmission.
the EBL computer for engine managment and the existing stock computer for trans control.
its only splicing a few wires and moving a few extra pins.

tayto said:

I think you mean B-bodies. The only TBI that came in G-bodies was the somewhat rare 4.3L V6

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Yup i was meaning B bodies.

International47 said:

You can use the duel computer set up if you wish to keep the electronic transmission.
the EBL computer for engine managment and the existing stock computer for trans control.
its only splicing a few wires and moving a few extra pins.

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Sure, but it'll suck because your new engine will want to shift 1000+ RPM higher at WOT.

evilunclegrimace said:

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That test just reinforces my conclusion stated earlier. The added exhaust duration trades torque for HP. A reverse split would likely even make more torque. Many of the early LS cams were reverse split and added a good bit of low-midrange torque compared to stock while increasing rpm and hp potential. They ran well down the track as well.

That being said if the intake lobe is tiny, the added exhaust duration is probably more of a benifit than a cam that has adequate intake duration for the powerband desired especially paired with a wider LSA. Cams like the 492' and 071' GM rollers have a larger split than most. The 492 I recently degreed was 200* @ 0.050 on the intake and 216* @ 0.050 on the exhaust with a 115.5 LSA.

The 071' is 208/221 @ 0.050. With GM fast burn heads and the proflow 4 manifold I ran the ZZ6 makes over 400 peak HP at 5,600 rpm with that tiny 208 @ 0.050 intake lobe. I doubt that 208* intake lobe would carry nearly as well without the 221* exhaust lobe and the somewhat wide 112 LSA.

The 492' cam and 185cc 2.02/1.60 valve Vortecs make the power peaks a little lower than the 071' cam/Fastburn combination but not by much.

Both the 492' and 071' cam have near stock idle quality and flawless low speed drivability in a 350 with 9.5:1 or more compression thanks to the smallish intake lobe and minimal overlap. The 492' cam is pulling 18.5 in/hg idle vacuum at 750 rpm with the a/c on and nearly 20 in/hg with the a/c off with 20* of timing advance it pulls even more vacuum if I add some timing. When I go to the P59 and can get idle timing into it, it will idle like a stock Vortec 350 at 625 rpm. With the 1.6 roller rocker I run the 492' cam gets closer in lift and duration to the 071 but has the wider 115.5 LSA. I also feel like another reason the 492' cam pulls so well upstairs and my setup is not overly sensitive to octane/timing is the 111* ICL closes the intake valve a little later. The 071' cam is on a 108 ICL by comparison. The 071' might be a little stronger in the midrange than the 492' but it would likely be splitting hairs to notice a difference real world in a vehicle and my 492' cam was less than 1/3 the cost of an 071 when I bought it.

International47 said:

You can use the duel computer set up if you wish to keep the electronic transmission.
the EBL computer for engine managment and the existing stock computer for trans control.
its only splicing a few wires and moving a few extra pins.

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Never thought about running dual computers tbh, are both stacked under the dash? Kinda interested in that. The stock 4l60e is on its way out anyways, it doesnt like the considerably more powerful engine at all. I may get it rebuilt and sell it, not sure yet though. If I can run 2 computers the truck may just stay an automatic with a rebuilt 4l60e.

transitionbikes93 said:

Never thought about running dual computers tbh, are both stacked under the dash? Kinda interested in that. The stock 4l60e is on its way out anyways, it doesnt like the considerably more powerful engine at all. I may get it rebuilt and sell it, not sure yet though. If I can run 2 computers the truck may just stay an automatic with a rebuilt 4l60e.

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I stacked them both under the dash.