Cam choice- LT1 or summit 8800?

[Hipster]

This info is starting to become more than I have learned in the past.|

I believe I grasp the differences between static and dynamic compression, but am unable to see the end result effect, or the negative result.

I was thinking that the almost stock nature of the parts used ,would result in a engine that would be stock like in power, reliability and tuning. Maybe resembling something closer to a LT1 cammed, 1995 Roadmaster, iron head LT1?

Has my choice of parts/machining creating an unsuitable or unrealible combonation?

Static sometimes referred to as mechanical is just that the sum of the parts assembly. Dcr in short is the cylinder pressure the engine sees. It's closely tied to the intake valve closing point but the other valve events and cam specs matter. Some engines achieve over 100% volumetric efficiency so cylinder pressures through the rpm range is a moving target. I generally do a compression test. It gives me a baseline I can relate to. L31 has pulled off 230 lbs. cranking compression. I've had stuff get temperamental about fuel in the mid to upper 190's psi range but was also not working with Vortec chambers and using slightly more aggressive cam profiles.

I didn't think you were anywhere near 10cr much less over, but i wasn't thinking about you swapping the dished pistons for flat tops. The best I was able info I was able to find for tbi pistons when I was looking years ago was 22+ cc volume spec, some info wa 24cc where you got 5cc. Huge difference.

"stock like in power, reliability and tuning." If that really what you want, shelve the go fast your trying to get to. Others may not agree but I would run the numbers with .039 hg see where they land, over 9cr put it together with the stuff on hand and go have fun. By time you get bored you'll be efi tuning guru. The higher the cr the more critical the tuning becomes.

 

[Supercharged111]

A thicker gasket makes the quench less effective and negates the effectiveness of the reduction in compression. With EFI I don't see a reason why this would be problematic, even if it is an ancient TBI setup.

 

[L31MaxExpress]

A thicker gasket makes the quench less effective and negates the effectiveness of the reduction in compression. With EFI I don't see a reason why this would be problematic, even if it is an ancient TBI setup.

I was running a L05 with 53cc 601 heads on it with TBI years ago. 210 psi cranking compression with the Melling MTC1 cam it had. The combination had fantastic low-midrange torque and great fuel mileage.

 

[Hipster]

I agree with most of that. I can say without a doubt, 95% of people on this board wanting something peppier than the stock engine would be absolutely ecstatic with how the L31 I built runs. That 1987 G20 van screams with that ubber basic 350, is decent on fuel and once the Proflow 4 ECM is pulled off will run like GM put the thing there from day 1. The engine is quiet as can be internally, idles smoothly with lots of vacuum, carries great oil pressure, broke in without any drama, it does not burn oil, and just flat runs great overall, PF4 ECM hiccups aside. When the P59 goes on it with a knock sensor I am not afraid to tune it to run on 87. Sure it has an aftermarket intake, throttle body and headers on it, but most of the internal engine is production GM engineering in some form or another and just works. I have spun it to the fuel kill at 6,000 rpm numerous times and it is silky smooth all the way up the rev range and just does not stop pulling until it is bouncing off the rev limiter.

Something like this is tons of fun to go out romping on Simple, worry free, low maintenance, can't kill it, miles of smiles hassle free..

 

[International47]

Static sometimes referred to as mechanical is just that the sum of the parts assembly. Dcr in short is the cylinder pressure the engine sees. It's closely tied to the intake valve closing point but the other valve events and cam specs matter. Some engines achieve over 100% volumetric efficiency so cylinder pressures through the rpm range is a moving target. I generally do a compression test. It gives me a baseline I can relate to. L31 has pulled off 230 lbs. cranking compression. I've had stuff get temperamental about fuel in the mid to upper 190's psi range but was also not working with Vortec chambers and using slightly more aggressive cam profiles.

I didn't think you were anywhere near 10cr much less over, but i wasn't thinking about you swapping the dished pistons for flat tops. The best I was able info I was able to find for tbi pistons when I was looking years ago was 22+ cc volume spec, some info wa 24cc where you got 5cc. Huge difference.

"stock like in power, reliability and tuning." If that really what you want, shelve the go fast your trying to get to. Others may not agree but I would run the numbers with .039 hg see where they land, over 9cr put it together with the stuff on hand and go have fun. By time you get bored you'll be efi tuning guru. The higher the cr the more critical the tuning becomes.

I agree, I was not thinking or planning on 10:1cr
Other than the new pistons, and attempting to help the less than ideal heads, its still real close to stock motor.
Flat top pistons were stock in the F and G bodies TBI motors of the same years. so that was the thought process.

The only actual " go fast' parts are the Edelbrock intake, comp ultra pro magnum roller rockers, and the LT1 cam... I guess headers as well-I needed them for space, But these parts are nothing out of the ordinary and not "racing" in my books.

I will have to play with the head gasket values and see where the CR ends up at.
I created this avenue and now I have to walk it's path.

I always knew the tuning adventure with EBL-flash was going to be an eye opening, learning experience, now its going to be much more.

 

[transitionbikes93]

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.

 

[tayto]

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

 

[L31MaxExpress]

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

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.

I also have a small block TBI manifold with dual 2" bores and the EGR cast shut from the factory that was on a 1987 G30 cutaway bus. No 02 sensor, no EGR, 454 TBI unit on it from GM.

The 1987 G20 I have was also weird in some ways too. It was roller cam and flat top pistons,, the 187 heads had a groove machined into them between the intake ports, stainless U clips over the gasket. The valve covers had torx bits. I wish I had taken more pictures when I pulled it apart because I have never seen the intake gasket retention clips it had on another TBI engine. Must have not worked well though, because 2 of them had come apart and the engine had eaten part of them at some point.

 

[L31MaxExpress]

This is an actual documented GM produced TBI 307 Oldsmobile manifold that was on a 442.

You must be registered for see images attach

 

[Hipster]

I agree, I was not thinking or planning on 10:1cr
Other than the new pistons, and attempting to help the less than ideal heads, its still real close to stock motor.
Flat top pistons were stock in the F and G bodies TBI motors of the same years. so that was the thought process.

The only actual " go fast' parts are the Edelbrock intake, comp ultra pro magnum roller rockers, and the LT1 cam... I guess headers as well-I needed them for space, But these parts are nothing out of the ordinary and not "racing" in my books.

I will have to play with the head gasket values and see where the CR ends up at.
I created this avenue and now I have to walk it's path.

I always knew the tuning adventure with EBL-flash was going to be an eye opening, learning experience, now its going to be much more.

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.