sbc 400 in a 97 suburban

[Aloicious]

yeah, the OBDI setups are a totally different thing, thats for sure, and I'm definitely not an OBDI kinda guy. but, in the OBDII tables, typically you can alter the KR settings to get better function out of the knock sensor rather than disabling it. for example when the knock sensor begins pulling timing due to KR, it will keep building up the amount of retarded timing until the knock goes away, then the amount of timing that was retarded will decay away. so you'll slowly return to 100% timing, but you can increase the decay rate a good amount, which will allow the safety of the knock sensor but will get you back to 100% timing after the knock is gone much quicker....you can also limit the max retard based on RPM incase you wanted to limit or expand the possible amount of max timing the KR can play with...

I've had some good luck altering my timing tables, but then again I'm fairly far from stock, like you said, a stock or mildly modified engine, the stock tables do pretty well. one benefit of a more advanced PCM like the 411 is the use of multiple timing tables that can be used to dictate the timing for high vs low octane, etc...

I just realized I have completely derailed this thread....sorry to the OP.

 

[silver97]

No apologies needed. I learn something new on every post. I have only built a couple of carbed motors so I am like a sponge trying to soak up info. The reason I am asking about this 400 is that it does not need a rebuild and is basically free to me. It looks that there isn't any benefit power wise unless I can put a rollercam in it. With the billet aluminum cover I was talking about that Efi connection sells can I use a cam button to keep a rollercam in check? What else do I need?

 

[Aloicious]

free is a reasonable price....I wouldn't say there is NO benefit in power, more displacement is more displacement...a roller cam would definitely be beneficial though, that is for sure, and the power benefit would probably be marginal without it....I'm not sure on that aluminum cover, that SOB is expensive though, very nice and well built, but very expensive.

even with a free block, you may want to calculate out how much it would cost to retrofit stuff to the 400 vs just building a 383 out of your current 350, a mild 383 can be built on a budget, and it may be more beneficial too. just food for thought.

 

[silver97]

I don't want my truck to be down for more than a weekend or two, so i would need to have the new longblock on the stand ready to go. I called 3 machine shops in the area, Two were backed up with race engines and told me to buy a crate motor. The last one wants to assemble the short block which is $250 on top of the machine work charges. I was looking at Summit racing's 350 vortec block that is clearanced for the stroker crank. With a cast rotating assembly I would be at $1500 without a new cam. So can I get the 400 to work for less than $1500?

 

[SixSpeedSS]

You could source another L31 for cheap and rebuild it using a stroker kit. I just rebuilt my L31 with new sealed power pistons, and all new USA made components (clevite, melling, sealed power, Hastings, etc) and I have $650 in machining/parts & $100 in a pair of used Vortec heads. I haven't checked on a crank kit but I'm certain a budget crank can be had for under $500 (I can buy an Eagle for my Pontiac for not much more - I know they are made offshore, but lots of people have had very good luck with them). A little bit of clearancing for the block and I bet you could be in under $1500.

But you could also put a roller in the 400 for less than that. The difference is I would imagine you did not build the 400 and you would know exactly what you have with building your own motor.

When sourcing a flat tappet cam for the 400, your biggest hurdle will probably be getting sometihing that makes good torque/power, but gives you proper LSA for streetabilty with the SEFI. This is where the Hydraulic roller will benefit you. The L31 Vortec is pretty stout to begin with. Especially compared to the TBI setup that was used in '87-'95 trucks.

 

[DGA1]

You could source another L31 for cheap and rebuild it using a stroker kit. I just rebuilt my L31 with new sealed power pistons, and all new USA made components (clevite, melling, sealed power, Hastings, etc) and I have $650 in machining/parts & $100 in a pair of used Vortec heads. I haven't checked on a crank kit but I'm certain a budget crank can be had for under $500 (I can buy an Eagle for my Pontiac for not much more - I know they are made offshore, but lots of people have had very good luck with them). A little bit of clearancing for the block and I bet you could be in under $1500.

But you could also put a roller in the 400 for less than that. The difference is I would imagine you did not build the 400 and you would know exactly what you have with building your own motor.

When sourcing a flat tappet cam for the 400, your biggest hurdle will probably be getting sometihing that makes good torque/power, but gives you proper LSA for streetabilty with the SEFI. This is where the Hydraulic roller will benefit you. The L31 Vortec is pretty stout to begin with. Especially compared to the TBI setup that was used in '87-'95 trucks.

Did you keep your stock crank and displacement? Any balance problems with your setup?

 

[Tempted]

Did you keep your stock crank and displacement? Any balance problems with your setup?

You can buy 383 kits that use 350 style cranks and internal balancing.

 

[DGA1]

Yeah, that's what I was looking at. An internally balanced 383 kit with a 4x4 cam, with all the prerequisite valve train bits to support more lift. My other main parameter is to stay within stock injectors capabilities.

Since I'm betting that I have 2-bolt mains is this a hindrance with a stroker kit?

 

[Tempted]

No. There isn't anything wrong with a 2 bolt, they hold 400+hp.

 

[DGA1]

Thanks for the info.