L29 intake manifold question

[Reggiecab]

*This may be a dumb question*
After some reading here the L29s intake manifold seems to be a weak link as far as design and efficiency goes, outside of carb swapping is there any other manifold options? Dual part OEM style or otherwise? Thought process was that I’ll need to get in there for injectors at some point as the truck is new to me without much in the way of records and the Bosch revised style injectors I’m sure would be happier with a better flowing and easier to work around manifold.

 

[Scottm]

Not many options. Emissions legal or not? I did a ton of work to mine. I ground so much out to improve the line of sight flow path that I had to build it up with weld on the outside. Flow improved about 15 cfm iirc. Check out "99 L29 build" near the top.

 

[yevgenievich]

Aftermarket available with adapter for throttle body. But all will be shorter runners. On my motor was running out of air by 3900-4000rpm with ported stock intake. Gained 2k rpm switching intakes. Still want to go back to stock looking intake somehow

 

[Reggiecab]

Not many options. Emissions legal or not? I did a ton of work to mine. I ground so much out to improve the line of sight flow path that I had to build it up with weld on the outside. Flow improved about 15 cfm iirc. Check out "99 L29 build" near the top.

Emissions aren’t a concern, I’m definitely not qualified to attempt screwing with the flow.

 

[Reggiecab]

Aftermarket available with adapter for throttle body. But all will be shorter runners. On my motor was running out of air by 3900-4000rpm with ported stock intake. Gained 2k rpm switching intakes. Still want to go back to stock looking intake somehow

Would that setup be worth it for an engine that’s probably just getting that and injectors along with a tune? Because 2k extra would be nice.

 

[Komet]

No, the cam in the stock L29 is very small. It's a perfect match for the stock manifold because it's designed to maximize torque production down low. If you only shorten the runners, you'll lose torque down low but the gains up top will be minimal without a bigger cam to support the higher rpm. Cam and intake though, some pretty big gains up top can be had.

 

[L31MaxExpress]

Not cheap but I have seen a couple of guys over the years that have sent the L29 manifolds to get them extrude honed. Pretty decent power gains from what I have seen. A spare manifold can still be found fairly affordibly so that it can be sent out for minimal down time. One guy had a HT502 in his Suburban and the extrude hone process really added some power to it. It still passed smog, as aside from the 502 badging on the valve covers that could be replaced with 454 badging or the stock 454 valve covers, it looked stock and had all the stock emissions parts.

Over the years I have also seen several TPI SBC manifolds sent for extrude honing. Added a good chunk of power to those as well without hurting torque.

The stock cam is terrible for low rpm torque as it closes the intake valve fairly late. There are many options that will really add some low-midrange torque.