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Hey guys, thought I'd give you a little update. I have 600 miles on the engine build. I updated a few things. I put a set of DW 48lb injectors and a GZ vacuum pump. I have the vacuum pump set at 8" of vacuum. What a difference it made! After all it's a 1/1/2mm ring package in a stock block! lol.. I will post a few videos. They don't come close to being in the car. It's a beast for NA. Small, high flowing, proper high velocity, makes it a acceleration beast!
Video of rolling at 1000 rpm, notice how fast it finds 6000+
Video of rolling in OD and notice how fast the car accelerates!
Do you have anything else helping out that rapid acceleration or do you think this is mostly just the high port velocity doing it's magic? (light weight rotating assembly? TC Stall speed / size?)
Pistons are the Mahle PowerPak with the thin metric rings? How much DID the vacuum pump help out? Is the vacuum pump extra beneficial because of the thin rings or because of the combo of a stock block (without a recent torque plate hone) and the thin rings?
On a slight tangent to this post, but not a tangent when we've got Chad Speier posting on ThirdGen: If you had a customer who INSISTED on keeping a long-runner, TPI-style intake (much larger, better flowing FIRST) and to take advantage of the intake's RPM range wanted the long stroke and faster piston speeds of an SBC 396 stroker, what direction would you go with their heads?
-I know you've got some SBC small bore-specific focused heads, but with the 395 aren't you just becoming REALLY valve size limited? Don't you top out with a 2.05" intake valve on a 4.030" bore and a 45 deg valve seat angle? Do you end up oversizing the intake port CSA for the cubic inches to try and help the engine's airflow keep up closer with the high piston demand or just say heck with that on a long-runner intake and just let the freight train of air flow catch up with piston demand after BDC so you need the high velocity from a smaller port and higher discharge coefficient of a typically sized intake port and valve?
Going for broke on max hp long-runner hp questions: The ideal cam LSA for a 3.875" stroke 396 is considerably tighter vs. a 350, but with consistent or increasing durations, the overlap is going to get bigger and bigger; Brian Tooley has previously said that high velocity exhausts+ significant overlap cams really cause issues with long-runner intakes (and he was talking about LS Truck intakes as long-runner then, vs the super-long TPI intakes) as they tend to drop the pressure in the long runner intake track and pressure recovery takes considerably longer with a long-runner intake (assuming lower RPMs). (Edit: A street solid roller cam's shorter adv / seat to seat durations would help with overlap and getting more curtain area with the valve size limitations by throwing the valve open faster, just curious whether changes to the heads' valves or intake ports could help this bad situation out.)
-What kind of voodoo magic head work can help this situation out? -Larger intake valves and larger ports than typical sizing guidelines so that you can get away with less durations and therefore overlap? (50 deg valve seat angles to reduce effective overlap?)
I feel like there's still plenty of area just not adequately explored with long-runner, long stroke TPI builds despite TPI's age as they've just been written off in performance circles for so long...
(I like the idea of the faster piston speeds at the RPM range of the long-runner intakes, but it should also mean a higher velocity quench which might help with highish compression TPI builds' propensity to knock around the torque peak; just seems extra beneficial in a long-runner build, AFAIK.)
Adam
Last edited by newbvetteguy; Jul 21, 2021 at 11:46 AM.
But you lose to much torque with the single plane efi conversion 🤣. These vids prove why it's irrelevant, and why long runner tpi/first stuff is a waste for anything except stock, a truck, or if you have to pass smog check.
