High compression 347 with Texas Giant?
High compression 347 with Texas Giant? A local guy here built a high compression Ls1 347 (12.5 to 1) with ported ls1 heads and a Fast 102 intake. I tried to talk him out of putting a Texas Giant cam in it being stock displacement but he did it anyway. My buddies shop tuned it and only made 430rwhp through a M6. This guy is saying that something is wrong with the tune and it should have made more power but I think it is because the parts are so mis-matched. What do you guys think? I think he would have made more power with a smaller cam that was cut for the 346 instead of a stroker motor.
The FAST 102 is fine imo because the LS motor is only going to pull in as much air as it needs. That's why FAST only makes the 102 now. It has to be the cam, he needs something more suitable for the 346 and he should see nice numbers.
I'm going to have to jump on the bandwagon and blame the heads as well. That thing will need to turn some serious RPM to reach the HP peak with that cam. The heads and valvetrain need to be up to the task.
Can you give us info on the full build? For all we know it has 1 5/8 shorty headers on it.
Was it through full exhaust? What was the exhaust.
How'd the AFR look?
Was there gain seen adding/subtracting timing?
Could be the heads.. Could be the valve train.. Could be lots of stuff.
Was it through full exhaust? What was the exhaust.
How'd the AFR look?
Was there gain seen adding/subtracting timing?
Could be the heads.. Could be the valve train.. Could be lots of stuff.
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That's Jared's build, right? What heads did he put on there and what headers/exhaust?
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With un touched 243 heads, ls6 intake, ported stock tb and stock bottom end (stock compression ratio), my car did 423. With ported heads and more comp, I would assume more power. That FASTwith that high reving wanting cam, I would think ~450. Street manners would probably suck though...
With un touched 243 heads, ls6 intake, ported stock tb and stock bottom end (stock compression ratio), my car did 423. With ported heads and more comp, I would assume more power. That FASTwith that high reving wanting cam, I would think ~450. Street manners would probably suck though...
Everyone talks about street manners sucking with big cams.. I find it funny as can be. My little single plain wearing Trexed 347ci motor with 11-1 cr fires up with out and throttle and goes right to idle weather it's hot or cold out. Idle's at a solid 850-900 rpm. Doesn't surge even at 1800rpm with the converter locked. But hey, I guess that means it has horible street manners..
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Joined: Apr 2002
Posts: 537
Likes: 2
From: Lehighton Pa
PS I don't have anything against the texas giant since it is in my 402 but I think his setup is just mismatched.
From what I was told they were ported by "some local guy" and they are flowing something like 340 CFM? But from everythiing I have read about LS1's isnt there something special to porting them compared to a standard SBC and BBC head? Also I love whe guys talk about PEAK flow when its easy to forget about velocity and flow throughout the entire lift range...
I would also guess heads. They could be fubar if the wrong person got a hold of them. The intake seems good, and although the cam is huge for the displacement, something is wrong if he falling off hard after 6400.
Street manners is all in the tune and completely dependent upon the driver. I can tolerate quite a lot. The MS4 is still a large cam for the 346 and it has great street manners. If it wasn't for my cylinder 7 ring being fucked up, it would drive perfect in all weather conditions. Starts right up, idles around 1000-1150 when cold and around 850-900 when warm. Whenever I clean the intake (read cylinder 7 ring problem), it runs like a dream, no idle hunt, and I never buck or surge.
Street manners is all in the tune and completely dependent upon the driver. I can tolerate quite a lot. The MS4 is still a large cam for the 346 and it has great street manners. If it wasn't for my cylinder 7 ring being fucked up, it would drive perfect in all weather conditions. Starts right up, idles around 1000-1150 when cold and around 850-900 when warm. Whenever I clean the intake (read cylinder 7 ring problem), it runs like a dream, no idle hunt, and I never buck or surge.
Everyone talks about street manners sucking with big cams.. I find it funny as can be. My little single plain wearing Trexed 347ci motor with 11-1 cr fires up with out and throttle and goes right to idle weather it's hot or cold out. Idle's at a solid 850-900 rpm. Doesn't surge even at 1800rpm with the converter locked. But hey, I guess that means it has horible street manners..
I have a relatively large cam (242/248 111 lsa), and what I mean by street manners is always driving over 2k rpms, idle dropping when coming to a quick stop, ac at lights (when not fully warmed up) likes to low idle, making slow turns likes to drop idle....well my car at least. Bucking and surging is a issue, but if you drive the car how you should with a large cam, it can be avoided. Mine does not go straight to idle, it likes to cold idle..but...4600 elevation does that. In Phoenix my cam acts a lot better then where I am at currently.