LT1 Intake conversion - Still strangled top end???
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 878
Likes: 2
From: BC
LT1 Intake conversion - Still strangled top end???
Hi all,
been getting to work with the tune on the LT1 intake conversion - i have the lower part of the tables sorted now and the car is feeling pretty smooth.
One thing that I have noticed though is that I don't actually seemed to have gained that many RPM's - sure it pulls better from 4-5k but still feels strangled at that point.
Don't get me wrong it pulls hard up to the gear change (4.7k) where it just starts to back off but I just expected a bit more when locked into gear.
Here is my setup - I think its probably exhaust manifold and maybe cam that is killing the fun??
L83
128 Al Heads
~ 11:1 Compression
204/214@.50 420/442 with 1.5 rockers
LT1 Intake converted
730ECM - MAP, no MAF
Cut Air Filter Lid
Standard Manfolds
Gutted Pre-cats
Cat Replacement main cat
Monza Mufflers
Where is my restriction here?
been getting to work with the tune on the LT1 intake conversion - i have the lower part of the tables sorted now and the car is feeling pretty smooth.
One thing that I have noticed though is that I don't actually seemed to have gained that many RPM's - sure it pulls better from 4-5k but still feels strangled at that point.
Don't get me wrong it pulls hard up to the gear change (4.7k) where it just starts to back off but I just expected a bit more when locked into gear.
Here is my setup - I think its probably exhaust manifold and maybe cam that is killing the fun??
L83
128 Al Heads
~ 11:1 Compression
204/214@.50 420/442 with 1.5 rockers
LT1 Intake converted
730ECM - MAP, no MAF
Cut Air Filter Lid
Standard Manfolds
Gutted Pre-cats
Cat Replacement main cat
Monza Mufflers
Where is my restriction here?
Pro
Joined: Jul 2007
Posts: 670
Likes: 0
From: Culver City California
go to long tube headers with 113 heads and a cam and 1.6rr to match and you will be making some great power! you have several bottlenecks but look at the entire exhaust system first and you will notice decent gains.
Last edited by kowalski340; Mar 3, 2008 at 05:00 PM.
Race Director
Joined: Sep 2003
Posts: 16,839
Likes: 341
From: Database Error Indiana
The heads/cam are at their limmits now. I have stock 128s on a carbed car and they just will not make power above 5400. I tried tweaking timing, the carb, a bigger cam and upgrading valve springs. The heads are the weak point.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 878
Likes: 2
From: BC
I know we have only just started this year but I plan to build a 383 Stroker next winter. I've already got the block it just needs a bit of work to get it up together. I will probably go for some 195 heads and deffinately get a more aggressive cam when I build this.
For now I just want to try and optimise what I've got.
From what I've listed - would the Headman Street Headers (only option avilible in the UK) help my performance? I can still take these off and use them on the next motor is my thinking.
For now I just want to try and optimise what I've got.
From what I've listed - would the Headman Street Headers (only option avilible in the UK) help my performance? I can still take these off and use them on the next motor is my thinking.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
it's the cam, move up to something in the 22xdeg@.50 range and you will have much easier time pulling to 6000. comp has a nice 224 lobe with .502 lift on a 1.5 rocker that works really well on 113s
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Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
LT headers will give you more power but will affect RPM very little. Your heads and cam are holding you back. You can use Hedman Elites and possibly use them on future heads, but I would make a decision on the heads you will use on the stroker and check first.
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
if you don't go in the motor you will have a hard time making more power without nitrous 
the valvesprings aren't going to like 1.6 rockers, the cam doesn't move enough air at higher rpms. Basically stick with what you have and enjoy. You really do need a cam, more head flow and better springs to up the rpms and the hp. the other question there is the bottom end and how well it will live. if you think through all the cash you might find where you are is not all that bad.
the valvesprings aren't going to like 1.6 rockers, the cam doesn't move enough air at higher rpms. Basically stick with what you have and enjoy. You really do need a cam, more head flow and better springs to up the rpms and the hp. the other question there is the bottom end and how well it will live. if you think through all the cash you might find where you are is not all that bad.
Thread Starter
Burning Brakes
Joined: Aug 2006
Posts: 878
Likes: 2
From: BC
thats sound advice - I'll enjoy it for this summer, I hope not to have to turn a spanner for once (Yeah - right). I wasn't sure if it was JUST the manifolds that was holding me back or not. If it was then I would have swapped them out but as it is I'm happy to stay where I am for now.
I've got a trip to the Le Mans 24hr race planned in June so I need to make sure everything is prep'ed for that trip anyway.
Cheers for everyones advice
I've got a trip to the Le Mans 24hr race planned in June so I need to make sure everything is prep'ed for that trip anyway.
Cheers for everyones advice
Pro
Joined: Feb 2005
Posts: 560
Likes: 0
From: Hamilton New Jersey
