can anyone help me in this area?i was thinking of doing a 4.1 with stock 3.8 crank & rods ported irons 212/roller 80lb.inj. & 6766 turbo. .I was running this same combo at 27psi boost in my 3.8..what would be the ups & downs of using this same combo in a 4.1 & should i use my stock manifolds or hooker headers that i have...?please give me all of your valuable input on this....
3.8 or 4.1 ?
- Thread starter 007gn
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thanks for responding.my car is street driven and raced at the track.the car has run 11.05 at 126mph.with a bad 60ft.on 275 50 15 hoosiers. im hoping the 4.1 would be good for solid 10.5s or faster.but i need this to run 10.s with no problems and be reliable.so can you tell me what to do to get there?
4.1 is more expensive to build correctly. To get forged pistons for the 4.1 you have to buy expensive custom forgings (unless you find used ones). The production 4.1 blocks aren't as beefy in the bottom end as the 109 casting. There are at least 5 different casting numbers for the 4.1 with various deck thicknesses and options (some don't even have knock sensor provision). Most are 14 bolt pan but I do believe the later ones were 20 bolt. They have a lot more casting flash in the lifter valley like other earlier blocks, not smooth and beefy like the 109. Majority of 4.1 builds are running hyper pistons due to the cost of forged ones. High HP applications probably would benefit from billet caps or a girdle, I won't pretend to have been there or done that, but I have looked into it a little bit. May be other perils. If it cost the same as a 3.8, with similar strength, there'd be a whole lot of 109's for sale and the 4.1s would be very sought after.
What boost, timing, and 60ft did you run?
Fast Farmer
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- Jan 24, 2012
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- May 26, 2001
Not to be dis-respectful, but it appears no one in this thread has built and run a 4.1 in a GN?
My first one was about 15 years ago and was a reliable low 10 sec. ride with MANY passes. Nothing "exotic" like todays builds, as it had a stock crank and rods with Champion alum heads.
I did blow a head gasket once when the boost spiked, but no cracked or split block?
I then built the first TA alum block 4.1 and sold the complete production 4.1 engine to an owner in Cali. After a few more years I heard from the third owner who was still running the crap out of it!
I have build many production 4.1's since then, a couple for myself and lots for customers. No broken blocks or cracked decks so far.
A typical 4.1 build does not cost any more than a comparable 3.8 build, as all our builds use custom forged pistons made to our specs. Why would anyone put anything but a good forged piston in a $8-10K performance build?
Unless the customer insists, we do not install a girdle, but do put in the 2 steel center caps. The availability of forged cranks is the best thing ever to replace the weak cast crank, and give us needed reliability into the 9's, or 650-700 HP.
For the same engine cost and comparable overall build, I will take on any street GN with a 3.8! The low end torque and acceleration is awesome.
With my personal experience running a 4.1 at the track, it will easily run into the 9's and 130 MPH+ with 16 PSI in a street driven TR.
I presently have two 4.1 builds in process, with a just finished one on the stand, all these have a stroker crank which gives a total of ~270 cu.in., yes, I AM a big fan of the turbo 4.1!
My first one was about 15 years ago and was a reliable low 10 sec. ride with MANY passes. Nothing "exotic" like todays builds, as it had a stock crank and rods with Champion alum heads.
I did blow a head gasket once when the boost spiked, but no cracked or split block?
I then built the first TA alum block 4.1 and sold the complete production 4.1 engine to an owner in Cali. After a few more years I heard from the third owner who was still running the crap out of it!
I have build many production 4.1's since then, a couple for myself and lots for customers. No broken blocks or cracked decks so far.
A typical 4.1 build does not cost any more than a comparable 3.8 build, as all our builds use custom forged pistons made to our specs. Why would anyone put anything but a good forged piston in a $8-10K performance build?
Unless the customer insists, we do not install a girdle, but do put in the 2 steel center caps. The availability of forged cranks is the best thing ever to replace the weak cast crank, and give us needed reliability into the 9's, or 650-700 HP.
For the same engine cost and comparable overall build, I will take on any street GN with a 3.8!
The low end torque and acceleration is awesome.With my personal experience running a 4.1 at the track, it will easily run into the 9's and 130 MPH+ with 16 PSI in a street driven TR.
I presently have two 4.1 builds in process, with a just finished one on the stand, all these have a stroker crank which gives a total of ~270 cu.in., yes, I AM a big fan of the turbo 4.1!
NyBlankets
Active Member
- Joined
- Mar 17, 2003
"With my personal experience running a 4.1 at the track, it will easily run into the 9's and 130 MPH+ with 16 PSI in a street driven TR."
Nick, Interested in which turbo(s) can run 9s @ 16lb of boost in a full weight TR?
Nick, Interested in which turbo(s) can run 9s @ 16lb of boost in a full weight TR?
- Joined
- May 26, 2001
My turbo is BB70-HPQ.
It has run a 9.8 @ 136 MPH at 18 psi in the "rare" weather with a 2000' or so DA.
Last Saturday night I was testing and temp was at 90 degrees, ran 10.1 @ 134.49 MPH with an easy launch 60' of 1.56 instead of my usual 1.43'. The boost log reads 16-17 psi on that pass.
My car weighs 3500#'s with a full cage.
Fast Farmer
Member
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- Jan 24, 2012
Nick, is your motor a stock stroke or 3.625 stroke?
- Joined
- May 26, 2001
It is a 3.625" stroke.
Normally I shift at 6600 RPM, but peak numbers for torque and HP are over 7000 RPM.
Normally I shift at 6600 RPM, but peak numbers for torque and HP are over 7000 RPM.
What kind of headgaskets are holding on these high HP 4.1's coppers or cometics?It is a 3.625" stroke.
Normally I shift at 6600 RPM, but peak numbers for torque and HP are over 7000 RPM.
- Joined
- May 26, 2001
I use Felpro 1026 head gaskets.
Fast Farmer
Member
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- Jan 24, 2012
Nick, what cars are the best 4.1 blocks found in? And will the roller cams, etc. for the 3.8's work in the 4.1's? This has really peaked my interest. I know where there is a clean Regal in a salvage yard that is begging for a set up like this. Sage green. What a sleeper!
black owned
black pride
- Joined
- Jun 15, 2008
Nick,what are the specs and brand of pistons you used?I will be putting together a 4.1 over the winter and will be using a stroker crank as well,thanksIt is a 3.625" stroke.
Normally I shift at 6600 RPM, but peak numbers for torque and HP are over 7000 RPM.
- Joined
- May 26, 2001
We use pistons from both Ross and CP, and they are located on West coast.
There is no standard spec we use, as there are many considerations to take in account for each build.
For example, the final bore size depends on the ring package as we also have heavier ring lands and file fit rings, so we have make these compatible.
Also other factors like compression ratio, rod length, valve relief if wanted, pin strength, gas porting and other items depending on customer requirements.
In an expensive build like what you have planned, it is best to work with the engine builder, and especially have him order the pistons. If there is a screw up, he is responsible.
We just went through this with our latest build, Ross made a mistake. We sent the pistons back and they made everything right.
There is no standard spec we use, as there are many considerations to take in account for each build.
For example, the final bore size depends on the ring package as we also have heavier ring lands and file fit rings, so we have make these compatible.
Also other factors like compression ratio, rod length, valve relief if wanted, pin strength, gas porting and other items depending on customer requirements.
In an expensive build like what you have planned, it is best to work with the engine builder, and especially have him order the pistons. If there is a screw up, he is responsible.
We just went through this with our latest build, Ross made a mistake. We sent the pistons back and they made everything right.
It is a 3.625" stroke.
Normally I shift at 6600 RPM, but peak numbers for torque and HP are over 7000 RPM.
Just to clear things up , your not talking about a production 4.1 in the above statement are you?
Thanks, Kip
