4.1 Production block how high are you guys running the boost.

[wickedtt]

I'm building a 4.1 production block(291 cast) and was wondering what boost levels people are running. If the tune is right can you run the same boost levels as the 3.8 109 motors or are you more likely to blow the head gaskets on the 4.1 ?

 

[87GNSteve]

The head gasket will be the limiting factor. The 109 head gasket will not fit.
I didnt like the Felpro 1000s, very flimsy, have lotsa extra bolt holes for stage heads.
If you tune right have plenty of fuel /alky and use RJC or Cometic head gaskets you can easily run 25-30psi.

 

[tom j]

I ran 30psi on mine with cometics

 

[Nasty Wendy]

I ran 30psi on mine with cometics

Tom did you do anything special to get the Cometics to seal around the water passages that the gaskets don't have an embossment around?

 

[87GNSteve]

Tom did you do anything special to get the Cometics to seal around the water passages that the gaskets don't have an embossment around?

I know you asked Tom but I bought mine from Champion at reynolds and he told me to put a very thin coat of RTV around all the water.
Did so and never had a problem, upon tear down it came off easily. Key is to not overdo it.

 

[Nasty Wendy]

I know you asked Tom but I bought mine from Champion at reynolds and he told me to put a very thin coat of RTV around all the water.
Did so and never had a problem, upon tear down it came off easily. Key is to not overdo it.

Cool. Thanks.

 

[Brookgn]

I ran mine between 25-27# with Cometics. I used copper spray on them. I broke the crank and the block but the head gaskets were fine!

 

[wickedtt]

Thanks guys this is what i wanted to here ..Anyone have the part# for the ARP head studs, I,am using the GN1 alum heads with the 4.1??

 

[boostingbuick]

Fel-pro 1000's here. 19lbs on pump gas no alky, 10.91 at 128, full weight. 24 lbs on 110. I run the 14 GN1r head and I have had great luck with them. I will stick with what works for me. Putting alky on it right now, so I hope to see some low tens and will stay with the Fel-pro gaskets.

 

[dr_frankenstein]

felpro 1007s.............. 25+ PSI never a problem, just make sure you have a good machinest for the reciever grooves.

A.j.

 

[wickedtt]

Fel-pro 1000's here. 19lbs on pump gas no alky, 10.91 at 128, full weight. 24 lbs on 110. I run the 14 GN1r head and I have had great luck with them. I will stick with what works for me. Putting alky on it right now, so I hope to see some low tens and will stay with the Fel-pro gaskets.

I thought we couldn't run the Felpro 1000's with Alum GN1 heads because it had a steel fire ring?? How long has this been working for you? What size bore is the block?

 

[Steve]

Tom did you do anything special to get the Cometics to seal around the water passages that the gaskets don't have an embossment around?

If you are building a motor and plan to use Cometics make sure to the have the block and head surface finished to 50RA or smoother by the machine shop like Cometic recommends and nothing is needed with the Cometics. When you use the Cometics with an existing motor without the recommended finish smoothness then copper coat ot RTV will likely be required. It cost me about $90 extra in machine work to get the recommended smoothness on my motor but well worth it in my opnion-I put the gaskets on dry and never had any problems.