Twin PT61s for 400 cube V8?

[WFO]

Planning out a twin turbo blow thru for my '65 Plymouth.Got a PT61 on the GN right now and have a spare PT60 that needs rebuilt.Figure I can have the 61 wheels put into the 60 when it's being rebuilt.

Big question is whether two 61's is too much for 400 cubes with 8.8:1 compression,comp 270 cam(224/470)and Brodix B1-bs heads...

It's a street/strip car with 3.23s,2800 stall and I would like full boost as quick as possible.

Both turbos have .63 ex housings and I have a .85 for the 61.I'm sure I could score another .85 if need be.

I'm only looking for about 600 horsepower as it's a fresh stock rebuild with cast crank/pistons,so it'll only take so much. Should be an attainable goal on pump gas/methanol.

Thanx.

 

[Dusty Bradford]

Planning out a twin turbo blow thru for my '65 Plymouth.Got a PT61 on the GN right now and have a spare PT60 that needs rebuilt.Figure I can have the 61 wheels put into the 60 when it's being rebuilt.

Big question is whether two 61's is too much for 400 cubes with 8.8:1 compression,comp 270 cam(224/470)and Brodix B1-bs heads...

It's a street/strip car with 3.23s,2800 stall and I would like full boost as quick as possible.

Both turbos have .63 ex housings and I have a .85 for the 61.I'm sure I could score another .85 if need be.

I'm only looking for about 600 horsepower as it's a fresh stock rebuild with cast crank/pistons,so it'll only take so much. Should be an attainable goal on pump gas/methanol.

Thanx.

With the 61's it'll make 600hp with 2 plug wires off the car

You're trying to spool a 61 with 200ci and a tight stall. You'll have to loosen the stall or run smaller turbo's. You don't want big power, you could make 600 with two stock GN turbo's and keep you're tight stall.

 

[WFO]

Good point.Never thought of it that way.

You think two stockers will be about right at the lower boost levels I'll be running for now?Can't imagine I'd need to run over 10-12 psi to reach the power I'm looking for.Especially with those good heads...

 

[Dusty Bradford]

Good point.Never thought of it that way.

You think two stockers will be about right at the lower boost levels I'll be running for now?Can't imagine I'd need to run over 10-12 psi to reach the power I'm looking for.Especially with those good heads...

I think the GN turbo's would work well. We all know one GN turbo will support 400hp so 2 will easily make 600 without pushing them. They're small enough to work with a tight stall.

 

[WFO]

And they're cheap too .

Beside the fact that it'll be easy enough to upgrade later when my built short block comes along.

Thanx a lot man.

Hey since we're on the subject what's the hot setup for running alky on a blow thru?

 

[WFO]

Oh one more thing-I was planning on running stock GN cast elbows also.

When do those start being a restriction?

And what size downpipe are they made for?Was hoping I could run 2 1/2" duals straight off the cast elbows and keep the internal wastegates for compact trouble free boosting goodness .

Thanx again.

 

[Dusty Bradford]

I'd have to suggest a digital 7 MSD box if your using a carb. It has a ton of features but mainly allows you to plot a timing curve. The 7531 and possibly the 7530T utilize a MAP sensor to adjust timing according to boost, just like an EFI system. There may even be cheaper alternatives like a boost retard box to be used a cheaper ignition control. Either way, you need a way to adjust timing. Alky will be more forgiving of the a/f ratio. I'd go to someone like CSU for a carb because they have a lot of experience with boosted carbs.

We have had GN's make 500hp (6.80's at 100mph in the 1/8) through a stock elbow and downpipe. I can't see any reason they would be restrictive at your level in a twin set-up. May even work well to over 800. Stock downpipe is 2 1/4 I believe. Vendors have made 2 1/2 downpipes for them.

 

[WFO]

Yeah,I was gonna look into the right ignition next.Was figuring an MSD billet distributor and a boost referenced ignition box.

500hp thru a stock elbow is good news:biggrin: .I wonder who has 2.5" flanges to bolt to the stock elbows so I can run downpipes to my exhaust.Or I might be able to plasma out a couple of stock 2.25"s to 2.5" .

Is the 3 bolt flange some kind of standard part that someone might sell flanges for?

I'm gonna try my hand at a DIY carb and if it doesn't work like I want it to I'll call CSU.

 

[Dusty Bradford]

The stock downpipe used a donut gasket and flange. I haven't seen any vendor just selling that part. I think Poston made a 2 1/2 downpipe. I guess I'd hit up the local muffler shops to try and find a 2 1/2 flange, pipes and gasket to work with the stock housing.

Try spdexhaust.com for the turbine flange. I think it's a T3/T4 or something like that.