347 Dyno Results

[NZGTRA17]

A few months back I purchased a used 347 shortblock out of the States via E Bay for US$500. Had been recently built using a std roller block, Eagle crank, Eagle rods and JE forged pistons. I pulled this down and found all machining and parts to be OK, block and crank were crack tested etc.

I built this back up and replaced the balancer, rebalanced the engine and replaced the bearings. Spent a lot of time detailing the webs in the block to help prevent stress cracking in this area.


The short block was combined with the same Brodix CNC heads, 224/232 Comp Cams custom grind, Edelbrock Air Gap dual plane manifold, 650 Mighty Demon carb etc that I used on the 5.0. This combo on the 5.0 made approx 335/335 rear wheel hp and tq. In the 347 the cam was retarded 4 degrees to help bump power over 5500rpm. 347 compression is 10.5 : 1.

To help the engine rev quicker I used a lightweight steel flywheel and Quarter Master 3 plate clutch. Saved lots of rotating pounds with this.



Dynoed the car today using the same Dynojet dyno as we did all the development on the 5.0. 347 peak hp was 388 and tq 392 at the rear wheels. Peak hp was at 5800 rpm and peak tq at 4500. Very flat torque curve and the 347 is making the 5.0's peak torque before 3000rpm. Graph below is a comparison of the 5.0 Vs the 347.



Overall I am very happy with the results as they are slightly up on what I had expected. Have attached a link to a video of 1 of the dyno runs;



Kel.

[David Eastman]

Kel,

As allways thanks for sharing your results. Making more power than you expected is a good thing.

David

[jmimac351]

Kel, that's great stuff. Did you have the block machined with the stud girdle on?

[eric1h]

VERY Impressive!

[NZGTRA17]

Originally Posted by jmimac351

Kel, that's great stuff. Did you have the block machined with the stud girdle on?

Jim, the block had already been completely machined and run in the States. I did not do any additional machining except for hand detailing of all parts prior to balancing (incl block webs).

When I received the engine it already had a girdle on it however I swapped mine from the 5.0 onto the 347 as my was 3/8 thick Vs the skinny one that came with the 347 (1/4" perhaps).

The style of girdle that I run has spacers that go between the maincaps and the underside of the girdle. I usually pull up 1 and 5 main studs to 40 - 50 ftlbs and check for any significant gap between the girdle and main caps at 2,3 & 4 to check alignment. The thicker the girdle the more important this would be so that you didnt preload the block. This could cause premature web cracking otherwise.

Kel.

[NZGTRA17]

Originally Posted by eric1h

VERY Impressive!

Cheers Eric. From the playing I have done with these engines now, I am confident that 450+ rwhp will be reasonably easy to achieve but will require an aftermarket block for longevity.

I do not forsee this engine having a happy ending at the power level it is at now, even with keeping revs to 5800 (block will fail at some stage). This years 6 hour is coming up in May so we will find out then!

Kel.

[jmimac351]

Kel, the reason I asked is a pair of father and son racers who have built engines for their Factory Five roadster and coupe had some issues with the engines coming apart even though they were being very careful about how they put things together. They were using a main girdle as well. What they discovered was that the engine needs to be machined with the girdle in place. Since they did that they've had zero engine problems. I think they were able to verify this through measurement of some sort. Since they told me that I have run across other professional engine builders stressing the same thing. Just thought I'd share...

[jmimac351]

By the way, check this out, you may find it interesting...

http://www.hardcore50.com/vbulletin/...ad.php?t=52378

[eric1h]

Originally Posted by jmimac351

Kel, the reason I asked is a pair of father and son racers who have built engines for their Factory Five roadster and coupe had some issues with the engines coming apart even though they were being very careful about how they put things together. They were using a main girdle as well. What they discovered was that the engine needs to be machined with the girdle in place. Since they did that they've had zero engine problems. I think they were able to verify this through measurement of some sort. Since they told me that I have run across other professional engine builders stressing the same thing. Just thought I'd share...

Probably the same idea behind bolting a torque plate to the block when boring/honing the cylinders. to add the tension that torque heads will apply and make sure the cylinders are still round under pressure

[Panoz26]

Kel , very nice, very nice indeed.

Devin

[jmimac351]

Yep. It never ocurred to me that it was important but they stressed it a lot. Several of us got into a conversation about what they were doing for engines since we've all been thinking about which way to go. That also tells me those girdles must really be doing something if they can cause things to flex like that. Hopefully they are doing a good thing.

[NZGTRA17]

Originally Posted by jmimac351

Kel, the reason I asked is a pair of father and son racers who have built engines for their Factory Five roadster and coupe had some issues with the engines coming apart even though they were being very careful about how they put things together. They were using a main girdle as well. What they discovered was that the engine needs to be machined with the girdle in place. Since they did that they've had zero engine problems. I think they were able to verify this through measurement of some sort. Since they told me that I have run across other professional engine builders stressing the same thing. Just thought I'd share...

Thanks Jim, interesting info. Are you able to find out a little more about what sort of failures they experienced and what machining had to be done with the girdle fitted?

Kel.

[Gatorac]

Originally Posted by NZGTRA17

Thanks Jim, interesting info. Are you able to find out a little more about what sort of failures they experienced and what machining had to be done with the girdle fitted?

Kel.

The main bearing clearance was the issue. The stud girdle would oval the mains slightly. Just check your main clearances with the girdle on. If they are fine, you shouldn't have a problem.

[NZGTRA17]

Originally Posted by Gatorac

The main bearing clearance was the issue. The stud girdle would oval the mains slightly. Just check your main clearances with the girdle on. If they are fine, you shouldn't have a problem.

Thanks Jim, that makes sense. Main bearing clearance checked at 6000rpm on the dyno............!! Yup, was plastiguaged in the shed prior to assembly.

Kel.

[PanozDuke]

Kel,
I believe you are right, it got the 6000 rpm test and passed with an A With the 5.0 block, align honing with the girdle in place seems highly advisable given the load flexing possible. Might be good insurance for cylinder boring and honing as well? Can a block even be set up on a boring machine with main caps and girdle in place?

I am wondering if the rotating assembly was internally or externally balanced? By the looks of the dampner, I'm guessing externally. Given the vulnerable main webbing, I am wondering if internal balancing would reduce the crank harmonic flexing by reducing the weight on the end of the crank and moving it closer to the center? I think reducing the flywheel and clutch weight is a good move from that standpoint as well. I've been wondering how to maximize the capability of the 5.0 block to make power reliably. The only thing else I could think of is using block filler to fill a couple of inches to add some structure around the main webbing area and using screw in freeze plugs.

What are your thoughts about internal balancing effects and some partial block filling? What about using stronger main caps in conjunction with the girdle?

Looking forward to hearing that you get a great result in the 6 hours!

Mike