New option for PLOG

**Phantom** · 07-07-2010

I thought that I would share my finding and see if anyone has tried the dorman and what the results were.
Dorman Products - 674-540

The above link looks like a cast version of ZZP's PLOG but $100 less expensive at ~$63 (I think that is what autozone showed them for).

I contacted Dorman about the inside diameters of the manifold they responded with this.
The manifold is cast iron
The inlet is 1.55"
The outlet is 2.029"

So lets compare the measurements of
Stock Vs. ZZP Vs. Dorman
1.53" Vs. 1.625" Vs. 1.55" Inlet
1.63" Vs. 2.25" Vs. 2.029" Outlet
(The stock and ZZP #s are from ZZ Performance )

Now for the last two important dimensions stock exhaust port and crossover inside diameters.
Exhaust = 1.53"
Crossover = 1.91"

I think that the dorman could actually be better that the PLOG in a way. How so the inlet is only slightly larger than the head exhaust port should not make a big difference. Now the outlet to the crossover is where I see it being better as the crossover in 1.91" the stock piece gets larger by 0.32" while the PLOG gets smaller by 0.34" and the Dorman gets smaller by 0.119". That with less transitions in the exhaust it should keep the gas velocity up due to less turbulance giving better performance. Plus the pipes have a more gradual curve to them and no cap at the end.

Is my logic off or am I missing something?

It seams that this is an adequate solution to the PEM/PLOG and being cast it could still be ported if needed.

Has anyone tried the Dorman front manifold?

Also what do you think of this?

**blueguy** · 07-07-2010

Nice find...I assume it would help...better than stock...is it worth the money to spend on the PLOG? ...waiting for a dyno test nooooow...

**BillBoost37** · 07-07-2010

Biggest question on my mind is .. does it neck down like the stock manifold. Our stock manifold really isn't restrictive at the inlet and the outlet isn't going to make that much of a difference IMO. It's the necking part of the manifold that restricts flow.

**GTP 40TH** · 06-17-2011

Old post I know. Any other info on this? Has anyone used these to replace original? Improvements? Shortcomings?

Looking for any input. Considering purchasing one.

**Durk Diggler** · 06-17-2011

One is on ebay for $59 w/ F/S. Wish I saw this before I bought my PEM.

**GTP 40TH** · 06-17-2011

Here is part of the response I received from Dorman whenever I asked about their manifold:

"Our products are reverse engineered to fix the issue the factory part had."

I asked if they could be more specific. Still awaiting an answer. Will post their reply.

Would still like to hear if anyone on here has any experience with these.

**Phantom** · 06-17-2011

from what I remember its on club gp singer one bought one and they are the same as stock. I'm on my phone but search my name there I believe I made the same topic there.