Porting and Polishing

[opethmike]

My block is rotting, so it wouldn't be a usable engine, but you're welcome to it (sans heads) for a reasonable price if you'd like to come to Rochester to get it.

Or with the heads for a slightly less reasonable price, lol.

[Christian Dietrich]

My block is rotting, so it wouldn't be a usable engine, but you're welcome to it (sans heads) for a reasonable price if you'd like to come to Rochester to get it.

Or with the heads for a slightly less reasonable price, lol.

You mean you will give me head..... for a price.....? Hmmm that definitely might be worth the trip! How bad is the block rot? Well I already talk to you about wanting to buy the heads from you here eventually

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[opethmike]

You mean you will give me head..... for a price.....? Hmmm that definitely might be worth the trip! How bad is the block rot? Well I already talk to you about wanting to buy the heads from you here eventually

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It isn't terrible; it's just the start of it. Shoot me a PM on Facebook and we can talk details.

[Alex Brooks]

My engine in 11035 has the Spec 1 exhaust/no cats mod, larger air box with a K&N filter and CAI tube and a throttle body spacer. Stock heads and cams......... for now and i will say from a seat of your pants feeling, it is definitely a night and day difference over a stock DeLorean and it is much more responsive and the throttle is much more snappier and I have no problem hitting 60mph off the line. I'd say with the mods, that im probably pushing a 25hp gain? It feels it. A good porting and polishing will probably free up between 5 to 7 horsepower it's like Mike said and you polish the seeding real well. I dunno, mabye another 30 hp with cams. I will be really interested to see someone go from a stock engine and have it dynoed then slowly do mods to it from simple bolt ons to full cams and head work to see the gains. Simply getting rid of this cars induction system and exhaust system really does make the PRV engine way better then in stock form. I know I'm loving how my setup is and I have no problem revving my car to redline at times and she pulls very nice. 200hp (engine, not wheels) can be easily done with the right tricks.

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Christian,
Where did you get that air box ? I would love to add it my car. Thank you Alex

[Christian Dietrich]

Christian,
Where did you get that air box ? I would love to add it my car. Thank you Alex

DeLoreanAutoParts.com Glad you like it. I believe its adds a bit of performance due to the larger opening.

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[sdg3205]

DeLoreanAutoParts.com Glad you like it. I believe its adds a bit of performance due to the larger opening.

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And with the plexiglass on the top you actually see the ponies just flying into the engine!

[Christian Dietrich]

And with the plexiglass on the top you actually see the ponies just flying into the engine!

It would be ponies and not horses lol!

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[dn010]

When I had a stock engine I cut around the base of my air box (the part the filter sits in) so that there was no longer anything below the filter, no more hose, no housing, etc. and I didn't notice any difference in performance. I did have to clean the K&N filter more often though. Run it with no filter box at all and there's not a difference. The NA engine can only consume so much air, if you're looking for performance you need to start doing more expensive, involved work to the PRVs.

[FABombjoy]

I logged MAP at the throttle edge vacuum fitting on my turbo car. At full load / WOT the I saw up to a .8bar pressure drop. So while it's possible there is some restriction in the intake it might take a draw-thru turbo to find it. Naturally aspirated I doubt you'd really find much gain on a dyno outside of the realm of measurement error.

That aftermarket airbox deletes the PCV tube which will expose more of the air filter element to the engine, but at the expense of increased crankcase pressure at higher load. In trying to find free HP the meter flap probably is the greater enemy.

[Grover]

I'll throw in my .02 since I have port and polished heads.

I have a thread in the Mod section about my engine build, but long story short, with high compression pistons, port and polished heads, a 1mm shave on the heads and aggressive camshafts, my car dyno'd 147whp.

Now, if the statement is that a Stage II is 140whp (I don't know since I haven't seen an actual stage II dyno'd), that leaves 7 extra horsepower. But, is that from the port and polish or the high compression pistons and compression raise from shaving the heads?

I will say this, looking at my dyno graph I have a big drop in power between 3500 and 4500 RPM. The graph shows that the car leans out in that range, raising to a perfect full fuel enrichment ratio after 4500rpm. So, the engine has more air than fuel available to pump (I have raised the fuel pressure as well and the full enrichment switch is working). Because of the lean condition I had to reduce my engine timing to 15 degrees, thus losing more power.

Because of this I plan to look into modifying the fuel system some, but that is a different topic.

Back on topic, I know Josh at DPI has told me that they stopped port and polish when they did offer that service, saying he found it was actually worse. I have no proof to back this up. I can say that one the two cars I drove that are setup the same except for the pistons and port and polish, they have a smoother power band whereas when my fuel enrichment catches up it has a VERY noticeable kick up in torque/power (http://dmctalk.org/showthread.php?50...-Upgrade/page5 - Post #42).