Engine rebuild (OE vs Aftermarket)

[Vtecwreck]

What’s up guys,

I recently picked up an RDOT short block for a fair price. I made a 600 mile round trip to get it but it’s the second one I came across, the first one slipped out my hands.

Here’s a little background info as to how this came to be: The current engine in my caR is out of an OBD1 Gsr. My main goal for my car was to bring it back to OE specs eventually. The PO has stopped answering my text and with that I lost hope of ever owning my original engine and trans. Back in March of this year I was down in Atlanta for a trip and while searching the FB marketplace I found a jdm B18c shortblock, picked that up bought an ITR cylinder head and just before I was getting ready to mate them a “itr longblock” popped up on FB. I immediately contacted the seller and he sent me the stamping. To cut to the end, I drove down picked it up, sold the gsr head and sold the jdm spec short block.

Fast forward to this past Monday, I dropped the short block and head at my local machine shop to have the motor rebuilt and to my surprise the guy is recommending I go with an aftermarket setup. I’m conflicted because I’m not looking to go that route, I was expecting to just build it back to OE specs. The machinist is saying that it’s only a few more bucks and it’ll make some more power. Although this sounds good, I’m looking to go with the setup that will have the longer lifespan and reliability. Surprisingly enough I couldn’t find anything on this. With all that being said, I would like to hear some feedback from people who know the actual outcomes. Note* I’m not too knowledgeable on this.

[Dave7CDMTYPER]

Might depend on how much you will drive it, and if value of car will be affected by going aftermarket vs oem.

[Stin1]

Its your car, do what YOU want.

[aklackner]

What exactly are they recommending?
my 2 cents:
To get power out of aftermarket cams you'll need to increase compression.
You can increase compression by reducing the combustion chamber (trimming the head down) or increasing the height of the piston. In either case you'll need to watch valve clearance and timing may need to be adjusted. This means cam gears and tuning to get things right since A/F will be affected even by drop-in cams. It also likely means improvements to flow of intake and exhaust (i.e. larger bore TB and decat.).

Generally one upgrade is going to require several more within linked systems so if you're looking to keep stock I'd say try to stay as close to that as possible.


As far as power gains I don't think you'd really see much outside of cams.

I don't know that there's an argument to upgrade springs if you're not upgrading cams (in fact OEM springs will cause less stress and wear on valve train, if you don't need additional lift or to move heavier valves)

I've not heard of issues with OEM retainers (within oem redline). If planning to live in the redline then ti retainers might be a good idea but some brands will wear or are made to seat better on a matched valve spring. Poorly matched retainers can cause them to wear. Aftermarket retainers should be inspected regularly for wear.

Upgraded valve guides are probably arguable on OEM or near spec these again will handle heat better but do so with more material so impact air flow. (probably very minor impact)

Aftermarket valve seals are not going to get you any power over OEM but you'll want to replace with something that's the highest quality accessible.

A quality valve job might deliver a bit of improvement on it's own, but of course would go further with more modification and tuning to maximize. PortFlow did mine and he has a custom valve profile for ITR valve seats that he's designed. I was very happy with the results.

[RTW DC2R]

Yeah, what exactly are they recommending? Is this a Honda specific shop you are using? If not, you might want to rethink using them for the rebuild and find another shop. Ive had many motors built over the years and learned to stick with the guys that know the motor.

I just did a OEM rebuild last year on my high mileage R. I thought about things like using stronger pistons and rods and rods but ultimately I settled on completely OEM for longevity. Swapped to some JDM ITR pistons .25 over bored, OEM bearings and rings. Fresh valve guides, seals and valve job. Done and done.

[Vtecwreck]

Alanker,
I forgot to mention that the head was built for a high Hp configuration. Buddy club spec 3 cams, titanium valve springs and retainers, it was previously ported, etc., I mentioned a Hp goal of 220 and that might’ve been what he stuck to. Thanks for the feedback.

Ryan,
With the Hp number in mind he recommended a forge piston for valve clearance due to the beefy stage 3 cams. He is very familiar with Honda’s as he builds all the local race car engines. I believe he leans toward going aftermarket for that reason. However, after reading your post I called him and went over your specs and he said he can do that but obviously I’d not hit my HP goal. I told him that wasn’t as important as the reliability. If you don’t mind, I’d like to get some more specifics on your rebuild kit. Thanks for the feedback!


Now I’m in between oem parts and aftermarket. I would like to stick to oem pistons and such but he’s looking to bore out .50 but if I can not obtain Oe pistons at those specs he’d be ok using the .25 over. Aftermarket brands that I’ve came across are rs machine and nippon. If I’m correct nippon is the manufacture of the oem Honda pistons? If so I’d like to go with them in order to fulfill his recommendation. As for bearings I believe he mentioned “kings”. He states these are great aftermarket and are oem comparable. My main concern is reliability and longevity.

[GeHonda]

My humble opinion having been around some built and stock motors over the years, you can't beat OE reliability.

Based on your last reply, you are going to have to have aftermarket ECU tuning (Hondata or similar) to maximize anyway, so going aftermarket on the motor isn't a deal breaker, but the tune will be critical.

I think going with JDM ITR pistons is the ideal setup, as long as your head work will be compatible.

For NA, you don't need a "stronger" rod (heavier) and the stresses it places on the short block.
For reliability, I don't like forged pistons, which have different expansion properties (noise, oil control issues, clearances) that to me do not work well for reliability. The OE pistons just seem to perform better to me.

The only time I would recommend upgrading the bottom end would be for extreme high RPM, or forced induction, applications.

Possibly just update to ARP rod bolts (rebushed) with OE bottom end, and JDM ITR pistons is your best bet.
I would only use OEM rod and main bearings. They should be the exact color code to match your block stamps (A,B,C,...)

[RTW DC2R]

Sorry, didnt realize you had a hp goal in mind. Unfortunately 220whp is not gonna happen with a stock-ish B18C5 motor. As mentioned above you will need a lot of complementing upgrades and tuning to get near that number.

For reference, my motor is very stock. Other than .25 JDM ITR pistons, the longblock is entirely stock. Still running a stock intake (removed resonator box) with Spoon filter, Toda rep header, T1R test pipe and B pipe, and stock ITR muffler. That is the extent of my build. Then its literally just suspension and gearing. The setup makes around 195whp on a tuned ECU. But also runs excellent on the stock ECU which is great for state inspections. I typically only run the tuned ECU at track days so I can take advantage of the mid-range power and higher redline. I usually run the stock ECU on the street.

One of the scariest things I ever came across was worn titanium retainers after 15K miles on one of my old all motor builds. The thought of retainers snapping at 10K RPM quickly made me go back to a stock valve train. Ive been through so many different types of builds that now I just want to be able to turn the key without worrying about it. Maybe add some oil every now and then and some basic maintenance and thats it.

Im not sure why he is recommending .50 unless the cylinders are that screwed up. And I have used ACL and OEM bearings without issue, never used King so cant comment on them (do a Google search as I recall possible issues with King). As long as you stay on top of oil changes Id say youll be fine either way. I will say my OEM bearings went 160K miles without a problem though and looked pretty good before my rebuild.

Really it all just comes down to what you want from the car, how you intend to use it, how much you want to spend. If you save a few bucks on a motor build, then put that into something like a 4.7 or 4.9 final drive. The final drive is one of the best mods you can do to an ITR. Im running a 4.9 right now with a GSR 5th. Its nice for highway cruising but not ideal on the track. If I did it again Id probably go with a 4.7 and keep the ITR 5th.

[DC231]

Yeah, what exactly are they recommending? Is this a Honda specific shop you are using? If not, you might want to rethink using them for the rebuild and find another shop. Ive had many motors built over the years and learned to stick with the guys that know the motor.

this^

be aware of bad quality machine work it will waste your money and time.

nippon p30 pistons will get you the compression you need and the valve reliefs should be plenty.. have the cylinder head and block been decked?

[3pedalJohn]

Stay way from Ti retainers, stick with a good quality steel retainer for durability.

The buddy club spec III look like a really nice cam from a quick google search.

Don't be afraid to run aftermarket rods and pistons there are some really nice products out there. It's more about the engine builder, his ability set all the clearances up correctly and keep things clean.

100% get it professionally tuned

My favorite mod on my Integra was the choice to go to an 84mm bore(sleeved B18c1), it's ~10.6:1 compression with ITR cams and man does the extra 135cc make a difference everywhere in the rev range. That and a 4.7FD ITR trans makes for a fun combo.