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Discussion Starter #1
We are building a D16A9 DOHC normally aspirated engine for circuit racing in the UK.
Looking to increase the power quite substantially but there is very little information to help us !
We have two engines stripped down to scavenge for bits. We have forged pistons and con rods on order, bearings ARP bolts ect ect for the bottom end. Standard crank.
We have lightweight flywheel, uprated inlet manifold and exhaust manifold.
It's the top end we are unsure about.
We are getting the head port matched and polished.
The only cams available for the DOHC are from CAT cams Belgium they have a few options for lift and duration but speaking to them, they cannot give me any information whether we will have any problems with valve overlap on the most wild cams.
Obviously we are looking at taking a big chunk off the head to raise compression ratio !
We will dry build first, but I just wanted to know any first hand information in regards to ideal comp ratio and best cam dimensions to use ?
I know it's a long shot but hey !!
Also I'm looking for uprated valve springs and caps for the engine but it seems that the SOHC and DOHC have different ones fitted.
Sorry for the long post
 

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90 crx si/96 accord
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Rocket motorsports offers a nice spring replacement set that you might want to look into.

Utilize the search button, for basically all posts by theacidbeaver in the dohc zc sub forum. Some of the best info I've ever learned from him, is info that comes out completely random.

From what I remember, you can cut 1.5 to 2mm off the head, you will more than likely have to use the Mitsubishi timing belt to accommodate for the loss of height from the head. Adjustable cam gears and a degree wheel will obviously be a requirement.

When my engine builder did mine with colt 282 cams, we ended up with the exhaust ~6° advanced, and the intake 1° retarded, but each engine will be a little different.
 

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89 EF 4wd sedan
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I'm running reground cams in mine, i scratched my head for ages trying to figure out what to do about the rocker adjustment. Basically, with the smaller base circle you have to adjust the rockers closer to the cams, so the lobes strike the pad on the rocker much closer to the side and then drop off the edge of the pad. I believe this would make it idle like trash and probably cause premature wearing.

Perhaps it wouldn't cause any problems, but i wasn't willing to risk it. I'm running non vtec b18 valves that have their tips ground down slightly, and then seated into the head. They're also larger in diameter than the OEM valve diameters which i would expect it to breathe better at higher rpm. From memory the valve guides needed reaming slightly as the diameters were slightly different...

There's not a lot of info about this though, as the VTEC B's have different head designs, but i ready a bit about it in 3G prelude forums.

I'm running a supercharger, so i don't really have much to say about the right cam/compression specs for an NA build.
 

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Discussion Starter #4
Thanks guys, have you any more information on this mitsubishi timing belt i may require for this ?
Its just a mindfield knowing which cams to choose without no recomendations. The only person on this forum who have used cat cams have gone with only fast rod / sports cams. I just would fancy going a bit heavier than this for competition
 

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Thanks guys, have you any more information on this mitsubishi timing belt i may require for this ?
Its just a mindfield knowing which cams to choose without no recomendations. The only person on this forum who have used cat cams have gone with only fast rod / sports cams. I just would fancy going a bit heavier than this for competition
I would recommend calling Geoff at colt cams to discuss your requirements, he was great to talk to, and colt cams have a good rep. Perhaps he'll have something that will suit you.
 

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Discussion Starter #7
Can anyone give me the information on using the B series vernier camshaft pulleys on the D-series D16A9 engine please. they are slightly different in some way ?
Thanks for your help so far guys
 

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Can anyone give me the information on using the B series vernier camshaft pulleys on the D-series D16A9 engine please. they are slightly different in some way ?
Thanks for your help so far guys
the gear on the exhaust camshaft needs to be rotated one tooth clockwise when installing the timing belt - the gear on the intake cam is o.k. - gears should look like this when installed - don't worry about the marks on the opposite side of the gears - just line up the two in the middle with the top of the head - the gears pictured have marks for both the B-series and DOHC ZC, D16A8, D16A9,D16Z5 - the gears you get will most likely have only the B-series marks


 

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Formerly weebeastie
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Good info in this thread. I also recommend calling Geoff at Colt Cams. He ships internationally and makes a great set of cams for the DOHC D. I run a turbo DOHC ZC, use Rocket valve springs and will be running a set of Colt Cams in the near future.

I also agree, search out theAcidBeaver on here. He probably won't reply if you message or email him, but invest the time and read his posts in the ZC forum on here. Excellent information.


I've run quite a few different aftermarket camshafts, and the Colt TriFlow cams are really top notch.

Pretty sweet to see you guys building a DOHC D
 

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90 crx si/96 accord
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My dohc zc, css block, colt 282 cams, dsm 14b, w/7cm^2 turbine housing, stock wastegate on 91. Retune at the end of this month, switching to Bosch 600cc, BP 93. And hoping to crank the boost to 16~18 psi
 

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Discussion Starter #12
Thanks for all the help so far. Had a fantastic chat with Geoff @ Colt cams. We are getting a stage 2 regrind as it will save a fortune and keep standard valvetrain.
Most parts are here now. The bottom end is with the engineers getting a +1mm rebore for the new 76mm pistons, notching to accept the rods and pistons converting to fully floating, once done and the cams are back, then we will dry build and see how much of a chunk to take off the cylinder head.
Realistic expectations are 160hp. Car currently is dynoed at 131whp. Been out in the car as it is and is good, just needs a little more and it will be competitive in its class for sure.
 

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Discussion Starter #16
The Stage 2 is cheaper than the tri-flow. The only difference with tri-flow is that is better for anything under 4k revs. It's a scatter kind of profile. We don't need this for our competition, if I'm under 4k revs I'm pulling off the start line of recovering from a spin !!!
Think it's something like 300 canadian bucks. Geoff certainly have me confidence that he knows what's he's doing.
With no mods, no adjustable oulleys, drop straight in stage 2 normally sees 18-20whp gain.
 

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When I had my engine built, and cams degreed, the exhaust cam was advanced 4*, and the intake retarded ~1.5°.

So, getting everything degreed should be something to consider ��*♂
 

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Discussion Starter #18
Hi Guys, cams are due back soon. Only problem I have is getting hold of an oil pump for a D16A9. Can get a sohc pump but they are different. I want a new one really but can't see any worldwide and honda says not available. Any advice guys, or If I get a sohc d series oil pump can I swap the internals over?
 

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Hi Guys, cams are due back soon. Only problem I have is getting hold of an oil pump for a D16A9. Can get a sohc pump but they are different. I want a new one really but can't see any worldwide and honda says not available. Any advice guys, or If I get a sohc d series oil pump can I swap the internals over?
hy,you hawe aftermarket ACL on ebay...cheers
 
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