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View Full Version : 150hp cam vs ?cam for rebuild



skikir
11-08-2006, 01:18 PM
I'm looking at an engine rebuild and definately am going to do something about the cam. I'm not sure how I'm going with this but have been thinking of the Euro spec 150hp cam. Does anyone have any experiance with one? Any pros/cons? I'm also going with the good parts 3XZS system.

Alan_Myers
11-08-2006, 02:20 PM
Hi,

You're off to a good start... by asking questions!

I have a TR4, so can't give you specifics about the setup you are considering. However, do *a lot* of homework about the camshaft, before you commit to buying one. If at all possible, work with a supplier who can also provide you with proven, matched components, either all at once or possibly in stages of upgrade.

A camshaft is central to an overall performance upgrade plan. It's got to coordinate well with all other engine factors: displacement, compression, gas flow (porting/valves/intake/exhaust), valve train geometry, valve timing, etc., etc. Heck, even cooling can come into the equation.

So, take your time, keep asking questions and surfing the Internet for info, and try to establish a working relationship with a primary vendor who can give you solid advice, based upon their own testing and development.

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trfourtune
11-08-2006, 03:25 PM
here's my 2 cents worth,
i have gone round and round and round on my camshaft choice for my tr4 (sorry not applicable). a year's worth of research ++. information from around the world (literally) and advise from ALL the experts including someone with f1 ties and connections as well as experience, and i have come to this.......i think...... at this time....i will have a cam ground by elgin cams for MY engine with MY combination and MY exhaust system and intake system with My head and displacement and compression for MY weight of car and gearing. every bit and piece of information has an effect. it comes down to buying ONE cam for MY motor/car. i may pay more than an off the shelf cam but every car is different. put the big money in your head first.optimize the rest.
rob

Brosky
11-08-2006, 03:43 PM
If one has the smarts to compile all of that info and knows exactly what power range they want to benefit, it is the ideal way to go. Even if you can give the info to Elgin and ask them to recommend a grind combo that will help either low rpm, high rpm, street, etc. it will pay big benefits.

swift6
11-08-2006, 04:05 PM
One of the drawbacks of the original 150hp PI cam was that it had terrible idle characteristics. The cam profile was one of the changes when the HP rating dropped to 125 in the later cars. That and they were using a less optimistic method of measuring HP when the 125hp PI cars were introduced. As you are already planning on using RG's 3XZS system, you might also consider talking to him about his camshaft choices. He has spent copious amounts of time arriving at his specific cam grinds (GP2 & GP3). Including Dyno time with his 3XZS system and various header and exhaust systems.

I know of several people that swear by his GP2 cam (some on the BCF here) and I am using his GP3 cam with 3XZS. The GP3 definitely has a lope and won't idle smoothly under 1100rpm. Definitely sounds tough. The GP2 is hard to discern by ear and idle characteristic though it does develop very smooth power.

Bob Claffie
11-08-2006, 08:14 PM
I prefer a custom ground cam rather than "off the shelf" style. Years ago I had a custom cam ground for my roadracing Spitfire. Schooler cams in Fla had a poop sheet / check list on which I listed all my engine and gearing specs and required characteristics such as preferred max / min revs and absolute redline, and their computer program designed the cam profile, duration etc. At the time I could run with the Kastner reccommended A6 factory grind. Bob

swift6
11-09-2006, 01:06 AM
Did you ever figure out what the difference was in lift, duration etc... between your cam and the Kastner grind? Maybe they were closer than you think.

You bring up a good point though. Which is why I suggested using one of Richard Good's Camshafts to go along with his Triple Stromberg set up. He has designed them to all work together afterall. He is also very easy to discuss other engine options with such as Compression Ratio, level of head work and which header worked in what areas etc...

Simon TR4a
11-09-2006, 09:46 AM
Just to add my opinion.....
I agree with Shawn; the 150hp cam has a reputation for poor idle vacuum, no doubt the result of big overlap. More modern cams are designed to have steeper ramps so that a good amount of lift is achieved earlier and less overlap is needed. This causes faster acceleration of the valve train which means greater pressures on the cam lobes lifters and rockers, so check the condition of the rockers and use new valve springs.
Another important point is that the old cams are designed to be symetrical, which means the timing of the opening and closing of the exhaust valves is a mirror image of the intake valves, which is usually not ideal. Modern cams are designed with the benefit of computer modelling and can produce wider power bands with less effect on the idle.
If you want to use a more radical cam Richard Good's roller rockers might be worthwhile for their extra stiffness, and stronger pushrods might be a good idea. Whoever supplies the camshaft you choose should be able to give you some guidance here.

I feel that unless you are building an all out race engine, or are prepared to do the thorough research that Rob has done on all aspects of the engine's specification, that you are better off buying an "off the shelf" cam from a reputable supplier like Elgin, Kent,Piper, Web, Richard Good etc. For various reasons I think it is better to buy a cam ground from a new blank than to regrind your present cam. In particular I would have concerns about the hardening treatment done after the profile is reground.

As others said, make sure all the modifications you plan will work well together, and tell the supplier what rev range you want to use.

Hope this is helpful, Simon.

skikir
11-09-2006, 10:43 AM
Thanks guys. This is the first foray into rebuild peformance upgrades. My #5 cylinder is dead at low revs and the rods rattle before oil pressure comes up and milage has droped from 28 to 22 mpg. I was embarrased by a civic the other day. Time to do something. The engene in it now will be junked. It turns out to be a GT6 engine and it had lost oil to the rockers. The wear between the rocker shaft and the rocker must have been 3/8" and all that grinding went straight down the push rods into the cam. I was really supprised it ran as well as it did. I replaced the rocker shaft and most of the rockers with some old useable ones I had and put an external oil feed line in a couple of years ago as a stop gap while I redid the body. Now she really looks great but now I want to put some teeth into those looks.

11-09-2006, 11:25 AM
Oooh a GT6 bottom and a TR6 top.

Don't junk it, fix it and supercharge it - it'll rev to 7.5k and the loss in displacement will be more than made up for by the fi.

You'll have teeth aplenty then.

trfourtune
11-09-2006, 01:24 PM
here is some cam info i found to be quite useful. go to this web site.
www.mintylamb.co.uk/?page=camcompare.htm (https://www.mintylamb.co.uk/?page=camcompare.htm)
rob

skikir
11-09-2006, 04:30 PM
[ QUOTE ]
Oooh a GT6 bottom and a TR6 top.

Don't junk it, fix it and supercharge it - it'll rev to 7.5k and the loss in displacement will be more than made up for by the fi.

You'll have teeth aplenty then.

[/ QUOTE ]

?! could you elaborate (sp) on that? Is there something here I don't understand about the GT6? Unfortunately I haven't the $ for a super charger. That's almost the cost of a complete engine reglue. Not that I wouldn't mind one but for that total cost ($6K) I could get a nice complete running TR.

swift6
11-09-2006, 04:47 PM
The 2.0 litre GT6 engine doesn't have the long stroke of the 2.5 litre TR6 engine. In fact, the TR6 engine is a "stroked" 2.0 litre engine. Since the stroke and bore are close to the same dimension on the 2.0 litre its closer to what they call a 'square' engine. What that begins to translate to is that the 2.0 revs easier than the 2.5 due to the base design of the engine. Higher RPM can mean more horsepower (at that higher RPM). The longer stroke of the 2.5 gives it more low end power through greater torque. Supercharging the 2.0 litre would help in the low end power department yet the engine could still rev fairly high fairly easily. Fuel Injection could allow the release of a few more ponies without causing driveability issues. Interesting idea all in all.

Clear as mud? or does that make sense?

11-09-2006, 07:10 PM
In addition to Shawns post above, I'd add that the design of the crank (and mounts) is better. This allows it to rev higher - to about 7.5k rather than the 6.2-6.5 that the TR6 is constrained to.

If you happen to already have a TR6 head on it, you'd get a better return if you put $ into this engine. A cheap (but not skimping) rebuild, a new cam and a supercharger will blow the doors off any 6k rebuilt TR6 engine you care to mention. You won't be embarrassed by any stock civic ever again.

If your block isn't totally shot, and you DO have a TR6 head on it, I would seriously urge you to consider this as an option.

swift6
11-09-2006, 08:13 PM
I doubt it has a TR6 head on it unless it was really shortened. The head thicknesses were supposedly quite different between the two but the intake and exhaust port spacing is the same.

TR6 engines can be built to rev to 8,000rpm. But not with the stock crank.

11-09-2006, 08:22 PM
And not for $6000.
A billet crank is 4k...

swift6
11-10-2006, 12:20 AM
Right, TR6 engines that can rev to 8K are pretty much full race engines and can cost near $20,000! A far sight from the $6,000.

Actually, $6,000 is a decent price for an outsourced TR6 engine if it comes with a warranty (which it should if your doing a stock rebuild). Buying another TR6 for $6,000 is another option, but how long would it be until that TR6 needed a rebuilt engine too? Just something to think about.

trfourtune
11-10-2006, 05:25 PM
one more point about cams. if you increase capacity, bore or stroke, the quoted rpm range of a cam is no longer correct. increasing capacity "detunes" the cam to operate at lower revs (gross generalization).
rob

11-10-2006, 06:58 PM
[ QUOTE ]
I doubt it has a TR6 head on it unless it was really shortened. The head thicknesses were supposedly quite different between the two but the intake and exhaust port spacing is the same.

[/ QUOTE ]

The reason I though this might be the case is that its already in a TR6. If the block went on the first car someone might have gotten cheap and took a scrap GT6 block, mated it to the top end off the original TR6 and shoved it back in the car. I still think its a possibility, but without seeing the engine have no idea if that happened...

swift6
11-10-2006, 07:15 PM
[ QUOTE ]
[ QUOTE ]
I doubt it has a TR6 head on it unless it was really shortened. The head thicknesses were supposedly quite different between the two but the intake and exhaust port spacing is the same.

[/ QUOTE ]

The reason I though this might be the case is that its already in a TR6. If the block went on the first car someone might have gotten cheap and took a scrap GT6 block, mated it to the top end off the original TR6 and shoved it back in the car. I still think its a possibility, but without seeing the engine have no idea if that happened...

[/ QUOTE ]

Valid reasoning on both counts. Anything new on your car yet in regards to the fueling problem? I'm anxious for you to not only being able to drive your car with the triple strombergs but also see the continuation of the supercharged and fuel injected project. Really interested to see what kind of power your recipe will make. /ubbthreads/images/graemlins/thumbsup.gif

/ubbthreads/images/graemlins/cheers.gif

11-10-2006, 07:23 PM
The pump I ordered from Summit was supposed to be low pressure (no more than 6PSI). It puts out over 15. A different pump is on order and I'm waiting for it to arrive...

On the up side removing the stuff in the trunk seems to have helped a little with the flow from the stock pump.

On the down side the (remanufactured) Toyota tranny is leaking like crazy out of the rear seal - with 10 miles on it and out of warranty because the whole deal has taken so long...

No matter what I'm taking a break from mods until after next summer, and I'd like to be able drag it to VTR - its only 3 hours from me this time round. I *have* to get some driving in before it comes off the road for the next round of changes.

I was thinking of rewiring it though as a nice filler winter project - assuming I get it back before winter...

swift6
11-10-2006, 08:24 PM
Too much pressure is certainly a bad thing. Good luck with getting some drive time back in before the next round. Give yourself and your mechanic a break once you get it up and running reliably anyway.

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