Cocktail Motor - How much HP do combo mismatches cost

[Dusty]

Cocktail Motor Build

By

Dusty Kennett

Building what you want for a motor entails one very important factor – having what you want in the first place. But what if you have to make do?

No doubt here that most of you are wondering what a ‘cocktail motor’ is. Let me paint the picture and you will get it for sure. Here at GFN we have a number of race cars in various states of completion. There are two road race fox bodied 5.0 Mustangs. One DV intends to race when he can find time. The other is about 2/3rds finished as far as the rolling chassis is concerned and DV made me a deal. It went something like this. If you can find enough parts lying around to build an engine then you can drive the second car. This second car is intended for NASA’s American Iron series. This series has a limit on the power and torque to weight ratio that can be run so a huge amount of power is not what’s required.

In essence the challenge here is almost reversed from normal. Instead of selecting parts based on them making an optimally functioning combo I have to put together what ever is available and make do. This is going to be an exercise that looks at what can cause a loss of output when parts selecting and see the consequences when done.

The first thing I inherited here is a short block used for a protracted dyno session. This was built for us by the guys at Speed-O-Motive. I could not use the heads, intake or valve train from this as these were prototype parts being researched. This meant pulling the heads etc and just using the short block – well almost just the short block.

When built by Speed-o-Motive the short block contained stock rods with ARP bolts and a set of KB forged pistons. Since this motor was on the dyno for more than 3 months I thought I had better check the bearings so off came the pan. Everything looked barely used so all the original bearings were retained.

As for bores and pistons these looked barely broken in so I had to assume that the Speed-O-Motive build was a good one.

At this point I had to look around for a road race worthy pan and pickup. As it happened we had a nice Moroso pan and pickup that I could ‘borrow’ until needed for another build that was still some ways off. So that is what went on – for now. As far as function was concerned there appeared to be no compromise here. So far so good.

Along with the block came a really neat windfall. As it happens for the testing that this Speed-O-Motive block was to be used for we needed to be able to retime cams in really quick and for this Jesel built us a belt drive setup custom fit to the block. This in so many words meant that getting to use the block more or less meant getting to also use the belt drive as well. Now I realize that something like this would only happen one in a thousand or more instances like we are dealing with here but sometimes luck goes the right way and I was due.

Jesel belt drives; they may be expensive (but certainly far from over priced) but nothing that’s really this good comes cheap. As for timing in the cam a Jesel belt drive makes the whole job a 3 minute deal start to finish.

Cylinder Heads.

At this point I needed some heads. We had just had a catastrophe with another motor where the crank had broken and it caused pretty much all the valves to get bent in the Edelbrock Performer heads that were being tested. Some of the seats were a little damages but nothing a valve job would not fix. DV gave the go-ahead on the use of these heads. Now this I was excited about. These Edelbrock Performer heads produce good results and if the extensive testing done here is anything to go by they are about as goof proof as you can get. I was however short of a set of valves. Here GFN’s president and ad man made a suggestion. “The valves that SuperTech make look pretty sharp – why don’t you give them a try?” So we did – and also told them we were in a rush to have the engine finished over the weekend. The valves arrived next day and on top of that they looked real nice to boot. Check them out at SUPERTECH V 2.0 ::::::::::::

So much for the valves. Now for the heads. These needed a valve job so I got on the Serdi and lightly re-cut all the seats. With a clean-up the heads looked as per the following shots:-

Seen here is an intake port (left) the chambers and an exhaust port of our Edelbrock Performer heads. These are emission legal parts and experience on about half a dozen engines shows them to be well named.




Apologies for the marking blue still showing but we wanted to get this motor built over the weekend so no time for niceties.

With the KB flat top pistons we had and the 61 cc’s in the head (instead of the original 60) from the valve job the CR worked out to 8.9/1. A little on the low side for a race engine but at least running it on pump gas would be no problem with detonation. That however did not mean no problems at all!

Camshaft

I hunted around for a camshaft and lifters It seemed we either had one or the other but nothing that made a working combo. There was a street flat tappet cam but no lifters or pushrods even close to the right length. The best I could come up with was a big Xtreme Energy hydraulic roller from Comp. I asked DV if this cam, ground on a 110 LCA was a working proposition in a 5.0. I got the answer that is was essentially a hot deal with the right combo. But what was the right combo? Not, as it happened, a motor with an 8.9/1 CR. Basically a cam this big, for an application such as we have here, needs a minimum of 10.5/1 with a 12/1 being about right. But why am I worrying we have no spare hydraulic lifters but then I get fed a piece of info that changes the picture somewhat. I find a set of Crane solid lifters. I ask DV if there is any chance I can get away with a set of solid lifters on a hydraulic cam. “Sure – if the lash is carefully set”. It seems that if the lash at the lifter can be set to about 0.006-0.008 thousandths that a solid will work just about as if it is a hydraulic but without any collapse. But that operating window appears relatively tight so the lash cannot get too far out as the cam has no great length in terms of a tappet ramp.

So far so good. The next thing of significance I find is that for some reason this cam has been ground with a smaller than usual base circle. When I drop in the Crane lifters the waisted part of the lifter, which allows oil to pass along the lifter oil galley, when on the base circle of the cam, drops low enough top shut of the oil flow. To compensate for this I grind off the top corner of the lifter to allow oil flow along the galley.

Well I now have a cam and lifter setup – but it is hardly a good match for the low compression this motor will have with the heads being used. Normally I would get on the mill and cut the heads about 0.050 but that would mean cutting the intake as well. All that takes a lot of time when you are not really set up to do the job and have to improvise. At this point I asked around to get some idea of the potential loss of output due to the big cam and relatively low CR. As you well might expect there was a range. At the low end I got “at least 30” On the high end I heard “could be as much as 50”. A check on some past builds done in the GFN shop showed an 11.5/1 engine with the same heads (as-cast Performers) using a 244 @ 0.050 solid street roller Crane cam and 0.550 lift valve train netted 450 hp and 390 lbs-ft. Induction was by means of a cleaned up port matched single plane Victor Jnr intake and a BG 650 race Demon carb. That became the yard stick by which I could judge our efforts.

Here is our Speed-O-Motive short block with the cam and lifters installed. The head gaskets used are the top of the line FelPro mutli-layer ones. Not the cheapest and arguable over kill for what we have here but this was Sunday and this is what we had hanging up on the wall. I was going to clean off the pistons but DV said not to as a thin layer of carbon acts, to an extent, like a piston coating so I left it as per the boss’s instructions. The damper is a Professional Products piece. We have now used a lot of these and they look to be getting the job done for a very reasonable price.

At this point the head gaskets were positioned on the block and the heads installed. Next item to worry about was the intake manifold.

The rockers used were Crane budget Blue Racer’s. When checking the pushrods for optimal length I found that we did not have any but had some that could be managed on. These were about 0.050 too long and gave away a little in the tip sweep geometry and lost a bout 0.015 lift. But we had them.

Crane’s Blue Racer rockers are a cost effective alternative to their nominally more expensive Gold Race rockers. As you can see there is nothing ‘blue’ about them but why pay for anodizing when they can’t be seen in operation anyway.[/center]

Induction.

As well as a 12/1 CR what I would have liked here was a Victor Jnr and a carb around 700 cfm but neither were on hand. What I did have was a two plane Edelbrock Performer and a race BG 650 carb. The carb concerned was one of this companies up market replaceable sleeve ones. This allows the end user to select the size of the main venturi to optimize it for the engines requirements. I was advised to leave this with the green sleeves in as they allowed about 650 cfm plus delivered a good booster signal. So carb wise I was in a good position but the intake manifold, as good as these Performer Air Gaps are, is intended for an engine with something a little less than a race cam. Here it was expected that this two plane could well make the torque of a Victor Jnr. but could well be 15 to 20 hp off as far as peak power was concerned. To allow the Performer to show of it’s best it was port matched to the heads.

Edelbrock’s Performer Air Gap 5.0 Ford two plane intake has consistently shown strong curves for both the torque and peak hp. It givers away at the higher rpm to a Victor Jnr but for all around street ability it has few equals. Top right shows the port matching done. The ports are slightly necked down toward the manifold face thus facilitating port matching without having to do any filling.




The BG 650 RS Race Demon is seen here on a 1.5 inch spacer. This is an open spacer for each half of the intake front to back but side to side it is still divided.

Ignition and Exhaust

For sparks I used one of our spare Performance Distributors HEI units for a Ford. This was the easiest part of the deal as we always have a spare one of these units about as it is a standby for when other ignition companies are late delivering or the unit malfunctions. It is often said around here that when all else fails we have our Performance Distributors unit ready to go. For plug cables I used some of Acell’s high temperature boot ones. These stand up well on the dyno to all the heat involved. If they live here they will live even longer on the vehicle.

For headers a set of BBK long tube ones were on hand. This is the style of headers I would have chosen for the job even if more were available.

Last on the list of significant parts was a Mezier water pump. We often use these for dyno testing because of sheer convenience. In case you are wondering they are worth between 7 and 10 hp on engines turning up to about 7000 rpm. We don’t really see much increase until about 3000 rpm but then the differences between a mechanical water pump and an electric one start to show.

About now I had a finished engine ready to hit the dyno. So starting Friday morning with pile of parts and not knowing if we had what it took to complete a motor too Sunday night and dyno ready was a minor adventure in itself. As you can see from the following shot the motor looks really good. Now it’s time to see what it performed like.

The dyno test was to be done at T&L in Stanfield and so was duly dragged over there. It made 350 lbs-ft and 375 hp. Not staggering but that will be more than enough to power a NASA American Iron car.

All this though begs the question as to how much each ‘make do’ when things were less than optimal, cost in the way of output. The biggest loss by far is from the lack of compression with the big cam. An engine we built like this (same heads, intake and exhaust) about 3 years ago but with a short hydraulic cam and 9.3/1 CR made 395 hp and 375 lbs-ft so this cam to compression interaction seems to be a really important issue to address when building an engine. The bottom line here is that cam, compression and intake manifold selection looks to have cost 45 lbs-ft and 75 hp compared to the motor mentioned near the beginning of this feature. Now I have gone some way toward quantifying these common build errors I don’t expect you guys to build into your engines the same parts mismatch!

And by the way as time goes by I hope to fix the parts combo to see where I finally get to in terms of output with this 5.0. Will keep you posted.

Dusty Kennett

[Mwilson]

I sure hope I didnt mess this up!

[Horsewidower]

Looks like you've fallen into the normal American Iron trap when it comes to building an engine. With the hp you're putting out, you'll have a car that weighs in excess of 3500 lbs. You won't be anywhere close to competitve with the spec 275 tire. My observation of the class is that most people over build their motors and then choke the crap out of them in order to get down to the rules limited hp/tq numbers. Engine failure is a common outcome. If you get to the 395 hp, you might as well throw out an anchor, you'll have a car that has to weigh 3,750.

I went a different direction, a turbo 2.3. I get to build a real race engine, and with the same tires, I weigh 1,000 less. Now I just have to stop blowing them up as I experiment with EFI and turbos.

I don't mean to be bustin' your chops on this, but to optimize an AI combo, you need to get the lightest car possible and then build the engine to the hp/tq limits applicable to the weight. Lighter car = better brakes, better tire usage.

Best of luck.

Bob

On edit: I may have been hasty. You're talking about crank horsepower not rwhp. Assuming 15% loss, you're looking at a 3,028 lb car. Lots of guys are running at that weight . Although its still quite a ways over minimum.

[Cammer]

I totally disagree with your camshaft/lifter choice.

Perform a few late night valve jobs for friends on that Serdi and buy a proper camshaft/lifter combination for the engine.

Steal parts off of David's engine! Just kidding!

You will quickly discover that a well set up car and a good driver are your greatest assets.

You are going to have a blast driving in American Iron!