Race Engine Forum UK

Guy and All Hi,

If this is not the correct place to put this post I apologize in advance. Please move if needed.

Some basic engine info:
1800 Fiat TC block
2000 Fiat TC crank 90mm stroke
85mm bore

I recieved the package in fine shape. I was wondering if you could supply me with a accurate compressed head gasket thickness on the Nava Linea #80079 head gasket. You mentioned that it was about
1.5 mm (.059") compressed.

The bottom end was mocked using the new rods and an old piston that I machined to the X.XXX compression height and to the skirt height I needed to clear the larger throughs and counter weights.
I am including a photo of the areas of the block I needed to remove material from for rod and crank clearence. I will be running an electric fuel pump due to needing to machine off the eccentric from the intermediat shaft. The rods will be slightly machines at the cap's bottom corners down to the diameter of the rod bolt flange. A 30 degree chamfer should do. This should give me a bit more block clearence.

Can any body suggest a minimum rod to block clearence I should be running on this Fiat? Currently I will have a minimum of .050".

The pistons have arrived from my supplier and I have taken the block to the machine shop for boring (photo attached). The manufacturer recommends a .003" piston to bore clearence. Does this sound acceptable for the Fiat? I traditionaly run 4.00" to 4.50" forged slugs at .004".

A few piston specs for referance:
Piston Only Weight XXX grams
Comp Height: X.XXXXX Recomended Bore Dia: 3.3464"
Ring groove widths: Top=.041, Middle=.049, Oil=.080
Dome and Valve Pockets: Volume=-2.8 cc
Intake Pocket: Dia.= XXXX" Depth= .XXXXX @ 32.0 Degrees
Exhaust " " : Dia.= XXXXX" Depth =. XXXX"@ 32.0 Degrees

I am particularly happy with the rods. I requested a small big end profile th minimize block machining and cutting of the block. They also allowed the use of the factory 1800 oil pan. I fully expected to need a deeper pan to make room for the larger rotating assembly. They are billet cnc machined and heat treated to 43 Rockwell "C" scale. This should yeild a material tensil of 202,000 psi as compared to a stock rod @29 RCS and 137,000 psi.
A few rod specs for referance:
Total Weight= 522 g (1800 TC Rod 695 g)
Rotating weight=376 g (1800 TC 520 g)
Reciprocating Weight= 146 g (1800 TC 176)
Note: My TC rod weights may be off due to a lack of a proper fixture

The cams being used on this build are 42/82 billet units. 304 adv duration ( 260 deg @ .050 and 10.6mm lift. I think they are the same as Alquati 42\82. I am a bit concerned that they might be a bit big with the 10.2 compression I will be running. I can run the intake cam at 108 or 105 to preserve cylinder pressure at low speed if necessary.

Any how that is about it for now. If any body has any suggestions they would be appreciated as I am as you know a Fiat newbie.

Thanks Robert

MODEL POST!


Robert, hi

some good stuff going down there, you won't have a problem with those cams, the lift integral is fine with that CR. You could run much wilder.

I imagine you know this but just in case you don't, make sure you mod the aux d/s as shown or it will (well, cannot be too sure with your rods) clobber no 2 rod. You won't find out till you swing it over with the belt on.

Interesting post, anyhow, thanks. Always great to see folks getting stuck-in.

G

Guy Hi,
Thank you for the encouragment.
I have machined the aux d/s fuel pump drive to completly round (no eccentric) at about .625" diameter. The test reassemble showed plenty of clearence between it and the rod. I suppose I felt at the time that 30 minutes in front of my lathe was the easier way but the heat treated shaft was tough to turn. Your picture of parting the end off and plugging is the better way I am sure.

Do you have a more exact compressed head gasket thickness? I will soon be calculating the amount of material to be removed from the block. I shall be running a piston to head clearence of .035" to acheive maximum induced turbulence.

The 0 degree quench band I am using is fairly common on many domestic high performance engines. I usualy try to end up at around 35%
quench band to bore area. It has proven to be insturmental in improving low speed torque and throttle responce in the engines I build for use at above 5000 feet. The Fiat will be at 8500 ft mostly and will see a max MAP of 21 inhg.

Any suggestion cam timming to start and on jetting the IDF's
40mm idf's
34 mm chokes
ported waffle manifold.
43 and 37.5 mm valves
messaged CC's (shaped and deshrouded)
nice 4 into 1 header 28" stepped primarys 1.625 to 1.750 /2.250 collector-back of car.
A straight through racing muffler as resonator and straight through muffler.

Guy Thanks In Advance for All the Great Information
Robert Kenney

Robert, hi

thanks!

Now, you will get used to it (have to get used to it?!) - I don't get too involved in very exact CR and thus no, cannot give you and exact compressed thickness, about 1.5mm is all I would say. There is no defined relationship between CR and anything at all, so no point at all in going to Olympian standards of accuracy with it. I know there are folks who like to dwell extensively on it, but trust me, it really is pointless. Your setup will produce excellent torque/power (assuming the cams really so share the Alquati characteristics) with anything from 9/1 to 11/1 and you would be hard put to notice any difference in perfomance between 10.5/1 and 10/1 really.

Your point about altitude is of course interesting and yes I understand that gasket thickness has a bearing on the thickness of the squish (quench) band. The thing to note is that the fire ring stands above the core by a small amount and thus is will compress to core thickness and not much beyond that, say about 2-5 thou tops. I have written quite a lot on the site about squish, try the search engine. Improved performance at altitude (the engine having lower vol effy - due to reduced inlet charged density) with higher squish than another engine of the same spec will have more to do with mixing of fuel/air in cylinder and thus burn quality than anything else.
Whether an improvement in engine response at high altitude is due to CR - rather than increased squish-induced turbulence- is an interesting point. I suspect the former. Too-high squish is well-known to sap power because of the energy lost in vortex generation, whereas high CR has a proven benefit in increasing thermal efficiency.

I can certainly give you jetting, but first I'd like you to search by 'idf' in the search facility; this will do two things, give you a good read of things way beyond merely that, and buy me some time too!

GC

Guy, Thanks

I will for sure take your advise about searching more on those topics. I have done a lot of it already but never could do to much.

I would like also to know more about the cam specifics. They seem to have a makers mark that looks like a single cam lobe profile laser etched into the shaft (see picture) . Any ideas on maker? I will have to do some investigating while I degree them.

Thanks
Robert

I know that maker's logo and cast iron billet type, they are very good, super hard.
Any markings on the cam ends?

GC

Guy Hi,
Good to hear they are quality cams. Sorry no markings on the end but there is a HE7 on the shaft in another location
Is the makers mark the blank mfg. only or is it the grinder's mark also.
I usualy have my own cams made by Comp cams or a similar domestic company of my lobe and C/L choice. These came with very little info 0 infact except for the general data on the suppliers site. I like to have the full cam card with all applicable data. Do you think I might be able to contact the maker and get this information?

I may have been vauge about my IDF setting questions. I will be tunning for sea level not at 8500' for initial run in. I will be leaning for altitude only with main circuit settings so it will be easy to drive up and down the mountains. Sorry for not making it clear.

Thanks So Much
Robert

Robert, hi

can you remind me at a later date on jetting please?

As for cams the firm that makes the blanks is not the firm who profiles them, so the latter is whom you should approach for tech data. I have no idea what HE7 means, sorry, don't have nay of them in stock at present to compare. If you know the lift-degree sum (cam area) and the clearance at which it is quoted maybe let me have it.

GC

Guy, Hi
Understood about the jetting. It is still a bit in the future anyhow.
The cam info I have is 304deg + 10.6 at 0 lash 260deg @ .050 follower lift
recommended running lash is .014" I & E.

Thanks Again
Robert

Robert, hi

doesn't tell you much unfortunately. At the risk of re-publishing (sorry members who are au-fait with this) if you refer to the graph below, you can see that duration in terms of degrees per-se never tells the whole story, which is that it is the area under the cam curve at effective lift (ie: after lash/running clearance) has been allowed for and the rate of acceleration (degrees to achieve peak lift) and the dwell at full lift that really governs the airflow.
The 3A which on paper has shorter duration will easily outperform the Alquati profile (very similar to the 42/82 you mentioned) at all engine speeds.

You should get your cams mapped lift by degrees and examine their characteristic.

GC

Guy, Hi

the vendor prefers to publish very limited data on what they sell. But the effect of valve lifting velocity on torque and power is not foreign to me. I have not had access to a custom Fiat cam profiler until now and have been forced to choose from what I have access to.

I will be fixing this affliction by having you supply me with a suitable set of cams.

I am thinking about having max HP around 7200-7500 with strong mid range power. What would you suggest.

Would the GC ST3 Race work well for me? Only a couple degrees differance between it and the Forest Rally @.050, but substantially more lift.

I will be contacting you offline.

Thank You again
Robert Kenney

Guy Hi,
As usual you have been a great help. I can't wait to recieve the cams and springs from you and, hear the girl sing her first song.

I would have to say it is your advice that is priceless. Any one would be hard pressed to put a price on your experience and generousity of information.

Would you suggest going to 36 mm chokes or staying with 34's?

Robert

I'd stay with 34mm chokes on 40 IDF Rob


GC